B-17620053-riza Nensy Marantika.pdf

JASA EKOSISTEM PERTANIAN

Dosen Pengampu: Dr. Dwi Suheriyanto, S.Si, M.P

Disusun Oleh: NAMA

: RIZA NENSY MARANTIKA

NIM

: 17620053

KELAS

: BIOLOGI B

JURUSAN BIOLOGI FAKULTAS SAINS DAN TEKNOLOGI UNIVERSITAS ISLAM NEGERI MAULANA MALIK IBRAHIM MALANG 2019

KATA PENGANTAR Alhamdulillah, puji syukur kehadirat Allah SWT yang telah melimpahkan segala nikmat-Nya. Dengan kemurahan yang telah diberikan oleh Tuhan Yang Maha Esa sehingga penulis dapat menyelesaikan makalah dengan judul “Jasa Ekosistem Pertanian” ini dengan baik dan tepat pada waktunya. Makalah ini disusun untuk memenuhi tugas mata kuliah Keanekaragaman Ekosistem. Ungkapan rasa terima kasih ingin penulis sampaikan kepada semua pihak yang telah membantu dengan bimbingan, dorongan, motivasi, penjelasan, informasi, maupun pengarahan yang telah diberikan sehingga membantu selesainya makalah ini. Penulis menyampaikan terimakasih pula pada pihak-pihak yang tidak bisa disebutkan satu persatu. Mungkin apa yang telah penulis hasilkan ini bukanlah yang terbaik, namun penulis berharap apa yang telah ditulis ini akan bermanfaat dan bisa digunakan dengan sebaik mungkin bagi yang membaca. Oleh sebab itu, saran dan kritik yang sifatnya membangun sangat diharapkan.

Malang, 24 Pebruari 2019

Penulis Riza Nensy Marantika NIM: 17620053

ii

DAFTAR ISI Kata Pengantar

........................................................................ ii

Daftar Isi

........................................................................ iii

BAB I Pendahuluan

........................................................................ 1

1.1.

Latar Belakang

........................................................................ 1

1.2.

Tujuan

........................................................................ 1

1.3.

Manfaat

........................................................................ 2

BAB II Pembahasan

........................................................................ 3

2.1 Kajian Keislaman Ekosistem Pertanian ................................................ 3 2.2 Pengertian Jasa Ekosistem

................................................ 4

2.3 Karakteristik Ekosistem Pertanian

................................................ 5

2.4 Jasa Ekosistem Pertanian ........................................................................ 6 2.5 Analisis Jasa Ekosistem Pertanian

................................................ 7

2.6 Keberlanjutan Ekosistem Pertanian

................................................ 9

BAB III Kesimpulan

........................................................................ 11

Daftar Pustaka

........................................................................ 12

Lampiran

........................................................................ 13

iii

BAB I PENDAHULUAN 1.1 Latar Belakang Jasa ekosistem merupakan keuntungan yang diperoleh manusia dari suatu ekosistem. Ada tiga jenis jasa yang secara langsung menyumbang secara langsung pada kesejahteraan manusia, seperti: jasa penyediaan, jasa pengaturan, dan jasa budaya. Jasa ekosistem mempengaruhi semua komponen kesejahteraan. Jasa ekosistem meningkatkan rasa aman bagi orang yang tinggal di sekitarnya. Jasa ekosistem juga berhubungan langsung dengan pendapatan dan jaminan pangan (Locatelli et al, 2012). Ekosistem terbagi menjadi dua jenis, yaitu ekositem alami dan ekosistem buatan. Ekosistem buatan merupakan suatu ekosistem yang mendapat sentuhan manusia secara terus menerus dan terjadi perubahan dalam habitat. Ekosistem pertanian merupakan salah satu ekosistem buatan. Disebut demikian karena adanya campur tangan manusia melalui proses pengolahan lahan, pengairan, penyiangan, penyemprotan pestisida, panen, dan pembakaran perladangan yang berpindah (Sembel, 2015). Pertanian bertujuan untuk menghasilkan bahan pangan bagi kesejahteraan makhluk hidup lainnya. Apabila ekosistem pertanian mengalami kerusakan, maka akan timbul kekhawatiran di masa depan terkait peningkatan kebutuhan manusia akan jasa-jasa ekosistem pertanian. Dengan demikian, manusia harus paham mengenai konsep jasa ekosistem pertanian. 1.2 Tujuan Tujuan dari penulisan makalah ini, yaitu: 1. Untuk mengetahui kajian keislaman ekosistem pertanian. 2. Untuk mengetahui apa pengertian jasa ekosistem. 3. Untuk mengetahui karakteristik ekosistem pertanian. 1

4. Untuk mengetahui jasa ekosistem pertanian. 5. Untuk mengetahui analisis jasa ekosistem pertanian. 6. Untuk mengetahui keberlanjutan ekosistem pertanian. 1.3 Manfaat Manfaat dari penulisan makalah ini yaitu: 1. Diharapkan masyarakat mengetahui kajian keislaman ekosistem pertanian. 2. Diharapkan masyarakat mengetahui apa pengertian jasa ekosistem. 3. Diharapkan masyarakat mengetahui karakteristik ekosistem pertanian. 4. Diharapkan masyarakat mengetahui jasa ekosistem pertanian. 5. Diharapkan masyarakat mengetahui analisis jasa ekosistem pertanian. 6. Diharapkan masyarakat mengetahui keberlanjutan ekosistem pertanian.

2

BAB II PEMBAHASAN 2.1 Kajian Keislaman Ekosistem Pertanian Lingkungan merupakan kondisi sosial dan kultural yang berpengaruh terhadap individu atau komunitas, lingkungan terbentuk dalam sebuah sistem yang merupakan suatu jaringan saling ketergantungan antar komponen dan proses, dimana energi dan materi mengalir dari satu komponen ke komponen sistem lainnya. Sistem lingkungan atau yang sering disebut ekosistem merupakan contoh bagaimana sebuah sistem berjalan. Ekosistem merupakan suatu gabungan atau kelompok hewan, tumbuhan dan lingkungan alamnya, dimana di dalamnya terdapat aliran atau gerakan atau transfer materi, energi dan informasi melalui komponen-komponennya. Ekosistem dapat pula dimaknai sebagai suatu situasi atau kondisi lingkungan dimana terjadi interaksi antara organisme (tumbuhan dan hewan termasuk manusia) dengan lingkungan hidupnya. Sebagai sebuah sistem, lingkungan harus tetap terjaga keteraturannya sehingga sistem itu dapat berjalan dengan teratur dan memberikan kemanfaatan bagi seluruh anggota ekosistem. Manusia sebagai makhluk yang sempurna, yang telah diberikan amanah untuk menjadi khalifah memiliki peran penting dalam menciptakan dan menjaga keteraturan lingkungan dan system lingkungan ini. Untuk itulah manusia dituntut untuk dapat mengembangkan akhlaq (perilaku yang baik) terhadap lingkungan (Fua, 2014). Menurut syari’at Islam, manusia harus menyadari bahwa segala sesuatu yang ada di alam semesta ini adalah milik Allah SWT (al-Maidah ayat 117). Tetapi Allah SWT dengan kasih sayang-Nya telah memberikan hak kepada manusia untuk menfaatkan alam ini dengan sebaik-baiknya dan mengolah sumbernya untuk kemakmuran manusia (al-Baqarah 29). Sebagai makhluk yang memperoleh hak menggunakan alam ini, manusia haruslah mematuhi ketentuan-ketentuan yang diatur oleh pemiliknya yaitu Allah SWT. Manusia tidak berhak

3

memanfaatkan dan menggunakan alam ini secara sembarangan dan bertentangan dengan ketentuan yang ditetapkan Allah SWT (Manan, 2015). Allah SWT berfirman dalam Al-Quran Surah Saba’ ayat 15-16, Artinya : “Sesungguhnya bagi kaum Saba’ ada tanda (kekuasaan Tuhan) di tempat kediaman mereka yaitu dua buah kebun di sebelah kanan dan di sebelah kiri. (Kepada mereka dikatakan): “Makanlah olehmu dari rezeki yang (dianugerahkan) Tuhanmu dan bersyukurlah kamu kepada-Nya. (Negerimu) adalah negeri yang baik dan (Tuhanmu) adalah Tuhan Yang Maha Pengampun. Tetapi mereka berpaling, maka Kami datangkan kepada mereka banjir yang besar dan Kami ganti kedua kebun mereka dengan dua kebun yang ditumbuhi (pohon-pohon) yang berbuah pahit, pohon Atsl dan sedikit dari pohon Sidr.” (QS. Saba’ : 15-16) Bumi yang satu-satunya ini, telah diciptakan oleh Allah SWT dengan kekuasaan-Nya, dan diserahkan kepada manusia untuk dimanfaatkan demi kemaslahatan bersama. Bagaimanapun dan apapun keadaan isi bumi ini, yang jelas tidak ada sesuatu yang diciptakan oleh Allah dengan sia-sia, asalkan dikelola dengan baik dan penuh keimanan untuk kebaikan manusia, tanpa itu semua, hanya kerusakan yang akan menimpa dunia ini. Oleh karena itu, hendaknya diusahakan agar jangan sampai bumi ini rusak di tangan manusia (Manan, 2015). Allah memberikan bahan pangan bagi manusia melalui pertanian ataupun perkebunan, maka sebagai khalifah hendaknya manusia memanfaatkan dan tidak merusak ekosistem atau lingkungan pertanian supaya dapat diperoleh manfaat atau hasil darinya. 2.2 Pengertian Jasa Ekosistem Jasa ekosistem adalah manfaat yang diperoleh populasi manusia secara langsung atau tidak langsung dari fungsi ekosistem. Jasa ekosistem terdiri dari aliran bahan, energi, dan informasi dari alam dan merupakan persediaan pokok yang digabungkan dengan manufaktur dan usaha manusia untuk menghasilkan kesejahteraan (Costanza et al., 1997). Sejumlah jasa ekologi ini tidak dikonsumsi 4

oleh manusia secara langsung, tetapi dibutuhkan untuk mempertahankan ekosistem itu sendiri. Jasa tidak langsung tersebut termasuk penyerbukan tanaman dan siklus hara, tetapi klasifikasi tidak jelas (Bolund, 1999). Jasa ekosistem adalah kondisi dan proses melalui ekosistem alami dan spesies yang menyusunnya, mendukung dan memenuhi kehidupan manusia. Jasa ekosistem memelihara keanekaragaman hayati dan produksi barang-barang ekosistem seperti makanan laut, tumbuhan, kayu, bahan bakar biomassa, serat alami, produk industry, dan banyak obat-obatan. Pemanenan serta perdagangan barang-barang hasil dari suatu ekosistem ini merupakan bagian penting dari perekonomian manusia. Selain produksi barang, jasa ekosistem adalah fungsi pendukung kehidupan yang sebenarnya, seperti pembersihan, daur ulang, dan pembaruan, dimana jasa ekosistem memberikan banyak manfaat estetika dan budaya yang tidak terhingga. (Daily, 1997). Jasa ekosistem adalah manfaat yang diperoleh orang dari ekosistem. Ini termasuk jasa penyediaan makanan dan air, mengatur jasa seperti regulasi banjir, kekeringan, degradasi lahan, dan penyakit. Jasa pendukung seperti pembentukan tanah dan siklus hara, serta jasa budaya seperti rekreasi, spiritual, agama, dan manfaat non-materi lainnya (Alcamo et al, 2003). 2.3 Karakteristik Ekosistem Pertanian Agroekosistem ekosistem

binaan

memperoleh

atau

ekosistem

manusia

produk

pertanian

yang

pertanian

merupakan

perkembangannya yang

diperlukan

satu

bentuk

ditujukan untuk

untuk

memenuhi

kebutuhan manusia. Agroekosistem tidak memiliki kontinyuitas temporal (tidak stabil). Keberadaannya hanya dalam waktu

yang terbatas dan sering

mengalami

perubahan

iklim

mendadak

manusia,

seperti

pencangkulan,

mikro

secara

penyiangan,

akibat

tindakan

pengairan

dan

sebagainya. Struktur agroekosistem didominasi oleh jenis tanaman tertentu yang dipilih

oleh

manusia

dan

sering

merupakan

tanaman

baru

yang

dimasukkan ke dalam ekosistem tersebut. Agroekosistem pada umumnya tidak memiliki keragaman biotik dan genetik yang tinggi sehingga kurang stabil. Umur 5

tanaman yang ada dalam agroekosistem relatif seragam. Selain itu, terdapat pula masukan berupa pupuk, pestisida dan air irigasi, sehingga jaringan tanaman menjadi kaya akan unsur hara dan air. Akibat dari sifat-sifat tersebut di atas, dalam agroekosistem sering terjadi letusan populasi organisme pengganggu tumbuhan (OPT) (Pusat Penelitian dan Pengembangan Holtikultura, Tanpa Tahun). 2.4 Jasa Ekosistem Pertanian Pertanian (termasuk hutan tanaman) secara konvensional memasok makanan, serat, dan bahan bakar atau disebut dengan jasa penyediaan dalam lingkup jasa ekosistem. Petani juga membantu menjaga alam atau mendukung jasa ekosistem yang membuat pertanian produktif, seperti penyerbukan, hama, dan pembaruan nutrisi tanah. Dalam teori, ekosistem terkelola yang sama yang menyediakan produk-produk yang dipasarkan ini bisa menghasilkan jenis jasa ekosistem yang lain jika ada insentif yang sesuai (Swinton et al, 2006). Penyediaan makanan adalah fungsi utama dan ekosistem utama jasa ekosistem pertanian. Sistem pertanian tergantung pada jasa ekosistem yang mendukung fungsi produksi dan sumber pertanian serta jasa ekosistem nonpertanian. Jasa ekosistem dikategorikan sebagai penyediaan, pengaturan, dukungan, dan budaya. Tingkat pendistribusian berbagai jasa ditentukan oleh kombinasi sifat ekosistem, termasuk tanah, vegetasi, iklim, dan proses ekologis yang dihasilkan (Palm et al, 2014).

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2.5 Analisis Jasa Ekosistem Pertanian

Struktur tanah dan kesuburan memainkan peran besar dalam menentukan di mana berbagai jenis pertanian berlangsung dan kuantitas serta kualitas hasil pertanian.

Cacing

tanah,

makro-

invertebrata,

dan

mikro-invertebrata

meningkatkan struktur tanah melalui lubang atau gips dan meningkatkan kesuburan tanah melalui pencernaan parsial dan menjadi bahan organik tanah. Siklus nutrisi juga menjaga kesuburan tanah. Mikroorganisme (bakteri, jamur, actinomycetes) adalah mediator kritis jasa ekosistem ini. Misalnya, bakteri meningkatkan ketersediaan nitrogen melalui fiksasi nitrogen dari atmosfer. Ini paling sering terjadi pada tanaman yang memiliki hubungan simbiosis dengan bakteri pengikat N, tetapi bakteri tanah yang hidup bebas dapat memperbaiki nitrogennya juga. Mikroorganisme juga meningkatkan kesuburan tanah dengan membebaskan nutrisi dari detrital bahan organik (misal: daun tanaman) dan mempertahankan nutrisi dalam biomassa mereka yang mungkin hilang. Tanaman non-panen juga bisa menjadi kunci kesuburan tanah karena tanaman tersebut dapat digunakan untuk mengisi kembali nutrisi pertanian tanah selama periode 7

saat belum ditanami atau melalui yang disebut "efek rotasi". Selain proses untuk menjaga kesuburan tanah, retensi tanah adalah kunci untuk menjaga nutrisi tersebut di tempat dan tersedia untuk tanaman. Praktek-praktek pertanian tertentu, seperti membajak, menanam, mengolah, dan pemanenan dengan menggunakan mesin dapat memusnahkan aliran jasa ekosistem berbasis tanah karena mengganggu fungsi komunitas mikroba tanah (Zhang, 2007). Penyerbukan tanaman merupakan jasa ekosistem paling terkenal yang dilakukan oleh serangga. Produksi pangan tergantung pada penyerbukan hewan. Lebah terdiri dari taksa dominan menyediakan jasa penyerbukan tanaman, tetapi burung, kelelawar, ngengat, lalat dan serangga lain juga bisa menjadi media penyerbukan (Zhang, 2007). Burung, laba-laba, kepik, belalang, lalat, dan tawon, serta jamur entomopatogenik merupakan beberapa jenis makhluk hidup sebagai kontrol alami hama tanaman. Jasa ekosistem ini menekan kerusakan hama dan meningkatkan hasil, sementara di jangka panjang mempertahankan keseimbangan ekologis yang mencegah serangga herbivora mencapai status hama. Hilangnya keanekaragaman hayati, praktik pertanian modern, dan perubahan alami manusia semakin mengancam jasa ekosistem ini. Misalnya, penggunaan insektisida dalam pertanian cenderung untuk memusnahkan populasi musuh alami, sering memiliki konsekuensi yang tidak diinginkan baik memperburuk hama, atau benar-benar mengarah pada munculnya hama baru (Zhang, 2007). Penyediaan dan pemurnian air harus memenuhi persyaratan seperti, kuantitas, waktu, dan kemurnian yang cukup untuk produksi pertanian. Tutupan vegetasi di daerah aliran sungai hulu dapat mempengaruhi jumlah, kualitas, dan stabilitas air pasokan ke pertanian. Hutan bisa menstabilkan tanah untuk mengurangi beban sedimen di sungai. Di Australia, pohon dapat meningkatkan resapan air di dalam hutan, mengurangi limpasan permukaan dan salinisasi tanah. Lahan basah dan vegetasi riparian bisa juga meningkatkan kualitas air dan melemahkan banjir (Zhang, 2007).

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Jasa ekosistem dalam bentuk abiotik untuk pertanian melibatkan iklim, termasuk suhu dan curah hujan, serta frekuensi dan tingkat keparahan cuaca ekstrem, kekeringan, banjir, dll. Iklim yang menguntungkan memberikan keuntungan biaya bagi petani. Iklim yang cocok dan stabil bergantung pada atmosfer (Zhang, 2007). 2.6 Keberlanjutan Ekosistem Pertanian Kata “keberlanjutan” sekarang ini digunakan secara meluas dalam lingkup program pembangunan. Keberlanjutan dapat diartikan sebagai “menjaga agar suatu upaya terus berlangsung”, “kemampuan untuk bertahan dan menjaga agar tidak merosot”. Dalam konteks pertanian, keberlanjutan pada dasarnya berarti kemampuan untuk tetap produktif sekaligus tetap mempertahankan basis sumber daya. Pertanian berkelanjutan adalah pengelolaan sumber daya yang berhasil untuk usaha pertanian guna membantu kebutuhan manusia yang berubah sekaligus mempertahankan atau meningkatkan kualitas lingkungan dan melestarikan sumber daya alam (Reijntjes et al, 1992). Kualitas

sumber

daya

alam

harus

dipertahankan dan kemampuan

agroekosistem secara keseluruhan dari manusia, tanaman, dan hewan sampai organisme tanah ditingkatkan.. kedua hal ini akan terpenuhi jika tanah dikelola dan kesehatan tanaman, hewan, serta masyarakat dipertahankan melalui proses biologis (regulasi sendiri). Sumber daya lokal dipergunakan seemikian rupa sehingga kehilangan unsur hara, biomassa, dan energi bisa ditekan serendah mungkin serta mampu mencegah pencemaran. Tekanannya adalah pada penggunaan sumber daya yang bisa diperbarui. Selain itu, semua bentuk kehidupan (tanaman, manusia, hewan) harus dihargai (Reijntjes et al, 1992). Dalam pembangunan di bidang pertanian, peningkatan produksi seringkali diberi perhatian utama. Namun, ada batas maksimal produktivitas ekosistem. Jika batas ini dilampaui, ekosistem akan mengalami degradasi dan kemungkinan akan runtuh sehingga hanya sedikit orang yang bisa bertahan hidup dengan sumber daya yang tersisa. Prinsip ekologi dasar mewajibkan manusia untuk menyadari 9

bahwa produktivitas pertanian memiliki kemampuan terbatas (Reijntjes et al, 1992). Pertanian intensifikasi yang bertujuan meningkatkan produksi pangan dapat mempengaruhi komponen dan proses dalam ekosistem. Intensifikasi dapat mengganggu banyak hal yang mengatur dan mendukung jasa ekosistem, termasuk siklus nutrisi, regulasi iklim, regulasi kualitas dan kuantitas air, penyerbukan, dan pengendalian hama. Itu juga dapat mengubah keanekaragaman hayati yang menopang banyak jasa ekosistem ini. Sementara beberapa praktik pertanian dapat menurunkan dan dapat pula meningkatkan atau mempertahankan jasa ekosistem. Meningkatkan produksi pangan dengan mengorbankan jasa ekosistem dapat merusak keberlanjutan agroekosistem termasuk produksi tanaman (Palm et al, 2014).

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BAB III KESIMPULAN Manusia sebagai khalifah di bumi Allah hendaknya melakukan apa yang telah diperintahkan Allah seperti yang tertulis dalam Q.S As-Saba ayat 15-16 yang menganjurkan manusia untuk bercocok tanam agar menghasilkan manfaat bagi yang lain. Kegiatan bercocok tanam erat hubungannya dengan pertanian. Hasil dari ekosistem pertanian yang paling besar adalah bahan pangan. Produktivitas dalam ekosistem pertanian bergantung pada jasa ekosistem pertanian, yang meliputi struktur dan kesuburan tanah, penyerbukan, pengontrolan alami hama tanaman, penyediaan air, iklim, curah hujan dan suhu di suatu daerah pertanian tersebut. Dalam mencapai produktivitas yang tinggi di sektor pertanian, manusia tidak boleh melupakan suatu prinsip pemanfaatan. Salah satu contohnya, manusia tidak boleh melakukan eksploitasi karena dapat berpegaruh pada jasa ekosistem seperti disebutkan di atas.

11

DAFTAR PUSTAKA Alcamo, Joseph, et al. 2003. Ecosystems and Human Well-Being. USA: Island Press. Bolund, Per and Sven Hunhammar. 1999. Ecosystem Services in Urban Areas. Ecological Economics. Vol 29. Costanza, Robert, et al. 1997. The Value of the World’s Ecosystem Services and Natural Capital. Nature. Vol 387. Daily, Gretchen C. 1997. Nature’s Services: Societal Dependence on Natural Ecosystems. USA: Island Press. Fua, Jumarddin La. 2014. Aktualisasi Pendidikan Islam Dalam Pengelolaan Lingkungan Hidup Menuju Kesalehan Ekologis. Jurnal At-Ta’dib. Vol 7. No 1. Locatelli, Bruno, et al. 2012. Menghadapi Masa Depan yang Tak Pasti: Bagaimana Hutan dan Manusia Beradaptasi Terhadap Perubahan Iklim. Bogor: Cifor. Manan, Abdul. 2015. Pencemaran dan Perusakan Lingkungan Dalam Perspektif Hukum Islam. Jurnal Hukum dan Peradilan. Vol 4. No 2 Palm, Cheryl, et al. 2014. Conservation Agriculture and Ecosystem Service: An Overview. Agriculture, Ecosystems and Environment. Vol 187. Pusat

Penelitian

dan

Pengembangan

Holtikultura.

Tanpa

Tahun.

http://hortikultura.litbang.pertanian.go.id/Modul%20PTT/Bawang_Merah/Ag roekosistem.pdf Reijntjes, Coen, et al. 1992. Pertanian Masa Depan. Yogyakarta: Penerbit Kanisius. Sembel, Dentje T. 2015. Toksikologi Lingkungan. Yogyakarta: Penerbit Andi. Swinton, Scott M, et al. 2006. Ecosystem Services from Agriculture: Looking Beyond the Usual Suspects. American Agriculture Economics Association. Vol 88. No 5. Zhang, Wei, et al. 2007. Ecosystem Services and Dis-Services to Agriculture. Ecological Economics. Vol 64. 12

LAMPIRAN

13

14

15

Ecological Economics 29 (1999) 293 – 301

ANALYSIS

Ecosystem services in urban areas Per Bolund a, Sven Hunhammar a,b,* a

En6ironmental Strategies Research Group, Natural Resource Management, Department of Systems Ecology, Stockholm Uni6ersity, Stockholm, Sweden b Stockholm En6ironment Institute, Stockholm, Sweden

Abstract Humanity is increasingly urban, but continues to depend on Nature for its survival. Cities are dependent on the ecosystems beyond the city limits, but also benefit from internal urban ecosystems. The aim of this paper is to analyze the ecosystem services generated by ecosystems within the urban area. ‘Ecosystem services’ refers to the benefits human populations derive from ecosystems. Seven different urban ecosystems have been identified: street trees; lawns/parks; urban forests; cultivated land; wetlands; lakes/sea; and streams. These systems generate a range of ecosystem services. In this paper, six local and direct services relevant for Stockholm are addressed: air filtration, micro climate regulation, noise reduction, rainwater drainage, sewage treatment, and recreational and cultural values. It is concluded that the locally generated ecosystem services have a substantial impact on the quality-of-life in urban areas and should be addressed in land-use planning. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Ecosystem; Ecosystem services; Urban areas

1. Introduction Humanity is rapidly urbanizing, and by 2030 more than 60% of the world population is ex-

* Corresponding author. fms, Box 2142, 103 14 Stockholm, Sweden. Tel.: + 46-8-4023808; fax: +46-8-4023801. E-mail address: [email protected] (S. Hunhammar)

pected to live in cities (UN, 1997). But even if humanity is increasingly urban, we are still as dependent on Nature as before. Cities are, for example, dependent on the large hinterlands needed to provide input and take care of output from the city. In a study of the 29 largest cities in the Baltic Sea region, it was estimated that the cities claimed ecosystem support areas at least 500–1000 times larger than the area of the cities themselves (Folke et al., 1997).

0921-8009/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 8 0 0 9 ( 9 9 ) 0 0 0 1 3 - 0

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When humanity is considered a part of nature, cities themselves can be regarded as a global network of ecosystems. If compared with true, natural ecosystems, the man-made ones are however immature due to features like their rapid growth and inefficient use of resources such as energy and water (Haughton and Hunter, 1994). Odum (1971) even observes cities to be ‘‘only parasites in the biosphere’’. But there is also a presence of natural ecosystems within the city limits. As will be discussed in this paper, the natural urban ecosystems contribute to public health and increase the qualityof-life of urban citizens, e.g. improve air quality and reduce noise. Most of the problems present in urban areas are locally generated, such as those due to traffic. Often the most effective, and in some cases the only, way to deal with these local problems is through local solutions. In this respect, the urban ecosystems are vital. The aim of this paper is to analyse some of the ecosystem services generated by urban ecosystems and discuss their importance for the quality of urban life. The emphasis is to identify the services and whenever possible also quantify and value them, with greatest relevance to cities in Europe and North America. Examples will be taken from the city of Stockholm in Sweden. It is difficult to generalize a discussion like the one in this paper to reflect the importance of ecosystem services in all cities of the world. Both the actual service and its value are site-specific and can vary significantly around the world. Cities differ, since they are built in all kinds of climates, their sizes vary from small towns to huge megacities, and the wealth of city inhabitants ranges from extreme poverty to excessive luxury. Methodologically, the identification and valuation of ecosystem services could be viewed as an input to a cost-benefit analysis (CBA) aiming at more efficient land-use in urban areas. The benefits of ecosystems are often neglected in ordinary CBAs and if increased values (both monetary and non-monetary) could be allocated to ecosystems, the results of CBAs on new infrastructure or conservation projects could change.

We begin with a general discussion of urban ecosystems and their ecosystem services. A number of local and direct services relevant for Stockholm are then discussed. The paper is concluded by a synthesis and a discussion on the consequences for land use.

2. Urban ecosystems An ecosystem can be defined as ‘‘a set of interacting species and their local, non-biological environment functioning together to sustain life’’ (Moll and Petit, 1994). However, the borders between different ecosystems are often diffuse. In the case of the urban environment, it is both possible to define the city as one single ecosystem or to see the city as composed of several individual ecosystems, e.g. parks and lakes (Rebele, 1994). For simplicity, we have chosen to use the term urban ecosystems for all natural green and blue areas in the city, including in this definition street trees and ponds. In reality, street trees are too small to be considered ecosystems in their own right, and should rather be regarded as elements of a larger system. We identify seven different urban ecosystems which we call natural, even if almost all areas in cities are manipulated and managed by man. The ecosystems are street trees, lawns/parks, urban forests, cultivated land, wetlands, lakes/sea, and streams. Street trees are stand-alone trees, often surrounded by paved ground. Lawns/parks are managed green areas with a mixture of grass, larger trees, and other plants. Areas such as playgrounds and golf courses are also included in this group. Urban forests are less managed areas with a more dense tree stand than parks. Cultivated land and gardens are used for growing various food items. Wetlands consist of various types of marshes and swamps. Lakes/sea includes the open water areas while streams refers to flowing water. Other areas within the city, such as dumps and abandoned backyards, may also contain significant populations of plants and animals. It should be possible, however, to place most urban ecosystems or elements in one of the above mentioned categories.

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Our classification is crude and has to be adopted to site-specific conditions. Stockholm has a large and varied ecological structure. In the City of Stockholm, parks and green space occupy 56 km2 (26%), and water areas cover 28 km2 (13%) of the total area of 215 km2 (Miljo¨fo¨rvaltningen, 1995). This is considerably more water and green space than possessed by most other cities, and gives Stockholm its unique character. The city is situated on a number of islands between the fresh water lake Ma¨laren and the brackish Baltic Sea. Stockholm also has a special feature with a number of green wedges pointing towards the city centre. This allows the ecosystems close to the city centre to be linked with larger ecosystems outside of the city. The City of Stockholm has about 700 000 inhabitants. Greater Stockholm has 1.5 million inhabitants.

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generated services relevant for Stockholm. From the 17 groups of services listed by Costanza et al. (1997), six are considered to have a major importance in urban areas: air filtering (gas regulation), micro-climate regulation, noise reduction (disturbance regulation), rainwater drainage (water regulation), sewage treatment (waste treatment), and recreational/cultural values. Other services, such as food production and erosion control, could also have been included, but are not considered significant for Stockholm. For each of the addressed services the following aspects are discussed: “ Which kind of problem does the service contribute to the solution of? “ What ecosystems are involved in the generation of the service, and how? “ Quantification and valuation of the service with examples from the literature. “ Examples from Stockholm.

3. Locally generated ecosystem services

3.1. Air filtering Ecosystem services are defined as ‘‘the benefits human populations derive, directly or indirectly, from ecosystem functions’’ by Costanza et al. (1997) and they also identify 17 major categories of ecosystem services. A number of these ecological services are not consumed by humans directly, but are needed to sustain the ecosystems themselves. Such indirect services include pollination of plants and nutrient cycling, but the classification is not obvious. Another aspect of ecosystem services is that they have different spatial cover. Services can be available on the local or global scale according to the scope of the problem they are connected to and the possibility of transferring the service from where it is produced to the city where humans benefit from it. Such a transfer can take place both by man-made transport and by natural means (e.g. atmospheric transport). Easily transferred services with a global scope, like CO2 sequestering, do not necessarily have to be produced close to the source of the problem. Services which are impossible to transfer must, however, be generated close to where they are consumed (e.g. noise reduction). Since this paper focuses on issues relevant for urban areas, the attention is on direct and locally

Air pollution caused by transportation and heating of buildings, among other things, is a major environmental and public health problem in cities. It is clear that vegetation reduces air pollution, but to what level seems to depend on the local situation (Svensson and Eliasson, 1997). The reduction is primarily caused by vegetation filtering pollution and particulates from the air. Filtering capacity increases with more leaf area, and is thus higher for trees than bushes or grassland (Givoni, 1991). Due to the larger total surface area of needles, coniferous trees have a larger filtering capacity than trees with deciduous leaves (Stolt, 1982). This capacity is also greater because the needles are not shed during the winter, when the air quality is usually worst. However, coniferous trees are sensitive to air pollution and deciduous trees are better at absorbing gases (Stolt, 1982). A mix of species therefore seems to be the best alternative. In general, vegetation is much better than water or open spaces for filtering the air. The location and structure of vegetation is important for the ability to filter the air. Bernatzky (1983) reports that up to 85% of air pollution in a

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park can be filtered out, and in a street with trees, up to 70%. Thick vegetation may simply cause turbulence in the air while a thinner cover may let the air through and filter it (Bernatzky, 1983). According to some estimates (Tolly, 1988; Bramryd and Fransman, 1993), 1 ha of mixed forest can remove 15 t of particulates per year from the air while a pure spruce forest may filter two or three times as much. The trees of the Chicago region have been estimated to remove some 5500 t of air pollutants, providing more than US$9 million of air quality during 1 year (McPherson et al., 1997). In Stockholm the percentage of vegetated area, as well as of water area, is clearly above the European average (Eurostat, 1995). In fact, approximately 10% (22 km2) of the land area in the City of Stockholm is forested. Such a large amount of forest has a significant air filtering capacity which leads to an improvement of air quality. The total filtering service of Stockholm vegetation has not been estimated.

tioning substantially in urban areas by shading houses in summer and reducing wind speed in winter. In Chicago it has been shown that an increase in tree cover by 10%, or planting about three trees per building lot, could reduce the total energy for heating and cooling by US$50–90 per dwelling unit per year. The present value of long-term benefits by the trees was found to be more than twice the present value of costs (McPherson et al., 1997). The micro-climate in Stockholm is regulated to a great extent by the large bodies of water in the city, as the city is situated on a number of islands. Mean annual temperatures are reported to be 0.6°C higher in downtown Stockholm as compared to areas outside the central city (Alexandersson et al., 1991). Stockholm also benefits from the vegetation, for example by reduced heating costs.

3.3. Noise reduction 3.2. Micro-climate regulation, at street and city le6el Local climate and even weather are affected by the city. In studies of US cities, some of these differences have been quantified, and expressed as changes compared with surrounding country-side: air temperature is 0.7°C higher measured as the annual mean, solar radiation is reduced by up to 20%, and wind speed is lowered by 10 – 30% (Haughton and Hunter, 1994). The phenomenon, sometimes called the urban heat island effect, is caused by the large area of heat absorbing surfaces, in combination with high amounts of energy use in cities. All natural ecosystems in urban areas will help to reduce these differences. Water areas in the city will help even out temperature deviations both during summer and winter. Vegetation is also important. A single large tree can transpire 450 l of water per day. This consumes 1000 MJ of heat energy to drive the evaporation process. In this way city trees can lower summer temperatures of the city markedly (Hough, 1989). Vegetation can also decrease energy use for heating and air condi-

Noise from traffic and other sources creates health problems for people in urban areas. The overall costs of noise have been estimated to be in the range of 0.2 –2% of GDP in the EU (Kommunfo¨rbundet, 1998). In Sweden, maximum noise levels of 55 dB(A) outside and 30 dB(A) inside buildings have been established as the long-term goal (Naturva˚rdsverket, 1996). The distance to the source of the noise is one key factor, and a doubling of the distance decreases the equivalent level by 3 dB(A). Another key factor is the character of the ground. A soft lawn, rather than a concrete pavement, decreases the level by another 3 dB(A) (SOU, 1993). Vegetation also contributes to the decrease, but at what level is uncertain. One source states that a dense shrubbery, at least 5 m wide can reduce noise levels by 2 dB(A) and that a 50-m wide plantation can lower noise levels by 3–6 dB(A) (Naturva˚rdsverket, 1996). Another source claims that 100 m of dense vegetation is only reported to decrease noise by 1–2 dB(A) (Kommunfo¨rbundet, 1998). Sounds propagate long distances on water (Naturva˚rdsverket, 1996).

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Society is prepared to pay large sums for lowered noise levels. Technical solutions to decrease noise include, for example, 3 – 5-m high walls at a cost of at least 5000 SEK (8 SEK : US$1) per m (Kommunfo¨rbundet, 1998). A wall like this decreases the noise by 10 – 15 dB(A) immediately behind it. However, the urban visual landscape would be destroyed if such walls were built everywhere. Another example of a technical solution is insulated windows in houses, but they are only effective for indoors. In Stockholm, about 20% of the population is exposed to noise levels of over 55 dB(A) outside their homes, the maximum recommended level by the Swedish Environmental Protection Agency. Some 630 km of streets have average roadside noise levels of 60 dB(A) or more (Miljo¨fo¨rvaltningen, 1995). Increasing the areas with soft ground and vegetation may decrease these noise levels. Vegetation may also contribute by shielding the visual intrusion of traffic and thus making it less disturbing: Evergreen trees are preferred in this case.

3.4. Rainwater drainage The built-up infrastructure, with concrete and tarmac covering the ground, results in alterations of water flow compared to an equivalent rural catchment. A higher proportion of rainfall becomes surface-water run-off which results in increased peak flood discharges and degraded water quality through the pick-up of e.g. urban street pollutants (Haughton and Hunter, 1994). The impervious surfaces and high extraction of water cause the groundwater level of many cities to decrease. Vegetated areas contribute to solving this problem in several ways. The soft ground of vegetated areas allows water to seep through and the vegetation takes up water and releases it into the air through evapotranspiration. Even if the built city surface primarily seals the ground from rainwater, it has been suggested that urbanization also creates some new, unintended pathways for recharge. These include leaking water mains, sewers, septic tanks, and soakways (Lerner, 1990).

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In vegetated areas only 5–15% of the rainwater runs off the ground, with the rest evaporating or infiltrating the ground. In vegetation-free cities about 60% of the rain water is instead led off through storm water drains (Bernatzky, 1983). This will of course affect both the local climate and the groundwater levels. Valuation of this service depends on the local situation. Cities with a high risk of flooding will benefit more from green areas that take up water than do other cities. The drinking water in Stockholm is supplied by lake water. Therefore, the ground water levels in the city are not heavily affected. Stockholm could however benefit from improved rainwater drainage through soft ground since the building and maintenance of the storm water drainage system involve large costs. Using the ecosystem service could lower the cost.

3.5. Sewage treatment Stockholm sewage treatment plants annually treat more than 150 million m3 of sewage (Stockholm Vatten, 1998). Taking care of sewage costs cities large amounts of money, and the nutrients that are still released contribute to eutrophication of the surrounding water ecosystems. In many cities, large scale experiments are taking place where natural systems, mainly wetlands, are being used to treat sewage water. The wetland plants and animals can assimilate large amounts of the nutrients and slow down the flow of the sewage water, allowing particles to settle out on the bottom. Up to 96% of the nitrogen and 97% of the phosphorous can be retained in wetlands, and so far wetland restorations have largely been successful, increasing biodiversity and substantially lowering costs of sewage treatment (Ewel, 1997). The cost of nitrogen reduction through wetland restoration has been calculated to 20–60 SEK while the cost in a sewage treatment plant is 33–350 SEK (Gren, 1995). Other benefits of wetlands, e.g. biomass production and biodiversity, have not been included in these figures. Stockholm has very few natural wetlands available for sewage treatment, but it is possible to

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construct more wetlands for cleaning sewage water. If all converted wetlands of the Stockholm catchment were restored, the cost of halving the nitrogen load to the archipelago could be lowered by 20% (Gren, 1995).

3.6. Recreational and cultural 6alues A city is a stressful environment for its citizens. The overall speed and number of impressions cause hectic lifestyles with little room for rest and contemplation. The recreational aspects of all urban ecosystems, with possibilities to play and rest, are perhaps the highest valued ecosystem service in cities. All ecosystems also provide aesthetic and cultural values to the city and lend structure to the landscape. Botkin and Beveridge (1997) argue that ‘‘Vegetation is essential to achieving the quality of life that creates a great city and that makes it possible for people to live a reasonable life within an urban environment’’. According to the Swedish economist Nils Lundgren, a good urban environment is an important argument for regions when trying to attract a highly qualified workforce (N. Lundgren, Nordbanken, personal communication). The appearance of fauna, e.g. birds and fish, should also be accounted for in recreational values. In Stockholm, a central stream of water provides excellent opportunities for fish to spawn and the area is one of the best places to fish in the entire country. Approximately 30 different species are found here (Stadbyggnadskontoret, 1995). Green spaces are also psychologically very important. One example is a study on the response of persons put under stress in different environments (Ulrich et al., 1991). This study showed that when subjects of the experiment were exposed to natural environments the level of stress decreased rapidly, whereas during exposure to the urban environment the stress levels remained high or even increased. Another study on recovery of patients in a hospital showed that patients with rooms facing a park had 10% faster recovery and needed 50% less strong pain-relieving medication compared to patients in rooms facing a building wall (Ulrich, 1984). These studies imply that green

spaces can increase the physical and psychological well-being of urban citizens. The scientific values of ecosystems are also included in this group, e.g. providing information services. The urban ecosystems can function as indicators of the state of the urban environment. Lichens, for example, cannot grow in areas with polluted air, and can thus be used to indicate the air quality (Miller, 1994). The citizens of Stockholm highly value their green spaces: more than 90% visit parks at least once during the year, 45% do so every week, and 17% more than three times a week (Stadbyggnadskontoret, 1994). In a stated preference study, performed in Stockholm and a few other Swedish cities, people were willing to pay 360–530 SEK/ month to live near a park, they were prepared to pay 370–540 SEK/month to live close to a larger urban forest and 330–570 SEK/month to live close to water areas (Transek, 1993).

4. Synthesis In the previous section, the ecosystem services were listed individually. It is however obvious that each ecosystem generates a number of different services simultaneously. This is shown in a matrix (Table 1) where we can see that all ecosystems contribute to climate regulation as well as providing recreational and cultural values. Wetland also seems to be a valuable ecosystem type since it contributes to all services. This corresponds to the study by Costanza et al. (1997) where wetlands were ranked as the most valuable terrestrial ecosystem per ha. If the aim is to assess the total value of ecosystems in urban areas, it is important to add the value of all cells in a matrix of this kind. The individual values might be small, but taken together the total value of urban ecosystems is potentially significant. It should also be remembered that the services discussed in this paper are only a subset of the existing services. The purpose of this paper is to analyze the benefits received from ecosystems, but ecosystems can also cause problems. The main reason for building houses, as well as cities, has been to

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Table 1 Urban ecosystems generating local and direct services, relevant for Stockholm.

Air filtering Micro climate regulation Noise reduction Rainwater drainage Sewage treatment Recreation/cultural values

Street tree

Lawns/parks

Urban forest

Cultivated land

Wetland

Stream

Lakes/sea

X X

X X

X X

X X

X X

X

X

X

X X

X X

X X

X

X

X

X

X X X X

X

X

protect humans from nature. The ecosystems kept in cities contribute to urban well-being but may also create negative aspects. Some common city tree species, for example pine (Pinus spp.), oak (Quercus spp.), and willow (Salix spp.), emit volatile organic compounds that may contribute to urban smog and ozone problems (Slanina, 1997). Animals, such as birds at municipal solid waste dumps or frogs in wetlands, could cause disturbing noise and the restoration of wetlands could cause problems such as increased mosquito hatching and bad odors. The parks could be dangerous places during the dark hours. In a complete cost-benefit analysis of land use and urban ecosystems, such negative aspects should also be reviewed.

5. Land use One important issue in the debate on sustainable cities is whether expansion should be directed at increasing urban density or rather allowing urban sprawl. Sprawled cities can produce more urban ecosystem services while occupying a larger amount of land. Even if a number of problems are created by the urbanization process, e.g. disrupted nutrient cycles and concentration of pollutants, urbanization also creates opportunities. If people live in dense concentrations, environmentally benign solutions like public transport and district heating become feasible (Rees and Wackernagel, 1996). European cities are often dense and to a large extent dependent on ecosystem services from the outside. Some Chinese cities on

the other hand are reported to recycle organic waste efficiently and produce much of their own food (Yufang et al., 1994). However, it is not evident that more self-sufficient urban areas are simultaneously more sustainable. Urban ecosystems are threatened by the process of increasing the density of buildings. Trees are sometimes lost at a faster rate than they are replanted. The American Forestry Association found in a survey quoted in Moll (1989) that New York City had a net loss of approximately 175 000 street trees, or 25% of its total tree stand, during 1977–1987. In Stockholm about 8% of the green space was lost during the 1970s, 7% during the 1980s and, the process still continues in the 1990s (La¨nsstyrelsen, 1996). Urban ecosystems are also often of poorer quality than their rural equivalents. By studying an urban-to-rural gradient in New York City, a scientific team discovered that forests at the urban end of the gradient exhibited reduced fungal and microarthropod populations and poorer leaf litter quality than the more rural forests (McDonnell et al., 1997). For the preservation of fauna, the size and nature of the urban green areas are also important. An area with a variety of biotopes will have a large number of ecological niches that can be occupied by many different species, and will thus increase biodiversity. To have a high diversity of plants and species in the city requires that the connections between the ecosystems surrounding the city and the green spaces in the city are not disrupted. The small city parks and urban forests are often too small to sustain a varied flora and

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fauna in themselves. Through the migration of organisms from larger core areas outside the city, the diversity in urban ecosystems can still be maintained. For example, Italian cities have been shown to contain almost 50% of all species of the total Italian avifauna (Dinetti et al., 1996) and over 1000 different vascular plant species have been identified in central Stockholm (La¨nsstyrelsen, 1996). However, the roads and railroads and large built-up areas around cities often cause major barrier effects to the migration of many species, and can thus lower the stabilizing effect of outer core areas (Bolund, 1996). Since land is so valuable in urban areas, a combination of different land uses on the same piece of land is probably needed in order to safeguard and improve the generation of ecosystem services. Different strategies can be used to increase vegetation, e.g. trees in parking spaces or narrow lawns as lane-separators. Some creative thinking is needed.

6. Concluding discussion We have tried to identify, and whenever possible also quantify and value, the ecosystem services generated in urban areas. For most general ecosystem services, the share generated by ecosystems within the urban area is expected to be limited compared to the total service. However, even if the generation of the services can often be made at a distance from the city, there are reasons why part of the services should be produced locally. It can be advantageous to generate ecosystem services locally for pure efficiency reasons, but also on ethical and educational grounds. It is also clear that urban ecosystem services contribute to the quality of urban life even if urban citizens are still dependent on global ecosystem services for their survival. The quality of life for urban citizens is improved by locally generated services, e.g. air quality and noise levels that cannot be improved with the help of distant ecosystems. It should however be remembered that it is only the effects of these problems that are decreased, not the cause of the problem that is solved. It is necessary to work to both ends.

Hopefully, an increased awareness of the ecosystem services could contribute to a more resource-efficient city structure and design. The urban ecosystems could then be fully appreciated for their contribution to urban life and valued accordingly when the land is claimed for exploitation. An understanding of the importance of ecosystem services could also mean that unexploited urban areas can be maintained or even expanded. As cities are expected to grow at a rapid rate in the coming decades, it is important that the ecosystem services in urban areas and the ecosystems that provide them are understood and valued by city planners and political decisionmakers.

Acknowledgements This paper has been written within the HUSUS (Households and Urban Structures in Sustainable Cities) project which is funded by BFR (Swedish Council for Building Research). Two anonymous reviewers provided useful comments on an earlier draft.

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The Value of the World's Ecosystem Services and Natural Capital by

Robert Costanza1, Ralph d'Arge2, Rudolf de Groot3, Stephen Farber4, Monica Grasso5, Bruce Hannon6, Karin Limburg7, Shahid Naeem8, Robert V. O'Neill9, Jose Paruelo10, Robert G. Raskin11, Paul Sutton12, & Marjan van den Belt13

Published in Nature, 1997, Vol 387 pp. 253-260 1. Center for Environmental and Estuarine Studies, Zoology Dept., and Institute for Ecological Economics, University of Maryland, Box 38, Solomons, MD 20688, USA 2. Economics Department (emeritus), University of Wyoming, Laramie, WY, 82070, USA 3. Center for Environment and Climate Studies, Wageningen Agricultural University, PO Box 9101, 6700 HB Wageningen, The Netherlands 4. Graduate School of Public and International Affairs, University of Pittsburgh, Pittsburgh, PA 15260, USA 5. University of Maryland Institute for Ecological Economics, Box 38, Solomons, MD 20688, USA 6. Geography Department and NCSA, University of Illinois, Urbana, IL 61801, USA 7. Institute of Ecosystem Studies, Millbrook, NY, USA (current address: Department of Systems Ecology, University of Stockholm, S-106 91 Stockholm, Sweden) 8. Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN 55108, USA 9. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA 10. Department of Ecology, Faculty of Agronomy, University of Buenos Aires, Av. San Martin 4453, 1417 Buenos Aires, Argentina 11. Jet Propulsion Laboratory, Pasadena, CA 91109, USA 12. National Center for Geographic Information and Analysis, Department of Geography, University of California at Santa Barbara, Santa Barbara CA 93106, USA 13. Ecological Economics Research and Applications, Inc., PO Box 1589, Solomons, MD 20688, USA

We estimated the current economic value of 17 ecosystem services for 16 biomes, based on a synthesis of published studies and a few original calculations. For the entire biosphere, the value (most of which is outside the market) is estimated to be in the range of $16 - 54 trillion/yr., with an average of $33 trillion/yr. Because of the nature of the uncertainties, this must be considered a minimum estimate. Global GNP is around $18 trillion/yr.

The services of ecological systems and the natural capital stocks that produce them are critical to the functioning of the earth's life support system.

They contribute significantly to

human welfare, both directly and indirectly, and therefore represent a significant portion of the total economic value of the planet. Because these services are not fully captured in markets or adequately quantified in terms comparable with economic services and manufactured capital, they are often given too little weight in policy decisions.

This neglect may ultimately

compromise the sustainability of humans in the biosphere. The economies of the earth would grind to a halt without the services of ecological life support systems, so in one sense their total value to the economy is infinite. However, it is instructive to estimate the "incremental" or "marginal" value of ecosystem services - the estimated rate of change of value with changes in ecosystem services from their current levels. There have been many studies in the last few decades aimed at estimating the value of a wide variety of ecosystem services. We synthesized this large (but scattered) literature and present it in a form useful for ecologists, economists, policy makers, and the general public. From this synthesis, we estimated values for ecosystem services per unit area by biome, and then multiplied by the total area of each biome and summed over all services and biomes. While acknowledging the many conceptual and empirical problems inherent in producing such an estimate, we think this exercise is essential in order to (1) make the range of potential values of the services of ecosystems more apparent; (2) establish at least a first approximation of the relative magnitude of global ecosystem services; (3) set up a framework for their further 1

analysis; (4) point out those areas most in need of additional research; and (5) stimulate additional research and debate. Most of the problems and uncertainties we encountered indicate that our estimate represents a minimum value, which would probably increase: (1) with additional effort in studying and valuing a broader range of ecosystem services; (2) with the incorporation of more realistic representations of ecosystem dynamics and interdependence; and (3) as ecosystem services become more stressed and "scarce" in the future.

Ecosystem Functions and Ecosystem Services Ecosystem functions refer variously to the habitat, biological, or systems properties or processes of ecosystems. Ecosystem goods (e.g. food) and services (e.g. waste assimilation) represent the benefits human populations derive, directly or indirectly, from ecosystem functions. For simplicity, we will refer to ecosystem goods and services together as ecosystem services. A large number of functions and services can be identified.1-4 Daily5 provides a detailed recent compendium on describing, measuring, and valuing ecosystem services. For the purposes of this analysis we grouped ecosystem services into 17 major categories. These groups are listed in Table 1. We included only renewable ecosystem services, excluding non-renewable fuels and minerals and the atmosphere. Note that ecosystem services and functions do not necessarily show a one-to-one correspondence. In some cases a single ecosystem service is the product of two or more ecosystem functions whereas in other cases a single ecosystem function contributes to two or more ecosystem services.

It is also important to emphasize the interdependent nature

of many ecosystem functions. For example, some of the net primary production in an ecosystem ends up as food, the consumption of which generates respiratory products necessary for primary production. Even though these functions and services are interdependent, in many cases they can be added because they represent "joint products" of the ecosystem which support human welfare. To the extent possible, we have attempted to distinguish joint and addable products from products which would represent "double counting" (because they represent different aspects of

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the same service) if they were added. It is also important to recognize that a minimum level of ecosystem "infrastructure" is necessary in order to allow production of the range of services shown in Table 1. Several authors have stressed the importance of this "infrastructure" of the ecosystem itself as a contributor to its total value.6,7 This component of the value is not included in the current analysis.

Natural Capital and Ecosystem Services In general, capital is considered a stock of materials or information which exists at a point in time. Each form of capital stock generates, either autonomously or in conjunction with services from other capital stocks, a flow of services which may be used to transform materials, or the spatial configuration of materials, to enhance the welfare of humans. The human use of this flow of services may or may not leave the original capital stock intact. Capital stock takes different identifiable forms, most notably in physical forms including natural capital, such as trees, minerals, ecosystems, the atmosphere, etc.; manufactured capital, such as machines and buildings; and the human capital of physical bodies.

In addition, capital stocks can take

intangible forms, especially as information such as that stored in computers and in individual human brains, as well as that stored in species and ecosystems. Ecosystem services consist of flows of materials, energy, and information from natural capital stocks which combine with manufactured and human capital services to produce human welfare. While it is possible to imagine generating human welfare without natural capital and ecosystem services in artificial "space colonies," this possibility is too remote and unlikely to be of much current interest. In fact, one additional way to think about the value of ecosystem services is to determine what it would cost to replicate them in a technologically produced, artificial biosphere. Experience with manned space missions and with Biosphere II in Arizona indicates that this is an exceedingly complex and expensive proposition. Biosphere I (the earth) is a very efficient, least-cost provider of human life support services.

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Thus we can consider the general class of natural capital as essential to human welfare. Zero natural capital implies zero human welfare because it is not feasible to substitute, in total, purely "non-natural" capital for natural capital. Manufactured and human capital require natural capital for their construction.7 Therefore, it is not very meaningful to ask the total value of natural capital to human welfare, nor to ask the value of massive, particular forms of natural capital. It is trivial to ask what is the value of the atmosphere to humankind, or what is the value of rocks and soils infrastructures as support systems. Their value is infinite in total. However, it is meaningful to ask how changes in the quantity or quality of various types of natural capital and ecosystem services may impact human welfare. Such changes include both small changes at large scales and large changes at small scales. For example, changing the gaseous composition of the global atmosphere by a small amount may have large scale climate change effects that will affect the viability and welfare of global human populations. Large changes at small scales include, for example, dramatically changing local forest composition. These changes may dramatically alter terrestrial and aquatic ecosystems, impacting the benefits and costs of local human activities. In general, changes in particular forms of natural capital and ecosystem services will alter the costs or benefits of maintaining human welfare.

Valuation of Ecosystem Services The issue of valuation is inseparable from the choices and decisions we have to make about ecological systems.6,8 Some argue that valuation of ecosystems is either impossible or unwise, that we cannot place a value on such "intangibles" as human life, environmental aesthetics, or long-term ecological benefits. But, in fact, we do so every day. When we set construction standards for highways, bridges and the like, we value human life (acknowledged or not) because spending more money on construction would save lives. Another frequent argument is that we should protect ecosystems for purely moral or aesthetic reasons, and we do not need valuations of ecosystems for this purpose. But there are equally compelling moral arguments that

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may be in direct conflict with the moral argument to protect ecosystems; for example, the moral argument that no one should go hungry. Moral arguments translate the valuation and decision problem into a different set of dimensions and a different language of discourse6; one that, in our view, makes the valuation and choice problem more difficult and less explicit. But moral and economic arguments are certainly not mutually exclusive. Both discussions can and should go on in parallel. So, while ecosystem valuation is certainly difficult and fraught with uncertainties, one choice we do not have is whether or not to do it. Rather, the decisions we make as a society about ecosystems imply valuations (although not necessarily exchange values expressed in money terms). We can choose to make these valuations explicit or not; we can undertake them using the best available ecological science and understanding or not; we can do them with an explicit acknowledgment of the huge uncertainties involved or not; but as long as we are forced to make choices, we are doing valuation. The exercise of valuing the services of natural capital "at the margin" consists of determining the differences that relatively small changes in these services make to human welfare. Changes in quality or quantity of ecosystem services have value insofar as they either change the benefits associated with human activities or change the costs of those activities. These changes in benefits and costs either impact human welfare through established markets or through non-market activities. For example, coral reefs provide habitat for fish. One aspect of their value is to increase and concentrate fish stocks. One effect of changes in coral reef quality or quantity would be discernible in commercial fisheries markets, or in recreational fisheries. Other aspects of coral reefs’ value, such as recreational diving and biodiversity conservation, do not show up completely in markets, however. Forests provide timber materials through wellestablished markets, but the associated habitat values of forests are also felt through unmarketed recreational activities. The chains of effects from ecosystem services to human welfare can range from extremely simple to exceedingly complex. Forests provide timber, but also hold soils

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and moisture, and create microclimates, all of which contribute to human welfare in complex, and generally non-marketed ways.

Valuation Methods Various methods have been used to estimate both the market and non-market components of the value of ecosystem services.9-16 In this analysis, we synthesized previous studies based on a wide variety of methods, noting the limitations and assumptions underlying each. Many of the valuation techniques used in the studies covered in our synthesis are based, either directly or indirectly, on attempts to estimate the willingness-to-pay of individuals for ecosystem services. For example, if ecological services provided a $50 increment to the timber productivity of a forest, then the beneficiaries of this service should be willing to pay up to $50 for it. In addition to timber production, if the forest offered non-marketed aesthetic, existence, and conservation values of $70, those receiving this non-market benefit should be willing to pay up to $70 for it. The total value of ecological services would be $120, while the contribution to the money economy of ecological services would be $50, the amount that actually passes through markets. In this study we have tried to estimate the total value of ecological services, regardless of whether they are currently marketed. Figure 1 shows some of these concepts diagramatically. Figure 1a shows conventional supply (marginal cost) and demand (marginal benefit) curves for a typical marketed good or service. The value that would show up in Gross National Product (GNP) is the market price p times the quantity q, or the area pbqc. There are three other relevant areas represented on the diagram, however.

The cost of production is the area under the supply curve, cbq.

The

"producer surplus" or "net rent" for a resource is the area between the market price and the supply curve, pbc. The "consumer surplus" or the amount of welfare the consumer receives over and above the price paid in the market is the area between the demand curve and the market price, abp. The total economic value of the resource is the sum of the producer and consumer

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surplus (excluding the cost of production), or the area abc on the diagram. Note that total economic value can be greater or less than the price times quantity estimates used in GNP. Figure 1a refers to a human-made, substitutable good. Many ecosystem services are only substitutable up to a point, and their demand curves probably look more like figure 1b. Here the demand approaches infinity as the quantity available approaches zero (or some minimum necessary level of services), and the consumer surplus (as well as the total economic value) approaches infinity. Demand curves for ecosystem services are very difficult, if not impossible, to estimate in practice. In addition, to the extent that ecosystem services cannot be increased or decreased by actions of the economic system, their supply curves are more nearly vertical, as shown in figure 1b. In this study we estimated the value per unit area of each ecosystem service for each ecosystem type. To estimate this "unit value" we used (in order of preference) either (1) the sum of consumer and producer surplus; or (2) the net rent (or producer surplus); or (3) price times quantity as a proxy for the economic value of the service, assuming that the demand curve for ecosystem services looks more like figure 1b than figure 1a, and that therefore the area pbqc is a conservative underestimate of the area abc. We then multiplied the unit values times the surface area of each ecosystem to arrive at global totals.

Ecosystem Values, Markets, and GNP As we have noted, the value of many types of natural capital and ecosystem services may not be easily traceable through well-functioning markets, or may not show up in markets at all. For example, the aesthetic enhancement of a forest may alter recreational expenditures at that site, but this change in expenditure bears no necessary relation to the value of the enhancement. Recreationists may value the improvement at $100, but transfer only $20 in spending from other recreational areas to the improved site.

Enhanced wetlands quality may improve waste

treatment, saving on potential treatment costs. For example, tertiary treatment by wetlands may

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save $100 in alternative treatment. Existing treatment may cost only $30. The treatment cost savings does not show up in any market. There is very little relation between the value of services and observable current spending behavior in many cases. There is also no necessary relation between the valuation of natural capital service flows, even on the margin, and aggregate spending, or GNP, in the economy. This is true even if all capital service flows impacted well-functioning markets. A large part of the contributions to human welfare by ecosystem services are of a purely public goods nature. They accrue directly to humans without passing through the money economy at all. In many cases people are not even aware of them. Examples include clean air and water, soil formation, climate regulation, waste treatment, aesthetic values, and good health, as mentioned above.

Global Land Use and Land Cover In order to estimate the total value of ecosystem services, we needed estimates of the total global extent of the ecosystems themselves. We devised an aggregated classification scheme with 16 primary categories as shown in Table 3 to represent current global land use. The major division is between Marine and Terrestrial systems. Marine was further subdivided into Open Ocean and Coastal, which itself includes Estuaries, Seagrass/Algae Beds, Coral Reefs, and Shelf systems.

Terrestrial systems were broken down into two types of Forest (Tropical and

Temperate/Boreal), Grasslands/Rangelands, Wetlands, Lakes/Rivers, Desert, Tundra, Ice/Rock, Cropland, and Urban. Primary data were from Matthews17 as summarized in de Groot4 with additional information from a number of sources.18-22 We also used data from Bailey,23 as a cross-check on the terrestrial estimates and Houde & Rutherford24 and Pauly & Christensen,25 as a check on the marine estimates. The 32 landcover types of Matthews were re-categorized for Table 3 and figure 2. The major assumptions were: (1) chaparral and steppe were considered rangeland and combined with grasslands; and (2) a variety of tropical forest and woodland types were combined into "tropical forests."

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Synthesis We conducted a thorough literature review and synthesized the information, along with a few original calculations, during a one-week intensive workshop at the new National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California at Santa Barbara. Table 2 (with accompanying notes and references) lists the primary results for each ecosystem service and biome. It is voluminous and could not be included in the printed version, but is available directly from the first author, and is also posted at Nature's web site http://www.america.nature.com.

Table 2 includes all the estimates we could identify from the

literature (from over 100 studies), their valuation methods, location, and stated value. We converted each estimate into 1994 US$ ha-1 yr-1 using the US consumer price index and other conversion factors as needed. These are listed in the notes to Table 2. For some estimates we also converted the service estimate into US$ equivalents using the ratio of purchasing power GNP per capita for the country of origin to that of the US. This was intended to adjust for income effects. Where possible the estimates are stated as a range, based on the high and low values found in the literature, and an average value, with annotated comments as to methods and assumptions. We also included in Table 2 some estimates from the literature on "total ecosystem value," mainly using energy analysis techniques.10 We did not include these estimates in any of the totals or averages given below, but only for comparison with the totals from the other techniques. Interestingly, these different methods showed fairly close agreement in the final results. Each biome and each ecosystem service had its special considerations. Detailed notes explaining each biome and each entry in Table 2 are given in notes following the table. More detailed descriptions of some of the ecosystems, their services, and general valuation issues can be found in Daily.5 Below we briefly discuss some general considerations that apply across the board.

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Sources of Error, Limitations, and Caveats Our attempt to estimate the total current economic value of ecosystem services is limited for a number of reasons, including:

1. While we have attempted to be as comprehensive and inclusive as possible, our estimate leaves out many categories of services, which, for one reason or another, have not yet been adequately studied for many ecosystems. In addition, we could identify no valuation studies at all for some major biomes (desert, tundra, ice/rock, and cropland). As more and better information becomes available, we expect the total estimated value to increase. 2. Current prices, which form the basis (either directly or indirectly) of many of the valuation estimates, are distorted for a number of reasons, including the fact that they exclude the value of ecosystem services, household labor, the informal economy, and many other problems. In addition to this, there are differences between total value, consumer surplus, net rent (or producer surplus), and p*q, all of which are used to estimate unit values (see figure 1). 3. In many cases the values are based on the current willingness-to-pay of individuals for ecosystem services, even though these individuals may be ill-informed and their preferences may not adequately incorporate social fairness, ecological sustainability, and other important goals.16

In other words, if we actually lived in a world that was ecologically sustainable,

socially fair, and where everyone had perfect knowledge of their connection to ecosystem services, both market prices and surveys of willingness-to-pay would yield very different results than they currently do, and the value of ecosystem services would probably increase. 4. In calculating the current value, we generally assumed that the demand and supply curves look something like figure 1a. In reality, supply curves for many ecosystem services are more nearly inelastic vertical lines, and the demand curves probably look more like figure 1b,

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approaching infinity as quantity goes to zero. Thus the consumer and producer surplus and thereby the total value of ecosystem services would also approach infinity. 5. The valuation approach taken here assumes that there are no sharp thresholds, discontinuities, or irreversibilities in the ecosystem response functions. This is almost certainly not the case. Therefore this valuation yields an underestimate of the total value. 6. Extrapolation from point estimates to global totals introduces error. In general, we estimated unit area values for the ecosystem services (in $ ha-1 yr-1) and then multiplied by the total area of each biome. This can only be considered a crude first approximation and can introduce errors depending on the type of ecosystem service and its spatial heterogeneity. 7. To avoid double counting, a general equilibrium framework that could directly incorporate the interdependence between ecosystem functions and services would be preferred to the partial equilibrium framework employed in this study (see 12 below for more on this). 8. Values for individual ecosystem functions should be based on sustainable use levels, taking account of both the carrying capacity for individual functions (e.g. food-production or waste recycling) and the combined effect of simultaneous use of more functions. Ecosystems should be able to provide all the functions listed in Table 1 simultaneously and indefinitely. This is certainly not the case for some current ecosystem services due to overuse at existing prices. 9. We have not incorporated the "infrastructure" value of ecosystems, as noted above, leading to an underestimation of the total value. 10. Intercountry comparisons of valuation are affected by income differences. We attempted to address this in some cases using the relative purchasing power GNP per capita of the country relative to the US, but this is a very crude way to make the correction. 11. In general, we have used annual flow values and have avoided many of the difficult issues involved with discounting future flow values to arrive at a net present value of the capital stock. But a few estimates in the literature were stated as stock values, and it was necessary to assume a discount rate (we used 5%) in order to convert them into annual flows.

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12. Our estimate is based on a static "snapshot" of what is, in fact, a complex, dynamic system. We have assumed a static and "partial equilibrium" model in the sense that the value of each service is derived independently and added. This ignores the complex interdepencies between services.

The estimate could also change drastically as the system moved through critical

non-linearities or thresholds. While it is possible to build "general equilibrium" models in which the value of all ecosystem services are derived simultaneously with all other values, and to build dynamic models that can incorporate non-linearities and thresholds, these models have rarely been attempted at the scale we are discussing. They represent the next logical step in deriving better estimates of the value of ecosystem services.

We have tried to expose these various sources of uncertainty wherever possible in Table 2 and its supporting notes, and state the range of relevant values. In spite of the limitations noted above, we believe it is very useful to synthesize existing valuation estimates, if only to determine a crude, initial "ballpark" magnitude. In general, because of the nature of the limitations noted, we expect our current estimate to represent a minimum value for ecosystem services.

Total Global Value of Ecosystem Services Table 3 is a summary of the results of our synthesis. It lists each of the major biomes along with their current estimated global surface area, the average (on a per ha basis) of the estimated values of the 17 ecosystem services we have identified from Table 2, and the total value of ecosystem services by biome, by service type, and for the entire biosphere. We estimated that at the current margin, ecosystems provide at least $33 trillion dollars worth of services annually. The majority of the value of services we could identify is currently outside the market system, in services such as gas regulation ($1.3 trillion/yr), disturbance regulation ($1.8 trillion/yr), waste treatment ($2.3 trillion/yr), and nutrient cycling ($17 trillion/yr).

About 63% of the estimated value is contributed by marine systems ($20.9

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trillion/yr). Most of this comes from coastal systems ($10.6 trillion/yr). About 38% of the estimated value comes from terrestrial systems, mainly from forests ($4.7 trillion/yr) and wetlands ($4.9 trillion/yr). We estimated a range of values whenever possible for each entry in Table 2. Table 3 reports only the average values. Had we used the low end of the ranges in Table 2, the global total would have been around $19 trillion. If we eliminate nutrient cycling, which is the largest single service, estimated at $17 trillion, the total annual value would be around $16 trillion. Had we used the high end for all estimates, along with estimating the value of Desert, Tundra, and Ice/Rock as the average value of Rangelands, the estimate would be around $54 trillion. So the total range of annual values we estimated were from $16 - $54 trillion. This is not a huge range, but other sources of uncertainty listed above are much more critical. It is important to emphasize, however, that despite the many uncertainties included in this estimate, it is almost certainly an underestimate for several reasons, as listed above. There have been very few previous attempts to estimate the total global value of ecosystem services with which to compare these results. We identified two, based on completely different methods and assumptions, both from each other and from the methods employed in this study. They thus provide an interesting check. One was an early attempt at a static general equilibrium input-output model of the globe, including both ecological and economic processes and commodities.26,27 This model divided the globe into 9 commodities or product groups and 9 processes, two of which were "economic" (urban and agriculture) and 7 of which were "ecologic," including both terrestrial and marine systems. Data were from about 1970. Although this was a very aggregated breakdown and the data was of only moderate quality, the model produced a set of "shadow prices" and "shadow values" for all the flows between processes, as well as the net outputs from the system which could be used to derive an estimate of the total value of ecosystem services. The I-O format is far superior to the partial equilibrium format we employed in this study for differentiating gross from net flows and avoiding double counting. The results yielded a total value of the net output 13

of the 7 global ecosystem processes equal to the equivalent of 9.4 trillion 1972 US$. Converted to 1994 US$ this is about $34 trillion - surprisingly close to our current average estimate. This estimate broke down into $11.9 trillion (or 35%) from terrestrial ecosystem processes and $22.1 trillion (or 65%) from marine processes, also very close to our current estimate. World GNP in 1970 was about $14.3 trillion (in 1994 US$), indicating a ratio of total ecosystem services to GNP of about 2.4 to 1. The current estimate has a corresponding ratio of 1.8 to 1. A more recent study28 estimated a "maximum sustainable surplus" value of ecosystem services by considering ecosystem services as one input to an aggregate global production function along with labor and manufactured capital. Their estimates ranged from $3.4 to $17.6 trillion/year, depending on various assumptions. This approach assumed that the total value of ecosystem services is limited to that which impacts marketed value, either directly or indirectly, and thus cannot exceed the total world GNP of about $18 trillion. But, as we have pointed out, only a fraction of ecosystem services affect private goods traded in existing markets which would be included in measures like GNP. This is a subset of the services we estimated, so we would expect this estimate to undervalue total ecosystem services. The results of both of these studies indicate, however, that our current estimate is at least in approximately the same range. As we have noted, there are many limitations to both the current and these two previous studies. They are all only static snapshots of a biosphere that is a complex, dynamic system. The obvious next steps include building regional and global models of the linked ecological economic system aimed at a better understanding of both the complex dynamics of physical/biological processes and the value of these processes to human wellbeing.29,30 But we do not have to wait for the results of these models to draw the following conclusions.

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Conclusions What this study makes abundantly clear is that ecosystem services provide a significant portion of the total contribution to human welfare on this planet. We must begin to give the natural capital stock which produces these services adequate weight in the decision-making process, otherwise current and continued future human welfare may drastically suffer. We estimate in this study that the annual value of these services is $16 - 54 trillion, with an estimated average of $33 trillion. The real value is almost certainly much larger, even at the current margin. $33 trillion is 1.8 times the current global GNP. One way to look at this comparison is that if one were to try to replace the services of ecosystems at the current margin, one would need to increase global GNP by at least $33 trillion, partly to cover services already captured in existing GNP and partly to cover services that are not currently captured in GNP. This impossible task would lead to no increase in welfare since we would only be replacing existing services, and it ignores the fact that many ecosystem services are literally irreplaceable. If ecosystem services were actually paid for, in terms of their value contribution to the global economy, the global price system would be very different than it is today. The price of commodities utilizing ecosystem services directly or indirectly would be much greater. The structure of factor payments, including wages, interest rates, and profits would change dramatically. World GNP would be very different in both magnitude and composition if it adequately incorporated the value of ecosystem services. One practical use of the estimates we have developed is to help modify systems of national accounting to better reflect the value of ecosystem services and natural capital. Initial attempts to do this paint a very different picture of our current level of economic welfare than conventional GNP, some indicating a leveling of welfare since about 1970 while GNP has continued to increase.31-33 A second important use of these estimates is for project appraisal, where ecosystem services lost must be weighed against the benefits of a specific project.8 Because ecosystem services are largely outside the market and uncertain, they are too often ignored or undervalued, leading to the error of constructing projects whose social costs far outweigh their benefits. 15

As natural capital and ecosystem services become more stressed and more "scarce" in the future, we can only expect their value to increase. If significant, irreversible thresholds are passed for irreplaceable ecosystem services, their value may quickly jump to infinity. Given the huge uncertainties involved, we may never have a very precise estimate of the value of ecosystem services. Nevertheless, even the crude initial estimate we have been able to assemble is a useful starting point (we stress again that it is only a starting point). It demonstrates the need for much additional research and it also indicates the specific areas that are most in need of additional study.

It also highlights the relative importance of ecosystem services and the

potential impact on our welfare of continuing to squander them.

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13. Aylward, B.A. & Barbier, E.B. Valuing environmental functions in developing countries. Biodiversity and Conservation 1, 34 (1992) 14. Pearce, D. Economic values and the natural world. (Earthscan, London, 1993) 15. Goulder, L.H. & Kennedy, D. Valuing ecosystem services: philosophical bases and empirical methods. pp. 23-48 in: Nature's services: societal dependence on natural ecosystems. (Island Press, Washington, D.C. 1997) 16. Costanza, R. & Folke, C. Valuing ecosystem services with efficiency, fairness, and sustainability as goals. pp. 49-70 in: Nature's services: societal dependence on natural ecosystems. (Island Press, Washington, D.C., 1997) 17. Matthews, E. Global vegetation and land-use: new high-resolution data bases for climate studies. Journal of Climate and Applied Meteorology. 22, 474-487 (1983) 18. Deevey, E. S. Mineral cycles. Scientific American, September 1970, pp. 148-158 19. Ehrlich, R., Ehrlich, A. H., & Holdren, J. P. Ecoscience: population, resources, environment (W. H. Freeman and Company, San Francisco, 1977) 20. Ryther, J. H., Photosynthesis and fish production in the sea. Science, 166, 72-76 (1969) 21. United Nations Environmental Programme, First Assessment Report, Intergovernmental Panel on Climate Change (United Nations, NY, 1990) 22. Whittaker, R. H. & Likens, G. E. The biosphere and man. pp 305-328 in: Lieth, H. & Whittaker, R. H. (Eds) Primary production of the biosphere,. (Springer-Verlag, NY, 1975) 23. Bailey, R. G. Ecosystem geography. (Springer, New York 1996) 24. Houde, E. D. & Rutherford, E. S. Recent trends in estuarine fisheries: predictions of fish production and yield. Estuaries, 16, 161-176 (1993) 25. Pauly, D. & Christensen, V. Primary production required to sustain global fisheries. Nature, 374, 255-257 (1995)

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26. Costanza R. & Neil, C. The energy embodied in the products of the biosphere. pp. 745-755 in: Mitsch, W.J. , Bosserman, R. W. & Klopatek, J. M., (eds.) Energy and ecological modeling. (Elsevier, New York, 1981) 27. Costanza, R. & Hannon, B.M. Dealing with the mixed units problem in ecosystem network analysis. pp.90-115 in: Wulff, F., Field, J. G. & Mann, K. H., (Eds.), Network analysis of marine ecosystems: methods and applications (Springer-Verlag, Heidelberg, 1989) 28. Alexander, A., List, J., Margolis, M., & d'Arge, R. Alternative methods of valuing global ecosystem services. Ecological Economics (submitted) 29. Costanza, R., Wainger, L., Folke, C. & Mäler, K-G. Modeling complex ecological economic systems: toward an evolutionary, dynamic understanding of people and nature BioScience 43, 545-555 (1993) 30. Bockstael, N., Costanza, R., Strand, I., Boynton, W., Bell, K., & Wainger, L. Ecological economic modeling and valuation of ecosystems. Ecological Economics 14, 143-159 (1995) 31. Daly, H.E. & Cobb, J. For the common good: redirecting the economy towards community, the environment, and a sustainable future. (Beacon Press, Boston, 1989) 32. Cobb, C. & Cobb, J. The green national product: A proposed Index of Sustainable Economic Welfare (University Press of America, New York, 1994) 33. Max-Neef, M. Economic growth and quality of life: a threshold hypothesis. Ecological Economics 15, 115-118 (1995)

Acknowledgments. This project was sponsored by the National Center for Ecological Analysis and Synthesis (NCEAS), an NSF-funded Center at the University of California at Santa Barbara. The authors met during the week of June 17-21, 1996 to perform the major parts of the synthesis activities. The idea for the study emerged at a meeting of the Pew Scholars in New Hampshire

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in October of 1995. Steve Carpenter was instrumental in encouraging the project. Monica Grasso performed the initial identification and collection of literature sources. We thank S. Carpenter, G. Daily, H. Daly, A. M. Freeman, N. Myers, C. Perrings, D. Pimentel, S. Pimm, S. Postel, and one anonymous reviewer for helpful comments on earlier drafts.

Correspondence and requests for materials should be addressed to R. C. (e-mail: [email protected])

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Table 1. Ecosystem services and functions used in this study.

#

ECOSYSTEM SERVICE*

ECOSYSTEM FUNCTIONS

EXAMPLES

1

Gas regulation

Regulation of atmospheric chemical composition.

2

Climate regulation

3

Disturbance regulation

Regulation of global temperature, precipitation, and other biologically mediated climatic processes at global or local levels. Capacitance, damping, and integrity of ecosystem response to environmental fluctuations.

CO2/O2 balance, O3 for UVB protection, and SOx levels. Green-house gas regulation, DMS production affecting cloud formation.

4

Water regulation

Regulation of hydrological flows.

5

Water supply

Storage and retention of water.

6

Retention of soil within an ecosystem.

7

Erosion control and sediment retention Soil formation

8

Nutrient cycling

9

Waste treatment

10

Pollination

Storage, internal cycling, processing, and acquisition of nutrients. Recovery of mobile nutrients and removal or breakdown of excess or xenic nutrients and compounds. Movement of floral gametes.

11

Biological control

12

Refugia

13

Food production

That portion of gross primary production extractable as food.

14

Raw materials

15

Genetic resources

That portion of gross primary production extractable as raw materials. Sources of unique biological materials and products.

16

Recreation

17

Cultural

Soil formation processes.

Trophic-dynamic regulations of populations. Habitat for resident and transient populations.

Providing opportunities for recreational activities. Providing opportunities for noncommercial uses.

*We include ecosystem “goods” along with ecosystem services.

Storm protection, flood control, drought recovery, and other aspects of habitat response to environmental variability mainly controlled by vegetation structure. Provisioning of water for agricultural (e.g., irrigation) or industrial (e.g., milling) processes or transportation. Provisioning of water by watersheds, reservoirs, and aquifers. Prevention of loss of soil by wind, runoff, or other removal processes, storage of silt in lakes and wetlands. Weathering of rock and the accumulation of organic material. Nitrogen fixation, N, P, and other elemental or nutrient cycles. Waste treatment, pollution control, detoxification. Provisioning of pollinators for the reproduction of plant populations. Keystone predator control of prey species, reduction of herbivory by top predators. Nurseries, habitat for migratory species, regional habitats for locally harvested species, or over wintering grounds. Production of fish, game, crops, nuts, fruits by hunting, gathering, subsistence farming, or fishing. The production of lumber, fuel, or fodder. Medicine, products for materials science, genes for resistance to plant pathogens and crop pests, ornamental species (pets and horticultural varieties of plants). Eco-tourism, sport fishing, and other outdoor recreational activities. Aesthetic, artistic, educational, spiritual, and/or scientific values of ecosystems.

Figure 1. Supply and demand curves, showing the definitions of cost, net rent, and consumer surplus for normal goods (a) and some essential ecosystem services (b). See text for further explanation.

Figure 2 Global map of the value of ecosystem services. See Supplementary Information and Table 2 for details.

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2014

AKTUALISASI PENDIDIKAN ISLAM DALAM PENGELOLAAN LINGKUNGAN HIDUP MENUJU KESALEHAN EKOLOGIS Oleh: Jumarddin La Fua Jurusan Tarbiyah STAIN Sultan Qaimuddin Kendari Abstrak Isu lingkungan merupakan bagian dari krisis global yang sangat serius yang dialami oleh umat manusia sekarang ini. Krisis ini tidak hanya menyangkut masalah lingkungan saja tetapi juga menyangkut berbagai masalah yang semakin kompleks dan multidimensional yang menyentuh setiap aspek kehidupan. Salah satu pendekatan yang dianggap efektif dan mengatasi aktifitas kerusakan lingkungan adalah pendekatan agama yang diharapkan mampu untuk mengharmoniskan hubungan antara manusia dengan lingkungan. Dalam konteks inilah Islam sebagai agama yang memiliki ajaran spritul diharapkan mampu untuk mengingatkan sekaligus mengatur tata hubungan antara manusia dengan alam. Tulisan ini diharapkan dapat menjadi media transformasi dalam merespon aktivitas kerusakan lingkungan melalui aktulisasi pendidikan islam berbasis pelesatarian lingkungan melalui pesanpesan ajaran agama Islam yang bersumber dari Al Qur’an dan Hadis nabi Muhammad SAW yang diharapkan dapat memberi pengaruh jangka panjang kepada manusia sehingga dapat menyadarkan manusia akan pentingnya alam semesta dan menghasilkan kesalehan ekologis dalam berinteraksi dengan alam dan lingkungan. Kata Kunci : Pendidikan Islam, pengelolaan lingkungan, dan ekologi. A. Pendahuluan Kesadaran manusia yang lebih menitikberatkan posisinya sebagai Khalifah, akan menyebabkan manusia merasa paling berhak untuk menguasai dan mengeksploitasi alam dalam rangka memenuhi segala kebutuhannya. Namun manusia seringkali bertindak mengeksploitasi alam melebihi batas kebutuhannya. Tindakan manusia tersebut pada akhirnya

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menciptakan krisis-krisis global.1. Krisis ekologi saat ini terutama disebabkan oleh perubahan iklim yang berasal dari Revolusi Industri dari Abad ke-18, ketika bahan bakar fosil seperti batu bara dan minyak mulai digunakan sebagai sarana untuk menghasilkan energi. Dari waktu ke waktu planet ini telah mengalami tingkat percepatan pertumbuhan ekonomi dan kemajuan teknologi yang cepat sehingga memungkinkan pengembangan mesin yang digunakan untuk menghancurkan hutan seperti kegiatan industri pertambangan yang telah berperan dalam mempercepat terjadinya degradasi lingkungan. Eksploitasi yang dilakukan secara terus menerus pada akhirnya akan mengganggu keseimbangan alami ekosistem dan akhirnya mengancam ciptaan Allah SWT termasuk manusia. Hal ini seolah-olah membenarkan ramalan malaikat ketika manusia diangkat sebagai khalifah Allah SWT di bumi, yaitu ramalan tentang sifat destruktif manusia dan saling bermusuhan. Menurut Fachruddin M Mangunjaya 2 bahwa terdapat tiga tantangan utama yang dihadapi oleh umat manusia dalam mengatasi krisis lingkungan pada abad 21 yaitu (1) terjadinya peningkatan populasi, (2) degradasi dan hilangnya sumberdaya, dan (3) perubahan iklim. Isu lingkungan merupakan bagian dari krisis global yang sangat serius yang dialami oleh umat manusia sekarang ini. Krisis ini tidak hanya menyangkut masalah lingkungan saja tetapi juga menyangkut berbagai masalah yang semakin kompleks dan multidimensional yang menyentuh setiap aspek kehidupan, kesehatan dan mata pencaharian, kualitas lingkungan dan hubungan sosial, ekonomi, teknologi dan politik. Negaranegara dunia termaksud Indonesia telah menyadari efek dari krisis lingkungan ini akan mengakibatkan ketegangan antar bangsa (seperti kasus kebakaran hutan Kalimantan yang menganggu negara Maleysia, Brunai Darusalam dan Singapura) serta permasalahan perebutan sumberdaya, bahan mentah dan daerah teritori yang amat penting bagi kehidupan. Disamping problem tersebut fenomena perubahan iklim juga dipengaruhi oleh “pemansanan global” yang mengakibatkan meningkatnya suhu global dan diperkirakan akan menyebabkan terjadinya 1

Amat Zuhri, Tasawuf Ekologi (Tasawuf Sebagai Solusi dalam Menanggulangi Krisis Lingkungan). Jurusan Ushuluddin STAIN Pekalongan, Jl. Kusumabangsa No. 9 Pekalongan. 2 Fachruddin M Mangunjaya, 2013. Islam and Natural Resource Management. Durrell Institute of Conservation and Ecology (DICE), University of Kent, Canterbury, Kent CT2 7NZ, United Kingdom.

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perubahan-perubahan lain seperti naiknya permukaan air laut, meningkatnya intensitas fenomena cuaca yang ekstrem, serta perubahan jumlah dan pola presipitasi. Disamping itu, akibat lain dari pemanasan global adalah terpengaruhnya hasil pertanian, hilangnya gletser, dan punahnya berbagai jenis hewan.3 Dari berbagai fenomena degradasi lingkungan yang terjadi baik skala nasional mapun global tidak murni terjadi karena faktor alam semata, tetapi juga akibat pendekatan tata hubungan yang tidak harmonis atau tidak sehat (keserakahan dan tindakan eksplotatif) antara manusia dan alam, situasi inilah yang lebih dikenal dengan istilah krisis lingkungan hidup yang sekarang menjadi isu global. Oleh karena itu, perlu kiranya dikembangkan sikap menghargai, menghormati dan menyayangi lingkungan sehingga keberlanjutannya tetap terjaga dan berkesinambungan, konsep ini dikenal dengan istilah kearifan ekologi. Menurut Hamzah Tauleka4 bahwa kearifan ekologi merupakan bentuk hubungan dimana manusia harus belajar melihat alam sebagai kawan kita. Kawan senasib sepenanggungan, karena pada dunia yang padat nanti ketergantungan manusia terhadap alam akan bertambah. Seperti juga peningkatan dan pemeliharaan alam akan lebih tergantung pada pemeliharaan aktif oleh manusia. Keserasian dengan alam dengan manusia, diperlukan untuk menghadapi masa depan, bukan persoalan pengetahuan dan konsepsi intelektual semata- mata. Ia meliputi perasaan rasa, yaitu induk penglihatan dan pemikiran kita. Ia tidak lepas dari kemampuan intuitif, ekspresif, dan estetik manusia serta kemampuannya berkomunikasi secara non verbal. Bebagai upaya telah ditempuh untuk menanggulangi kerusakan lingkungan yang terjadi. Beberapa pertemunan internasional, nasional dan lokal yang menghasilkan beberapa kesepakatan-kesepakatan menunjukkan belum mampu untuk mengurangi aktivitas perusakan terhadap lingkungan. Oleh karena itu, dibutuhkan pendekatan ideal dalam menekan laju kerusakan lingkungan. Salah satu pendekatan yang dianggap efektif dan mengatasi aktifitas kerusakan lingkungan adalah 3

Pemanasan Global, http://id.wikipedia.org/wiki/Pemanasan_global, Diakses tgl 30 Januari 2014. 4 Hamzah Tauleka, Teologi Lingkungan Hidup Dalam Prespektif Islam, Fakultas Ushuluddin IAIN Sunan Ampel

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pendekatan agama yang diharapkan mampu untuk mengharmoniskan hubungan antara manusia dengan lingkungan (alam). Dalam konteks inilah Islam sebagai agama yang memiliki ajaran spritul diharapkan mampu untuk mengingatkan sekaligus mengatur tata hubungan antara manusia dengan alam. Hal ini sebagaimana pandangan Fachruddin M Mangunjaya 5 bahwa islam memberikan panduan yang luas pada keseimbangan hidup sebagai manifestasi rahmatan lil'alamin (rahmat bagi alam semesta) sebagaimana firman Allah SWT dalam Surat Al Anbiya ayat 107 yang atinya “ Kami tidak mengutusmu, kecuali sebagai rahmat bagi semesta alam". Dengan demikian Islam membawa ajaran yang mengadung sistem nilai yang mampu menjawab tantangan zaman. Sehingga dalam konteks inilah menurut Maulana Ismail 6 bahwa Islam sebagai pengembang kesadaran lingkungan mempunyai pijakan yang amat kuat dalam pelestarian lingkungan. Fondasi ajaran Islam tidak hanya berupa ayat-ayat Al Qur’an tetapi lebih dari itu menyentuh pada dimensi keimanan seorang individu dimana Alam Semesta menrupakan manifestasi Tuhan yang dengan memahaminya bisa mengantarkan manusia untuk sampai kepada Allah SWT. Nilai-nilai yang terkandung di dalam Al Qur’an dan Hadist dapat dijadikan sebagai landasan berpikir dan bertindak bagi umat islam dalam menyikapi kerusakan lingkungan, dengan kekayaan nilai yang terkandung dalam ayat-ayat Al Qur’an maupun Hadist Nabi Muhammad SAW dapat menjadi pendorong bagi umat Islam dalam melastarikan alam dan lingkungan karena merupakan perintah suci. Untuk mengkatulisasikan perintah suci dalam melestarikan lingkungan menurut Maulana Ismail7 dapat dilakukan melalui pendidikan agama berbasis pelestarian lingkungan yang diharapkan mampu untuk memberikan jalan keluar terhadap kerusakan lingkungan serta dapat menghasilkan individu-

5

Fachruddin M Mangunjaya, 2013. Islam and Natural Resource Management. Durrell Institute of Conservation and Ecology (DICE), University of Kent, Canterbury, Kent CT2 7NZ, United Kingdom. 6 Maulana Ismail, Pendidikan Lingkungan Prespektif Al-Qur’an dan Aktualisasinya Dalam Pendidikan Islam. Skripsi Jurusan Pendidikan Islam Fakultas Tarbiyah UIN Sunan Kalijaga, 2009. 7 Maulana Ismail, Pendidikan Lingkungan Prespektif Al Qur’an dan Aktualisasinya Dalam Pendidikan Islam. Skripsi Jurusan Pendidikan Islam Fakultas Tarbiyah UIN Sunan Kalijaga, 2009.

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individu yang memiliki kesalehan ekologi dalam berinteraksi dengan alam dan lingkungan. B. Keseimbangan Lingkungan Dalam Prespektif Islam Manusia sebagai makhluk hidup senantiasa berinteraksi dengan lingkungan tempat hidupnya. Manusia terkadang mempengaruhi lingkungan, dan terkadang lingkungan yang mempengaruhi manusia. Kelangsungan hidup manusia tergantung pada kemampuannya untuk menyesuaikan diri dengan sifat lingkungan hidupnya. Ketergantungan ini ditentukan oleh proses seleksi selama jutaan tahun dalam evolusi manusia. Manakala terjadi perubahan pada sifat lingkungan hidup yang berada di luar batas kemampuan adaptasi manusia, baik perubahan secara alamiah maupun perubahan yang disebabkan oleh aktivitas hidupnya, maka kelangsungan hidup manusia akan terancam.8 Manusia ditakdirkan Allah SWT untuk menempati planet bumi bersama dengan makhluq-makhluq lainnya. Bumi yang ditempati manusia ini disiapkan Allah SWT mempunyai kemampuan untuk bisa menyangga kehidupan manusia dan makhluq-makhluq lainnya. Akan tetapi sesuai pula dengan sunnatullah (hukum Allah), bumi juga mempunyai keterbatasan, sehingga bisa mengalami kerusakan bahkan kehancuran. Konsep inilah yang di dalam beberapa ayat Al-Qur’an dinyatakan bahwa setiap sesuatu ciptaan Allah itu mempunyai “ukuran” (qadr), dan oleh karena itu bersifat relatif dan tergantung kepada Allah. Jika sesuatu ciptaan Allah (termasuk manusia) itu melanggar hukum-hukum yang telah ditetapkan baginya dan melampaui “ukuran” nya, maka alam semesta ini akan menjadi kacau balau.9 Hal ini mengandung makna bahwa setiap tindakan atau perilaku manusia (muslim) harus dilandasi oleh pemahaman atas konsep Keesaan dan Kekuasaan Tuhan disamping itu manusia sebagai makhluk Tuhan sekaligus sebagai hamba Tuhan (abdul Allah)

8

Otto Soemarwoto, Analisis Dampak Lingkungan, cet. x (Yogyakarta: Gadjah Mada University Press, 2003), hlm. 18 9 Mujiddin Mawardin, Gatot Supangkat, dan Miftahulhaq. 2011. Ahlaq Lingkungan : Panduan Berperilaku Ramah Lingkungan. Deputi Komunikasi Lingkungan dan Pemberdayaan Masyarakat Kementerian Lingkungan Hidup dan Majelis Lingkungan Hidup Pimpinan Pusat Muhammadiyah.

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harus senantiasa tunduk dan patuh kepada aturan-aturan atau hukumhukum yang telah ditetapkan oleh Allah SWT. 10 Islam mempunyai ajaran atau konsep yang bernama khilafah. Konsep khilafah ini dibangun atas dasar pilihan Allah dan kesediaan manusia untuk menjadi khalifah (wakil atau wali) Allah di muka bumi (Q.S. Al-Baqarah: 30, Al Isra : 70, Al-An’am: 165 dan Yunus: 14). Sebagai wakil Allah, manusia wajib (secara aktif) untuk bisa merepresentasikan dirinya sesuai dengan sifat-sifat Allah. Salah satu sifat Allah tentang alam ini adalah bersifat sebagai pemelihara atau penjaga alam (al-rab al’alamin). Jadi, sebagai wakil (khalifah) Allah di muka bumi, manusia harus aktif dan bertanggung jawab untuk menjaga bumi. Menjaga bumi ini berarti menjaga keberlangsungan fungsi bumi sebagai tempat kehidupan makhluk Allah termasuk manusia, sekaligus menjaga keberlanjutan kehidupannya. Khilafah bisa juga bermakna kepemimpinan. Manusia adalah wakil Tuhan di muka bumi ini yang telah ditunjuk menjadi pemimpin bagi semua makhluk Tuhan yang lain (alam semesta termasuk bumi) dan seisinya (atmosfer, dan sumberdaya alam yang dikandungnya termasuk tumbuhan dan hewan). Makna ini mengandung konsekuensi bahwa manusia harus bisa mewakili Tuhan untuk memimpin dan memelihara keberlangsungan kehidupan semua makhluk.11 Untuk menjalankan misi khilafah ini manusia telah dianugerahi oleh Tuhan kelebihan dibandingkan dengan makhluk lain, yakni kesempurnaan ciptaan dan akal budi. Dengan berbekal akal budi (akal dan hati nurani) ini manusia mestinya mampu mengemban amanat untuk menjadi pemimpin sekaligus wakil Tuhan di muka bumi. Sebagai pemimpin, manusia harus bisa memelihara dan mengatur keberlangsungan fungsi dan kehidupan semua makhluk, sekaligus mengambil keputusan yang benar pada saat terjadi konflik kepentingan dalam penggunaan atau pemanfaatan sumberdaya alam. Pengambilan 10

Mujiddin Mawardin, Gatot Supangkat, dan Miftahulhaq. 2011. Ahlaq Lingkungan : Panduan Berperilaku Ramah Lingkungan. Deputi Komunikasi Lingkungan dan Pemberdayaan Masyarakat Kementerian Lingkungan Hidup dan Majelis Lingkungan Hidup Pimpinan Pusat Muhammadiyah. 11 Mujiddin Mawardin, Gatot Supangkat, dan Miftahulhaq. 2011. Ahlaq Lingkungan : Panduan Berperilaku Ramah Lingkungan. Deputi Komunikasi Lingkungan dan Pemberdayaan Masyarakat Kementerian Lingkungan Hidup dan Majelis Lingkungan Hidup Pimpinan Pusat Muhammadiyah.

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keputusan ini harus dilakukan secara adil, bukan dengan cara memihak kepada individu atau kelompok makhluk tertentu, akan tetapi mendholimi atau mengkhianati individu atau kelompok makhluk lainnya dalam komunitas penghuni bumi. Konsep ini menurut Fachruddin12 tergambar ketika Ketika Umar Ibnu Khaththab Radiyallahu Anhu diangkat menjadi menjadi Khalifah (586-644) di Madinah Semenanjung Arab dimana beliau memperkenalkan konsep pengelolaan lingkungan dengan memberikan beberapa sudut pandang; yaitu pertama, sumberdaya alam akan terancam apabila dieksploitasi secara berlebihan, kedua, memperkenalkan pemanfaatan lahan yang telah ditingalkan dan diberikan kepada masyarakat untuk dikelola secara produktif, ketiga, tidak diperkenankan melakukan eksploitasi secara berlebihan terhadap sumberdaya karena dikhawatirkan akan menganggu hak generasi berikutnya, dan keempat, melakukan pemanfaatan tanah dengan mendistribusikan tanah yang tidak dipakai/digunakan oleh pemiliknya selama tiga tahun kepada masyarakat secara adil sehingga dapat menghasilkan produktivitas lahan yang baik. Padangan yang telah disampaikan oleh Umar Ibnu Khaththab RA tentang konsep pengelolaan lingkungan merupakan bentuk manifestasi ajaran islam yang bersumber dari Al Qur’an dan hadist Nabi Muhammad SAW tentang pengelolaan lingkungan. Prinsip-prinsip ajaran ini dapat dieksplorasi untuk mendidik masyarakat dan meningkatkan kesadaran tentang lingkungan dan pengelolaan sumber daya alam. Konsep Islam menegaskan bahwa segala sesuatu di ekosistem ini adalah makhluk ciptaan Allah SWT dan mereka semua tunduk di dihadapan Allah SWT sebagaimana firman-Nya dalam Qs 17:44 yang artinya “ Langit yang tujuh, bumi dan semua yang ada di dalamnya bertasbih kepada Allah. Dan tak ada suatupun melainkan bertasbih dengan memuji-Nya, tetapi kamu sekalian tidak mengerti tasbih mereka. Sesungguhnya Dia adalah Maha Penyantun lagi Maha Pengampun”. Berdasarkan ayat tersebut Mujiddin Mawardin dkk13 menyatakan bahwa bahwa manusia perlu memahami 12

Fachruddin M Mangunjaya, 2013. Islam and Natural Resource Management. Durrell Institute of Conservation and Ecology (DICE), University of Kent, Canterbury, Kent CT2 7NZ, United Kingdom. 13 Mujiddin Mawardin, Gatot Supangkat, dan Miftahulhaq. 2011. Ahlaq Lingkungan : Panduan Berperilaku Ramah Lingkungan. Deputi Komunikasi Lingkungan dan

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sebagai bagian dari alam semesta, manusia serta elemen lain dari alam ekosistem semuanya tunduk dan mematuhi hukum-hukum Allah SWT atau apa yang sekarang kita sebut hukum alam. Ini berarti bahwa manusia tidak selalu melihat alam sebagai obyek eksploitasi tanpa benar-benar memahami makna, esensi, dan fungsi dari ekosistem serta cara menggunakan dan upaya untuk mempertahankan atau menyeimbangkan ekosistem sebaimana firman Allah SWT Qs 54:49 “ Sesungguhnya , segala sesuatu telah Kami dibuat dalam proporsi dan ukuran “. Banyak fenomena kerusakan lingkungan sekarang ini seperti tanah longsor , banjir bandang , angin puting beliung dan perubahan iklim, dianggap hasil langsung dari gangguan terhadap ketidakseimbangan ekosistem seperti ketika kawasan hutan dan lahan dengan kemiringan ekstrim dibersihkan untuk tujuan budidaya, maka lahan tersebut menjadi tidak stabil dan menyebabkan tanah longsor dan banjir, hal ini karena tanaman yang tumbuh pada kemiringan tertentu tidak lagi memiliki kemampuan untuk menahan air selama musim hujan sehingga fungsi-fungsi ekologinya menjadi tidak berfungsi lagi. Lingkungan merupakan kondisi sosial dan kultural yang berpengaruh terhadap individu atau komunitas, lingkungan terbentuk dalam sebuah sistem yang merupakan suatu jaringan saling ketergantungan antar komponen dan proses, dimana energi dan materi mengalir dari satu komponen ke komponen sistem lainnya. Sistem lingkungan atau yang sering disebut ekosistem merupakan contoh bagaimana sebuah sistem berjalan. Ekosistem merupakan suatu gabungan atau kelompok hewan, tumbuhan dan lingkungan alamnya, dimana di dalamnya terdapat aliran atau gerakan atau transfer materi, energi dan informasi melalui komponen-komponennya. Ekosistem dapat pula dimaknai sebagai suatu situasi atau kondisi lingkungan dimana terjadi interaksi antara organisme (tumbuhan dan hewan termasuk manusia) dengan lingkungan hidupnya.14 Sebagai sebuah sistem, lingkungan harus tetap terjaga keteraturannya sehingga sistem itu dapat berjalan dengan Pemberdayaan Masyarakat Kementerian Lingkungan Hidup dan Majelis Lingkungan Hidup Pimpinan Pusat Muhammadiyah. 14 Mujiddin Mawardin, Gatot Supangkat, dan Miftahulhaq. 2011. Ahlaq Lingkungan : Panduan Berperilaku Ramah Lingkungan. Deputi Komunikasi Lingkungan dan Pemberdayaan Masyarakat Kementerian Lingkungan Hidup dan Majelis Lingkungan Hidup Pimpinan Pusat Muhammadiyah.

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teratur dan memberikan kemanfaatan bagi seluruh anggota ekosistem. Manusia sebagai makhluk yang sempurna, yang telah diberikan amanah untuk menjadi khalifah memiliki peran penting dalam menciptakan dan menjaga keteraturan lingkungan dan system lingkungan ini. Untuk itulah manusia dituntut untuk dapat mengembangkan akhlaq (perilaku yang baik) terhadap lingkungan. Alam diciptakan Allah dalam keberagaman kualitatif maupun kuantitatif seperti ukuran, jumlah, struktur, peran, umur, jenis kelamin, masa edar dan radius edarnya. Walaupun demikian, alam dan ekosistem ciptaan Tuhan yang sangat beragam ini berada dalam keseimbangan, baik keseimbangan antar individu maupun antar kelompok (QS: Al-Mulk: 67). Keseimbangan ini merupakan hukum Tuhan yang juga berlaku atas alam termasuk manusia. Keseimbangan ini bisa mengalami gangguan (disharmoni) jika salah satu atau banyak anggota kelompok atau suatu kelompok mengalami gangguan baik secara alamiah maupun akibat campur tangan manusia. Jika terjadi gangguan terhadap keseimbangan alam, maka alam akan bereaksi atau merespon dengan membentuk keseimbangan baru yang bisa terjadi dalam waktu singkat, atau bisa pula dalam waktu yang cukup lama tergantung pada intensitas gangguan serta sifat kelentingan masing-masing sistem alam yang bersangkutan. Keseimbangan baru yang terbentuk ini sudah barang tentu bisa berbeda secara kuantitatif maupun kualitatif dengan keseimbangan sebelumnya. Demikian pula keseimbangan baru ini bisa bersifat merugikan, bisa pula menguntungkan bagi anggota komunitas atau kelompok yang bersangkutan. Perilaku dan perbuatan manusia terhadap alam termasuk antar manusia yang diharamkan (dilarang), sebenarnya bertujuan agar keseimbangan atau harmoni alam tidak mengalami gangguan. Larangan untuk tidak bertengkar, berkata kotor, berbohong, berburu, melukai atau membunuh hewan dan tanaman pada waktu ihram bagi orang yang sedang berhaji atau umrah, sebenarnya mengandung pesan bahwa keseimbangan lingkungan dan harmoni kehidupan tidak boleh diganggu dengan perbuatan-perbuatan yang merusak (haram).15 16

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Miftahulhaq, 2012. agama dan http://muhammadiyahgoesgreen .blogspot.com/ lingkungan.html.

penyelamatan lingkungan . 2012/04/agama-dan-penyelamatan-

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C. Model Pengelolaan Lingkungan Melalui Pendidikan Konservasi Dalam Ajaran Islam Sumber daya alam diklasifikasikan menjadi dua kategori yaitu sumberdaya alam terbarukan dan tidak terbarukan . Sumber daya tak terbarukan adalah sumber daya alam yang pada akhirnya akan habis dalam jangka waktu tertentu , seperti minyak berbasis karbon dan mineral. Sedangkan sumberdaya alam terbaharukan merupakan sumberdaya alam yang dapat di subsititusi dalam jangka waktu tertentu, seperti pohon, tanaman pertanian dan lain-lain. Kegiatan eksploitasi secara berlebihan terhadap sumberdaya alam melebihi daya dukungnya akan menyebabkan gangguan terhadap keseimbangan lingkungan yang pada akhirnya akan berdampak kelangsungan sumberdaya alam tersebut. Seperti modifikasi hutan mangrove menjadi peruntukkan lain akan menyebabkan beberapa fungsi mangrove akan menjadi hilang seperti penyerapan karbon, penyaringan air asin, pencegahan intusi air laut, peternakan area untuk krustasea dan ikan. Eksploitasi yang berlebihan ini bisa terjadi baik karena kurangnya pengetahuan atau sengaja dengan mengikuti keinginan seseorang atau keserakahan. Islam dengan tegas melarang eksploitasi yang berlebihan tanpa ada ilmu pengetahuan dan tanggung jawab. Dalam Al Quran Allah berfirman "Tetapi orang-orang yang zalim, mengikuti hawa nafsunya tanpa ilmu pengetahuan; maka siapakah yang akan menunjuki orang yang telah disesatkan Allah? Dan tiadalah bagi mereka seorang penolongpun”. (Qs 30:29 ) Demikian pula pada ayat lain Allah berfirman ”Allah melarang manusia dari melakukan apapun yang merusak kegiatan di bumi sebagaimana firman Allah SWT “dan carilah pada apa yang telah dianugerahkan Allah kepadamu (kebahagiaan) negeri akhirat, dan janganlah kamu melupakan bahagianmu dari (kenikmatan) duniawi dan berbuat baiklah (kepada orang lain) sebagaimana Allah telah berbuat baik, kepadamu, dan janganlah kamu berbuat kerusakan di (muka) bumi. Sesungguhnya Allah tidak menyukai orang-orang yang berbuat kerusakan”.(Qs 28:77). Pada ayat lain pula Allah SWT juga berfirman “ Dan janganlah kamu membuat kerusakan di muka bumi, sesudah (Allah) 16

Syafieh Yanti , Islam Dan Kelestarian Lingkungan: Studi Tentang Fiqh Al-Biah Sebagai Solusi Alternatif Terhadap Kerusakan Lingkungan, http://syafieh.blogspot.com/2013/03/islam-dan-kelestarian-lingkunganstudi.html#ixzz2yuFJ2ea4

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memperbaikinya dan berdoalah kepada-Nya dengan rasa takut (tidak akan diterima) dan harapan (akan dikabulkan). Sesungguhnya rahmat Allah amat dekat kepada orang-orang yang berbuat baik.” (Qs 07:5), disamping itu pula Allah SWT berfirman pada ayat yang lain yaitu, "Jadi makan dan minum dari rezeki yang diberikan oleh Allah , dan tidak melakukan kejahatan atau kerusakan di (muka dari ) bumi. "(2:60).17 Dalam Islam di kenal tiga macam bentuk pelestarian lingkungan. Pertama, dengan cara ihya'. Yakni pemanfaatan lahan yang dilakukan oleh individu. Dalam hal ini seseorang mematok lahan untuk dapat digarap dan difungsikan untuk kepentingan pribadinya. Orang yang telah melakukannya dapat memiliki tanah tersebut. Mazhab Syafi’i menyatakan siapapun berhak mengambil manfaat atau memilikinya, meskipun tidak mendapat izin dari pemerintah. Lain halnya dengan Imam Abu Hanifah, beliau berpendapat, Ihya' boleh dilakukan dengan catatan mendapat izin dari pemerintah yang sah. Imam Malik juga berpendapat hampir sama dengan Imam Abu Hanifah. Akan tetapi, beliau menengahi dua pendapat itu dengan cara membedakan dari letak daerahnya. Kedua, dengan proses igta'. Yakni pemerintah memberi jatah pada orang-orang tertentu untuk menempati dan memanfaatkan sebuah lahan. Adakalanya untuk dimiliki atau hanya untuk dimanfaatkan dalam jangka waktu tertentu. Ketiga, adalah dengan cara hima. Dalam hal ini pemerintah menetapkan suatu area untuk dijadikan sebagai kawasan lindung yang difungsikan untuk kemaslahatan umum. Dalam konteks dulu, hima difungsikan untuk tempat penggembalaan kuda-kuda milik negara, hewan, zakat dan lainnya. Setelah pemerintah menentukan sebuah lahan sebagai hima, maka lahan tersebut menjadi milik negara. Tidak seorang pun dibenarkan memanfaatkannya untuk kepentingan pribadinya (melakukan ihya'), apalagi sampai merusaknya.18 Islam memiliki tradisi panjang untuk melindungi tanah melalui hima seperti yang ditemukan di Timur Tengah yaitu Area Bird (IBA) 17

Syafieh Yanti , Islam Dan Kelestarian Lingkungan: Studi Tentang Fiqh Al-Biah Sebagai Solusi Alternatif Terhadap Kerusakan Lingkungan, http://syafieh.blogspot.com/2013/03/islam-dan-kelestarian-lingkunganstudi.html#ixzz2yuGhZIi9 18 Fachruddin M Mangunjaya, 2013. Islam and Natural Resource Management. Durrell Institute of Conservation and Ecology (DICE), University of Kent, Canterbury, Kent CT2 7NZ, United Kingdom.

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selama berabad-abad atau sekitar 1.500 tahun telah menjadi tempat hidup populasi burung.19 Hima merupakan kawasan yang dilindungi untuk kemaslahatan umum dan pengawetan habitat alami. Hima adalah suatu kawasan yang khusus dilindungi oleh pemerintah (Imam Negara atau Khalifah) atas dasar syariat guna melestarikan (mengkonservasi) dan mengelola hutan dan semak belukar, daerah aliran sungai dan kehidupan liar. “Sesungguhhnya pionir hima dicontohkan pada dua kota suci (Mekah dan Madinah) sejak zaman Rasulullah Muhammad SAW. Beliau mengumumkan hal itu saat penaklukan Mekah melalui sabdanya: Suci karena kesucian yang diterapkan Allah padanya hingga hari kebangkitan. Belukar pohonnya tidak boleh ditebang, hewannya tidak boleh diganggu dan rerumputan yang baru tumbuh tidak boleh dipotong. (HR. Muslim). Disamping itu, Rasulullah SAW pernah mencagarkan kawasan sekitar Madinah sebagai hima guna melindungi lembah, padang rumput dan tumbuhan yang ada di dalamnya melalui sabdanya: Sesungguhnya Ibrahim memaklumkan Mekkah sebagai tempat suci dan sekarang aku memaklumkan Madinah, yang terletak antara dua lava mengalir (lembah), sebagai tempat suci. Pohon-pohonnya tidak boleh ditebang dan binatang binatangnya tidak boleh diburu (HR. Muslim) . Sahabat Abu Hurairah mengatakan: Bila aku menemukan rusa di tempat antara dua lava mengalir, aku tidak akan mengganggunya; dan dia (Nabi) juga menetapkan dua belas mil sekeliling Madinah sebagai kawasan terlindung (hima) (Riwayat Muslim). Nabi juga melarang masyarakat mengolah tanah tersebut karena lahan itu untuk kemaslahatan umum dan kepentingan pelestarian Dalam sebuah hadistnya Rasulullah bersabda: tidak ada hima kecuali milik Allah dan Rasulnya (Riwayat Al Bukhari).20 Islam adalah Diin yang Syaamil (Integral), Kaamil (Sempurna) dan Mutakaamil (Menyempurnakan semua sistem yang lain), karena ia adalah sistem hidup yang diturunkan oleh Yang Maha Mengetahui dan Maha Bijaksana. Oleh karena itu aturan Islam haruslah mencakup semua sisi yang dibutuhkan oleh manusia dalam kehidupannya. Demikian tinggi, 19

Fachruddin M Mangunjaya, 2013. Islam and Natural Resource Management. Durrell Institute of Conservation and Ecology (DICE), University of Kent, Canterbury, Kent CT2 7NZ, United Kingdom. 20 Hendra, Pengelolaan Lingkungan Dalam Bingkai Alquran, http://okehendra52.blogspot.com/2013/01/pengelolaan-lingkungan-dalam-bingkai.html. diakses tgl 15 April 2014.

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indah dan terperinci aturan Sang Maha Rahman dan Rahim ini, sehingga bukan hanya mencakup aturan bagi sesama manusia saja, melainkan juga terhadap alam dan lingkungan hidupnya. D. Upaya Untuk Menumbuhan Kesalehan Ekologis Pendidikan lingkungan yang diajarkan secara Islami merupakan sarana penting bagi muslim untuk mengenal dan menyadari lingkungan hidup mereka secara baik dan benar sehingga mampu berperan secara sadar dan aktif dalam pengelolaan dan pembinaan lingkungan. Sebagai mayoritas penduduk Indonesia, muslim mempunyai kewajiban dan peran yang sangat besar dalam pengelolaan lingkungan tersebut. Dibutuhkan pengetahuan dan kesadaran yang mendalam bahwa Islam sangat memperhatikan lingkungan dan kesehatan. Hal ini membutuhkan peran pendidik, ulama, dan tokoh masyarakat untuk menanamkan pengetahuan dan kesadaran tersebut kepada masyarakat. Kesadaran bahwa alam semesta adalah milik Allah SWT merupakan langkah dasar dalam memahami kedudukan manusia di alam ini. Dalam ajaran Islam, khalifah lebih bersifat sebagai pengelola atau manajer di bumi ini sedangkan Allah SWT adalah pemilik mutlak dari bumi dan segala isinya. Allah SWT memberikan hak kepada manusia untuk mengambil manfaat dari bumi dan isinya namun Allah SWT juga memberi kewajiban pada manusia untuk menjaga bumi dan isinya.21 Hal ini sesuai dengan konsep pembangunan berkelanjutan yang menekankan pada pemanfaatan dan pengeloaan sumber daya alam bagi pembangunan dan kelanjutan pembangunan secara lestari. Pembangunan yang berkelanjutan adalah pembangunan disegala bidang (misalnya ekonomi, sosial, dan politik) yang tetap mengindahkan ketersediaan sumber daya alam yang memadai bagi generasi mendatang. Hal ini sesuai dengan saran Rasulullah SAW untuk hidup sederhana dan tidak berlebihan terhadap harta dan sumber daya yang kita miliki.22 Langkah awal yang harus kita lakukan untuk menangani masalah lingkungan dan membangun keseadaran ekologi masyarakat menurut Suseno 21

Agus Sofyan, Pengelolaan Lingkungan Yang Terpadu Menurut Ajaran Islam, http://www.imsa.us/index.php/blog/25-pengelolaan-lingkungan-yang-terpadu-menurut-ajaranislam. diakses tgl 15 April 2014. 22 Asmu’I, Islam, Manusia, dan Lingkungan Alam. http://idiaprenduan.com/islammanusia-dan-lingkungan-alam/, diakses tanggal 15 April 2014.

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sebagaimana yang dikutip oleh santoto23 adalah dengan memperkenalkan dan mengajak mereka untuk melaksanakan prinsip-prinsip kesalehan lingkungan dalam kehidupan sehari-hari. Etika lingkungan yang dimaksud adalah “sikap tanggung jawab terhadap alam, yaitu mengenai keutuhan biosfer maupun generasi-generasi yang akan datang” . Upaya untuk menumbuhkan kesadaran dan kesalehan terhadap lingkungan harus dimulai dari pengetahuan kita tehadap unsur-unsur etika lingkungan. Unsur-unsur untuk membangun kesadaran ekologis di antaranya yaitu manusia harus belajar untuk menghormati alam, harus memberikan suatu perasaan tanggung jawab khusus terhadap lingkungan lokal, karena manusia bagian dari biosfer maka ia harus merasa bertanggung jawab terhadap kelestarian biosfer. Kesadaran terhadap lingkungan menuntut tidak melakukan kerusakan, mengotori dan meracuni, dan solidaritas dengan generasi-generasi yang akan datang terhadap pemanfaatan sumber daya alam. Atas dasar itu, seseorang dikatakan memiliki kesalehan ekologi yang menurut Ghazali24 jika seseorang telah memiliki kesalehan ekologi maka orang tersebut akan mampu untuk memahami, memikirkan dan menginsyafi makna lingkungan, kegunaan dan kemanfaatan serta hakekat dari keberadaan lingkungan itu di dunia ini. Ada beberapa prinsip-prinsip yang harus dipenuhi untuk menumbuhkan kesadaran ekologi manusia dalam berinteraksi dengan lingkungan hidup. Berikut adalah prinsip-prinsip yang dapat menjadi pegangan dan tuntunan untuk membangun kesalehan ekologi bagi manusia dalam berinteraksi dengan alam, yaitu :25 1. Sikap Hormat terhadap Alam (Respect For Nature) Di dalam Al Qur’an surat Al-Anbiya 107, Allah SWT berfirman: Dan tiadalah kami mengutus kamu, melainkan untuk (menjadi) rahmat bagi semesta alam. Rahmatan lil alamin bukanlah sekedar motto Islam, tapi merupakan tujuan dari Islam itu sendiri. Sesuai dengan tujuan tersebut, maka sudah sewajarnya apabila Islam menjadi pelopor bagi pengelolaan alam dan lingkungan sebagai 23

Santoso, Heru. 2000. Landasan Etis bagi Perkembangan Teknologi. Yogyakarta: Tiara Wacana. 24 Ghazali, Bachtiar. 1996. Lingkungan Hidup dalam Pemahaman Islam. Jakarta: Pedoman Ilmu Jaya. 25 Ai Roudotul, Pengelolaan Lingkungan Hidup Dalam Perspektif Islam, http://aiirm59. blogspot.com/2013/04/pengelolaan-lingkungan-hidup-dalam.html. diakses tgl 15 April 2014.

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manifestasi dari rasa kasih bagi alam semesta tersebut. Selain melarang membuat kerusakan di muka bumi, Islam juga mempunyai kewajiban untuk menjaga lingkungan dan menghormati alam semesta yang mencakup jagat raya yang didalamya termasuk manusia, tumbuhan, hewan, makhluk hidup lainnya, serta makhluk tidak hidup. Hormat terhadap alam merupakan suatu prinsip dasar bagi manusia sebagai bagian dari alam semesta seluruhnya. Seperti halnya, setiap anggota komunitas sosial mempunyai kewajiban untuk menghargai kehidupan bersama (kohesivitas sosial), demikian pula setiap anggota komunitas ekologis harus menghargai dan menghormati setiap kehidupan dan spesies dalam komunitas ekologis itu, serta mempunyai kewajiban moral untuk menjaga kohesivitas dan integritas komunitas ekologis, alam tempat hidup manusia ini. Sama halnya dengan setiap anggota keluarga mempunyai kewajiban untuk menjaga keberadaan, kesejahteraan, dan kebersihan keluarga, setiap anggota komunitas ekologis juga mempunyai kewajiban untuk menghargai dan menjaga alam ini sebagai sebuah rumah tangga. 2. Prinsip Tanggung Jawab (Moral Responsibility For Nature) Terkait dengan prinsip hormat terhadap alam di atas adalah tanggung jawab moral terhadap alam, karena manusia diciptakan sebagai khalifah (penanggung jawab) di muka bumi dan secara ontologis manusia adalah bagian integral dari alam. Sesuai dengan firman Allah dalam surah al Baqarah : 30 “Ingatlah ketika Tuhanmu berfirman kepada para malaikat: "Sesungguhnya Aku hendak menjadikan seorang khalifah di muka bumi”. Kenyataan ini saja melahirkan sebuah prinsip moral bahwa manusia mempunyai tanggung jawab baik terhadap alam semesta seluruhnya dan integritasnya, maupun terhadap keberadaan dan kelestariannya Setiap bagian dan benda di alam semesta ini diciptakan oleh Tuhan dengan tujuannya masing-masing, terlepas dari apakah tujuan itu untuk kepentingan manusia atau tidak. Oleh karena itu, manusia sebagai bagian dari alam semesta, bertanggung jawab pula untuk menjaganya. 3. Solidaritas Kosmis (Cosmic Solidarity) Terkait dengan kedua prinsip moral tersebut adalah prinsip solidaritas. Sama halnya dengan kedua prinsip itu, prinsip solidaritas 33

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muncul dari kenyataan bahwa manusia adalah bagian integral dari alam semesta. Lebih dari itu, dalam perspektif ekofeminisme, manusia mempunyai kedudukan sederajat dan setara dengan alam dan semua makhluk lain di alam ini. Kenyataan ini membangkitkan dalam diri manusia perasaan solider, perasaan sepenanggungan dengan alam dan dengan sesama makhluk hidup lain. 4. Prinsip Kasih Sayang dan Kepedulian terhadap Alam (Caring For Nature) Sebagai sesama anggota komunitas ekologis yang setara, manusia digugah untuk mencintai, menyayangi, dan melestarikan alam semesta dan seluruh isinya, tanpa diskriminasi dan tanpa dominasi. Kasih sayang dan kepedulian ini juga muncul dari kenyataan bahwa sebagai sesama anggota komunitas ekologis, semua makhluk hidup mempunyai hak untuk dilindungi, dipelihara, tidak disakiti, dan dirawat. Sebagaimana dimuat dalam sebuah Hadis shahih yang diriwayatkan oleh Shakhihain: Dari Anas radhiyallahu ‘anhu bahwa Nabi shallallahu ‘alaihi wasallam bersabda, “Tidak seorang pun muslim yang menanam tumbuhan atau bercocok tanam, kemudian buahnya dimakan oleh burung atau manusia atau binatang ternak, kecuali yang dimakan itu akan bernilai sedekah untuknya.” Dalam hadis lain dijelaskan Dari Abu Hurairah radhiyallahu ‘anhu bahwa Nabi shallallahu ‘alaihi wasallam bersabda, “Jauhilah dua perbuatan yang mendatangkan laknat!” Sahabat-sahabat bertanya, ”Apakah dua perbuatan yang mendatangkan laknat itu?” Nabi menjawab, “Orang yang buang air besar di jalan umum atau di tempat berteduh manusia. E. Penutup Manusia ditakdirkan Allah SWT untuk menempati planet bumi bersama dengan makhluq-makhluq lainnya. Bumi yang ditempati manusia ini disiapkan Allah SWT mempunyai kemampuan untuk bisa menyangga kehidupan manusia dan makhluq-makhluq lainnya. Akan tetapi sesuai pula dengan sunnatullah (hukum Allah), bumi juga mempunyai keterbatasan, sehingga bisa mengalami kerusakan bahkan kehancuran. Konsep inilah yang di dalam beberapa ayat Al-Qur’an dinyatakan bahwa setiap sesuatu ciptaan Allah itu mempunyai “ukuran” (qadr), dan oleh 34

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karena itu bersifat relatif dan tergantung kepada Allah. Jika sesuatu ciptaan Allah (termasuk manusia) itu melanggar hukum-hukum yang telah ditetapkan baginya dan melampaui “ukuran” nya, maka alam semesta ini akan menjadi kacau balau. Untuk merespon aktivitas kerusakan lingkungan diperlukan adanya transformasi melalui aktualisasi pendidikan islam berbasis pelesatarian lingkungan yang bersumber dari Al Qur’an dan Hadis nabi Muhammad SAW yang diharapkan dapat menyadarkan manusia akan pentingnya pelestarian terhadap alam dan lingkungan. Dalam Islam di kenal tiga macam bentuk pelestarian lingkungan. Pertama, dengan cara ihya' yaitu pemanfaatan lahan yang dilakukan oleh individu. Kedua, dengan proses igta', yaitu pemerintah memberi jatah pada orang-orang tertentu untuk menempati dan memanfaatkan sebuah lahan. Ketiga, adalah dengan cara hima, yaitu pemerintah menetapkan suatu area untuk dijadikan sebagai kawasan lindung yang difungsikan untuk kemaslahatan umum. Pendidikan lingkungan yang diajarkan secara Islami merupakan sarana penting bagi muslim untuk mengenal dan menyadari lingkungan hidup mereka secara baik dan benar sehingga mampu berperan secara sadar dan aktif dalam pengelolaan dan pembinaan lingkungan. Upaya untuk menumbuhkan kesadaran dan kesalehan terhadap lingkungan harus dimulai dari pengetahuan kita terhadap unsur-unsur etika lingkungan. Unsur-unsur untuk membangun kesadaran ekologis untuk tidak melakukan kerusakan, mengotori dan meracuni, dan solidaritas dengan generasi-generasi yang akan datang terhadap pemanfaatan sumber daya alam. DAFTAR PUSTAKA Amat

Zuhri, Tasawuf Ekologi (Tasawuf Sebagai Solusi Dalam Menanggulangi Krisis Lingkungan). Jurusan Ushuluddin STAIN Pekalongan, Jl. Kusumabangsa No. 9. Pekalongan. Ai Roudotul, Pengelolaan Lingkungan Hidup Dalam Perspektif Islam, http://aiirm59. blogspot.com/2013/04/pengelolaan-lingkungan-hidupdalam.html. diakses tgl 15 April 2014 Asmu’i, Islam, Manusia, dan Lingkungan Alam. http://idiaprenduan.com/islam-manusia-dan-lingkungan-alam/

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Ghazali, Bachtiar. 1996. Lingkungan Hidup dalam Pemahaman Islam. Jakarta: Pedoman Ilmu Jaya. Hendra, Pengelolaan Lingkungan Dalam Bingkai Alquran, http://okehendra52.blogspot.com /2013/01/pengelolaan-lingkungandalam-bingkai.html. diakses tgl 15 April 2014. Ismail, M. 2009. Pendidikan Lingkungan Prespektif Al Qur’an dan Aktualisasinya Dalam Pendidikan Islam. Skripsi Jurusan Pendidikan Islam Fakultas Tarbiyah UIN Sunan Kalijaga. Mangunjaya, F.M. 2013. Islam and Natural Resource Management. Durrell Institute of Conservation and Ecology (DICE), University of Kent, Canterbury, Kent CT2 7NZ, United Kingdom. Mawardin, M., Supangkat, G., dan Miftahulhaq. 2011. Ahlaq Lingkungan : Panduan Berperilaku Rama Lingkungan. Deputi Komunikasi Lingkungan dan Pemberdayaan Masyarakat Kementerian Lingkungan Hidup dan Majelis Lingkungan Hidup Pimpinan Pusat Muhammadiyah. Miftahulhaq, 2012. agama dan penyelamatan lingkungan . http://muhammadiyahgoesgreen .blogspot.com/ 2012/04/agama-danpenyelamatan-lingkungan.html Soemarwoto, Otto, 2003. Analisis Dampak Lingkungan, Yogyakarta: Gadjah Mada University Press. Syafieh Yanti , Islam Dan Kelestarian Lingkungan: Studi Tentang Fiqh AlBiah Sebagai Solusi Alternatif Terhadap Kerusakan Lingkungan, http://syafieh.blogspot.com/2013/03/islam-dan-kelestarianlingkungan-studi. html#i xzz2yuFJ2ea4 Sofyan, Agus. Pengelolaan Lingkungan Yang Terpadu Menurut Ajaran Islam, http://www.imsa.us /index.php/blog/25-pengelolaan-lingkunganyang-terpadu-menurut-ajaran-islam. diakses tgl 15 April 2014 Santoso, Heru. 2000. Landasan Etis bagi Perkembangan Teknologi. Yogyakarta: Tiara Wacana. Tauleka, Hamzah. Teologi Lingkungan Hidup Dalam Prespektif Islam, Fakultas Ushuluddin IAIN Sunan Ampel Wikipedia, Pemanasan Global, http://id.wikipedia.org/wiki/Pemanasan_global, Diakses tgl 30 Januari 2014.

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PENCEMARAN DAN PERUSAKAN LINGKUNGAN DALAM PERSPEKTIF HUKUM ISLAM (Environmental Pollution and Damage in Islamic Law Perspective)

Abdul Manan Hakim Agung MA RI Jl. Medan Merdeka Utara No. 9-13, Jakarta Pusat Email :

Abstrak Peraturan yang mengatur tentang lingkungan hidup di Indonesia cukup banyak dan tersebar dalam berbagai peraturan. Tetapi tampaknya peraturanperaturan tersebut berdiri sendiri, tidak ada aktivitas dan efektivitasnya. Cara pengelolaan lingkungan hidup yang tidak terencana dan tidak terpadu secara serasi dan integral menyebabkan perusakan dan pencemaran lingkungan. Hukum Islam memiliki prinsip-prinsip yang wajib menjadi landasan dan titik tolak aktivitas kekuatan-kekuatan sosial agar terjamin kehidupan yang teratur, seimbang, dan harmonis sehingga tidak terjadi pencemaran dan perusakan lingkungan hidup yang menyebabkan hilangnya keseimbangan dan keserasian kehidupan di dunia ini. Diantara prinsipprinsip tersebut yaitu persamaan, keseimbangan, kemaslahatan, kegotongroyongan dan keadilan. Melalui implementasi prinsip-prinsip tersebut diharapkan aturan tentang lingkungan hidup yang telah ditetapkan itu dapat berjalan sebagaimana mestinya. Kata kunci : Pencemaran dan Perusakan, Lingkungan, Hukum Islam Abstract Regulations governing the environment in Indonesia are many and scattered in various regulations. But it seems that these regulations stand alone, no activity and effectiveness. How to environmental management are not planned and are not integrated in a harmonious and integral cause destruction and environmental pollution. Islamic law has principles that must form the basis and starting point of the activity of the social forces in order to ensure an orderly life, balance, and harmony so there is no pollution and environmental destruction that causes loss of balance and harmony of life in this world. Among these principles, namely equality, balance, benefit, mutual cooperation and justice. Through the implementation of these principles is expected to rule on the environment that has been set it can run properly. 223

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Keywords : Environmental Pollution and Destruction, Environment, Islamic law A. Pendahuluan Istilah lingkungan yang dipergunakan dalam makalah ini adalah merupakan terjemahan dari istilah “Environment” dalam bahasa Inggris, atau “I’evironemen” dalam bahasa Perancis, “Umwelt” dalam bahasa Jerman, “Millieu” dalam bahasa Belanda, “Alam Sekitar” dalam bahasa Malaysia, “Kapaligiran” dalam bahasa Tagalog, atau “Sinvat-lom” dalam bahasa Thai. (Munadjad Danusaputra: 1980). Istilah tersebut secara teknis dimaksudkan dengan lingkungan hidup atau lengkapnya lagi adalah lingkungan hidup manusia. Menurut UU No. 4 Tahun 1982 Pasal 1 Ayat (1) yang dimaksud dengan lingkungan hidup adalah kesatuan ruang dengan semua benda, daya, keadaan, dan makhluk hidup, termasuk di dalamnya manusia dan perilakunya yang memengaruhi kelangsungan perikehidupan dan kesejahteraan manusia serta makhluk hidup lainnya. UU No. 4 Tahun 1982 membuka kemungkinan untuk mengatur berbagai kebijaksanaan mengenai pemeliharaan lingkungan hidup dengan ketentuan sendiri. Oleh karena itu, untuk membentuk dan mengembangkan satu hukum lingkungan yang relatif sanggup menjangkau pengaturan semua aspek yang berhubungan dengan pengelolaan lingkungan hidup secara integral, masih diperlukan penyusunan dan perbuatan berbagai Undang-Undang dan ketentuan-ketentuan pelaksanaannya. Hal ini membutuhkan waktu yang cukup panjang sangat luas ruang lingkupnya. Sehubungan dengan hal tersebut di atas, banyak sekali ayat-ayat AlQur’an dan al-Hadist yang membicarakan tentang keharusan umat manusia menjaga kelestarian alam, kiranya di sinilah nilai-nilai yang ada dalam Syariat Islam dapat ditransformasikan ke dalam peraturan Perundangundangan yang dibentuk dan dilaksanakan dalam rangka mengatur tata lingkungan hidup di Indonesia ini. Dalam makalah ini, akan dikemukakan beberapa hal mengenai prinsip-prinsip Hukum Islam dalam mengelola lingkungan hidup, khususnya yang berkenaan dengan masalah pencemaran dan perusakan lingkungan B. Lingkungan Hidup di Indonesia Masalah lingkungan hidup di Indonesia diatur dalam UU No. 4 Tahun 1982 tentang Ketentuan-ketentuan Pokok Pengelolaan Lingkungan Hidup. Ada dua hal yang ditonjolkan oleh Undang-Undang ini, yaitu : (1) Undang-Undang ini hanya mengatur tentang lingkungan hidup secara garis besar dalam pokok-pokoknya saja, sedangkan aturan secara rinci diatur 224

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dalam peraturan pelaksana atau petunjuk pelaksanaan lainnya. (2) UndangUndang ini bukan mengatur tentang lingkungan hidup secara keseluruhan, akan tetapi hanya mengatur segi pengelolaannya saja (Abdurrahman, 1986). Dalam hubungannya dengan peraturan Perundang-undangan tentang lingkungan sebagaimana tersebut di atas, Munadjat Danusaputra (1980) menyatakan bahwa Undang-Undang No. 4 Tahun 1982 tentang Ketentuanketentuan Pokok Pengelolaan Hidup disusun untuk dapat berfungsi sebagai “Ketentuan Payung” atau Umbrella Provision bagi penyusunan peraturanperaturan Perundang-undangan tentang lingkungan hidup selanjutnya. Lebih lanjut dikemukakan bahwa sifat dari Undang-Undang Lingkungan Hidup itu secara khusus memberikan arah dan ciri-ciri bagi semua jenis tata pengaturan lingkungan hidup yang perlu dituangkan dalam bentuk pengaturan-pengaturan perundangan tersendiri. Undang-Undang ini harus mampu menjadi dasar dan landasan bagi pengembangan hukum lingkungan lainnya, termasuk di dalamnya pembaruan dan penyesuaian peraturanperaturan hukum lama. Peraturan yang mengatur tentang lingkungan hidup di Indonesia cukup banyak dan tersebar dalam berbagai peraturan sebagian dari peraturan itu sudah ada sejak zaman Belanda, dan sebagian lagi dibuat setelah zaman kemerdekaan. Tetapi tampaknya peraturan-peraturan tersebut berdiri sendiri, tidak ada aktivitas dan efektivitas dari peraturan itu (Abdurrahman, 1986). Dari inventarisasi mengenai peraturan yang menyangkut aspek lingkungan, nyatalah bahwa belum ada dan masih diperlukan peraturan untuk melindungi hidup manusia dan sumber alam dalam kaitannya dengan pembangunan, seperti masalah pestisida, pencemaran air dan sungai dan air laut oleh pengangkutan minyak dan pembuangan sampah dan kotoran oleh industri. Hal ini berarti bahwa problem perusakan dan pencemaran di bidang kehidupan lain, seperti dalam bidang sosial-budaya tidak begitu penting. Tentang masalah ini tetap mempunyai arti penting dalam penanggulangannya, hanya urutan prioritas penanganannya perlu diadakan (Siti Sundari Rangkuti, 1975). Urusan prioritas tersebut diperlukan karena kondisi yang tidak menguntungkan untuk dilaksanakan Undang-Undang tersebut sekaligus. Di samping itu, ada pula Undang-Undang yang secara konvensional sudah tidak sesuai lagi dengan prinsip-prinsip lingkungan hidup yang dikembangkan pada saat ini. Berdasarkan hal tersebut di atas, maka sangat diperlukan adanya penyempurnaan dari peraturan Perundang-undangan yang berlaku saat ini. Di samping itu, diperlukan juga suatu peraturan Perundang-undangan yang merangkum segala macam peraturan yang ada ke dalam suatu pola berdasarkan prinsip-prinsip pengelolaan lingkungan yang sudah digariskan.

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Karena itu diperlukan adanya suatu Undang-Undang yang memuat ketentuan pokok mengenai lingkungan hidup secara keseluruhan. Asas pengelolaan lingkungan hidup berdasarkan UU No. 4 Tahun 1982 adalah pelestarian kemampuan lingkungan yang serasi dan seimbang untuk menunjang pembangunan yang berkesinambungan bagi peningkatan kesejahteraan manusia. Sedangkan tujuannya adalah (1) Tercapainya keselarasan hubungan antara manusia dengan lingkungan hidup sebagai tujuan pembangunan manusia Indonesia seutuhnya, (2) Tercapainya dan terkendalinya pemanfaatan sumber daya secara bijaksana, (3) Terwujudnya manusia Indonesia sebagai pembina lingkungan hidup, (4) Terlaksananya pembangunan berwawasan lingkungan untuk kepentingan generasi sekarang dan mendatang, (5) Terlindunginya negara terhadap dampak kegiatan di luar wilayah negara yang menyebabkan kerusakan dan pencemaran lingkungan. Pasal 1 Ayat (4) Undang-Undang No. 4 Tahun 1982 dirumuskan bahwa ekosistem adalah tatanan kesatuan secara utuh menyeluruh antara segenap unsur lingkungan hidup yang saling memengaruhi. Lingkungan hidup Indonesia adalah lingkungan hidup yang ada dalam batas wilayah Negara Republik Indonesia. Menurut Penjelasan Umum UU No. 4 Tahun 1982, lingkungan hidup dalam pengertian ekologi tidaklah mengenai batas wilayah negara ataupun wilayah administrasi. Akan tetapi kalau lingkungan hidup dikaitkan dengan pengelolaannya, maka haruslah jelas batas wewenang pengelolaan tersebut. Jadi konsep tentang lingkungan hidup Indonesia bukanlah konsep ekologi semata tetapi juga konsep hukum dan politis. C. Pencemaran dan Perusakan Lingkungan UU No. 4 Tahun 1982 membedakan istilah pencemaran lingkungan dengan perusakan lingkungan. Pencemaran lingkungan adalah masuknya atau dimasukkanya makhluk hidup, zat, energi, dan/atau komponen lain ke dalam lingkungan dan/atau berubahnya tatanan lingkungan oleh kegiatan manusia atau proses alam, sehingga kualitas lingkungan turun sampai ke tingkat tertentu yang menyebabkan lingkungan menjadi berkurang atau tidak dapat berfungsi lagi sesuai dengan peruntukannya. Sedangkan perusakan lingkungan adalah tindakan yang menimbulkan perubahan langsung atau tidak langsung terhadap sifat-sifat fisik atau hayati lingkungan, yang mengakibatkan lingkungan itu kurang atau tidak berfungsi, lagi dalam menunjang pembangunan yang berkesinambungan (Abdurrahman, 1986). Ada beberapa peraturan yang telah diatur oleh pemerintah dalam penanggulangan pencemaran dan perusakan lingkungan hidup, antara lain:

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1. Di Dalam Bidang Pertambangan Guna terwujudnya keserasian dan keseimbangan dalam mengelola pertambangan, telah dikeluarkan UU No. 11 Tahun 1967 tentang Pokokpokok Pertambangan. Dalam peraturan ini dikemukakan bahwa pekerjaan usaha pertambangan tidak boleh dilakukan di wilayah yang tertutup untuk kepentingan umum, dan pada lapangan dan bangunan pertahanan (Pasal 16 Ayat (1) UUPP). Pemegang kuasa pertambangan diwajibkan mengembalikan tanah sedemikian rupa, sehingga tidak menimbulkan bahaya penyakit atau bahaya lainnya bagi masyarakat sekitarnya, apabila selesai melakukan penambangan bahan galian pada suatu tempat pekerjaan (Pasal 30 UUPP). 2. Di Dalam Lingkungan Kerja Mengenai lingkungan kerja diatur dalam UU No. 14 Tahun 1969 tentang Ketentuan-ketentuan Pokok Mengenai Tenaga Kerja. Tiap tenaga kerja berhak mendapatkan perlindungan atas keselamatan, kesehatan, kesusilaan, pemeliharaan moral kerja serta perlakuan yang sesuai dengan martabat manusia dan moral agama (Pasal 9 UUTK). Kemudian dalam UU No. 1 Tahun 1970 Pasal 2 Ayat (1) dikemukan bahwa yang dimaksud dengan keselamatan kerja adalah dalam segala hal di tempat kerja, baik di darat, di dalam tanah, di permukaan air, di dalam air maupun di udara yang berada di dalam wilayah kekuasaan hukum Republik Indonesia. 3. Di Bidang Perindustrian Di dalam bidang perindustrian telah dikeluarkan UU No. 5 Tahun 1985 tentang Perindustrian. Yang dimaksud dengan industri adalah kegiatan ekonomi yang mengelola bahan mentah, bahan baku, barang setengah jadi dan/atau barang jadi menjadi barang-barang dengan nilai yang lebih tinggi penggunaannya (Pasal 1 angka 2). Dalam rangka melaksanakan kegiatan industri, pengusaha diwajibkan untuk mencegah dan menanggulangi terjadinya gangguan dan pencemaran terhadap tata lingkungan. Kepada pengusaha diwajibkan untuk menyusun rencana keadaan darurat (emergency plan) dalam rangka menanggulangi kemungkinan terjadinya perusakan dan pencemaran lingkungan akibat lepasnya sesuatu bahan atau zat yang berbahaya. Rencana keadaan darurat berisi tindakan-tindakan penanggulangan untuk membatasi, membersihkan serta meniadakan pencemaran-pencemaran oleh bahan atau zat yang berbahaya itu, diajukan kepada Dirjen Pembinaan Industri Departemen Perindustrian untuk mendapat pengesahan.

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Pencemaran dan perusakan lingkungan menimbulkan kerugian, dan kerugian ini dapat terjadi (1) Kerugian ekonomi dan sosial (economic and social injury), (2) Gangguan sanitari (sanitary hazard), (3) Gangguan keseimbangan dalam kehidupan manusia, terutama dalam hal menyangkut ekologi. Kerusakan dan pencemaran lingkungan dapat digolongkan kepada beberapa kelompok, yaitu: (1) Kronis, dalam keadaan ini kerusakan dan pencemaran lingkungan terjadi secara progresif tetapi prosesnya lambat, (2) Kejutan atau akut, dalam keadaan ini perusakan dan pencemaran lingkungan terjadi secara mendadak dan kondisinya sangat berat, (3) Berbahaya, terjadi kerugian biologis cukup berat, dan dalam hal ada radioaktivitas maka terjadi kerusakan genetis, (4) Katastrofis, di sini kematian organis hidup cukup banyak, organisme hidup menjadi punah sama sekali (Sutamiharja, 1978). Pembicaraan tentang ganti rugi tidak bisa dipisahkan daripada tanggung jawab dari pihak pencemar dan perusakan lingkungan. Dalam Pasal 27 UU No. 4 Tahun 1982 ditegaskan bahwa dalam beberapa kegiatan yang menyangkut jenis sumber daya tertentu, tanggung jawab timbul secara mutlak pada perusak dan/atau pencemaran pada saat terjadinya perusakan dan pencemaran lingkungan yang pengaturannya diatur dalam peraturan Perundang-undangan yang bersangkutan. Ketentuan tersebut di atas mengandung prinsip yang dinamakan “Strict Liability”, atau menurut istilah Komar Kantaatmadja (1977) disebut “asas tanggung jawab mutlak” dan menurut Munadjat Danusaputra (1980) disebut tanggung jawab secara langsung dan seketika. Istilah-istilah tersebut mengandung arti bahwa kewajiban membayar ganti kerugian timbul segera dan seketika terjadinya kerugian dengan tidak mempersoalkan salah tindaknya penyebab kerugian tersebut. Sistem pertanggungjawaban yang demikian, adalah merupakan penyimpangan dari sistem ganti rugi penh (absolute liability) yang dikenal dalam hukum perdata, yang mendasarkan adanya pertanggungjawaban berdasarkan pada kesalahan (liability based on fault). Mengingat luas wilayah negara kepulauan Indonesia yang dua pertiga merupakan lingkungan laut, serta letak geografis yang sangat strategis, maka pelaksanaan prinsip strict liability merupakan upaya dan langkah yang dapat lebih menjamin kepentingan Indonesia sebagai negara kepulauan dengan sumber daya lautnya (Kusnadi Hardjasoemantri, 1982). Dan mengingat pula akan manfaatnya yang sedemikian besar daripada prinsip ini, maka adalah wajar bilamana prinsip pertanggungjawaban dan ganti rugi ini dijadikan dasar bagi sistem hukum lingkungan nasional negara Indonesia. Jadi, masalah perusakan dan pencemaran lingkungan sebenarnya merupakan slah satu masalah saja dari problematika lingkungan yang lebih 228

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mendasar. Hal ini terjadi karena cara pengelolaan lingkungan hidup yang tidak terencana dan tidak terpadu secara serasi dan integral. Oleh karena itu, pengamanan masalah lingkungan hidup merupakan pengamanan terhadap masalah hukum secara menyeluruh (Dirdjosisworo, 1991). D. Islam dan Lingkungan Hidup Berbicara mengenai kesadaran dan sikap hidup manusia maka unsur motivasi yang ampuh adalah keyakinan agama. Bagi negara Indonesia yang sebahagian besar masyarakat memeluk agama Islam, maka keyakinan agama Islam merupakan motivasi yang sangat besar bagi masyarakat muslim di Indonesia ini. Dalam kitab suci Al-Qur’an dijelaskan bahwa Allah SWT telah menciptakan manusia dalam bentuk yang paling sempurna dan indah bentuknya (at-Tiin ayat 4). Ini berarti bahwa manusia adalah lebih sempurna dari hewan, tumbuh-tumbuhan, jin bahkan malaikat sekalipun. Hal ini disebabkan karena manusia dibekali Allah SWT dengan akal, perasaan, nafsu, dan syahwat, sedangkan makhluk-makhluk lain hanya dibekali sebagian unsur-unsur tersebut. Kemampuan potensial yang ada pada manusia adalah lebih mampu memikul amanah dari Allah SWT, sedangkan langit, bumi, dan gunung-gunung takut dan tidak mampu memikul amanah dari Allah SWT ini, hanya manusialah yang bersedia memikul amanah Allah SWT tersebut (al-Ahzab ayat 72). Sehubungan dengan hal tersebut di atas itu, maka kehadiran manusia di muka bumi ini adalah untuk memenuhi amanah Allah SWT itu. Dalam rangkaian surat Al-Qur’an banyak tersimpan petunjuk bahwa amanah Allah SWT itu mencakup kewajiban dan tanggung jawab sesama manusia dan juga terhadap alam sekitarnya. Untuk melaksanakan amanah dengan baik sebagaimana diharapkan oleh Allah SWT, maka sudah sewajarnya manusia terlebih dahulu mengenal apa dan siapa ia berkewajiban bertanggung jawab melaksanakan amanah itu. Oleh karena itu, yang terpenting adalah mengenal Allah SWT terlebih dahulu, mengenal diri manusia itu sendiri, mengenal sesama manusia lain dan juga mengenal alam ini. Manusia di dunia ini diharapkan oleh Allah SWT agar menjadi insan kamil, sebab hal itu akan membedakan dirinya dengan makhluk yang lain. Sebagai insan kamil dan anggota masyarakat, ia harus berbuat baik dan mengelak untuk berbuat jahat terhadap sesama manusia dan alam ini. Dalam menjalani hidup di dunia ini, manusia harus menjaga keseimbangan dan keselarasan, keseimbangan antara hidup akhirat dengan kehidupan hidup dunia, keseimbangan dalam berbuat baik bagi masyarakat dengan berbuat baik untuk diri sendiri. Manusia harus memelihara keseimbangan alam dalam ekosistem, dan harus mencegah terjadi kerusakan bumi (Emil Salim, 1980). 229

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Manusia diperintahkan oleh Allah SWT untuk mencari apa yang telah dianugerahkan kepadanya di muka bumi ini, tetapi Allah SWT juga memerintahkan agar manusia tidak melupakan tentang persiapan untuk kepentingan akhirat. Allah SWT selalu memerintahkan manusia agar berbuat baik sesama manusia dalam kehidupan di dunia ini, Allah SWT juga mengecam terhadap orang-orang yang berbuat kerusakan di muka bumi ini dan Allah SWT juga mengatakan bahwa terhadap orang-orang yang berbuat kerusakan di bumi ini adalah paling tidak disukainya dan terhadap orangorang itu akan dimasukkan ke dalam api neraka di hari akhirat nanti (alQashash ayat 77). Berdasarkan ketentuan tersebut di atas, Allah SWT menghendaki agar manusia dalam hidup di dunia ini haruslah menegakkan hidup yang berimbang antara hidup ukhrawi dengan hidup duniawi. Pedoman keseimbangan ini juga digariskan oleh Rasulullah dalam sebuah hadis, di mana dikemukakan bahwa beramallah wahai manusia untuk kepentingan hidup di dunia ini seolah-olah kamu akan hidup selama-lamanya, dan ibadahlah wahai manusia seolah-olah kamu akan mati besok pagi (Hadis Riwayat Bukhari dan Muslim). Keseimbangan yang diciptakan Allah dalam suatu lingkungan hidup akan terus berlangsung dan baru akan terganggu bila terjadi sesuatu keadaan luar biasa, seperti terjadinya bencana alam. Bencana alam ini ada yang berada di luar penguasaan manusia seperti gempa tektonik, banjir bandang, gelombang pasang, angin puting beliung, dan sebagainya. Tetapi kebanyakkan bencana itu terjadi akibat ulah tangan manusia itu sendiri. Allah SWT mengatakan bahwa telah tampak kerusakan di darat dan di laut yang disebabkan oleh tangan manusia, kemudia Allah merasakan kepada mereka akibat dari perbuatan itu agar mereka kembali ke jalan yang benar (ar-Ruum ayat 41). Menegakkan hidup dalam keseimbangan antara kepentingan ukhrawi dengan kepentingan duniawi, mengharuskan manusia menempatkan dirinya sebagai bagian dari lingkungan alam. Sungguhpun manusia dalam Surah AtTiin disebutkan sebagai makhluk yang terbaik, tetapi akan menjadi orang yang amat rendah derajatnya jika ia tidak beriman dan beramal saleh. Hidup berimbang merupakan perwujudan daripada pertumbuhan iman yang kuat dan sikap orientasi hidup untuk beramal saleh. Semakin seimbang perikehidupan manusia di dunia ini maka semakin terbuka kemungkinan ia akan menjadi insan kamil. Dalam kerangka pikiran inilah perlu dikembangkan hubungan manusia dengan lingkungan hidup. Menurut ekologi, memang tidak ada makhluk, baik tumbuhtumbuhan, binatang, dan manusia saling kait-mengait dalam suatu lingkungan hidup. Bila terjadi gangguan terhadap salah satu jenis makhluk 230

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akan terjadilah gangguan terhadap lingkungan hidup secara keseluruhan. Karena itu yang penting adalah keserasian antara ilmu dan iman, keserasian antara kepercayaan terhadap kemahakuasaan Allah ikhtiar manusia. Syariat Islam menghendaki agar manusia memanfaatkan alam ini dengan sebaikbaiknya dengan bertanggung jawab. Manusia harus hidup dengan keseimbangan antara ukhrawi dan duniawi dan juga imbang antara kehidupan ekologi. Apabila terjadi gangguan terhadap keseimbangan maka diperlukan tindakan-tindakan untuk mengembalikan keseimbangan itu seperti semula, yang membutuhkan biaya yang tidak sedikit. Oleh karena itu, perlu diambil langkah-langkah yang baik agar jangan sampai keseimbangan lingkungan hidup itu terganggu. Pendekatan secara ekosistem sangat dianjurkan oleh Syariat Islam di dalam melaksanakan pembangunan di segala bidang, karena hal ini dapat mencegah terjadinya pengaruh sampingan yang merugikan, yang pada hakikatnya merupakan beban yang harus dipikul oleh masyarakat. Dengan pendekatan seperti ini diharapkan akan memperoleh hasil optimal dari usaha-usaha pembangunan bagi peningkatan kesejahteraan masyarakat sepanjang masa. E. Sikap Syariat Islam terhadap Pencemaran dan Perusakan Lingkungan Bumi yang satu-satunya ini, telah diciptakan oleh Allah SWT dengan kekuasaan-Nya, dan diserahkan kepada manusia untuk dimanfaatkan demi kemaslahatan bersama. Bagaimanapun dan apa pun keadaan isi bumi ini, yang jelas tidak ada sesuatu yang diciptakan oleh Allah dengan sia-sia, asalkan dikelola dengan baik dan penuh keimanan untuk kebaikan manusia, tanpa itu semua, hanya kerusakan yang akan menimpa dunia ini. Oleh karena itu, maka hendaknya diusahakan agar jangan sampai bumi yang satusatunya ini rusak di tangan manusia. Sehubungan dengan hal tersebut di atas, Ronald Higgins (1978) menyimpulkan bahwa ada tujuh macam ancaman yang menghadang manusia saat ini, yaitu (1) Ledakan pendudukan yang tetap mengancam bumi. Diperkirakan bahwa dalam waktu kurang dari empat puluh tahun ke depan nanti, bumi yang satu-satunya ini harus menampung kenaikan jumlah penduduk dari empat miliar menjadi delapan miliar jiwa dalam ruang lingkup yang tidak berubah, (2) Kelaparan dan kekurangan gizi mengancam jutaan penduduk negara-negara berkembang dan belum ada tanda-tanda bahwa krisis ini dapat segera diatasi di masa yang akan datang, (3) Semakin langkanya sumber alam berhadapan dengan kebutuhan yang semakin meningkat, seperti minyak bumi, mineral, kayu, dan sebagainya, (4) Menurunnya kualitas lingkungan hidup sehingga semakin sulit menopang kehidupan manusia, (5) Ancaman nuklir yang berkembang di tangan lebih 231

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banyak terdapat pada sebagian bangsa tanpa kendali, (6) Pertumbuhan ilmu dan teknologi yang pesat di luar kendali manusia, (7) Runtuhnya moral manusia dengan kadar kesadaran yang rendah dan agak sulit diperbaiki. Untuk memecahkan permasalahan tersebut di atas, Ronald Higgins (1979) telah mencari jawabannya dengan mengemukakan bahwa hal tersebut bisa dipecahkan asalkan manusia dikembalikan kepada dimensi spiritual masing-masing, dimensi spiritual ini perlu dikembangkan agar manusia kembali kepada ajaran Tuhannya. Lebih lanjut Higgins mengemukakan bahwa satu etika kesadaran baru (new ethic of conscousness) harus ditumbuhkan dengan dimensi kehidupan spiritual yang mampu mematahkan pemujaan manusia kepada kehidupan sekuler, yang mampu membangkitkan kesadaran bahwa manusia sangat tergantung kepada bumi ini, dan perlu adanya manusia sangat tergantung kepada bumi ini, dan perlu adanya jalinan persaudaraan spiritual yang kukuh antara sesama manusia untuk memecahkan tantangan permasalahan tersebut di atas. Menurut ajaran Islam, permasalahan tersebut di atas, tidaklah sulit untuk mencari jalan pemecahannya sekiranya manusia taat atas petunjuk Allah SWT. Manusia harus menyadari bahwa segala sesuatu yang ada di dalam alam semesta ini adalah milik Allah SWT (al-Maa’idah ayat 117). Tetapi Allah SWT dengan kasih sayangnya telah memberikan hak kepada manusia untuk menfaatkan alam ini dengan sebaik-baiknya dan mengolah sumbernya untuk kemakmuran manusia (al-Baqarah 29). Sebagai makhluk yang memperoleh hak menggunakan alam ini, manusia haruslah mematuhi ketentuan-ketentuan yang diatur oleh pemiliknya yaitu Allah SWT. Manusia tidak berhak memanfaatkan dan menggunakan alam ini secara sembarangan dan bertentangan dengan ketentuan yang ditetapkan Allah SWT. Manusia sebagai khalifah Allah di bumi ini haruslah mempergunakan alam ini secara bertanggung jawab sesuai dengan amanah yang diberikan Allah kepadanya. Di antara ketentuan Allah SWT dalam memanfaatkan alam ini adalah (1) Jangan berbuat kerusakan atau bencana terhadap bumi, tanam-tanaman, dan keturunan (al-Baqarah ayat 125), (2) Jangan mudaratkan diri sendiri maupun orang lain (HR. Bukhari dan Muslim), (3) Jangan memperoleh harta atau kekayaan dengan jalan yang tidak halal (al-Baqarah ayat 168). Oleh karena itu, manusia dalam memanfaatkan alam ini hendaknya meminta petunjuk kepada para ahli, dan mematuhi petunjuk para ahli tersebut dalam berbagai bidang profesi ilmu pengetahuan (Al-Anbiya ayat 7). Allah juga memperingatkan manusia agar menghindari perbuatan-perbuatan yang buruk dan tidak mencelakakan sesama manusia. Dalam Islam telah ada ajaran untuk menggerakkan hati manusia agar tidak merusak lingkungan dan sumber alam ini. Dalam sebuah 232

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Hadis Rasulullah SAW memerintahkan pengikut-pengikutnya agar tidak membuang air kecil pada air yang tenang, atau air yang dipergunakan untuk keperluan hidup manusia, seperti mandi, cuci, dan sebagainya (HR. Bukhari dan Muslim). Dalam hadis ini terdapat petunjuk kepada semua orang Islam agar tidak mencemarkan air dan lingkungan hidup manusia. Jadi ajaran tentang memelihara lingkungan dalam Islam sudah ada sejak zaman Rasulullah SAW, hanya pemahamannya yang perlu dikembangkan. Dahulu ketika manusia masih sedikit pemahaman hanya ditujukan kepada air sumur saja, tetapi sekarang setelah manusia semakin banyak, dan kehidupan semakin kompleks maka pemahaman itu diperluas menjadi lingkungan hidup secara menyeluruh dan sangat perlu dijaga keseimbangannya. Sehubungan dengan hal tersebut di atas, maka sekarang perlu mengkaji kembali ajaran Islam tentang lingkungan hidup ini, agar agama Islam tetap menjadi rahmat segala zaman, baik dalam kehidupan di dunia ini maupun di akhirat kelak. Hal ini penting karena Islam diturunkan ke bumi ini adalah untuk menjadi rahmat sekalian alam (al-Anbiya ayat 207). Salah satu segi yang memerlukan pendalaman kembali paham Islam dalam masalah lingkungan hidup ini adalah masalah pencemaran dan perusakan lingkungan hidup yang meliputi pemeliharaan pemukiman dan sumber alam. Dalam memelihara lingkungan hidup dari perusakan dan pencemaran dari limbah industri, limbah pemukiman dan kota, limbah kendaraan bermotor, limbah pertanian dan pariwisata yang menyebabkan rusaknya perairan sungai, danau, udara, dan tanah, ajaran Islam memerintahkan agar manusia tunduk kepada peraturan-peraturan yang telah ditetapkan oleh para penguasa yang sah (ulu amri) sebagaimana dijelaskan dalam Surah an-Nisaa’ ayat 59 bahwa ada kewajiban taat kepada Allah, Rasul, dan penguasa yang sah di mana pun manusia itu berada. Kewajiban seorang warga negara terhadap negara sangatlah erat hubungannya dengan kewajiban warga negara kepada pemerintah. Inti dari kewajiban ini adalah bahwa seorang warga negara harus taat dan patuh kepada pimpinan negara, selama pimpinan negara itu patuh kepada Allah dan Rasul-Nya (al-An’am ayat 2). Selain dari itu, seorang warga negara diwajibkan untuk menjadi warga negara yang baik, selalu siap sedia membela kepentingan negara. Seorang warga negara berkewajiban menaati hukum dan peraturan Perundang-undangan yang berlaku. Sebaliknya penguasa negara berkewajiban menghormati, menghargai martabat warga negaranya dan bersifat adil (al-Maa’idah ayat 4 dan al-An’am ayat 8).

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F. Prinsip-Prinsip Hukum Islam dalam Penegakan Hukum Lingkungan Di dalam Al-Qur’an, Allah SWT melukiskan betapa hebatnya kerusakan-kerusakan dan kehancuran baik di darat maupun di laut sebagai akibat dari perbuatan dan ulah tangan manusia (ar-Ruum ayat 41). Dalam kaitan dengan sinyalemen Al-Qur’an ini, maka manusia diwajibkan untuk mengendalikan diri dan mencegah agar tidak terjadi kerusakan dan kebinasaan di muka bumi dan permukaan laut. Manusia wajib memelihara kelestarian lingkungan hidupnya, karena dengan demikian manusia telah memelihara kelangsungan hidup generasi penerusnya yang akan datang. Kewajiban untuk memelihara lingkungan hidup ini, tidak lain adalah kewajiban untuk melindungi kepentingan manusia sendiri, karena dalam perut bumi ini tersedia beraneka ragam sumber kehidupan yang bermanfaat untuk manusia. Dalam rangka memelihara keseimbangan dan keserasian hubungan mansia dengan alam, memelihara terwujudnya ketertiban dan kesejahteraan sosial sesama manusia, Hukum Islam menegakkan prinsip-prinsip yang wajib menjadi landasan dan titik tolak aktivitas kekuatan-kekuatan sosial, sehingga terjamin kehidupan yang teratur, seimbang, dan harmonis. Dengan demikian akan terjadi kehidupan di dunia dengan penuh kedamaian dalam suasana alam dan lingkungan yang baik, terjaminnya perkembangan dan gerak sosial secara stabil dan teratur. Tidak terjadi pencemaran dan perusakan lingkungan hidup yang menyebabkan hilangnya keseimbangan dan keserasian kehidupan di dunia ini. Di antara prinsip-prinsip yang ditegakkan Hukum Islam dalam menegakkan hukum lingkungan, sebagai berikut : 1. Prinsip Persamaan Hukum Islam mempersamakan derajat dan kedudukan manusia di hadapan hukum, yakni semua manusia diperlakukan secara sama di muka hukum (equality before the lawi), tidak ada perbedaan kasta dan tidak ada pilih kasih dalam ketetapan hukum. Setiap individu dalam masyarakat di hadapan hukum dipandang beridir sama tinggi, duduk sama rendah dan yang membedakan nilai dan derajat di hadapan hukum adalah takwa dan amal nyata (al-Ahqaaf ayat 19). Dalam hubungannya dengan pelaksanaan dan penegakan hukum serta pelaksanaan prinsip equality before the law di atas, Nabi Muhammad SAW mengingatkan kepada para pengikutnya dengan mengatakan bahwa orang-orang yang sebelum kamu hancur binasa, oleh karena apabila golongan elitenya mencuri mereka membiarkan saja pencurian tersebut, tetapi apabila rakyat biasa yang mencuri mereka tegakkan hukum itu atas orang-orang tersebut dengan sungguh234

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2.

sungguh. Demi Allah; Andaikata Fatimah binti Muhammad mencuri, pasti akan aku potong tangannya juga (HR. Abu Daud dan Nasa’i). Dari teks hadis tersebut di atas, maka dapat ditarik dua kesimpulan, yaitu (1) Bahwa pelaksanaan hukum harus dipersamakan pada setiap orang, atau dengan kata lain bahwa persamaan di hadapan hukum adalah hak setiap orang, (2) Melaksanakan persamaan di dalam hukum adalah kewajiban penguasa. Dalam hubungan ini satu hal yang perlu dijaga yakni para penegak hukum dalam melaksanakan asas persamaan hukum itu harus menghindari perbuatan zalim (aniaya) dan wajib menegakkan keadilan serta menempatkan manusia pada martabatnya (al-Maa’idah ayat 8). Manusia sebagai pribadi wajib diperlakukan sesuai dengan martabatnya sebagai manusia yang mempunyai kemuliaan. Oleh karena itu, penguasa tidak boleh memperlakukannya dengan sewenangwenang. Penguasa wajib memberikan perlakuan hukum yang sama secara adil kepada warga negara. Prinsip Keseimbangan Menurut Hukum Islam, dalam tata kehidupan di dunia ini harus selalu terpelihara kepentingan antara individu-individu secara seimbang dalam kehidupan masyarakat, antara kepentingan pribadi dan kepentingan orang lain, antara urusan perorangan dan urusan umum, antara urusan individu dan urusan bersama. Jika harus ditempuh dalam suatu hal antara kedua kepentingan itu, maka kepentingan umum wajib diutamakan. Dalam konsepsi Hukum Islam, masyarakat tiada lain adalah perbuatan individu-individu yang saling berhubungan dan tukarmenukar kepentingan hidup satu sama lain, sehingga individu membentuk masyarakat dan masyarakat membentuk individu. Jika individu-individu dalam masyarakat itu lebih baik, maka masyarakatnya pun baik pula, sebaliknya jika individu-individu itu jelek, maka masyarakat yang dibentuk menjadi jelek pula. Oleh karena itu, Hukum Islam berusaha mendidik dan memperbaiki individu dengan berbagai ketentuan hukum supaya masing-masing individu itu menjadi insaninsan yang baik dan bermoral saleh (Zahri Hamid, 1975). Menurut Hukum Islam, individu masyarakat haruslah bermanfaat bagi masyarakatnya, sebaliknya masyarakat haruslah bermanfaat bagi masing-masing individunya. Dalam kehidupan di dunia ini, individu haruslah hidup berimbang dengan kepentingannya untuk kehidupan akhirat nanti, sama sekali tidak membuat kerusakan di atas bumi dan harus tunduk kepada aturan hukum yang dibentuk oleh penguasa yang sah. 235

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3.

4.

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Prinsip Kemaslahatan Hukum Islam sangat mengutamakan kebaikan, kemanfaatan, kesejahteraan dan kebahagiaan hidup manusia, menjauhkan kemudaratan, kerusakan dan kesulitan hidup. Kemaslahatan hidup manusia itu, baik selaku manusia individu maupun selaku anggota masyarakat, baik kemaslahatan ukhrawiyah maupun kemaslahatan duniawiyah adalah merupakan inti daripada prinsip-prinsip yang ditegaskan dalam Hukum Islam. Bahkan kemaslahatan manusia itulah yang menjadi tujuan pokok Hukum Islam. Tujuan pokok Hukum Islam ialah merealisir kemaslahatan hidup manusia, dan kemaslahatan ini meliputi tiga graduasi, yaitu (1) Kemaslahatan yang mesti adanya dalam hidup manusia, yang disebut dengan kemaslahatan dlaruriyat yang terdiri dari kemaslahatan agama, kemaslahatan jiwa, kemaslahatan akal, kemaslahatan keturunan, dan kemaslahatan harta, (2) Kemaslahatan Hajiyat, yaitu kemaslahatan yang berhubungan dengan kebutuhan hidup manusia, (3) Kemaslahatan Tahsiniyat, yaitu kemaslahatan yang berkenaan dengan keindahan hidup (Zahri Hamid, 1975). Kemaslahatan yang bersifat individual disebut dengan kemaslahatan khusus, sedangkan kemaslahatan yang bersifat kemasyarakatan, atau yang menyangkut mayoritas anggota masyarakat disebut dengan kemaslahatan umum. Dalam kaitannya dengan pengelolaan lingkungan hidup, maka baik individu maupun masyarakat haruslah memerhatikan kemaslahatan tersebut agar kehidupan di bumi ini tidak terjadi pencemaran dan perusakan, yang pada akhirnya akan terjadi bencana kepada umat manusia. Tentang hal ini sungguh tidak diinginkan oleh ajaran Islam yang sangat memerhatikan kepentingan umat manusia di muka bumi ini, dan juga kehidupan di akhirat kelak. Prinsip Kegotongroyongan Hukum Islam selalu mengharapkan agar selalu terdapat rasa terpanggil pada diri individu-individu dalam masyarakat untuk ikut membantu, menolong, dan meringankan beban sesama individu dalam kehidupan bersama dalam masyarakat. Prinsip ini diharapkan terpencar dari hati nurani masing-masing individu secara murni, dan didorong oleh rasa kemanusiaan yang sejati, jauh dari motif pamrih dan tujuan materi. Dengan tertanam rasa kegotongroyongan dalam hati sanubari masing-masing individu, maka secara serta-merta tanpa diminta apabila terjadi sesuatu musibah dan bencana yang menimpa sesama manusia, untuk bersama-sama memikul dan mengangkat beban sosial dalam kehidupan bersama menurut bakat dan keahlian masing-masing. Menurut Hukum Islam, manusia adalah makhluk sosial, karena itu betapapun majunya modernisasi dan teknologi suatu bangsa, dan

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5.

betapapun majunya peradaban manusia, tetapi manusia dalam kehidupannya pasti memerlukan bantuan orang lain untuk menyeleksinya. Semakin majunya masyarakat dalam melakukan aktivitas hidup di dunia ini, maka semakin banyak pula problem sosial yang memerlukan penyelesaiannya secara kegotongroyongan. Bagi bangsa Indonesia, prinsip kegotongroyongan ini merupakan watak kejiwaan yang asli dan berlaku sejak zaman dahulu. Prinsip Keadilan Setiap pemangku hak akan memperoleh dan menerima haknya secara baik dan ia dilindungi mempergunakan haknya itu. Kebalikan dari keadilan adalah kezaliman, yaitu memperoleh hak tanpa atau secara tidak benar. Keadilan berlaku antara individu dengan individu, antara individu dengan masyarakat dan antara masyarakat dengan pemerintah. Keadilan hukum mengandung asas persamaan hukum atau disebut equality before the law. Setiap orang harus diperlakukan sama terhadap hukum. Dengan kata lain hukum harus diterapkan terhadap siapa pun juga secara adil. Keadilan hukum sangat erat kaitannya dengan implementasi hukum. Keadilan hukum tidak akan tercapai apabila hukum tidak diterapkan secara adil. Untuk mencapai penerapan dan pelaksanaan hukum secara adil diperlukan hukum bagi para penegak hukum untuk melaksanakannya dengan baik. Dengan demikian, untuk mencapai keadilan hukum, maka faktor manusia yang bertanggung jawab terhadap pelaksanaan hukum sangat penting. Apabila mereka melaksanakan tugas dan kewajibannya dengan penuh kesadaran dan tidak dapat dipengaruhi oleh siapa pun juga, maka tercapailah keadilan hukum itu. Konsep keadilan hukum menurut Al-Qur’an dikemukakan bahwa “Hai orang-orang yang beriman, hendaknya kamu jadi manusia yang lurus karena Allah, menjadi saksi dengan adil, janganlah kebencianmu terhadap satu kaum menyebabkan kamu berlaku tidak adil. Berlakulah adil, karena adil itu lebih dekat kepada takwa dan takutlah kepada Allah, karena sesungguhnya Allah sangat mengetahui apa yang kamu kerjakan” (Surah al-Maa’idah ayat 8, an-Nisaa’ ayat 133). Dalam hubungannya dengan keadilan hukum ini, ada tiga hal yang perlu disimpulkan, bahwa (1) Keadilan hukum merupakan pusat gerak dari nilai-nilai moral yang pokok, (2) Keadilan hukum adalah suatu yang legal, lurus, sesuai dengan hukum yang diwahyukan. Tercakup dalam pengertian ini bahwa keadilan hukum adalah sama dengan kebenaran atau disebut Ia justice est la justesse, (3) Di dalam pengertian keadilan hukum, terdapat konsep-konsep persamaan. Ketiga hal ini menggambarkan secara lengkap bagaimana konsep keadilan hukum menurut Hukum Islam. 237

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Dari uraian tersebut di atas, maka dapat dirumuskan bahwa Hukum Islam dalam membangun suatu masyarakat agar tidak terjadi kerusakan dan bencana yang dapat memusnahkan masyarakat itu, sangat diperlukan prinsip-prinsip tersebut di atas dilaksanakan dengan baik dan bertanggung jawab. Dengan demikian aturan tentang lingkungan hidup yang telah ditetapkan itu dapat berjalan sebagaimana mestinya, sehingga lingkungan hidup yang serasi dan seimbang dalam pertumbuhannya dapat terwujud sebagaimana yang diharapkan oleh semua umat manusia. Dalam rangka menunjang secara aktif dan positif terhadap pembangunan yang dilaksanakan di Indonesia ini, maka umat Islam diharapkan ikut berpartisipasi aktif melaksanakan pembangunan itu dengan mengamalkan prinsip-prinsip Hukum Islam sebagaimana tersebut di atas itu.

Daftar Pustaka Abdurrahman, SH., (1986). Pengantar Hukum Lingkungan Indonesia, Jakarta, Arika Media Cipta. BPHN Departemen Kehakiman, (1977). Seminar Segi-segi Hukum dari Pengelolaan Lingkungan Hidup, Bandung, Bina Cipta. Curzon, L.B., (1977). Criminal Law, Macdonald and Evans, Plymouth. Danusaputra, Munadjat, (1980). Hukum Lingkungan, Buku I dan II, Jakarta, Bina Cipta. Departemen Agama RI, (1977). Al-Qur’an dan Terjemahannya, Proyek Pengadaan Kitab Suci Al-Qur’an. Dirdjosiswono, Soedjono, Prof. Dr. SH., MBA., (1991). Upaya Teknologi dan Menegakkan Hukum Menghadapi Pencemaran Lingkungan Akibat Industri, Bandung, Citra Aditya Bakti. Hamid, Zahri, H. Drs., (1975). Prinsip-prinsip Hukum Islam tentang Pembangunan Nasional di Indonesia, Yogyakarta, Bina Cipta. Hamzah, A. Dr. SH., (1995). Penegakan Hukum Lingkungan, Jakarta, Arika Media Cipta. Hardjasumantri, Kusnadi, (1982). Prospek Hukum Lingkungan di Indonesia, Kuliah Umum pada MUNAS ISMAILI Universitas Brawidjaya Malang. Husein, Harun M., SH., (1992). Berbagai Aspek Analisis Mengenai Dampak Lingkungan, Jakarta, Bina Aksara. Kantaatmadja, Komar, Prof. Dr., (1977). Konvensi Internasional tentang Polusi Minyak di Laut, Bandung, Lembaga Penelitian Hukum dan Kriminologi Fakultas Hukum Universitas Padjadjaran.

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Mahkamah Agung RI, (1993). TAP-MPR RI No. II/MPR/1993 tentang Garis-garis Besar Haluan Negara Republik Indonesia, Proyek MARI. Salim, Emil, Prof. Dr. H., (1982). Laporan Menteri Negara PPLH, pada Presiden pada peringatan Hari Lingkungan Hidup tanggal 5/6/1982 Jakarta. Ibid., (1990). Islam dan Lingkungan Hidup, Makalah dalam majalah Al Jami’ah IAIN Sunan Kalijaga Yogyakarta, No. 24. Silalahi, Daud, Dr. SH., (1992). Hukum Lingkungan dalam Sistem Penegakan Hukum Lingkungan Indonesia, Bandung, Alumni. Soedjono, D., (1979). Penggunaan Hukum Terhadap Pencemaran Lingkungan Akibat Industri, Bandung, Alumni. Soeginto, Aprilani, (1976). Bibliografi Beranotasi tentang Lingkungan Laut dan Pencemaran Laut, Jakarta, Lembaga Oceanologi Nasional LIPI. Sutamihardja, RTM., (1978). Kualitas dan Pencemaran Lingkungan, Pascasarjana IPB Bogor. Usman, Rachmadi. Pokok-pokok Hukum Lingkungan Nasional, Jakarta, Akademika Essiondo.

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Agriculture, Ecosystems and Environment 187 (2014) 87–105

Contents lists available at ScienceDirect

Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee

Conservation agriculture and ecosystem services: An overview Cheryl Palm a,∗ , Humberto Blanco-Canqui b , Fabrice DeClerck c , Lydiah Gatere a , Peter Grace d a

Agriculture and Food Security Center, The Earth Institute, Columbia University, PO Box 1000, Palisades, NY, United States Department of Agronomy and Horticulture, University of Nebraska, Lincoln, NE 68583-0915, United States Agrobiodiversity and Ecosystem Services Program, Bioversity International, Via de Tre Denari 472/a, 00057 Maccarese, Rome, Italy d Institute for Future Environments, Queensland University of Technology, GPO Box 2434, Queensland 4000, Australia b c

a r t i c l e

i n f o

Article history: Received 12 February 2013 Received in revised form 29 August 2013 Accepted 22 October 2013 Available online 16 November 2013 Keywords: Carbon sequestration Greenhouse gas emissions Soil quality Soil biodiversity Tillage Residue management

a b s t r a c t Conservation agriculture (CA) changes soil properties and processes compared to conventional agriculture. These changes can, in turn, affect the delivery of ecosystem services, including climate regulation through carbon sequestration and greenhouse gas emissions, and regulation and provision of water through soil physical, chemical and biological properties. Conservation agriculture can also affect the underlying biodiversity that supports many ecosystem services. In this overview, we summarize the current status of the science, the gaps in understanding, and highlight some research priorities for ecosystem services in conservational agriculture. The review is based on global literature but also addresses the potential and limitations of conservation agriculture for low productivity, smallholder farming systems, particularly in Sub Saharan Africa and South Asia. There is clear evidence that topsoil organic matter increases with conservation agriculture and with it other soil properties and processes that reduce erosion and runoff and increase water quality. The impacts on other ecosystem services are less clear. Only about half the 100+ studies comparing soil carbon sequestration with no-till and conventional tillage indicated increased sequestration with no till; this is despite continued claims that conservation agriculture sequesters soil carbon. The same can be said for other ecosystem services. Some studies report higher greenhouse gas emissions (nitrous oxide and methane) with conservation agriculture compared to conventional, while others find lower emissions. Soil moisture retention can be higher with conservation agriculture, resulting in higher and more stable yields during dry seasons but the amounts of residues and soil organic matter levels required to attain higher soil moisture content is not known. Biodiversity is higher in CA compared to conventional practices. In general, this higher diversity can be related to increased ecosystem services such as pest control or pollination but strong evidence of cause and effect or good estimates of magnitude of impact are few and these effects are not consistent. The delivery of ecosystem services with conservation agriculture will vary with the climate, soils and crop rotations but there is insufficient information to support a predictive understanding of where conservation agriculture results in better delivery of ecosystem services compared to conventional practices. Establishing a set of strategically located experimental sites that compare CA with conventional agriculture on a range of soil-climate types would facilitate establishing a predictive understanding of the relative controls of different factors (soil, climate, and management) on ES outcomes, and ultimately in assessing the feasibility of CA or CA practices in different sites and socioeconomic situations. The feasibility of conservation agriculture for recuperating degraded soils and increasing crop yields on low productivity, smallholder farming systems in the tropics and subtropics is discussed. It is clear that the biggest obstacle to improving soils and other ES through conservation agriculture in these situations is the lack of residues produced and the competition for alternate, higher value use of residues. This limitation, as well as others, point to a phased approach to promoting conservation agriculture in these regions and careful consideration of the feasibility of conservation agriculture based on evidence in different agroecological and socioeconomic conditions. © 2013 Elsevier B.V. All rights reserved.

∗ Corresponding author. Tel.: +1 646 244 1724; fax: +1 845 680 4870. E-mail address: [email protected] (C. Palm). 0167-8809/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.agee.2013.10.010

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1. Introduction Provision of food is a primary function and key ecosystem service (ES) of agriculture. There is growing recognition that agricultural systems are both dependent on ES that support production functions and a source of important agricultural and non-agricultural ES. Ecosystem services are categorized as provisioning, regulating, supporting, and cultural. The level of delivery of the different services is determined by a combination of ecosystem properties, including soils, vegetation, and climate and the resulting ecological processes (Fisher et al., 2009). Agricultural intensification aimed at increasing production can affect ecosystem components and processes. Intensification can disrupt many of the regulating and supporting ES, including nutrient cycling, climate regulation, regulation of water quality and quantity, pollination services, and pest control (Fig. 1; Power, 2010). It can also alter the biological diversity underpinning many of these ES. While some agricultural practices can decrease ES delivery (tradeoffs) others can enhance or maintain ES (synergies). Increasing food production at the expense of ESs can undermine agroecosystem sustainability including crop production. Conservation agriculture (CA) is a system of agronomic practices that include reduced tillage (RT) or no-till (NT), permanent organic soil cover by retaining crop residues, and crop rotations, including cover crops. Together these practices aim to increase crop yields by enhancing several regulating and supporting ESs. Though CA was originally introduced to regulate wind and water erosion (Baveye et al., 2011), it is now considered to deliver multiple ES. This paper focuses on the effects of CA on selected ES such as climate regulation as related to soil carbon sequestration and greenhouse gas emissions and the provision and regulation of water and nutrients through modification of several soil properties and processes. The role of biodiversity, particularly soil functional diversity is also discussed, where possible. Pest and disease control and pollination are briefly mentioned. These ES were selected because they are the ones most likely affected by CA practices. Conservation agriculture was originally designed as a response to the US Dust Bowl (Baveye et al., 2011). Since then, the adoption of CA has been rapid, particularly in North America, South America, and Australia (Derpsch and Theodor, 2009). It is primarily practiced on large-scale, mechanized farms, and requires large applications of herbicides to control weeds that are normally controlled by tillage. There are now concerted efforts that are promoting CA in smallholder systems in South Asia (Hobbs et al., 2008) and Sub Saharan Africa (Valbuena et al., 2012). Whether CA, which was designed in high-input systems in more temperate regions, can work and deliver ES in smallholder systems of the tropics and subtropics is unclear and warrants further consideration based on the evidence to date. Over the past ten years numerous research papers and reviews have looked at the extent to which ES are generated through CA compared to conventional practices. Much of that research has focused on effects of RT and NT compared with conventional tillage (CT) where the effects of residue management and crop rotations are often confounded with tillage. Previous reviews indicate that CA can reduce water and wind erosion due to protection of the soil surface with residue retention and increased water infiltration and decreased runoff with NT (Verhulst et al., 2010). Benefits of CA on other ES including nutrient cycling, carbon sequestration, and pest and disease control are quite variable, from positive, to neutral or even negative depending on site-specific context, management, soil type, and climate. This paper summarizes the state-of-knowledge of CA and ES and highlights the gaps and questions needed to provide a more predictive framework for ES delivered through CA. The summaries are based on the global literature including the growing literature

on CA from smallholder farming systems, particularly Sub Saharan Africa and South Asia. The types of experiments installed for testing CA and comparing with conventional practices (tillage, residue removal or incorporation and monocultures) do not necessarily have the design required to separate the individual and combined effects of the different CA practices on ES. Comparisons often come from experiments that include one or two of the practices, with comparisons of tillage practices with residues being the most common. The approach we used examines each ES and how CA practices influence soil and plant processes and ES outcomes as described in Palm et al. (2007). We also discuss how ES relates to crop productivity, with an emphasis on situations where increasing regulating and supporting ESs do not compromise, but instead bolster, production functions. 2. Climate Regulation The ES of climate regulation refers to processes that contribute to or mitigate the build-up of greenhouse gases (GHG) in the atmosphere or other factors, such as albedo, that contribute to global climate forcing (Millennium Ecosystem Assessment, 2005). The net potential of CA to contribute to climate regulation and serve as a global warming mitigation strategy depends on the direction and magnitude of changes in soil C, nitrous oxide (N2 O) and methane (CH4 ) emissions associated with its implementation compared to conventional practices. Collectively this is assessed in terms of the global warming potential of the farming practices which are soil, climate and management dependent (Robertson and Grace, 2004). For example, if there is an increase in soil C that is greater than the combined increase in N2 O or CH4 emissions (expressed as CO2 equivalents), the net global warming potential decreases. 2.1. Soil carbon sequestration Soil C sequestration refers to the increase in C stored in the soil by capturing atmospheric CO2 as a result of changes in land use or management (Powlson et al., 2011b; West and Post, 2002). While CA was not initially conceived as a practice to sequester soil C, it is now considered as a potential technology to mitigate greenhouse gas emissions and has become a focus of CA research. Several reviews summarize the effects of the different component practices of CA on soil C stocks compared to conventional practices (Branca et al., 2011; Corsi et al., 2012; Gattinger et al., 2011; Govaerts et al., 2009; Grace et al., 2012; Lal, 2011; Luo et al., 2010; Ogle et al., 2012; Ogle et al., 2005; Six et al., 2002; West and Post, 2002). Though most studies report changes in soil C stocks or storage, an increase in soil C stocks does not necessarily represent sequestration or climate mitigation potential if there is not a net transfer of CO2 from the atmosphere. As discussed by Powlson et al. (2011b), such situations relevant to CA are if residue retention results in increased C storage in the CA field but a reduction in soil C where the residue had been sourced. These factors are not usually considered in CA studies. In addition, some consider soil C sequestration as that C which is held in the more recalcitrant or protected forms and thus less susceptible to losses from decomposition (Powlson et al., 2011b; West and Post, 2002). Most studies however just report on the changes in the total C stored and not the changes in the recalcitrant fractions. As such we will refer to the changes in soil C reported in the studies to indicate the potential for CA to serve as a net sink of atmospheric CO2 . 2.1.1. Factors and processes affecting soil carbon sequestration Simply put, soil C content is the balance between the C inputs and decomposition. Understanding and quantifying the factors and processes that determine C inputs and decomposition, however, is not simple but necessary to build the scientific evidence needed to

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Fig. 1. Diagram showing the potential ecosystem services in agricultural ecosystems and how they can be modified by different agricultural management practices and landscape structure. (from Power, 2010).

manage soil C. The abiotic and biological factors, soil and plant processes, and management practices influencing soil C formation and decomposition are reviewed by Giller et al. (2009), Govaerts et al. (2009), Powlson et al. (2011a), and others. Factors that increase biomass production and C inputs will increase soil C, as long as decomposition rates do not increase similarly. Climate (rainfall and temperature), soil type (texture and mineralogy), and nutrient and water availability are the primary determinants of biomass production and decomposition rates. The CA practices of crop rotations and surface residue retention are intended to increase C inputs relative to conventional practices and NT to decrease decomposition through increased soil aggregation and a protection of soil C from decomposers. The balance of those two processes and the resulting soil C will vary with soil, climate and other management practices. The potential changes in soil C are larger in tropical moist climates followed by tropical dry, temperate moist, and temperate dry climates (Ogle et al., 2005). Several of the studies which show lower soil C with NT than with CT attribute the lower soil C to cooler and wetter climates. The lower soil C is related to reduced crop yields and C inputs caused by lower soil temperatures under surface residue retention compared with CT systems (Ogle et al., 2012). The effects of nutrient and water availability on crop production, C inputs and decomposition can be managed through fertilization (mineral or organic inputs), weed and pest control, irrigation, crop rotations and intensification, tillage practices, and residue management. Nitrogen (N) fertilizer applications increase crop yields and the C inputs to soils but may increase rates of decomposition of C inputs and soil C (Chivenge et al., 2011). The net effect on changes in soil C storage depends on the balance between these processes. Studies have generally shown that applications of fertilizer N are associated with increased levels of soil C compared to no application of N (Powlson et al., 2011b; Ladha et al., 2011). A study by Ghimire et al. (2012) though did not show an effect of N fertilization. The amount of residues added in this study was limited to 4 Mg ha−1 , which may be insufficient level of inputs to shift the balance to net soil C storage in this subtropical environment with high rates of decomposition. Higher soil C with certain crop rotations has also been attributed to a positive N balance either through Nfixing legumes or N fertilization (Corsi et al., 2012). A need exists for a better process-level understanding of differential effect of N, P, and S fertilization on the direction and magnitude of changes in soil C storage (Lal, 2011).

The potential for storing soil C may decrease in water limitedregions due to differences in the balance of C inputs and decomposition (Blanco-Canqui et al., 2011); this potential can be increased through water management. While rainfall, temperature and management determine the balance between production and decomposition, soil properties determine the level of C sequestration for a given climate. The primary soil factors are texture, mineralogy, soil structure (aggregation) and depth. There are limits to the amount of C that soils can sequester; this soil C saturation potential is determined by soil texture (fine silt + clay), physical protection, and perhaps the biochemical composition of the organic inputs (Hassink, 1996, Six et al., 2002). Soils with a large C saturation deficit will sequester more C than those close to saturation. 2.1.2. Soil C sequestration and conservation agriculture summary of findings Tillage: Reduced-tillage or NT as a CA component may increase soil C compared with CT but these increases are often confined to near-surface layers (<10 cm). At deeper depths, soil C in CA may be equal or even lower compared with CT. The potential of CA for storing C is not conclusive. It depends on antecedent soil C concentration, cropping system, management duration, soil texture and slope, climate (Appendix A; Govaerts et al., 2009; Luo et al., 2010). More data are available from temperate (i.e., USA) than from tropical regions. Across 100 comparisons, soil C stock in NT was lower in 7 cases, higher in 54 cases and equal in 39 cases compared with CT in the 0- to 30-cm soil depth after 5 years or more of NT implementation (Appendix A; Govaerts et al., 2009). These studies were primarily from USA and Canada and some from Brazil, Mexico, Spain, Switzerland, Australia, and China. A meta-analysis found increased soil C in the topsoil (0-10 cm) on conversion of CT to NT but no significant difference over the soil profile to 40 cm due to a redistribution of C in the profile (Luo et al., 2010). A problem with the summary findings is that a majority of studies published prior to 2009 reported soil C on a fixed depth basis rather than equivalent soil mass basis which can overestimate soil C sequestration for the treatment with higher bulk density, which is usually the NT treatment. This is discussed in more detail at the end of this section. Crop rotations: Crop rotations have less effect on soil C than tillage (West and Post, 2002). Crop rotations can affect soil C by increased biomass production and C inputs from the different crops in the system or through altering pest cycles, diversifying rooting

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patterns and rooting depth. Experimental designs have confounded crop rotations with tillage making it difficult to make conclusions about the effects of rotations alone. Crop rotations effects on soil C are often mixed (Corsi et al., 2012). High-residue producing crops may sequester more C than crops with low residue input. Intensification of cropping systems such as increased number of crops per year, double cropping, and addition of cover crops can result in increased soil C storage under NT (West and Post, 2002; Luo et al., 2010). West and Post (2002) found interactions with crop rotations and tillage practice; in general, crop rotations sequestered more C than monocultures on conversion to NT, though there were notable exceptions with corn-soybean rotations with less soil C than monoculture maize. It is generally recognized that the differential effects of rotations on soil C are simply related to the amounts of above and below ground biomass (residues and roots) produced and retained in the system (West and Post, 2002). Unfortunately, few studies have measured or reported the residue inputs, particularly root biomass or rooting patterns, to better explain rotation effects. In Brazil, Boddey et al. (2010) attributed higher soil C storage in NT than CT to the inclusion of legume intercrops or cover crops in the rotations, and not due simply to higher production and residue inputs. They indicated slower decomposition of residues and lower mineral N in NT compared to CT result in higher root:shoot ratios and belowground C input with NT (Boddey et al., 2010). Residue retention: Retention of crop residues is an essential component of CA for increasing or maintaining soil C. Factors that increase crop yields will increase the amount of residue available and potentially soil C storage. Fertility management may be the single most important factor to increase residue production and ultimately increase soil C storage, whether the system is NT or CT or incorporates crop rotations (Giller et al., 2009). This will be important for increasing C inputs and soil C in low input-low productivity systems found in much of Sub Saharan Africa and parts of South Asia (Paul et al., 2013; Thierfelder et al., 2013b; Dube et al., 2012; Ghimire et al., 2012; Hillier et al., 2012). As a rough comparison using average regional yields (Hazell and Wood, 2008) and a harvest index of 50% for maize, farms in the US generate 10 Mg ha−1 of maize residue while 3 and 1-2 Mg ha−1 are produced in South Asia and Sub Saharan Africa, respectively. A study by Paul et al. (2013) in Kenya illustrates the point that limited amounts of residue input may have little or no effects on increasing soil C. They found no differences in soil C concentration between CT and RT when both tillage systems received 4 Mg ha−1 of residue for six years. A similar lack of response to 4 Mg ha−1 of residue after four years of application was also seen in a subtropical area of Nepal (Ghimire et al., 2012). Soil C storage is affected more by quantity than by the type or quality of organic inputs. The quality of the residues is determined primarily by the C:N ratio and can be modified by the amounts of lignin and polyphenolics in the material (Palm and Sanchez, 1991). Quality may affect short-term soil C storage and dynamics but does not seem to influence the longer-term C stabilization and storage in the soil (Chivenge et al., 2011; Gentile et al., 2011). The quality of the residues may, however, affect soil fertility and thus the amount of residues produced for C inputs. For example, materials with high C:N, characteristic of cereal crop residues, reduce the available N in the soil due to N immobilization and could result in lower crop production, while residues with high N contents and low C:N ratios, as is the case with many legume residues and legume cover crops, increase soil N availability and possibly crop production (Powlson et al., 2011b; Palm et al., 2001). The amount of crop residue retained after harvest, either on the soil surface or incorporated, is a key component to CA performance. Unlike most temperate zone agriculture and other large scale farming systems, where NT or RT results in high production

and retention of crop residues, residue produced in many small scale farms in Sub Saharan Africa, parts of Latin America and South Asia is not only low but also has many competing uses (Erenstein, 2002). The fate of residues depends on many factors including human and livestock population density, production potential of an area, and fodder markets, (Magnan et al., 2012; Valbuena et al., 2012; Tittonel et al., 2007). The majority of smallholders are mixed crop-livestock farmers who use most crop residues as fodder for livestock. In some areas crop residues are simply burned to clear agricultural fields (Ghimire et al., 2012), while, in other areas, residues are removed from fields by termites (Giller et al., 2009). Tillage, Crop Rotation, and Residue Retention Interactions: Previous literature on soil C stocks has often discussed effects of tillage, rotations, and residue management separately. It is important to recognize that these CA components interact. For example, the types of crops, intensity of cropping, and duration of the cropping systems determine the amount of inputs and thus the ability of CA to store more C than CT (Appendix A; Govaerts et al., 2009; Luo et al., 2010). Intensification of cropping systems with high above and belowground biomass (i.e, deep-rooted plant species) input may enhance CA systems for storing soil C relative to CT (Luo et al., 2010). Moreover, CA practices such as NT may not store more soil C than CT if they leave limited amount of residues. While it is clear that increasing amount of residues is essential for increasing soil C storage, interaction of residues with soil texture and soil microclimate (moisture and temperature) will ultimately determine rates of residue decomposition and soil C turnover and storage. These multiple and complex interactions that ultimately determine soil C storage make it difficult to identify clear patterns and trends needed for developing practical guidelines. Models can be useful in evaluating the contribution of different practices and processes to soil C storage. Models can simulate how the interaction among different levels of residue retention, fertility levels, soil temperature and other factors can affect crop yields, residue decomposition rates, and soil C storage under CA (Probert, 2007; Ogle et al., 2012). Several simulation studies (Leite et al., 2004, 2009; Apezteguía et al., 2009) have confirmed relatively small gains in soil under NT due to enhanced sequestration in the slow soil organic matter pool (Chang et al., 2013) Farage et al. (2007), while using CENTURY and RothC for estimating soil C changes with tillage practices, found a small increase in soil C with conversion to NT on sandy soils of West Africa. Ogle et al. (2012) used CENTURY to look at the effects of temperature on crop yields and decomposition rates in the US. They estimated that decreased soil C due to lower crop production with NT under cool temperatures were offset by lower decomposition rates; once the C inputs were reduced by more than 15%, however, there was a decrease in soil C. These modeling exercises can be used to look for these types of threshold effects and interactions among the CA practices in determining the primary factors affecting soil C storage in different environments. Care must be taken to assure that these models are first validated for the soil, climate and crops of interest and that they adequately reflect changes in soil C due to different management practices, especially tillage and residue placement. 2.1.3. Methods for assessing soil carbon stocks Given the current attention to the potential of agricultural practices to climate change mitigation through soil C sequestration, it is of utmost importance that C stocks are estimated correctly. Differences in methods used for measuring and comparing soil C storage among management practices can lead to different results. This is particularly true when bulk density (the mass of soil per unit volume; g cm−3 ) and soil profile distribution of C between CT and NT differ (Blanco-Canqui and Lal, 2008; Kettler et al., 2000; Table 1, Appendix A). Tillage results in fairly uniform soil C concentration (g C kg soil−1 ) throughout the plow layer while NT results in a C

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Table 1 Bulk density, cumulative soil mass, soil C concentration, cumulative soil C by depth for conventional till and no till treatments. a. Plaza-Bonilla et al. (2010), b. Du et al. (2010). ESM C = the equivalent soil mass C. A. Depth

Bulk density Tillage

Bulk density No Tillage

Cumulative soil mass: Tillage Mg ha−1

Cumulative soil mass No Tillage Mg ha−1

Soil C concentration Tillage g kg−1

Soil C concentration No Tillage g kg−1

Cumulative C mass Tillage Mg ha−1

Cumulative C mass No Tillage Mg ha−1

cm

g cm−3

g cm−3

5 10 20 30 40 ESM C

1.34 1.33 1.33 1.32 1.33

1.29 1.45 1.44 1.47 1.42

705 1,410 2,790 4,160 5,640

655 1,420 2,950 4,500 5,990

6.3 6.3 5.9 6.1 5.7

12.9 7.9 5.4 4.3 3.6

4.4 8.9 17.0 25.4 33.8 27.4

8.4 14.5 22.8 29.4 34.8 29.4

Depth

Bulk density Tillage

Bulk density No Tillage

cm

g cm−3

g cm−3

Cumulative soil mass Tillage Mg ha−1

Cumulative soil mass No Tillage Mg ha−1

Soil C concentration Tillage g kg−1

Soil C concentration No Tillage g kg−1

Cumulative C mass Tillage Mg ha−1

Cumulative C mass No Tillage Mg ha−1

5 10 20 30 40 ESM C

1.3 1.42 1.51 1.6 1.6

1.4 1.52 1.61 1.62 1.58

650 1,360 2,870 4,470 6,070

700 1,460 3,070 4,690 6,270

11.8 11.2 11 7.5 4

14 12 9.1 7 3.9

7.7 15.6 32.2 44.2 50.6 45.5

9.8 18.9 33.6 44.9 51.1 44.9

B.

concentration gradient with the highest C concentrations in the topmost layers. Most studies show lower bulk density in the plow layer of CT compared to NT (Appendix A). These differences in soil C concentrations and bulk density between NT and CT can affect estimates of soil C stocks and thus require methods that account for these differences to make valid comparisons. Methods for reporting soil C data have changed over time, initially with soil C reported simply in terms of % C or g C/kg in different soil depths. The advent of C sequestration research in the late 1980’s required the calculation of soil C stocks on an area or volume basis, Mg C ha−1 . Most C stocks were computed on a fixed depth basis, which consisted of multiplying C concentration by bulk density, area, and depth. Soil C reported on a fixed depth basis, however, can lead to incorrect conclusions when soil bulk densities differ among the management practices for the same depth interval. Ellert and Bettany (1995) illustrated the importance of reporting soil C on an equivalent soil mass (ESM) basis, rather than fixed soil depth (Fig. 2). There is now general agreement that soil C stocks should be compared using ESM but many studies still do not use it because of methodological difficulties. The result of using fixed depth rather than ESM is that reports of changes in soil C stocks are confounded by management-induced changes in bulk density rather than outright changes in stock.

Fig. 2. Illustration showing the differences between sampling a soil that is tilled or not tilled to a fixed depth or an equivalent soil mass basis (from Ellert and Bettany, 1995).

To illustrate this point, we compared soil C sequestration in CT and NT systems by the fixed depth and ESM methods for a 17 year study of a wheat-barley rotation in Spain (Table 1a; Plaza-Bonilla et al., 2010). The fixed depth method indicates that NT stored 4 Mg C ha−1 more than CT to a depth of 30 cm. If the ESM method is used, an additional 2.3 cm of soil (340 Mg ha−1 of soil) from the next depth increment is needed from the CT treatment to attain an ESM as that contained in the top 30 cm in the NT treatment. If a C concentration equal to the average between the 30 and 40 cm depths is used (5.9 g kg−1 ), the C in this additional mass of soil is 2 Mg ha−1 , reducing the difference between the two treatments from 4 to 2 Mg. Another example, using a 7 year wheat-corn rotation in China (Table 1b; Du et al., 2010), showed that CT had 0.7 Mg C ha−1 less than NT by the fixed depth method but CT had 0.6 Mg C more than NT by the ESM method (Table 1b). A number of ESM methods are available including the original method of Ellert and Bettany (1995), maximum and minimum ESM (Lee et al., 2009), cumulative mass coordinate (Gifford and Roderick, 2003), material coordinate system (McBratney and Minasny, 2010), and the most recent cubic spline method (Wendt and Hauser, 2013). Lee et al. (2009) compared the original ESM, maximum, and minimum ESM against the fixed depth approach and concluded that fixed depth approach is not appropriate and can be less accurate than simply reporting soil C concentration. They also showed that not all ESM methods yielded the same results. Wendt and Hauser (2013) compared the cumulative mass coordinates and cubic spline function against the original ESM method (Ellert and Bettany, 1995) and found that these three gave the same soil C results. While any ESM method is better than the fixed depth method, there are still some advantages and disadvantages among all ESM methods. To date, most researchers, if not all, have used the original ESM approach (Ellert and Bettany, 1995) but the cumulative mass coordinates and cubic spline function appear to have the best potential for more widespread use as these methods incorporate the bulk density measurement with the soil sampling and thus do not require a separate, tedious measurement of bulk density. Sampling depth is also critical for comparing CA with conventional practices. The IPCC reference depth is 30 cm (IPCC, 2006) but many advocate sampling deeper than 30 cm, even up to 100 cm (Baker et al., 2007; Blanco-Canqui and Lal, 2008; Boddey et al.,

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2010). Referring to the studies in Tables 1a and 1b, the soil C concentration and bulk densities among treatments do not differ after 30 cm layer in the study by Du et al. (2010), whereas the differences are still evident as deep as 40 cm in the study by (Plaza-Bonilla et al., 2010). Boddey et al. (2010) suggested that increasing sampling depth to 100 cm may in fact lead to reduced estimates of C sequestration in NT in temperate systems but may increase estimates on NT in the well-structured Oxisols of the tropics and subtropics. In summary, for the purposes of comparing soil C stocks of different soil management and tillage systems and the prominence given to soil C sequestration as a climate mitigation strategy, we recommend: Sampling and reporting soil C on an ESM basis either with the original ESM or cumulative mass coordinate/cubic spline method and sampling to a depth of at least 50 cm plus 10 cm to adjust for ESM if needed. Revising the IPCC protocol to compare C stocks on an ESM basis to a depth of 50 cm. The IPCC protocol currently used the fixed depth method and has a reference depth of 30 cm (IPCC, 2006) and may not capture the C changes resulting from management practices. 2.1.4. Summary, information gaps and research recommendations 1. Earlier reviews indicated that CA had considerable potential for storing soil C (West and Post, 2002; Lal, 2004). This optimistic view has been scaled back and it is now recognized that soil C storage with CA practices compared to conventional shows considerable variation, including some studies showing a decrease in soil C with CA. It is not clear for those studies that showed increased soil C with NT what factors differentiate them from the studies that do not show increases. As mentioned earlier, those determining factors can be climate, soil type, amount of residues, type of crops included in rotations, duration of the study or other factors. Achieving a predictive understanding of the impacts of CA practices on soil C requires an integrated approach that links crop production to generation of inputs of crop residues and roots, and finally to soil C formation and decomposition. Unfortunately there is a lack of information provided in most CA studies or studies comparing different CA practices such as detailed soils information, the amount of residues returned or cover crop biomass, root biomass and rooting patterns, all of which are necessary to understand the factors and processes resulting in the observed soil C storage differences with CA. This lack of supporting data hinders a predictive understanding of where and under what management practices CA results in increased soil C storage, though some general insights are emerging. Future studies should follow standard data collection in CA experiments (Brouder and Gomez-Macpherson, 2013). 2. The amount of residues retained in the system is key component to the amount of C stored in the soil but there is little indication of the amount of residues needed to maintain or increase soil C. Data on the amount of residue produced and how it is managed should be linked to crop productivity levels to allow for predictive capabilities through simple relationships or for use in detailed process models. The amount of residues required to increase soil C and benefits derived from it depends on the crop types, yields obtained, and the balance between C inputs and decomposition which vary with soils and climate. Soil C models should be used more to understand these complex interactions and the relative importance of the different factors. 3. There are relatively few studies on C sequestration from low input, smallholder farming systems in tropical regions, limiting the ability to assess the effectiveness and feasibility of CA under these circumstances. We compiled ten studies from Sub Saharan Africa, only four met the criteria of sampling to at least 30 cm and a duration of 5 years or more but they only reported %C and not bulk density. A review of soil carbon sequestration in Africa by

Vagen et al. (2005) was only able to report results to a depth of 10 cm, the most common sampling depth. The lack of longevity (> 5 years) and sampling problems does not allow valid comparisons of soil C sequestration of CA and conventional practices. On-going experiments should be maintained and resampled using the methods recommended in this paper. New experiments should be commenced replicating smallholder management in strategic agro-ecological zones. These new experiments should also reflect different levels of residue inputs and N fertilization rates to reflect current practices and increased rates that are required increasing yields in the region. 4. Using ESM soil sampling methods is essential for measuring and comparing soil C stocks between CA and conventional practices, especially when comparing different tillage practices. Comparing different ESM methods is needed to develop a simple, standard, and unbiased recommendation. We also recommend recalculating soil C stocks according to ESM methods as was shown in Table 1, as existing data permits. The current summary is likely biased to include more studies with significant C storage due to the fixed depth method. 2.2. Climate regulation – emissions of greenhouse gases In this section we deal with the net emissions of N2 O and CH4 from soils as a result of CA practices. It is also important to note that there can be considerable impacts of CA compared to conventional agriculture with changes in the intensity of mechanical tillage, less irrigation, and possibly less N fertilization and the associated reduced use of fossil fuels with CA (Pathak, 2009; West and Marland, 2002). These effects are not considered in this paper. 2.2.1. Nitrous oxide N2 O is a potent and long-lived GHG, having a global warming potential 298 times that of carbon dioxide (CO2 ) and remaining in the atmosphere for up to 114 years. N2 O is produced in soils in the microbiological processes of nitrification and denitrification. Nitrification - the oxidation of ammonium to nitrate - occurs in aerobic conditions while denitrification - the reduction of nitrate (NO3 − ) to N2 O and N2 - takes place in anaerobic conditions. The relative contribution of these two N pathways to N2 O formation depends on episodic changes in soil aeration and water filled pore space (WFPS). The frequency and magnitude of N2 O emissions is linked to soil structure which is a function of bulk density, soil C and aggregation, all influenced by tillage practices and residue inputs. Nitrification is the main source of N2 O at low WFPS below 40% (Dalal et al., 2003; Kiese et al., 2002; Werner et al., 2006) while the contribution from denitrification increases above 65-75% WFPS. The N2 /N2 O ratio increases with little N2 O produced at WFPS above 80-90% (Weier et al., 1993; Dalal et al., 2003). Soil bulk density is generally higher with NT compared to conventional practices; therefore, WFPS is higher so anaerobic conditions and denitrification are potentially induced sooner at the same water content with NT. Residues management and crop rotations can affect N2 O emissions by altering the availability of NO3 − in the soil, the decomposability of C substrates (Firestone and Davidson, 1989). The reduction of N2 O to N2 is inhibited when NO3 − and labile C concentrations are high (Hutchinson and Davidson, 1993; Weier et al., 1993; Senbayram et al., 2012). The retention of crop residues and higher soil C in surface soils with CA play major roles in these processes. Under anaerobic conditions associated with soil water saturation, high contents of soluble carbon or readily decomposable organic matter can significantly boost denitrification (Dalal et al., 2003) with the production of N2 O favored with high quality C inputs (Bremner, 1997).

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Emissions of N2 O increase with applications of N fertilizers by increasing N availability in the soil (Davidson, 2009). The quantity and quality of residues or cover crops of CA systems can also affect N2 O emissions. Legume residues can result in higher N2 O–N losses (Baggs et al., 2000; Huang et al., 2004; Millar et al., 2004) than those from non-legume, low N residues (Aulakh et al., 2001; Millar et al., 2004; Yao et al., 2009). The N2 O emissions with legume Nrich residues compared to N mineral fertilizers, however, is lower per unit N added compared to the inorganic source (Baggs et al., 2000). One the other hand, low quality cereal crop residues (C:N ratio generally greater than 25) combined with surface application of residues in CA systems could result in immobilization of N and ultimately decreased N2 O production compared to conventional systems. Though legume residues may lead to higher N2 O emissions than cereal residues the quantity of legume residues returned to soil is substantially less (Peoples et al., 2009). The net result of CA on N2 O emissions will depend on the crop rotation practices and the types and amounts of crop residue in CA systems compared to conventional. There is no clear response on the effects of NT or RT compared to CT on N2 O emissions (Snyder et al., 2009). With NT, residues are returned to the soil resulting in surface mulches which may lower evaporation rates and hence increase soil moisture and increase labile organic carbon C (Galbally et al., 2005) and consequently increase N2 O emissions compared to CT. Increased bulk density with CA compared to CT may also increase emissions. On the other hand, lower soil temperatures and better soil structure under NT may reduce the incidence of soil saturation and reduce emissions of N2 O. Evidence from the field shows wetter soil conditions combined with higher available C under NT increase emissions of N2 O (Liu et al., 2006; Regina and Alakukku, 2010; Venterea et al., 2005; Yao et al., 2009). Studies in Australia show large effects of tillage with 0.13% and 15.4% of applied NO3 − lost as N2 O from CT and NT, respectively (Dalal et al., 2003). Other studies have reported lower N2 O emission under NT or RT (Almaraz et al., 2009; Mutegi et al., 2010; Pandey et al., 2012; Smith et al., 2012; Ussiri et al., 2009; Wang et al., 2011) or no difference in emissions (Bavin et al., 2009; Fuss et al., 2011; Garland et al., 2011; Lee et al., 2009; Oorts et al., 2007; Pelster et al., 2011). Rochette’s (2008) extensive summary concluded that NT only increased N2 O emissions in poorly aerated soils. Interestingly, many of the studies showing no difference include a high proportion of longer term trials where CA practices have been imposed for considerable periods of time. This observation is consistent with Six et al. (2004) who found N2 O emissions from NT declined with time. The inconsistent results of N2 O emissions with CA practices are potentially due to the lack of comparability of studies and methodological issues on the measurement of N2 O in the field. These issues include 1. a lack of long-term observations at any site, most studies are single season or from one year of measurements, 2. the high temporal and spatial variability in N2 O, and to a lesser extent CH4 , emissions, and, 3. problems associated with chamber based field methodologies. For example, sampling frequency varies from several days to one month with interpolation to develop seasonal N2 O emissions estimates. Annual N2 O emission estimates can be overestimated by nearly 200% if measured only every 30 days (Rowlings et al., 2013) as highly significant episodic events are missed. Fuss et al. (2011) observed consistently lower background emissions in NT to CT but consistently higher emissions in NT till during the high magnitude episodic events. The diurnal patterns of emissions are also not captured in most chamber based studies. 2.2.2. Methane Methane has a lifetime of 12 years and a global warming potential 25 times that of CO2 over a 100 year time horizon. Agricultural

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soils contribute to CH4 emissions as a result of methanogenic processes in waterlogged conditions that are usually associated with rice production. Flooded rice production contributes 15% of total global CH4 emissions (IPCC, 2001). The magnitude of CH4 emissions is primarily a function of water management with the addition of both mineral and organic fertilizers having a significant influence. The addition of organic fertilizers has the potential to increase emissions by over 50% relative to non-organic fertilizers (Denier van der Gon and Neue, 1995; Yagi et al., 1997; Yao et al., 2009). In contrast to N2 O (Chapuis-Lardy et al., 2007), CH4 can be consumed (oxidized) by soil microorganisms and resulting in a CH4 sink which is sensitive to both temperature and soil water content (Dalal et al., 2008; King, 1997). The total CH4 flux from soils is therefore the difference between the production of CH4 under anaerobic conditions and CH4 consumption. Agricultural soils, particularly those that have been fertilized, have a significantly lower CH4 oxidation rate compared to natural soils (Bronson and Mosier, 1993; Jacinthe and Lal, 2005; Smith et al., 2000) and higher oxidation rates are observed in temperate compared to tropical soils (Dalal et al., 2008). The effect of tillage practices on the rate of CH4 consumption, in general, depends on the changes in gas diffusion characteristics in soil (Gregorich et al., 2006; Hutsch, 1998). A decrease in CH4 consumption and a potential net emission of CH4 could be expected with RT or NT due to increased bulk density and WFPS. Yet no significant tillage effect on CH4 oxidation rates have been detected (Bayer et al., 2012; Jacinthe and Lal, 2005; Smith et al., 2012). Evidence supporting a decrease in CH4 oxidation or an increase in CH4 emissions with crop residue retention under CA is more conclusive than for N2 O. Residue retention provides a source of readily available C, which enhances CH4 emissions from rice paddies which are generally under anaerobic conditions (Cai et al., 1997; Watanabe et al., 1995; Zou et al., 2005). Crop residues may affect CH4 oxidation in upland soils and emission patterns in flooded soils differently depending on their C/N ratio; residues with a high C/N ratio have little effect on oxidation while residues with a narrow C/N ratio seem to inhibit oxidation (Hiitsch, 2011). Flooded rice (with the practice of puddling the soil) is a large contributor of CH4 emissions from agriculture. Reduced or NT is currently being promoted in the Indo-Gangetic Plains (IGP) in ricewheat systems (Gathala et al., 2013) With this system, direct-drill seeded rice does not require continuous soil submergence, thereby could either reduce or eliminate CH4 emissions for lowland rice when it is grown as an aerobic crop (Pathak, 2009). The overall impact of RT in this environment, however, appears to be relatively minor. Grace et al. (2012) estimated an average of 29.3 Mg ha−1 of GHGs emitted over 20 years in conventional rice-wheat systems across the IGP; this decreased by only 3% with the widespread implementation of CA. 2.2.3. Summary, information gaps and research recommendations 1. The lack of definitive conclusions and contradictory findings on N2 O emissions from CA compared to conventional practices highlights the multitude of factors that effect N2 O emissions. Some of the factors that increase N2 O emissions also lead to increased CH4 emissions or decreased CH4 oxidation yet the thresholds and management practices to mitigate these different gas emission pathways are not necessarily the same. Studies examining the impact of different CA practices on all relevant GHGs, including soil C sequestration, and the resulting net global warming potential are rare, yet such studies are crucial for developing comprehensive management options for climate change mitigation in different environments. One of the few comprehensive studies over multiple years (Dendooven et al., 2012a, 2012b) found no differences in either N2 O or CH4 emissions between CA and CT in a long term

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dryland cropping trial in central Mexico. CA was found to have a significantly lower global warming potential in comparison to CT due to the changes in soil C alone. Datasets from such studies are needed to investigate the relative roles, interactions and impacts of residue management, tillage, cropping systems, and nutrient management on soil physical and chemical properties and the resulting GHG emissions and crop yields for different climate and soil types. The current information is fragmented and poorly documented and its interpretation is potentially confounded due to the lack of information on the major controlling variables. These datasets should be coordinated with on-going CA trials and other crop-soil simulation initiatives to ensure maximum utility and cost-effectiveness. An more mechanistic understanding of soil N dynamics with CA could lead to improved management strategies which increase N use efficiency and reduce N2 O emissions (and N losses generally). In particular, the net emissions related to the types (quality) and amounts of inputs from crop residues or different rotations with cereals and legumes and cover crops as they affect N and C availability and N2 O and CH4 emissions needs to be elucidated for selection of the rotations and residues types that minimize net emissions while not compromising yields. Improved understanding of management strategies that alter the N2 O/N2 ratio could also prove effective in mitigation combined with improved N use efficiency. Management strategies that can be aligned with NT to keep soil in the oxidative state and promote aerobic organic matter decomposition are potential mitigation strategies for reducing CH4 emissions (Ortiz-Monasterio et al., 2010). Reducing the duration of flooding is also being promoted as a practical solution to reduce CH4 emissions in CA rice production systems generally, but these may be offset partially by an increase in N2 O emissions (Ortiz-Monasterio et al., 2010). 2. Periodic sampling methods commonly used for measuring greenhouse gas emissions can lead to incorrect estimates and increase the uncertainty surrounding the impact of CA practices. Advances in the use of low cost portable, automated chamber and analysis systems in recent years is tackling many of these sampling related problems (Rosenstock et al., 2013; Rowlings et al., 2012; Scheer et al., 2012a,b; Werner et al., 2006; Butterbach-Bahl et al., 2002). Such systems should be included in future CA gas emission studies.

3. Soil quality, biodiversity and the regulation and provision of water and nutrients Many ecosystem processes and ES are provided by soils and the biodiversity in them (Palm et al., 2007; Wall et al., 2004; Daily et al., 1997). Soil quality refers to a range of soil properties and functions that support plant productivity and ES (Oberholzer and Hoper, 2007; Karlen et al., 1997) and is assessed by soil biological, physical, and chemical means. Many soil quality properties are determined, in part, by soil texture and mineralogy but can be modified by soil organic matter (SOM) content and composition and the activities of soil biota (Palm et al., 2007) both of which are affected by management practices (Oberholzer and Hoper, 2007). A review by Verhulst et al. (2010) provides a detailed assessment the effects of CA practices on soil quality compared with conventional practices. The reader is referred to this comprehensive review; a brief summary of the general trends is presented below and in Table 2. Verhulst et al. (2010) has been augmented by more recent research on CA and soil quality. The summary below follows the effects of CA on water and nutrient cycling and retention through changes in the biological, physical, and chemical aspects of soil quality.

3.1. Soil biological properties and ecosystem services Soil organic matter is an integrator of several soil functions and as such is a key component of soil quality and the delivery of many ecosystem services (Palm et al., 2007). The CA practices of NT and residue retention are key to maintaining or increasing SOM in the topsoil which in turn provides energy and substrate for soil biota activities and their contributions to soil structure and nutrient cycling, as well as many other soil processes and ES (Brussaard, 2012). In general, CA practices increase SOM and other soil biological properties (Table 2a). These effects are, however, generally confined to the topmost soil layer (0-5 cm or 0-10 m) but are often not evident over 0-15 cm (Bissett et al., 2013; Verhulst et al., 2010). These differences in SOM concentrations and distribution combined with lack of soil disturbance and crop rotations affect the abundance, diversity, community composition, vertical distribution within the soil profile, and activities of soil biota. These effects have concomitant changes in decomposition, nutrient cycling, bioturbation, soil aggregate stability, and other soil ecosystem services (Bignell et al., 2005). Biodiversity is often considered fundamental to the delivery of ES and especially the stability of delivery of these ES (Naeem et al., 2012). These relationships between biodiversity and ecosystem functions and services are complex; providing evidence and predictive understanding has been difficult (Naeem et al., 2009). CA alters below and above ground species differentially than conventional agricultural practices (McLaughlin and Mineau, 1995). This alteration in species drives a range of responses among different groups of organisms but most have greater abundance or biomass and diversity in NT than in conventional tillage (Table 2a; Gonzalez-Chavez et al., 2010; Rodriguez et al., 2006). These changes likewise have important effect on components of soil quality that are biologically mediated. In order to elucidate the contribution of biodiversity to service provision it is often grouped into pseudo functional groups based on body size and gross function (Kibblewhite et al., 2008; Bignell et al., 2005). Although these classifications mask important distinctions, they are useful to categorize information on soil biota especially when the taxonomic status is unclear and difficult to classify. More importantly it is the function of the biota that is important for ecosystem services rather than the taxonomic status. Soil microbial biomass, composed primarily of bacteria and fungi, is an indicator of soil quality due to its role in decomposition, nutrient cycling rates and patterns, formation of SOM, and soil aggregation. Microbial biomass is generally higher with residue retention. Reduced tillage is a secondary factor. Some authors have stated that fungal communities tend to dominate the soil surface of NT, whereas bacterial communities dominate in conventional tillage systems (Verhulst et al., 2010). This difference results in slower rates of nutrient mineralization and higher nutrient use efficiency with surface residue retention compared to conventional systems. Other long term studies however were not able to identify this shift between fungi and bacteria (Helgason et al., 2009) with minor overall impacts on decomposition and nutrient availability more likely (Bissett et al., 2013). The impacts of a shift in microbial composition may become more important on degraded soils (Verhulst et al., 2010). Fungi, particularly arbuscular mycorrhizal fungi, are also important for nutrient acquisition and drought resistance, particularly for low nutrient input systems. They also play a key role in forming stable soil aggregates. Hyphal length is shortened with tillage so the effects on aggregation and nutrient and water acquisition would be higher in CA compared to conventional (Oehl et al., 2005). Earthworms play a significant role in maintaining soil structure and nutrient cycling by their movement through the soil, by breaking down litter, and by binding soil particles with their excrement. They create stable soil aggregates as well as macropores,

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Table 2 Soil properties and processes as related to a) physical properties and processes and related water provision and regulating services, b) soil chemical processes related to nutrient cycling and retention, and c. soil biological properties as related to nutrient cycling, water infiltration, and pest control. The information is summarized from Verhulst et al. (2010); columns compare the properties, processes and ES between no-till (NT) and conventional tillage (CT) and surface residue retention vs no surface residue placement. a. Soil biological properties and processes

NT compared to CT

Residue retention

Soil organic matter in topsoil Particulate or labile organic matter fractions Soil microbial biomass Microbial functional diversity Fungal populations Enzymatic activity Beneficial micro-organisms (fluorescent Pseudomomas; Actinomycetes, some Fusarium strains) Pathogenic micro-faunal: Take-all Gaeumannomyces; Rhizoctonia, Pythium, and Fusarium root rots Free-living (beneficial) nematodes Plant-parasitic nematodes Earthworms Arthropod diversity

↑ ↑ ↑ ↑ ↑ ↑ ↑

↑ ↑ ↑ ↑ ↑ ↑ ↑

↑

↑

ns ↓ ↑ ↑ more so for predators then phytophagous arthropods

↑ ns ↑ ↑

b. Soil physical properties, processes and ecosystem services

NT compared to CT

Residue retention

Aggregate stability Bulk density Total porosity Macropores Mesopores Micropores Hydraulic conductivity Infiltration Runoff Evaporation Plant available water Erosion

↑ ↑ but small number of studies showing opposite ↓ ↓↑ avg size larger ↑ ↑ ↓ mixed results ↑ ↓ ↓ ↑ ↓

↑ ↓ ↑ ↑

↑ ↑ ↓ ↓ ↑ ↓

c. Soil chemical properties, processes and ecosystem services NT compared to CT Total nitrogen Nitrogen availability (N mineralization) P, K, Ca, Mg Cation exchange capacity pH Nutrient leaching

Residue retention

↑ follows pattern of soil organic matter generally ↓ at least in the short term and often long term P ↑ in top soil layer. K ↑ in surface layers, in general. Ca, Mg few differences no effect more often ↓ ??

both critical for soil and air movement, and they decompose and ingest organic materials increasing nutrient availability in soils. Earthworms are divided into three broad functional groups and size classes, the presence of all three appear necessary for maintaining soil structure (Verhulst et al., 2010). Reduced tillage and residue retention are both important for maintaining a stable environment (less physical disruption and higher soil moisture content, respectively) that favors earthworms, which are found to have higher abundance and diversity with CA compared to conventional systems (Table 2a; Nieminen et al., 2011). Differences in the composition of the earthworm community likely result in larger and more connected soil macropores in the CA system compared to conventional, with concomitant impacts on water infiltration and water regulation. A predominance of the large size class of earthworms can result in surface sealing and decreased infiltration (Verhulst et al., 2010). 3.2. Soil physical properties and ecosystem services: water infiltration, runoff-erosion, water quality and available water Erosion control is a main objective of reduced tillage and residue retention, contributing to both on-, and off-site ecosystem services. Reduced or NT and surface applied residues directly reduce

↑ ↑↓ depends on quality of residues K depends on type of crop residue ↑ but only in very top layer ↓ ??

erosion by minimizing the time that the soil is bare and exposed to wind, rainfall and runoff. CA and NT can reduce wind erosion due to the larger proportion of dry aggregates, less wind erodible fraction and greater crop residue cover of the soil surface (Singh et al., 2012; Verhulst et al., 2010). CA can also indirectly reduce erosion by water through the effects on soil properties and processes that increase water infiltration and reduce runoff. A summary of these effects show which soil physical properties are responsive to tillage and residue management (Table 2b). No-till management generally increases bulk density of the topsoil, reduces total soil porosity, and even hydraulic conductivity compared to CT systems. These changes would be expected to lower water infiltration rates in NT compared to CT; this however has not been shown–instead an increase in infiltration has been reported with NT. When residues are removed the reverse trend is observed (Kahlon et al., 2013; Verhulst et al., 2010). These somewhat contradictory effects of increased bulk density and reduced porosity but increased infiltration are likely due to the increased organic matter and biotic activity in the surface soil with surface residues and NT which lead to increased stability of soil aggregates and greater macropore connectivity from macrofaunal activity. Increased water infiltration translates into reduced water runoff and erosion with CA. There are fewer studies assessing crop rotation impacts on soil

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physical properties but thus far have shown few significant effects (Thierfelder et al., 2013b; Verhulst et al., 2010). Although the rates of erosion depend on soil type, topography, climate, and rainfall duration and intensity, repeated studies have shown signification reductions with CA practices compared to conventional practices in a range of conditions at field scale (Meijer et al., 2013; Montgomery, 2007; Zhang et al., 2007), at watershed/catchment scales (Prasuhn, 2012) and with climate change simulations (Zhang, 2012). Runoff and erosion are typically reduced by an order of magnitude with NT compared to conventional (Kay et al., 2009; Prasuhn, 2012). Reducing runoff and water erosion with CA should result in lower transport of sediments, nutrients and pesticides/herbicides and higher water quality. With NT or conservation tillage, N in sediments and runoff water have been reduced by as much as 60% (Kay et al., 2009) though there is a wide range with only a 9% reduction of N in runoff recently modeled by Liu et al. (2013a). Nitrogen losses in sediments were consistently lower with NT in a study by Richardson and King (1995) but losses of soluble N differ with the type of crop, with less soluble N lost with wheat compared to maize or sorghum. There are consistent reductions in P losses to surface waters with NT and herbicides in runoff have been reduced by 40 to 70% with NT (Richardson and King, 1995). The situation with pesticides is less straightforward. Though pesticides in runoff have been reduced by 40 to 70% with NT, the concentration of pesticides in runoff water can be higher than with CT, the overall impact is less clear (Kay et al., 2009). Some recommend incorporation of pesticides to increase absorption by soils, thus reducing losses by runoff or leaching (Kay et al., 2009; Reichenberger et al., 2007). In effect there are somewhat contradictory recommendations for reducing pesticide losses, NT to reduce losses by runoff and erosion but tillage to reduce losses by leaching. Similar types of factors need to be considered in determining the extent of nitrate leaching into groundwater (Verhulst et al., 2010). In general more research on the impacts of CA practices on water quality are needed. Conservation agriculture practices result in more plant available water than conventional practices. This is a result of increased water infiltration and lower evaporation with reduced mixing of the surface soil, more residue cover and less exposure to drying compared to conventional tillage. Water holding capacity of the topsoil is also generally higher due to increased SOM contents. Liu et al. (2013b) found soil moisture content was most affected by residues compared to tillage practice; soil moisture remained highest throughout the growing season with NT plus residue, intermediate levels of soil moisture with tillage plus residues, and lowest levels with NT without residues. Likewise Thierfelder et al. (2012, 2013b) found higher soil moisture contents in Zambia for each of five years with NT and surface residue compared to CT with residues removed. These difference extended beyond 30 cm in some years. This increased water content in the topsoil CA would be especially important for crop growth during prolonged dry periods with less variable yields than conventional practices. This effect of increased soil moisture with NT and residue retention compared to CT without residues resulted in 1.5 Mg ha−1 higher maize yields annually over a 12 year period, with large differences (4.7 Mg) in years with long dry spells (Verhulst et al., 2011). Thierfelder et al. (2013a) found higher infiltration rates with CA practices of RT and residues compared to conventional at several sites in Malawi; these difference were also reflected in higher yields though the effect differed by site and duration of practices. The impact of higher soil moisture with NT on yields or water use efficiency is also shown with irrigation. Studies have shown a 20-50% reduction in irrigation water with NT and residue retention with similar or higher crop yields (Grassini et al., 2011; Gathala et al., 2013). Verhulst et al. (2011) found higher yields with CT compared to NT with full irrigation in Mexico but no difference or higher

yields under NT under reduced irrigation levels due to higher soil aggregation and increased infiltration rates. 3.3. Soil chemical properties and ecosystem services: nutrient cycling and retention The distribution of organic soil N in the soil profile under CA is similar to that of soil C (Table 2c), though N availability, as measured by extractable mineral N, differs by studies and is confounded by rates of fertilizer N applications and the quality of crop residues or cover crops (Bissett et al., 2013; Powlson et al., 2011b; Bhardwaj et al., 2011). Nitrogen availability is often lower in CA systems due to slower decomposition and higher N immobilization with surface application of residues than in conventional practices (Boddey et al., 2010; Verhulst et al., 2010). The low quality surface residues may result in temporary N immobilization of fertilizer N, with higher N use efficiency and reductions of fertilizer N applications for similar crop yields (Bhardwaj et al., 2011). With low N input systems, though, this slower release of N may further reduce crop yields (Nyamangara et al., 2013). Higher N use efficiency and lower levels of soil inorganic N with CA may also result reduced N leaching. There is also a contradictory hypothesis that nitrate leaching is greater in CA due to higher mass water flow through more connected macropores compared with conventional practices (Kay et al., 2009). Soil nutrient differences as a result of CA practices are often confounded because mineral fertilizers are also applied. Potassium and phosphorus are concentrated and more available in the surface soils (0-5 or 0-10 cm) with NT and residue retention and exhibit a greater decrease with depth than conventional practices (Table 2c). Increases in potassium are usually attributed to the high concentrations in cereal crop residues, while phosphorus availability due to a a decrease in P-sorption with higher SOM content in CA topsoil. These differences in nutrient concentrations and distribution were not reflected by difference in plant nutrient concentrations but were reflected in higher yields with reduced tillage (Hulugalle and Entwistle (1997). Concentration of nutrients in the superficial soil layers with CA practices could present problems in years with prolonged drought periods because the roots could be distributed more superficially where nutrients are concentrated (Paul et al., 2003) but this may be offset by higher soil moisture in CA. 3.4. Relationship of soil quality to soil processes and ecosystem services Soil quality is key to crop production and several ES. Some soil quality indicators relate fairly directly to an ES, such as soil aggregation and macroporosity to soil water movement. Sometimes, however, several soil quality indicators may be correlated to ES delivery, but often it is not clear which of the numerous soil quality parameters are essential for the maintenance of that ES. Contradictory results from studies comparing soil quality parameters from CA or conventional practices (Bissett et al., 2013; Verhulst et al., 2010) also make it difficult to distinguish the key components of soil quality related to ES delivery. Similarly there is scant information on threshold levels of soil quality indicators required to deliver these ES. A study by Bhardwaj et al. (2011) approached this issue by looking at the relationship of 19 soil quality variables with crop production in several cropping systems including no till. They found that nine of the 19 variables did not show significant differences among treatments. Through principal component analysis they narrowed the variables to six including pH, NO3 - N, NH4 + N, bulk density, soil aggregate stability, and N nitrification. They assessed these six variables and computed an integrated soil quality indicator (SQI) for the different treatments and related it to crop

C. Palm et al. / Agriculture, Ecosystems and Environment 187 (2014) 87–105

production. Several treatments had similar yields (conventional, no-till and reduced input) but with different impacts on soil quality components and SQI. Reduced till exhibited the highest SQI while conventional was fourth out of five treatments. A message from this study is that one of the CA practices, NT, can maintain yields and soil quality parameters related to other regulating ES. A similar analysis was used by Thierfelder et al. (2013b) to determine the relative effects SOM, aggregate size and stability, and infiltration on crop yields in Malawi. Though the influence of CA on soil properties differed by site there was an overall greater contribution of SOC and infiltration to maize yields. Kirkegaard (1995), on the other hand, found that while NT may have positive effects on reducing erosion it may not be accompanied by increases in yields; likewise Richardson and King (1995) found a reduction in erosion and runoff but a reduction in yields on a clayey soil, especially during wet years. Integrated studies and assessments such as these are needed in CA to identify the key soil properties (and related processes) that contribute to crop production as well as to the regulating ES that are related to resource use efficiency and reduced losses to the environment. The key soil variables and components will likely change with soil type, climate, and time under CA but patterns could emerge with a network of trials. 3.5. Summary, information gaps and research recommendations 1. The CA practices of residue retention, NT, and certain crop rotations increase SOM in the topsoil that, in turn, impact soil physical properties and process that reduce erosion and runoff and biological and chemical properties that could lead to improved N use efficiencies and fewer N losses to the environment. The amount of SOM that is needed to drive these changes in soil properties and processes and related ES is not well known. Few studies have quantified the linkages among these different soil properties and processes and their relationships with the provision and regulation of nutrients and water and with crop productivity as the measurements are often taken by different groups of investigators. Existing CA experiments or strategically placed and newly designed experiments should be used for a comprehensive comparison of CA with conventional practices in a range of soils and climates. These experiments should include integrated assessments of the linkages of SOM with other soil quality parameters in relation to the actual delivery of ES. Threshold levels of SOM and the management practices needed to attain and maintain those levels could be investigated, including the time needed to achieve those levels of SOM. These studies could be the same experiments as discussed under soil C sequestration and greenhouse gases. 2. Soil physical properties such as aggregation and macroporosity are important for determining rates of water infiltration, runoff, plant available soil water, erosion, and others. These factors are usually greater with CA and are related to reduced erosion and runoff. Though there are fewer studies on water quality, in general, less sediment load and reduced N are observed with CA. There are some key questions that if addressed could identify the key CA practices that are required for maintaining or improving soil physical properties related to the ES of water regulation and provision on different soil types. Currently there is insufficient information to synthesize results according to soil type. • What is the amount of crop residue needed to improve and maintain soil properties and processes that result in reduced water runoff and soil erosion, or increased soil moisture levels? Govaerts et al. (2007a) suggest that it is possible to remove 50–70% of the crop residue while keeping adequate benefits to the soil but residue removal in excess of 50% have adversely affected

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soil quality as well as crop yields in the US (Blanco-Canqui, 2010). Recommendations for the amount of residue removal will depend on climate, soil type and topography. Whilst BlancoCanqui and Lal (2008) stress those similar recommendations may hold for cropping systems on heavy textured, flat soils in temperate regions, no residue should be removed from sloping and erosion-prone soils under NT conditions. Advice to remove half the residue would not hold for systems with low crop and residue production. In smallholder farming systems in Sub Saharan Africa and South Asia, there may be insufficient residue produced or retained due to other competing uses to provide these ES. Relating the amounts and types of C inputs required for delivering ES would be useful for assessing the feasibility of CA and better adapting CA management practices as needed (Baudron et al., 2013) for different climates and soils. • What levels of increased soil moisture content with CA result in higher crop productivity and/or less variable production with climatic variability? Studies along these lines are emerging but more studies are needed on a range of soils and CA practices. Such information will be especially important for drought prone areas and sandier soils. 3. A combination of soil biological and chemical properties and process determine N availability patterns. Differences in N availability between CA and conventional practices are sometimes implied as increased retention and nutrient use efficiency in CA systems compared to conventional. Few studies have documented these aspects, particularly with crop residues and crop rotations with different proportions of cereal crops and legume crops or cover crops. Further research should address the differences in N availability patterns and distributions, N use efficiencies and N losses under different CA crop rotations. • How do crop rotations with legumes (and which legumes) affect N availability and use efficiency differently in CA compared to conventional systems? • Does increased N use efficiency translate into reductions in the amount of fertilizer N needed to attain the same yields as with conventional agriculture? • Do the different patterns of N availability (increased immobilization and slower release) with CA result in decreased N leaching? Currently there are opposing processes that have been proposed, one that less available N results in less leaching and another that increased macropore continuity with CA will lead to increased losses of N through leaching. Answering this question requires combined information on infiltration, N concentrations and leaching–currently data that are often collected by groups with different interests so are not collected in the same experiments. 4. Few linkages have been made between soil biodiversity and ES though they are often implied by the occurrence of different soil functional groups between CA and conventional practices. Different studies report quite varied effects of CA practices on soil biological properties and soil biota. These differences are often related to different soils and climates, crop types and rotations, intensity of tillage, timing of operations, time of sampling, the suite of management practices, and the depth of the soil studied (Kladivko, 2001). It would be of value to determine if broad patterns exist between soil biotic abundance and functional diversity as modified by CA and the soil properties and processes and ES service provision in different environments. Such research would require using standard methods and comparisons among similar treatments across different environmental situations but would be useful to build a database on the value of biodiversity and ES under CA.

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4. Other ecosystem services and biodiversity Although not a focus of this paper, it is important to point out a few other ESs and the underlying biodversity that are relevant to CA compared to conventional agriculture. CA management practices can affect habitat suitability for soil pathogens or alter community composition of the predators or parasites of major disease organisms compared to conventional practices. More diverse soil communities suppress the impacts of the pathogens (Verhulst et al., 2010). Higher SOM levels with CA produce cooler and moister conditions favorable to pests and diseases and many fungal pathogens reside in crop residues of the host crop and thus may increase incidence and disease retention time in the soil (Cook, 2006). Crop rotations can reduce population size of these pathogens and change soil community composition (Cook, 2006). Soil borne pests and diseases such as fungi and nematodes are affected by CA practices (Table 2a) though the effect on these populations is mixed (Schroeder and Paulitz, 2006). A review by Stinner and House (1990) indicates that although some soil borne pests increase with NT, more pathogens actually declined with NT. No-till, irrespective of plant residue retention, has generally decreased the impact of pest species while residue retention is thought to increase disease incidence, at least in the first years of transition to CA (Verhulst et al., 2010). Increasing tillage frequency disrupts community diversity and stability and has a greater negative impact on species with slower response rates to disturbances; this typically includes loss of species higher in trophic chains, such as predators and parasites of disease organisms. A transition to NT allows the recolonization of such species. Crop rotations have shown reductions in pathogen populations that are usually associated with yield reductions but direct linkages are less clear. The combined effects of CA lead to a more diverse and stable soil community, including beneficial bacterial and fungal species that can suppress pathogens (Verhulst et al., 2010; Lupwayi et al., 1998). Increased abundances of meso-fauna such as arthropods (Dubie et al., 2011; Tabaglio et al., 2009; Brennan et al., 2006) and macrofauna such as spiders and hymenopteran parasitoids have been found with NT (Rodriguez et al., 2006; Marasas et al., 2001; House and Stinner, 1983; Stinner and House, 1990). Abundance and diversity of populations of natural enemies of parasitic nematodes may be higher with NT (Verhulst et al., 2010). Studies have shown initial increases in pests and diseases with the implementation of NT and residue retention, followed by gradual decreases (Gerlagh, 1968; Shipton, 1972). It is assumed to be related to the re-establishment of more diverse communities with CA. While yield losses to disease are also reduced with time, pre-disease outbreak yields are not recovered. The balance of these pests and beneficial organisms determines the overall effect on crop production; however, there is little information of the functional relationships between beneficial and detrimental soil organisms and the ultimate outcome on productivity. These effects could be investigated in the set of field studies recommended for the other ES. The effects of CA at the field scale can also be a mechanism though which biodiversity provides ES, particularly in heterogeneous landscapes (Fahrig et al., 2011). Two recent studies reported landscape scale effects of tillage on biodiversity and biological control. In the first study, the proportion of NT rape seed fields in a landscape was a predictor of parasitism rates by three univoltine parasitoid species (Rusch et al., 2011). In the second study, the proportion of RT fields at 1500-2000 m scales was positively correlated to parasitism rates on the pollen beetle in oilseed rape fields, showing an increase in biological control of this pest at the landscape scale related to RT (Rusch et al., 2012). The combined studies suggest that reducing field scale soil disturbance can have landscape scale impacts on ES, by providing more stable and diverse habitats that harbor parasitoids.

Studies of pollinators usually focus on the effects of herbicide applications. Several species of bees, however, use soil-based burrows and can be affected by soil disturbance. One study considered the impact of NT on pollinator diversity and found that pollinator abundance, particularly of the squash bee, was greater in NT than in CT (Shuler et al., 2005). In contrast, European honeybee abundance was not impacted by tillage. Most interventions to protect these key species have focused on conserving semi-natural vegetation in field margins or in push-pull systems. The combination of habitat provision and CA in providing ES of pest control and pollination similar to field margin conservation has not been sufficiently explored.

5. Conservation agriculture and ecosystem services in smallholder farming systems Conservation agriculture is being promoted widely in many areas of Sub Saharan Africa and elsewhere in the tropics to recuperate degraded soils (Erenstein et al., 2008). Whilst CA has been successfully introduced in high input and high yielding smallholder systems in the rice-wheat region of South Asia, the low input, low productivity systems characteristic of much of Sub Saharan Africa requires attention. Although there are still insufficient long term CA experiments and on-farm studies in Sub Saharan Africa (Thierfelder et al., 2012) it is clear that the biggest obstacle to improving soils and other ES is the lack of residues produced due to low productivity (Paul et al., 2013; Thierfelder et al., 2013b, Dube et al., 2012; Lahmar et al., 2012; Ngwira et al., 2012; Giller et al., 2009; Hengsdijk et al., 2005). Increases in topsoil C, as observed for the majority of CA studies from temperate regions, are critical for recuperating soils and the numerous ES associated with it. Even in cases where increased topsoil C has been found in experimental fields in Sub Saharan Africa (Thierfelder et al., 2013b; Chivenge et al., 2007; among others) the studies may not reflect the amounts of residues found in farmers fields. Insufficient levels of surface residue combined with NT does not result in increased SOM (Nyamangara et al., 2013), soil moisture (Liu et al., 2013b) or related ES and can even result in decreased yields (Blanco-Canqui, 2010; Giller et al., 2009). The amounts of residues required to deliver the different ES is not known. Several experiments in Sub Saharan Africa have shown increased and less variable crop yields due to increased soil moisture associated with surface residue retention and NT (Thierfelder et al., 2013a, 2013b; 2012; Verhulst et al., 2011). This benefit would be particularly important for many of the drier areas of Sub Saharan Africa, though the amount of residue required to retain soil moisture is not known. Fertility management, particularly N, is required to increased production and residue inputs in these low productivity systems (Nyamangara et al., 2013; Dube et al., 2012; Giller et al., 2009). Nyamangara et al. (2013) even reported reduced yields with surface applications of mulch when no fertilizer N was added. Improved access to mineral fertilizers in Sub Saharan Africa will be essential to the feasibility of CA in the region. Legume cover crops or trees may also provide organic sources of N but probably not in sufficient quantities in early stages of soil (Lahmar et al., 2012). The other constraint to sufficient levels of residue for CA in these smallholder systems is the multiple, economically important alternative uses of residues. Studies that investigate the amounts of residues required for providing ES are especially important such smallholder systems. Likewise, studies that investigate the costs or trade-offs incurred by farmers to retain crop residues relative to the gains in soil C (Giller et al., 2009), and other ES would be useful for developing incentives or payment for ES in order for farmers to be willing to retain residues. In mixed farming systems in Zimbabwe,

C. Palm et al. / Agriculture, Ecosystems and Environment 187 (2014) 87–105

increased use of small rates of fertilizer and manure resulted in an increase in biomass production, and partial retention of crop residues in the fields (Rufino et al., 2011). All three CA practices are currently not part of the traditional practices in Sub Saharan Africa making their adoption challenging. While RT or NT may be accepted due to lower labor requirements, the frequent weeding required throughout the cropping season with NT may negate those effects (Mashingaidze et al., 2012). Residue retention will be difficult to achieve in areas with substantial livestock without increasing the amounts available and perhaps providing incentives. Acceptance of crop rotations may be limited in areas of chronic food insecurity and staple crop production until functioning markets are established (Thierfelder et al., 2012). All these limitations point to nuanced approach to CA or the promotion of the different CA practices in Sub Saharan Africa. A sequence of interventions, as suggested by Lahmar et al. (2012), may be more appropriate. The first step is to increase crop production through nutrient management, followed by soil and water management practices that improve soil quality and water retention, and then gradually the introduction of CA practices if and where appropriate to the soil, climate and socioeconomic conditions. These steps must be based on evidence that the practice or suite of practices result in increased ESs without compromising increased yields. 6. Conclusions Conservation agriculture produces the soil conditions that result in reduced erosion and runoff and improved water quality compared to conventional practices. Likewise, water holding capacity and storage are enhanced with CA providing some buffer to crop production during drought conditions. SOM is almost invariably higher in the surface soil with CA practices compared to conventional practices and influences many other soil properties and processes involved in the delivery of ES. The deliveries of most other ES, including soil C sequestration, emission of GHGs, and pest control, are not so clear cut (as detailed in the section summaries). Some of the differences could be due to the duration of experiments or the experimental designs with some comparing NT, residue retention, or a combination of the two. The effects of crop rotation are less clear than for the other two practices. There is currently insufficient information from CA studies to explain the inconsistent results. Many of these differences may be due to soil type, topographic position, parent material, climate and their combination, and interactions with management. Yet it

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is this type of information that is essential for determining where and why CA does work in delivering ES, while increasing crop production. The study of ESs in agriculture requires approaches and methods from both agronomy and ecology, a bridge that is all too often incomplete, yet is critical to understanding the underlying processes and controls that lead to changes in production and other ES. As examples, agronomists will often measure SOM levels in the topsoil because it relates to soil fertility but to determine the ES of soil C sequestration requires the measurement of the total stock of soil C deeper in the soil. This requires measuring %C in several layers of the soil profile as well as the bulk density of the soil. As a consequence, data gathered in agronomic trials of CA may not be sufficient to assess some ESs. Likewise, ecologists may measure soil biodiversity in different agricultural management practices but they may not connect them to measures of soil processes that are important for ES or measure the resulting crop production. Unpacking the differential effects of CA management practices as well as their combination on soil process and ES and how these are modified by climate and soil type is necessary to develop a predictive understanding that can be used for improved, site specific CA management guidelines. In other words, to better assess, manage and target CA it is necessary to know the relative importance of tillage, residue management, crop rotations and their combination on the different ES and also how those ES relate to crop production. The types of experiments installed for testing CA and comparing with conventional practices (tillage, residue removal or incorporation and monocultures) do not necessarily have the design and controls that are required to separate the individual and combined effects of the different CA practices. Establishing a set of strategically located experimental sites that compare CA with conventional agriculture on a range of soil-climate types would facilitate establishing a predictive understanding of these relative controls of higher order factors (soil and climate) and management (tillage, residues, crop rotations) and ES outcomes, and ultimately in assessing the feasibility of CA or CA practices in different sites and socioeconomic situations. Acknowledgements We would like to thank the substantive comments from three anonymous reviewers. The comments were helpful in restructuring the paper. We would also like to thank Alison Rose and Clare Sullivan of the Agriculture and Food Security Center at Columbia University for their help in literature searches and other details.

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Appendix A. Studies comparing soil carbon, bulk density with depth in no-till (NT) and conventional tillage (CT). FD = fixed depth basis for assessing soil C stocks; ESM = equivalent soil mass basis. Location, Reference, fixed depth or equiv mass China Du et al. (2010) FD

Spain Plaza-Bonilla et al. (2010) FD

Spain Plaza-Bonilla et al. (2010) FD

Spain

536

Varvel and Wilhelm (2011) ESM Kansas (USA) Blanco-Canqui et al. (2011)

7

Crop Rotation

Wheat-corn

Wheat-chickpea Wheat-sunflower 584

Clayey

20

430

Silt loam

17

475

428

Lopez-Fando and Pardo (2011) ESM 430 Spain Morell et al. (2011) ESM Spain Hernanz et al. (2009) ESM Nebraska (USA)

Silt loam

Years

Loam

Loamy sand

20

16

Wheat-bare fallow Wheat-faba-bean Continuous wheat Wheat-barley

Wheat-barley

cheap pea-barley

Soil Depth (cm)

Bulk density CT (Mg/m3 )

Bulk density NT (Mg/m3)

Statistics (Bulk Density)

SOC CT (g/kg)

SOC NT (g/kg)

SOC CT (Mg/ha)

SOC NT (Mg/ha)

Statistic (SOC)

0-5 5-10 10-20 20-30 30-40 40-50 0-50 0-90 0-90

1.3 1.42 1.51 1.6 1.6 1.52

1.4 1.52 1.61 1.62 1.58 1.5

NT > CT NT > CT NT > CT ns ns ns

11.8 11.2 11 7.5 4 4

14 12 9.1 7 3.9 4

7.72 8.21 16.69 12.18 6.16 5.73 59.69

9.83 9.07 15.32 11.34 5.61 5.8 56.96

Measured but not reported by crop Measured but not reported by crop

NT > CT NT > CT CT > NT ns ns ns ns ns ns

0-90 0-90 0-90 10-20 20-30

Measured but not reported by crop Measured but not reported by crop Measured but not reported by crop 1.38 1.53 1.37 1.55

NT > CT NT > CT

5.9 6.1

5.4 4.3

8.169 8.409

8.288 6.655

ns NT > CT NT > CT ns ns

30-40 0-40 0-5 5-10 10-20 20-30

1.48

1.49

ns

5.7

3.6

1.2 1.4 1.54 1.48

1.16 1.47 1.59 1.59

ns ns ns ns

9.6 8.3 6.5 5.1

13.6 6.9 4.9 4.8

8.481 33.94 5.769 5.78 10.048 7.599

5.429 34.63 7.937 5.069 7.849 7.545

ns ns ns ns ns ns

30-40 0-40 0-5 5-10 10-20

1.53

1.59

ns

4.5

4.8

1.49 1.57 1.68

1.63 1.67 1.58

NT > CT NT > CT CT > NT

6.825 36.04 7.8 8.1 16.2

7.611 36.01 15.4 11.6 14.3

ns ns NT > CT NT > CT ns

20-30

1.67

1.57

ns

14.3

11.1

CT < NT

46.4 46

52.5 49.9

NT > CT NT > CT

9.7

11.5

NT > CT

131.61

171.22

NT > CT

128.3 104.7

124.7 104.9

ns ns

Barley

1.61 Measured but not reported by crop

ns

13

0-30 0-40

1.62

Loam

430

Loam

20

Wheat-vetch-pea

0-40

1.52

1.575

NT > CT

708

Silty clay loam

19

Continuous corn, continuous soybean, and corn-soybean

0-150

1.47

1.45

880 580

Loam Silt loam

23 45

Continuous wheat Wheat-sorghumfallow

0-100 0-100

1.23 1.62

1.23 1.66

ns ns

not reported

6.1

11.3 8.98

7.1

C. Palm et al. / Agriculture, Ecosystems and Environment 187 (2014) 87–105

Spain Lopez-Bellido et al. (2010) FD

Rainfall Soil Type (mm)

ESM

440

Silt loam

21

China Lou et al. (2012) FD

450

Sandy loam 12

Wheat-sorghumfallow Continuous corn

608

Loam

5

Continuous corn

Brazil Boddey et al. (2010) ESM

1800

Clayey

15

Brazil Boddey et al. (2010)

1750

Clayey

17

3-yr rotation soybean/maize/barley with black oats and vetch Wheat-soybean

1750

Clayey

17

1850

Clayey

26

1850

Clayey

26

Brazil Boddey et al. (2010) ESM

Maiz-wheatsoybean with black oat, black oat + vetch, and oil radish Maiz-wheatsoybean with black oat and oil radish Maiz-wheatsoybean with black oat and oil radish (The difference from the last experiment was the combination of crops within a rotation)

1.42

1.40

ns

12.17

20-40 40-60 60-80 80-100 0-100 0-5 5-10 10-20 20-40 40-60 60-80 80-100 0-100 0-100

1.43 1.45 1.5 1.52

1.44 1.46 1.52 1.53

ns ns ns ns

7.5 6.5 3 2.5

7.5 6.3 3.1 2.6

1.24 1.26 1.42 1.42 1.48 1.6 1.62

1.3 1.32 1.34 1.45 1.52 1.55 1.59

ns ns ns ns ns ns ns

11 10.6 10.2 7.9 7 4 3

13.5 10.6 8 7.9 7 4 3.1

0-100

0-100

0-100

0-100

128.2

136.6

ns

23.1 19.5 10.6 8.8 87.6 6.9 6.8 14.4 24.6 20 12.8 9.8 95.4 55

23.1 18.8 12 9.9 93.1 9 7.1 11.5 24.9 20.7 12.9 10.1 96.3 58.8

ns ns ns ns NT > CT NT > CT ns NT > CT ns ns ns ns ns NT > CT

Measured but not reported for all sites Measured but not reported for all sites

158.8

155

ns

163.5

172.3

NT > CT

Measured but not reported for all sites Measured but not reported for all sites

131.5

153.7

NT > CT

148.3

160.9

NT > CT

Not reported

C. Palm et al. / Agriculture, Ecosystems and Environment 187 (2014) 87–105

China Lou et al. (2012) FD

0-100

101

102

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Principal Paper Sessions Cultivating Ecosystem Services from Agriculture (Scott M. Swinton, Michigan State University, Organizer)

ECOSYSTEM SERVICES FROM AGRICULTURE: LOOKING BEYOND THE USUAL SUSPECTS SCOTT M. SWINTON, FRANK LUPI, G. PHILIP ROBERTSON, AND DOUGLAS A. LANDIS

managed agricultural and forest ecosystems could potentially provide. The same is true for the provision of habitat for wild species and the cultural, recreational, and informational ES. In fact, compared to more natural ecosystems, agriculture and forestry have much readier potential to expand their supply of currently nonmarketed ES for three reasons: (1) much is known about biophysical inputoutput relationships in the system, (2) there exist precedents for economic incentives that could induce greater ES supply, and (3) the past performance of agriculture suggests strong capability to supply goods and services in response to attractive incentives. The rest of this paper expands on these themes by exploring the history of public awareness and reaction to ES linked to agriculture, some precedents for inducing farmers to supply a different product mix, the existing research base on agriculture as viewed from an ES perspective, and research needs in order to augment the provision of currently nonmarketed ES from agricultural lands.

Scott Swinton is professor, Department of Agricultural Economics. Frank Lupi is associate professor, Departments of Agricultural Economics and Fisheries and Wildlife. Douglas Landis is professor, Department of Entomology, Michigan State University, East Lansing, MI 48824. Philip Robertson is professor, Department of Crop and Soil Sciences and W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, MI 49060. The authors gratefully acknowledge support from the National Science Foundation under the KBS-LTER Project: Long-Term Ecological Research in Row Crop Agriculture (http://lter.kbs.msu.edu/, NSF 0423627). This article was presented in a principal paper session at the AAEA annual meeting (Long Beach, CA, July 2006). The articles in these sessions are not subjected to the journal’s standard refereeing process.

In the midst of a century marked by the westward expansion of the plow across North America, George Perkins Marsh’s seminal book, Man and Nature highlighted the opportunity cost of agricultural land conversion (Marsh 1864, reprinted 2003). While Marsh did not explicitly discuss how farming could produce ES, he explored the loss of regulatory ES provided by forests for water purity, water flow, local climate, and soil nutrients, as well as the risks of invasive species. By 1913, George

History of Public Engagement with Ecosystem Services and Agriculture

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The concept of ecosystem services (ES) provides a transformative lens for thinking about the relation between humankind and nature. The lens is especially revealing when applied to agriculture, the most widespread managed ecosystem on the planet. ES are defined as “the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfill human life” (Daily 1997). By focusing on what ecosystems do for humans, the ES concept invites analysis of what humans do to ecosystems and why they do it. Agriculture (including planted forests) conventionally supplies food, fiber, and fuel—“provisioning services” in ES parlance (Millennium Ecosystem Assessment 2005). Farmers also help to maintain the natural “supporting” ES that make agriculture productive, such as pollination, biological pest regulation, and soil nutrient renewal. In theory, the same managed ecosystems that provide these marketed products could produce other types of ES if suitable incentives existed. The broad class of “regulation ES” covers climate regulation, water purity, surface water flows, groundwater levels, and waste absorption and breakdown. All of these offer benefits that are poorly captured by current markets, yet which

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produce (Antle and Capalbo 2002, Maier and Shobayashi 2001). Rapidly growing scientific understanding of ecosystem functions, including how these may interact at different scales, is creating the scientific preconditions for new processes of managing ecosystems, especially agriculture. Emerging Understanding of Agro-Ecosystem Functions Producing Services Agriculture has benefited from over a century of formal scientific research. The combination of reductionist science and capitalist markets has led to agricultural systems that focus sharply on optimizing productivity of the most profitable marketed outputs. While the simplicity of the resulting systems that dominate U.S. croplands has been criticized by some, the scientific research has clearly led to a better understanding of many functional relationships associated with genetics, nutrition, pest and disease control, temperatures, and other factors governing growing conditions and yield of marketable product. The most promising scientific breakthroughs for managing agricultural ecosystems in concert with ES derive from a systems approach to agricultural research (Robertson et al. 2004). The limitations of conventional problem-response research become readily apparent when a solution developed to solve one problem creates another problem elsewhere. A systems approach, by exploring how ecosystem components interact, tends to better exploit synergies and predict the effects of a specific management intervention on other parts of the system. Examples of services that can be provided in this way include climate regulation, wildlife conservation, and biological pest control and pollinator management. Climate Regulation Agriculture is responsible for over 20% of anthropic greenhouse gas emissions globally (Houghton et al. 2001). This includes 21%–25% of all anthropic carbon dioxide (CO2 ) fluxes, mainly from deforestation and fossil fuel use; 55%–60% of total methane emissions, mainly from ruminant livestock, rice cultivation, biomass burning, and animal wastes; and 65%–80% of total nitrous oxide fluxes, mainly from cultivated soils, animal wastes, and biomass burning. The magnitude of these fluxes and their sensitivity to

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Warren’s Farm Management identified supporting ES such as local climate, soil fertility, water supply and drainage as essential criteria for choosing a farm location (Warren 1913). By 1931, O.E. Baker warned that “in no other nation, without exception, is depletion of soil resources taking place so rapidly” due to soil fertility export through crops, nutrient leaching, and soil erosion (Baker 1931). The U.S. government responded to the serious damage to rural livelihoods wrought by low farm prices and Dust Bowl soil erosion with the Soil Conservation and Domestic Allotment Act of 1936, which paid farmers to shift land from soildepleting grain crops to grasses and legumes, addressing perceived oversupply of grain crops alongside soil erosion (Tweeten 1979). The Public Works Administration (1933) and the Soil Conservation Service (sometimes with help from the Civilian Conservation Corps) helped farmers build terraces to reduce erosion and developed hundreds of conservation demonstration projects (Cochrane 1993, pp. 291–92). Although A Sand County Almanac inspired many with Aldo Leopold’s poetic evocation of agriculture as part of a larger ecosystem community (Leopold 1949), it was Rachel Carson’s Silent Spring that really turned scientific and public attention to the negative externalities of farming (Carson 1962). Over the next three decades, a circle of public concern widened from DDT to general pesticide risks to human and wild animal health, then on wider water quality risks from excess nutrients (Reichelderfer and Hinkle 1989). Congress responded with a series of laws aimed at reducing negative externalities. Mitigating water pollution and soil erosion has been the focus of agricultural management to conform with the Clean Water Act, Safe Drinking Water Act, and two farm bill cost share programs—Environmental Quality Incentives Program (EQIP) and Conservation Reserve Enhancement Program (CREP), as well as the land retirement programs— Conservation Reserve Program (CRP) and Wetlands Reserve Program. If the harbinger of the last intellectual wave to wash over agriculture was Silent Spring, the bellwether of the next wave may be Nature’s Services, edited by Gretchen Daily (1997). The ES literature has only recently reached agriculture. Daily’s book and the first current of ES literature focused on marshalling awareness of the value of naturally produced ES. But an emergent current is exploring how managed ecosystems could change the mix of ES they

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Agricultural Landscapes and Insect-Mediated Ecosystem Service Insects provide important supporting ES to agriculture via pest regulation and pollination. Concepts from landscape ecology and conservation biology have led to an enhanced understanding of how insects supply ES to agriculture (Banks 2004). Suppression of pest insects by their natural enemies (predators, parasites, diseases) is believed to control most potential pests in most years, yet it is frequently unmeasured. Biological control (the deliberate manipulation of natural enemies by humans) relies on the ability of the landscape to provide habitat for natural enemies near crop environments. Finally, insect pollinators provide critical fertilization services to both crop and noncrop plants. Scientists are beginning to understand how these ES are influenced by the structure of agricultural landscapes (Tscharntke and Brandl 2004). For example, aphid predators in cereal crops have been found to inhabit field edges and hedgerows, and to be more abundant in smaller fields and in heterogeneous landscapes, especially near wetlands, and where land has been set aside under the Conserva¨ tion Reserve Program (Ostman, Ekbom, and Bengtsson 2001; Elliott et al. 2002). Beneficial parasitism can also be enhanced by structurally complex landscapes (Marino and Landis 1996; Thies and Tscharntke 1999). Similarly, the provision of ES by pollinators also depends upon habitat and landscape structure (Kremen et al. 2004).

Given the strong evidence for both field and landscape level influences on the provision of pest suppression and pollination services by beneficial insects, an interesting management possibility is to enhance insect natural enemies and pollinators by manipulating the diversity of plant communities. Because most insect enemies and all pollinators require plant-provided resources in the form of nectar and pollen (Wilkinson and Landis 2005), entomologists have sought to enhance these resources in and around agricultural fields, and current research emphasizes the biodiversity services of doing so using perennial native plants (Landis and Fiedler 2006). Wildlife Conservation Wildlife services have traditionally been recognized as a valuable resource associated with agriculture and forestry. In many parts of the United States there are long histories of feebased hunting access or leases tied in part to agriculture (Raskin et al. 1992) and especially range lands (Butler and Workman 1993). More generally, there has been wide recognition that noncropped agricultural lands can provide substantial wildlife habitat services (Issacs and Howell 1988). There is now growing appreciation of the general contribution of agricultural lands to the maintenance of wildlife populations and to the potential recovery of endangered species, especially in areas where development pressures are high (Bossi et al. 2006). The rise in the importance of landscape ecology has led to an increased appreciation of the role of spatial structure of landcover, including the recognition that habitat patch size and connectivity are often critically important to sustaining metapopulations of wildlife. The potential to manage cropped, and noncropped, lands for wildlife corridors, coupled with the development of landscapescale tools for measuring and managing for habitat conservation values (Bruggeman et al. 2005) suggests promise for landscape scale management incentives to partially defragment habitat (Shogren 2005). As the ecosystem processes underpinning these services become better understood, a number of technical questions relevant to the economics of future agricultural production of ES will need to be explored. Example questions include: 1. What trade-offs exist between production of alternative ES and marketed farm

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management makes agriculture an attractive part of several portfolio-based greenhouse gas stabilization schemes (Caldeira et al. 2004). Stabilization strategies for agriculture include five basic elements (Robertson 2004): (1) gains in energy efficiency for farm operations that consume fuel, including mechanical operations, grain drying, and irrigation; (2) carbon sequestration in soil from changes in tillage, crop residue management, animal waste handling, and cover crops; (3) biofuel production that can offset the use of fossil fuels for energy production and industrial feedstocks; (4) gains in the production or yield efficiencies for grain, livestock, and other agricultural products in order to defray the need to open new land for agricultural development and subsequent carbon loss; and (5) abatement of the non-CO2 greenhouse gases by better fertilizer and waste management.

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Institutions and Incentives Although the questions above are focused on technical relationships, many of the answers depend not only on biophysical relationships, but also on economic incentives and institutional rules. Apart from its sheer geographic extent, part of what makes agriculture a potentially important supplier of managed ES is its heritage of policy interventions to affect incentives (Tweeten 1979). Since the Agricultural Act of 1933, the United States has been in the business of trying to get farmers to change their mix of agricultural practices and inputs from what market forces alone would induce. Most U.S. agricultural policies focus on input use and production practices, rather than the outcomes of those practices (Ogg 1999; Ribaudo and Caswell 1999). The case is similar in Europe, where in spite of practices intended to foster the provision of nonmarketed ES, incentives have focused on land management rather than the results of that management (Kleijn et al. 2001). The precedent of government intervention is strong for agriculture, although interventions have tended not to focus on ES outcomes. Costa Rica and Colombia have introduced outcome-based payment for environmental services (PES) schemes benefiting farmers and foresters to ensure municipal water supplies. Implemented at the watershed level, many of these projects involve payments from municipal water companies to upland land owners to maintain vegetative cover and land management practices that ensure continuous availability of water to lower parts of the watershed (Pagiola, Bishop, and Landell-Mills 2002). The payments are financed in part by special fees in commercial water bills. Although still targeted at land management, programs such as these illustrate movements toward policies that more

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closely focus on ES outcomes and that are potentially self-financing. Interest is growing in the potential of agricultural engagement in environment credit trading, especially carbon sequestration credits (Ribaudo, Johansson, and Jones 2006). The Chicago Climate Exchange now certifies carbon credits for a variety of carbon sequestration activities, including no-till farming of row crops, planting of grassland, and forestry projects in selected regions and countries (Chicago Climate Exchange [CCX] 2006). Although the potential revenue gain is small with the standard soil carbon offset of 0.5 mt/ac/year for no-till farming trading near $2/mt/year, for many no-till practitioners, the carbon offset would require no supplementary effort beyond becoming certified. A market appears to be emerging for carbon credits and the modified farming and forestry practices that can produce them. Amid the scientific and political opportunities listed above, a powerful “push” factor is coming to bear to reorient current U.S. and European agricultural income support policies—the World Trade Organization trade rules. The United States’ loss of Brazil’s WTO damage suit against the U.S. cotton subsidies made clear that most current U.S. subsidies are trade distorting and must slowly be phased out (Josling 2005). The pressure to bring the United States into WTO compliance may lead to a system of subsidies based on environmental performance, and hence decoupled from agricultural commodity production levels (albeit likely to reward most of the same farm political constituency) (Zinn 2005). Research Gaps to Be Filled Despite the clear potential for agricultural provision of ES, major research gaps remain to be filled before many of the ideas mentioned above become practical on a commercial scale. The research gaps fall into three major areas: (1) the relationships between ecosystem function and production of ES, (2) measurement and valuation of ES, and (3) design of effective incentives for provision of ES that are not currently marketed. (Once these fall into place, a logical fourth research area would develop in technological innovation to improve efficiency of ES production.) Intentional production of ES requires an understanding of the underlying ecosystem processes. The microbial processes that lead to soil carbon sequestration and greenhouse

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products? Put differently, how does the production possibilities frontier (PPF) look? To what extent are some ES joint products? Is this a continuous PPF, or do discontinuities or threshold effects arise in shifting the output mix? 2. How would greater ES production affect the temporal flexibility of current systems to respond to market conditions? 3. How would ES production affect responses to risk? In particular, how would they affect the probability distributions of marketed joint products and flexibility of management to change input–output mixes?

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captures potential jointness in production of ES in agricultural processes (Antle and Valdivia 2006; Boisvert 2001). The last major research area is development of suitable incentives and delivery mechanisms to induce efficient provision of currently nonmarketed ES from agriculture. Key features for attractive, voluntary, governmental incentive structures include low transaction costs, an output orientation, site-specific targeting, and tailoring to specific ES (Batie 2005). Marketbased mechanisms to encourage ES provision will need willing buyers, willing sellers, and a payment system that can efficiently transfer funds in a way that induces and sustains ES output. Experiences with market-based ES provision from forests have showed that markets are very heterogeneous in scale and form, varying with the specific ES and the biophysical and socioeconomic settings where it is produced (Pagiola, Bishop, and Landell-Mills 2002). Hence, the design of viable incentive mechanisms for provision of ES from agriculture constitutes a massive research agenda, if it is to cover diverse ES, many agricultural commodities, and diverse biophysical and institutional settings. Conclusions The scientific and political planets are aligning to create both the demand for policy-relevant research into the ES available from agriculture and the means to create incentives for farmers to provide those services. Certain environmental services have a long history of interest and research, and soil conservation, water supply, water-quality protection, judicious agrochemical use, and preservation of agriculture and open-space will continue to be important. But looking beyond these “usual suspects,” a new suite of ES—many with stronger and more complex externality effects—is ripe for adapting emerging knowledge from basic biogeochemical, ecological, and evolutionary research into management practices and designing incentive mechanisms to induce farmers to produce those services. Among these promising areas are soil microbial community management for greenhouse gas mitigation and noncrop habitat management for biological pest control, pollinators, and wildlife. Much of the research needed will require collaboration of researchers who bring strength from their respective disciplines to team efforts. At present, only modest competitive grant opportunities exist for

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gas production, for example, are well known from over a century of laboratory study, but important aspects of their behavior in situ are poorly understood, and keep our ability to predict changes in response to ecological disturbance or agronomic management at a very modest level (Robertson and Groffman 2006). Likewise, for many important insect pests, natural enemies are known to suppress pest populations, yet much is unknown about the predators’ life cycles, habitat needs, and behavior outside the predation periods. Moreover, we are just beginning to understand ways to manage landscapes to provide a constant supply of natural enemies to crop fields (Landis, Wratten, and Gurr 2000). In order for markets and policies to evolve to encourage provision of ES as outputs, measurement systems will be needed. Ideally, accurate measurement systems can be paired with low-cost indicators that give highly correlated readings. Satellite remote sensing is one low-cost, geographically and temporally dense indicator technology for those ES whose provision correlates with spectral reflectance (e.g., CO2 uptake by growing plants, vegetative cover to retain soil or regulate water flows). Acoustic sensing could play a similar role for monitoring certain animal populations (e.g., song birds, frogs). Potential farmer providers of a given ES will want to know what they could earn, and policy makers and market makers will want to know how much they should offer to induce ES supply. Nonmarket valuation methods have been applied to many of the ES in question. However, linking on-farm practices to valued off-farm ES can pose several challenges. First, as with other environmental valuation efforts (Kopp and Smith 1993), linking physical changes in complex natural systems to changes in services valued by people often requires a high degree of knowledge of the system (Hoehn, Lupi, and Kaplowitz 2003). Second, appropriate valuation methods typically estimate demand-side willingness to pay in different units than would make sense for producer incentives. For example, Poe and Bishop (2001) estimated household willingness to pay for a change in nitrate concentration in drinking water. Converting such a demand-side measure into an annual payment per acre for altering farm nitrogen management requires several assumptions and detailed calculations (Labarta et al., 2002, pp. 33–34). Third, producers’ willingness to supply ES will likely need to be estimated within a willingness-to-accept framework that

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multidisciplinary collaborations through special programs under the U.S. Department of Agriculture and the National Science Foundation, with the latter much more broadly specified than agriculture. More long-term support will be needed in order to reach the critical mass of multidisciplinary research required to capitalize on this historic opportunity for agricultural provision of ES that meet broader public needs than in the past.

Antle, J.M., and S.M. Capalbo. 2002. “Agriculture as a Managed Ecosystem: Policy Implications.” Journal of Agricultural Research and Economics 27(July):1–15. Antle, J.M., and R. Valdivia. 2006. “Modeling the Supply of Ecosystem Services from Agriculture: A Minimum Data Approach.” Australian Journal of Agricultural Resource Economics 50:1–15. Baker, O.E. 1931. “The Outlook for Land Utilization in the United States.” Journal of Farm Economics 13(April):203–30. Banks, J.E. 2004. “Divided Culture: Integrating Agriculture and Conservation Biology.” Frontiers in Ecology and the Environment 2(10):537–45. Batie, S.S. 2005. “Concluding Discussion.” In S. Lynch and S.S. Batie, eds. Building the Scientific Basis for Green Payments. Washington DC: World Wildlife Fund, pp. 32–36. Boisvert, R.N. 2001. “Annex 2: Joint Production in Four Outputs: Two Agricultural Commodities and Positive and Negative Externalities.” In L. Maier and M. Shobayashi, eds. Multifunctionality: Towards an Analytical Framework. Paris: Organization for Economic Co-operation and Development, pp. 125–32. Bruggeman, D., M. Jones, F. Lupi, and K. Scribner. 2005. “Landscape Equivalency Analysis: Methodology for Estimating Spatially Explicit Biodiversity Credits.” Environmental Management 36(4):518–34. Butler, L.D., and J.P. Workman. 1993. “Fee Hunting in the Texas Trans Pecos Area.” Journal of Range Management 46:38–42. Caldeira, K., M.G. Morgan, D. Baldocchi, P.G. Brewer, C.T.A. Chen, G.-J. Nabuurs, N. Nakicenovic, and G.P. Robertson. 2004. “A Portfolio of Carbon Management Options.” In C.B. Field and M.R. Raupach, eds. The Global Carbon Cycle. Washington DC: Island Press, pp. 103–30.

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Carson, R. 1962. Silent Spring. Boston: Houghton Mifflin. Chicago Climate Exchange (CCX). 2006. “CCX Project Offset Types.” Chicago Climate Exchange. Available at www.chicagoclimateexcha nge.com /environment /offsets / offset project types.html Cochrane, W.W. 1993. The Development of American Agriculture, 2nd ed. Minneapolis: University of Minnesota Press. Daily, G.C., ed. 1997. Nature’s Services: Societal Dependence on Natural Ecosystems. Washington DC: Island Press. Elliott, N.C., R.W. Kieckhefer, G.J. Michels, and K.L. Giles. 2002. “Predator Abundance in Alfalfa Fields in Relation to Aphids, within-Field Vegetation, and Landscape Matrix.” Environmental Entomology 31:253–60. Hoehn, J.P., F. Lupi, and M.D. Kaplowitz. 2003. “Untying a Lancastrian Bundle: Ecosystem Valuation in Wetland Mitigation.” Journal of Environmental Management 68(3):263–72. Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, and D. Xiaosu, eds. 2001. Climate Change 2001: The Scientific Basis. Cambridge, U.K: Cambridge University Press. Issacs, B., and D. Howell. 1988. “Opportunities for Enhancing Wildlife through the Conservation Reserve Program.” Transaction of the North American Conference on Wildlife and Natural Resources 53:222–31. Josling, T. 2005. “The WTO Agricultural Negotiations: Progress and Prospects.” Choices 20(2nd Quarter):131–36. Kleijn, D., F. Berendse, R. Smit, and N. Gilissen. 2001. “Agri-Environment Schemes Do Not Effectively Protect Biodiversity in Dutch Agricultural Landscapes.” Nature 413(October):723– 25. Kopp, R.J., and V.K. Smith. 1993. “Natural Resource Damage Assessments: The Road Ahead” In R.J. Kopp and V.K. Smith, eds. Valuing Natural Assets. Washington DC: Resources for the Future: 307–36. Kremen, C., N.M. Williams, R.L. Bugg, R.L., J.P. Fay, and R.W. Thorp. 2004. “The Area Requirements of an Ecosystem Service: Crop Pollination by Native Bee Communities in California.” Ecology Letters 7:1109–19. Labarta, R., S.M. Swinton, J.R. Black, S. Snapp, and R. Leep. 2002. “Economic Analysis Approaches to Potato-Based Cropping Systems: Issues and Methods.” Agricultural Economics Staff Paper 02-32. Michigan State University, East Lansing. Landis, D.A., and A.K. Fiedler. 2006. “Enhancing Beneficial Insects/Pollinators with Native

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Adoption of Environmental Technology.” In F. Casey, A. Schmitz, S. Swinton, and D. Zilberman, eds. Flexible Incentives for the Adoption of Environmental Technologies in Agriculture. Norwell, MA: Kluwer Academic Pub., pp. 7– 25. Ribaudo, M., R. Johansson, and C. Jones. 2006. “Environmental Credit Trading: Can Farming Benefit.” Amber Waves, 4(February): Available at: http://www.ers.usda.gov/Amberwaves/ February06/Features/FeatureUpdate.htm Robertson, G.P. 2004. “Abatement of Nitrous Oxide, Methane, and the Other Non-CO2 Greenhouse Gases: The Need for a Systems Approach.” In C.B. Field and M.R. Raupach, eds. The Global Carbon Cycle. Washington DC: Island Press, pp. 493–506. Robertson, G.P., J. Broome, E. Chornesky, J. Frankenberger, P. Johnson, M. Lipson, J.A. Miranowski, E. Owens, D. Pimentel, and L. Thrupp. 2004. “Rethinking the Vision for Environmental Research in U.S. Agriculture.” BioScience 54:61–65. Robertson, G.P., and P. Groffman. 2006. “Nitrogen Transformations.” In E.A. Paul and F.E. Clark, eds. Soil Microbiology, Biochemistry, and Ecology. New York: Springer. Pages (in press). Shogren, J. 2005. Species @ Risk: Using Economic Incentives to Shelter Endangered Species on Private Lands. Austin, TX: University of Texas Press. Thies, C., and T. Tscharntke. 1999. “Landscape Structure and Biological Control in Agroecosystems.” Science 285:893–95. Tscharntke, T., and R. Brandl. 2004. “Plant–Insect Interactions in Fragmented Landscapes.” Annual Review Entomology 49:405–30. Tweeten, L.G. 1979. Foundations of Farm Policy. Lincoln, NE: University of Nebraska Press. Warren, G.F. 1913. Farm Management. New York: Macmillan. Wilkinson, T.K., and D.A. Landis. 2005. “The Role of Plant Resources and Habitat Diversification in Biological Control.” In F.L. Wackers, ¨ P.C.J. van Rijn, and J. Bruin, eds. Plant Provided Food and Plant-Carnivore Mutualism. Cambridge, UK: Cambridge University Press, pp. 305–25. Zinn, J. 2005. “Setting the Stage: The Political Context for Agriculture and Ecosystem Policy Change.” In S. Lynch and S.S. Batie, eds. Building the Scientific Basis for Green Payments. Washington DC: World Wildlife Fund, pp. 4–7.

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Plants.” Available at http://www.ipm.msu. edu/plants/home.htm Landis, D.A., S.D. Wratten, and G.M. Gurr. 2000. “Habitat Management to Conserve Natural Enemies of Arthropod Pest in Agriculture.” Annual Review of Entomology 45:173–201. Leopold, A. 1949. A Sand County Almanac, and Sketches Here and There. New York: Oxford University Press. Maier, L., and M. Shobayashi. 2001. “Multifunctionality: Towards an Analytical Framework.” Paris: Organization for Economic Cooperation and Development. Marino, P.C., and D.A. Landis. 1996. “Effect of Landscape Structure on Parasitoid Diversity and Parasitism in Agroecosystems.” Ecological Applications 6:276–84. Marsh, G.P. 1864 (reprinted 2003). In D. Lowenthal, ed. Man and Nature. Seattle: University of Washington Press. Millennium Ecosystem Assessment. 2005. Ecosystems and Human Well-Being: Synthesis. Washington DC: Island Press. Ogg, A.C.W. 1999. “Evolution of EPA Programs and Policies That Impact Agriculture.” In F. Casey, A. Schmitz, S. Swinton, and D. Zilberman, eds. Flexible Incentives for the Adoption of Environmental Technologies in Agriculture. Boston: Kluwer Academic Publishers, pp. 27– 42. ¨ Ostman, O., B. Ekbom, and J. Bengtsson. 2001. “Landscape Heterogeneity and Farming Practice Influence Biological Control.” Basic and Applied Ecology 2:365–71. Pagiola, S., J. Bishop, N. Landell-Mills, eds. 2002. Selling Forest Environmental Services: Marketbased Mechanisms for Conservation and Development. London: Earthscan. Poe, G.L., and R.C. Bishop. 2001. “Information and the Valuation of Nitrates in Ground Water, Portage County, Wisconsin.” In J. Bergstrom, K. Boyle, and G. Poe, eds. The Economic Value of Water Quality. Northampton, MA: Edward Elgar, pp. 38–65. Reichelderfer, K., and M. Hinkle. 1989. “The Evolution of Pesticide Policy: Environmental Interests and Agriculture.” In C. Kramer, ed., Political Economy of U.S. Agriculture: Challenges for the 1990s. Washington DC: Resources for the Future, pp. 147–77. Ribaudo, M.O., and M.F. Caswell. 1999. “Environmental Regulation in Agriculture and the

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a v a i l a b l e a t w w w. s c i e n c e d i r e c t . c o m

w w w. e l s e v i e r. c o m / l o c a t e / e c o l e c o n

Ecosystem services and dis-services to agriculture Wei Zhanga,⁎, Taylor H. Rickettsb , Claire Kremenc , Karen Carneyd , Scott M. Swintona a

Department of Agricultural Economics, Michigan State University, East Lansing, MI 48824-1039, United States Conservation Science Program, World Wildlife Fund — U.S., Washington, DC 20037, United States c Department of Environmental Science Policy and Management, University of California, Berkeley, CA 94720-3114, United States d U.S. Agency for International Development, Biodiversity and Forestry Team, Washington, DC 20523, United States b

AR TIC LE I N FO

ABS TR ACT

Article history:

Agricultural ecosystems are actively managed by humans to optimize the provision of

Received 17 May 2006

food, fiber, and fuel. These ecosystem services from agriculture, classified as

Received in revised form

provisioning services by the recent Millennium Ecosystem Assessment, depend in turn

19 January 2007

upon a web of supporting and regulating services as inputs to production (e.g., soil

Accepted 13 February 2007

fertility and pollination). Agriculture also receives ecosystem dis-services that reduce

Available online 30 March 2007

productivity or increase production costs (e.g., herbivory and competition for water and nutrients by undesired species). The flows of these services and dis-services directly

Keywords:

depend on how agricultural ecosystems are managed and upon the diversity,

Ecosystem services

composition, and functioning of remaining natural ecosystems in the landscape.

Agriculture

Managing agricultural landscapes to provide sufficient supporting and regulating

Pollination

ecosystem services and fewer dis-services will require research that is policy-relevant,

Soil fertility

multidisciplinary and collaborative. This paper focuses on how ecosystem services

Ecology

contribute to agricultural productivity and how ecosystem dis-services detract from it.

Hydrology

We first describe the major services and dis-services as well as their key mediators. We

Environmental economics

then explore the importance of scale and economic externalities for the management of

Environmental policy

ecosystem service provision to agriculture. Finally, we discuss outstanding issues in regard to improving the management of ecosystem services and dis-services to agriculture. © 2007 Elsevier B.V. All rights reserved.

1.

Introduction

Covering over a third of total global land area (FAOSTAT, 1999)1, agriculture represents humankind's largest engineered ecosystem. Agricultural ecosystems both provide and rely upon important ecosystem services (ES). Daily (1997) has defined ES as “the conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfill human life”. ES can be classified into four main categories: provisioning, supporting, cultural, and regulating services (Fig. 1) (MA, 2005). Agricultural ecosystems are primarily

managed to optimize the provisioning ES of food, fiber, and fuel. In the process, they depend upon a wide variety of supporting and regulating services, such as soil fertility and pollination (MA, 2005; NRC, 2005), that determine the underlying biophysical capacity of agricultural ecosystems (Wood et al., 2000). Agriculture also receives an array of ecosystem disservices (EDS) that reduce productivity or increase production costs (e.g., herbivory and competition for water). The flows of these ES and EDS (Fig. 2) rely on how agricultural ecosystems are managed at the site scale and on the diversity, composition, and functioning of the surrounding landscape (Tilman, 1999).

⁎ Corresponding author. Tel.: +1 517 355 4563; fax: +1 517 432 1800. E-mail addresses: [email protected] (W. Zhang), [email protected] (T.H. Ricketts), [email protected] (C. Kremen), [email protected] (K. Carney), [email protected] (S.M. Swinton). 1 Agriculture land use statistics compiled by FAO for 1992-1993. 0921-8009/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolecon.2007.02.024

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Fig. 1 – Classification of ecosystem services from the Millennium Ecosystem Assessment (adapted and simplified from (Alcamo et al., 2003)). Agricultural lands typically are managed to maximize provisioning services, but demand many supporting and regulating services to do so. Dark arrows indicate the flow of these services that are the primary topic of this paper.

Indeed, the vast scope of agriculture as a “managed ecosystem” (Antle and Capalbo, 2002) embedded in a web of natural ecosystems offers both challenge and opportunity for optimizing the relative flow of ES and EDS to and from agriculture. This paper focuses on ES and EDS to agriculture (see the introduction of this special issue for a discussion of ES and EDS from agriculture). We first describe the major ES and EDS to agriculture and the key mediators. We then explore the importance of scale of ES and EDS provision to agriculture for effective and efficient management and make recommendations for promoting coordinated management practices. Finally, we discuss several outstanding issues in

regard to management of ES and EDS to agriculture and recommend potential research directions.

2. Ecosystem services and dis-services to agriculture A wide variety of ES and EDS confer benefits and costs, respectively, to agriculture. These are supplied by varied species, functional groups, and guilds over a range of scales and influenced by human activities both intentionally and unintentionally. Here we briefly describe the range of major ES

Fig. 2 – Ecosystem services and dis-services to and from agriculture. Solid arrows indicate services, whereas dashed arrows indicate dis-services.

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and EDS to agriculture and summarize them in Fig. 2. Treatment of each service is necessarily cursory, and citations are indicative rather than exhaustive.

2.1.

Ecosystem services to agriculture

Soil structure and fertility play a large role in determining where different kinds of farming take place and the quantity and quality of agricultural output. Earthworms and macro- and micro-invertebrates increase soil structure via burrows or casts and enhance soil fertility through partial digestion and communition of soil organic matter (Edwards, 2004). Nutrient cycling maintains soil fertility. Microorganisms (bacteria, fungi, actinomycetes) are critical mediators of this ecosystem service. For example, bacteria enhance nitrogen availability through the fixation of nitrogen from the atmosphere. This occurs most often in plants that have symbiotic relationships with N-fixing bacteria, but free-living soil bacteria can fix nitrogen as well (Vitousek et al., 2002). Microorganisms also enhance soil fertility by liberating nutrients from detrital organic matter (e.g. plant leaves) and retaining nutrients in their biomass that might otherwise be lost downstream (Paul and Clark, 1996). Non-crop plants can also be key to soil fertility—they are used to replenish nutrients to agricultural land during fallow periods (Ramakrishnan, 1992) or through the so called “rotation effect” (Pierce and Rice, 1988). While the processes above maintain soil fertility, soil retention is key to keeping those nutrients in place and available to crops. To do this, cover crops are used to retain soil and nutrients between crop cycles while hedgerows and vegetation along waterways reduce erosion and runoff from fields. Certain farming practices, such as mechanical plowing, disking, cultivating, and harvesting can decimate the flow of soil-based ES via disturbing the functioning of soil microbial communities. Conservation tillage, including both no tillage and minimum tillage (Brown, 2003) represents a valid approach to conserving these ES. Insects provide vital ES to agriculture including dung burial, pest control, and pollination. Beetles in the family Scarabaeidae are especially efficient at providing dung burial services (Ratcliffe, 1970). They decompose wastes generated by large animals (a potential EDS from agriculture), thereby recycling nitrogen, enhancing forage palatability, and reducing pest habitat, resulting in significant economic value for the cattle industry (Losey and Vaughan, 2006). Crop pollination is perhaps the best known ES performed by insects (Losey and Vaughan, 2006). The production of over 75% of the world's most important crops that feed humanity and 35% of the food produced is dependent upon animal pollination (Klein et al., 2007). Bees comprise the dominant taxa providing crop pollination services, but birds, bats, moths, flies and other insects can also be important. Wild pollinators can nest within fields (e.g., ground nesting bees), or fly from nesting sites in nearby habitats to pollinate crops (Ricketts, 2004). There has been increasing evidence that conserving wild pollinators in habitats adjacent to agriculture improves both the level and stability of pollination, leading to increased yields and income (Klein et al., 2003a). Natural control of plant pests is provided by generalist and specialist predators and parasitoids, including birds, spiders,

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ladybugs, mantis, flies, and wasps, as well as entomopathogenic fungi (Naylor and Ehrlich, 1997). This ES in the short term suppresses pest damage and improves yield, while in the long-term maintains an ecological equilibrium that prevents herbivore insects from reaching pest status. This important ES, however, is increasingly threatened by biodiversity loss (Wilby and Thomas, 2002), modern agricultural practices (Naylor and Ehrlich, 1997), and human alterations of natural ecosystems. For instance, insecticide use in agriculture tends to decimate natural enemy populations, often having the unintended consequence of either exacerbating existing pest problems, or actually leading to the emergence of new pests (Krishna et al., 2003). For beneficial insects to provide the above direct ES to agriculture, a number of subsequent supporting and regulating services are required. For example, predators and parasitoids rely on a variety of plant resources such as nectar, pollen, sap, or seeds (Wilkinson and Landis, 2005) as alternative food sources to fuel adult flight and reproduction. Non-crop areas can provide habitat where beneficial insects mate, reproduce, and overwinter. Evidence shows that increased landscape complexity, which typically means increased availability of food sources and habitat for insects as compared to mono-culture landscapes, is correlated with diversity and abundance of natural enemy populations (Thies and Tscharntke, 1999), and with enhanced pest control in some cases (Thies et al., 2003). Enhanced abundance and diversity of natural enemies, however, do not necessarily provide enhanced pest control, since pest densities may also respond positively to landscape complexity (Thies et al., 2005). In the face of evidence of population declines among beneficial insects (Kremen et al., 2002), interest is rising in habitat management to foster beneficial species. “Conservation biological control” of crop pests is founded on creating a suitable ecological infrastructure within the agricultural landscape to provide resources such as food for adult natural enemies, alternative prey or hosts, and shelter from adverse conditions (Landis et al., 2000). For wild pollinators, the construction of nest boxes, planting of native plant species with sequential flowering, and soil stabilization have been proposed (Vaughan et al., 2004), along with Integrated Pest Management practices that minimize the use of pesticides toxic to pollinators. Beyond specific local practices to protect habitat for beneficial insects, there is a growing evidence that diversified landscapes hold great potential for the conservation of biodiversity and sustaining ES performed by insects (Bianchi et al., 2006). The issues of coordinated habitat management at landscape scales are discussed in a separate section. Water provision and purification fulfill requirements for water of sufficient quantity, timing, and purity for agricultural production. Vegetation cover in upstream watersheds can affect the amount, quality, and stability of the water supply to agriculture. It is not clear that maintaining forest cover increases the absolute amount of water supplied to downstream areas. Other vegetation may do just as well (Groffman et al., 2004). What is clearer is that forests stabilize water flow to reduce differences in flow between wet and dry seasons (e.g., Yangtze basin (Guo et al., 2000)). Forests can also stabilize soil to reduce sediment load in rivers. In Australia,

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trees can improve water infiltration within woodlands, reducing surface runoff and soil salinization (Eldridge and Freudenberger, 2005). Wetlands and riparian vegetation can also improve water quality and attenuate floods (Houlahan and Findlay, 2004). Genetic diversity provides the raw material for natural selection to produce evolutionary adaptations. Similarly, breeders of crops and domestic animals utilize existing genetic variation to select artificially for desirable traits. Failing to maintain sufficient genetic diversity in crops can incur high costs (Hawtin, 2000). For example, the Irish potato famine at the end of the 1830s can be attributed in part to the fact that there were so few different genetic strains of potatoes in the country, making the crop susceptible to the devastating potato blight fungus (Hawtin, 2000). The problem was resolved by using varieties in Latin America, where the potato had originated, that were resistant to the disease (EsquinasAlcázar, 2001). Genetic diversity is not only important to avoiding catastrophic losses, but also improving or maintaining agricultural productivity. Many important crops could not maintain commercial status without the regular genetic support of their wild relatives (de Groot et al., 2002). In addition, in many crop systems, particularly orchard crops and in the production of hybrid seed, different cultivars (genotypes) are required for seed or fruit set (Free, 1993; Delaplane and Mayer, 2000). Genetic diversity at the species level can also enhance biomass output per unit of land through better utilization of nutrients and reduced losses to pests and diseases (see Tilman, 1999 for a detailed discussion). Another (abiotic) form of ES to agriculture involves climate, including temperature and precipitation regimes but also the frequency and severity of extreme weather, droughts, floods, etc. Favorable climate confers a cost advantage to those who farm there. Suitable and stable climate relies on atmospheric regulation, which like many other ES is influenced by the functioning of multiple ecosystems.

2.2.

Ecosystem dis-services to agriculture

Crop pests, including herbivores, frugivores, seed-eaters, and pathogens (specifically, fungal, bacterial and viral diseases) decrease productivity and in the worst case can result in complete crop loss. Revenue loss from insect pests and pathogens can be disproportionately high for crops whose price depends heavily on quality, such as fresh produce (Babcock et al., 1992). Ironically, pesticide use has led to increases in pest outbreaks; over-reliance on pesticides in recent decades has led certain species to evolve genetic resistance to specific pesticide compounds, triggering pest outbreaks and resurgence. This can make chemical control more costly and result in unintended negative health outcomes for non-target organisms, including humans (Thomas, 1999). Non-crop plants can reduce agricultural productivity via competition for resources and allelopathy (Stoller et al., 1987). In fields, weed competition for sunlight, water and soil nutrients can reduce crop growth by limiting access to required resources (Welbank, 1963). Allelopathy also works at withinfield scale, for example via toxic root exudates of certain weed species that can impair crop growth (Weston and Duke, 2003).

Competition for ecological resources of value to agriculture also occurs at landscape scales. Water consumed by other plants can reduce water available to agricultural production. For example, trees can reduce the recharge of aquifers used for irrigation (e.g., conifers in South Africa (van Wilgen et al., 1998)). Trees can also transpire water away from rivers and canals (e.g., tamarisk in U.S. (Zavaleta, 2000)). Competition for pollination services from flowering weeds and non-crop plants can also reduce crop yields (Free, 1993).

3. Implications of ES for agricultural management Ecosystem services and dis-services to agriculture influence both where and how people choose to farm. For example, many major fruit-producing regions in temperate climate zones are located downwind of large bodies of water that helps to regulate local atmospheric temperature changes (Ackerman and Knox, 2006) and reduces the probability of late frosts that might damage fruit blossoms. The major cereal grain producing regions of the North American prairie, the Asian steppe and the South American pampas are all located on deep topsoil with high organic matter and good water holding capacity. Farmers chose these locations because flows of ES to agriculture made them potentially more profitable than elsewhere. ES to agriculture affect not only the location and type of farming, but also farmland's economic value. While determined in part by crop price, values of agricultural land also depend on production costs linked to ES such as soil fertility and depth, suitable climate and freedom from heavy pest pressure (Roka and Palmquist, 1997). The scales at which services are provided to agriculture are also critical to how management decisions are made. Many key organisms that provide services and dis-services to agriculture do not inhabit the agricultural fields themselves. Rather, they live in the surrounding landscape or they may move between natural habitats, hedgerows and fields. Table 1 summarizes the major actors and scales of provision for the ES and EDS described in the previous section. The scales at which ES and EDS are rendered determine the relevant management units for influencing their flows to agriculture. If they respond to factors on a small scale then it may be possible to manage them within a single farm. But if they respond to factors on a larger scale, then the management actions of individual farmers must be coordinated, with several different decision-makers involved (Weibull et al., 2003). Table 1 reveals that scarcely any ES or EDS are provided only at the field level, so management will be more effective if performed at larger scales. The appropriate scale at which to manage will depend upon each specific provisioning ES and the supporting and regulating ES on which it relies. Table 1 also highlights the importance of a farm's landscape context in managing many of the supporting and regulating ES and EDS. For example, landscapes that contain diverse habitat types typically are more compatible for beneficial insects and in most cases result in enhanced biological control of pests and provision of pollinators (Kremen and Chaplin-Kramer, in press).

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Table 1 – Major ecosystem services (ES) and dis-services (EDS) to agriculture, the scales over which they typically are provided, and main guilds or communities whose activities typically supply them ES or EDS

Field a

Services Soil fertility and formation, Microbes; invertebrate nutrient cycling communities; legumes Soil retention Cover crops Pollination

Ground-nesting bees

Pest control

Predators and parasitoids (e.g., spiders, wasps)

Water provision and purification Genetic diversity Climate regulation

Dis-services Pest damage

Competition for water from other ecosystems Competition for pollination services a b c d

Farm b

Landscape c

Vegetation cover Cover crops

Riparian vegetation; floodplain

Bees; other pollinating Insects; other pollinating animals animals Predators and parasitoids (e.g., spiders, wasps, birds, bats) Vegetation around Vegetation cover in watershed drainages and ponds

Crop diversity for pest and disease resistance Vegetation influencing Vegetation influencing microclimate microclimate (e.g. agroforestry)

Insects; snails; birds; mammals; fungi; bacteria, viruses; weeds Weeds Flowering weeds

Region/globe d

Vegetation cover in watershed

Vegetation cover in watershed Wild varieties

Vegetation influencing stability Vegetation and soils for of local climate; amount of carbon sequestration precipitation; temperature and storage

Insects; snails; birds; mammals; fungi; bacteria, viruses; weeds Vegetation cover near drainage ditches Flowering weeds

Insects; snails; birds; mammals; range weeds Vegetation cover in watershed

Vegetation cover in watershed

Flowering plants in watershed

Services provided from within agriculture fields themselves. Services provided from farm property, but not necessarily in active fields themselves. Services provided from landscape surrounding typical farms, not from farmer's property. Services provided from broader region or globe.

The distinct scales at which ES and EDS are provided to agriculture shape farmers' incentives over how to farm to optimize those services. ES provided at the field and farm scale chiefly affect the farm itself, so farmers have a direct, private interest in managing such ES as soil fertility, soil retention, pollination and pest control. At larger scales, farmers face classic economic externality and common pool resource problems. For example, integrated pest management strategies that restore landscape complexity could increase services from natural enemies and pollinators while reducing the pollutant effects of pesticide use (Ehler and Bottrell, 2000; Tilman et al., 2001). But greater landscape complexity is a common pool resource in the sense that i) it is costly for a farmer to exclude others from access to the enhanced pollinator and pest predator services (i.e., non-exclusive, Ostrom, 1990), and ii) to some extent the consumption of the services is rivalrous, so that other farmers that do not bear the costs of supplying these services may actually compete for them. Hence, while a farmer who reserves land for pest predator and pollinator habitat will enjoy some benefits, other benefits will be enjoyed by neighbors who avoid the need to rent bee hives or spray for pests without needing to give up income-generating cropland. Such economic externalities imply that the first farmer, acting alone, would lack the incentive to set aside the optimal amount of habitat for both the farmer and the neighbor (Meade, 1952). Although public policies exist that aim to create incentives for farmers to act on behalf of the collective good, current

policies are not designed to encourage coordinated behavior. For example, the United States currently has programs to reward farmers for voluntary adoption of land management practices that encourage natural pest control. The programs use government sharing of costs (Environmental Quality Incentives Program) and environmental stewardship payments (Conservation Security Program) to promote adoption of certain practices that are determined at the state level. While helpful at the farm and field scale, current programs are not designed to encourage coordinated farming practices across a landscape. Exploratory research into collective action has shown that incentives can be designed to induce coordinated habitat conservation by individual land managers across a landscape (Parkhurst et al., 2002). However no existing policies have been able to achieve this potential for coordinated habitat conservation (Parkhurst and Shogren, 2003).

4.

Major issues and research needs

The study of ES is still relatively young, and many unresolved issues remain. How well understood are the ecosystem functions behind the ES that affect agriculture's performance? Certain field-scale dimensions are familiar topics of agronomic research. Crop yield response to soil fertility and water supply has been extensively studied (e.g., Hanks and Ritchie,

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1991), as have crop yield responses to pest pressure (e.g., Cousens et al., 1987). However, these same topics have received much less attention at larger scales. Likewise, less attention has been paid to the mechanisms of microbial underpinnings of soil fertility. A major research agenda exists for disaggregating and separately describing those ES in order to identify 1) their separate contributions to agricultural productivity, 2) the most suitable scale for management, 3) context dependency, 4) trade-offs and valuation, 5) management intensity, and 6) the design of incentives to encourage ES provision. In general, research needs to document and track the individual ES flows and their contributions to agricultural production and/or land value. Much of this depends on better comprehension of the ecological processes that underpin these services (Kremen, 2005). For the non-marketed supporting and regulating ES, the dissemination of scientific information on their contributions to agricultural production could cause the prices of related marketed goods to adjust, resulting in better functioning markets that provide minimum economic incentives for ES conservation. Research needs in this case include measuring the ES in question and documenting their impacts on agriculture. We proceed by highlighting several important ES research needs that could contribute to better agricultural performance. First, while many ES are known to be important to agriculture, the mechanistic details of their provision remain poorly understood (Kremen, 2005). Although much is known about biochemical relationships, such as crop yield response to fertilizer or pest mortality from pesticides, far less is known about how species in natural ecosystems generate services that support agriculture. Specifically, for each ES, ecological data are needed to answer the following major questions (Kremen, 2005): Which species are most important? How do these species, communities and the services they provide respond to alternative management regimes? What are their requirements for persistence in agricultural landscapes? How stable are species, communities and services over space and time? Over what scales do they provide services to agriculture? Empirical evidence and well-developed models are in early stages for most ES. There is a need for more detailed case studies at the scale of typical land-use decisions (e.g., Guo et al., 2000; Ricketts et al., 2004), and then for meta-analyses to understand typical effect sizes and general trends (Kremen, 2005). A second need is for deeper understanding of the scales at which ecosystems provide services to people. The ecosystems that supply services to agriculture are often far from the fields that benefit from them (Table 1). This presents novel problems for landscape conservation and management. Typically conservation or farming decisions are informed by the in situ value of that parcel (e.g., importance of species that live there, or potential productivity for agriculture). Managing landscapes for ES, however, requires understanding the flows of services from one parcel to others (e.g., flow of pollinators from natural areas to surrounding crops (Ricketts, 2004), flow of water provision services from upland areas to areas downstream (Guo et al., 2000)). ES supply and demand must be analyzed spatially across the landscape, in order to make explicit the locations of ES providers and

consumers, and the flows of services from one to the other (Eade and Moran, 1996; Kremen, 2005; Naidoo and Ricketts, 2006). Third, many of the ES and the ecological functions that supply them are context-dependent (Kremen, 2005). Universal rules about what constitutes an ES and what underlies an ES rarely exist. The importance of a given species, community, or guild in providing ES to agriculture varies widely across crops and regions. For example, trees in the landscape provide an ES in southwestern Australia by improving water infiltration into soil (Eldridge and Freudenberger, 2005), but provide an EDS in South Africa by transpiring water and reducing groundwater recharge (van Wilgen et al., 1998). Note that it is not that trees provide different functions in different settings, but rather that the services or dis-services they provide have different relative values according to the ecological conditions of a given setting. Because the attributes that humans value differ from one setting to another, the same basic ecological processes are laden with different values. Different members of the same service-providing guild may respond differently to management of agricultural landscapes. In Indonesia, some wild bee species that provide pollination services to coffee decrease in abundance with increasing land-use intensity while others increase (Klein et al., 2003b). The impact of land-use change on coffee production therefore depends on which bees are the major coffee pollinators. Fourth, decisions regarding management of ES within agricultural landscapes will typically involve trade-offs, some of them among different services (MA, 2005). For example, managing a landscape to maximize food production will probably not maximize water purification for people downstream, and native habitats conserved near agricultural fields may provide both crop pollinators and crop pests (Steffan-Dewenter et al., 2001). The question of whether intensive or extensive agriculture best optimizes the various trade-offs associated with ES provision is an important issue requiring targeted research. Another form of trade-off is between private financial gains and social losses from alternative management choices. For example, controlling crop pests could be accomplished through (a) maintaining populations of natural predators, (b) by labor-intensive handspraying, or (c) by aerial spraying. While (a) and (b) are likely to lead to higher private costs, they may entail reduced social costs from ecological disturbance and public health hazards. The goal of public policy should be optimizing these tradeoffs to maximize socially desirable outcomes. To date, the majority of studies on ES have focused on a single service, but evaluating these trade-offs will require broader studies that include several ES in the same system (Eade and Moran, 1996). Evaluating the monetary value of ES that lack markets constitutes one widely understood approach to assessing trade-offs. During the past three decades, numerous empirical valuation studies have emerged for certain ES, such as regulation of air and water quality. The number of studies that have addressed ecological functions that potentially lead to beneficial services is much smaller, as is the number that have explored the values of combined ES (Cropper, 2000). For

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effective analysis of trade-offs, future valuation research should focus on policy decision endpoints, and it should address the “adding up” problem of multiple ES from the same decision (Cropper, 2000). Well-designed economic research in collaboration with ecologists continues to be needed both to estimate values to motivate policy and to design effective incentives. Monetary valuation of ES is not the only way to assess economic trade-offs. Indeed, concerns about the validity of many nonmarket valuation methods (Diamond and Hausman, 1994) and the difficulty of aggregating nonmarket values for different ES counterbalance their ease of use. Because preferences vary across individuals and groups, one useful alternative approach to integrated assessment of agricultural production systems is trade-off analysis that integrates disciplinary data and models to support informed policy decision making (Antle et al., 2003). Future research to aid in the evaluation of alternative agro-ecological systems should innovate in both valuation and trade-off approaches to integrated assessment. Although understanding the biophysical aspects of ES (e.g., which processes, which species, what habitat requirements, what scales) is necessary, it is not sufficient for improving the management of ES to agriculture. To evaluate trade-offs with other land management options, and to inform policy decisions, it is essential to estimate the economic value of ES with equal rigor to their biophysical relationships (Heal, 2000). But merely stating the economic value of a given service or set of services does not create incentives to maintain it. Policies will typically be required to create markets for currently nonmarketed ES or to compensate people whose ecosystem management provides beneficial externalities to others, internalizing ES value into land management decisions. Opportunities exist to manage landscapes to benefit agriculture by providing more supporting and regulating ecosystem services and fewer dis-services. To seize those opportunities will require research that is policy-relevant and collaborative, engaging at a minimum the fields of ecology, hydrology, economics and political science.

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