Bio Folio.docx

Human activities that threaten an ecosystem

Human activities often affect the whole ecosystems. With great advancements in the medical field, modern farming technique and better infrastructure, the world’s population has grown to over 6 billion today. Conflicts, therefore arise between the need to meet the immediate human demands in the short term and the need to protect and conserve ecosystems from long-term damage. Many of the problems related to the environment are the results of human activities and human interference with the ecosystems. Some human activities that have undesirable effects on the environment are shown in the table below.

Human activities that have undesirable effects on the environment

Deforestation

Overuse of fertilisers in inintensive farming

Dumping of domestic and industrial waste

Burning of fossil fuels

soil erosion

eutrophication

water pollution

air pollution

Deforestation The rapid destruction of woodlands or the removal of trees from forests is known as deforestation. Every year, vast areas of forests are cleared to make way for agriculture and development. It has been estimated that more than 50 million acres of rainforests are destroyed or seriously degraded every year.

Effects: Soil erosion Soil erosion is the removal and thinning of the soil layer due to the physical and climatic processes, such as high rainfalls. The absence of plant root systems makes the soil structure unstable. When there are heavy rains for a long period of time, the top layer of the soil crumbles. The eroded soil is then carried by moving water and deposited at the bottom of rivers.

Overuse of fertilisers in intensive farming Excessive use of land for intensive farming decreases the space and resources available for other species. In intensive farming, farmers often use inorganic fertilisers, which contain nitrates, phosphates and potassium ions, to improve crop yields. Since nitrate and ammonium ions are highly soluble, they do not remain in the soil for long and are quickly leached into the surrounding river and lakes.

Effects: Eutrophication

Dumping of domestic and industrial waste An increase in human population generates an increase in both domestic and industrial waste.

Effects: Water pollution Great danger to living organisms as toxic substances and other pollutants from the dumpsites leak into the ground and eventually pollute the nearby water sources.

Burning of fossil fuels The burning of fossil fuels adds about 75% of carbon dioxide to the atmosphere. An increase in carbon dioxide level is associated with the greenhouse effect and global warming.

Effects:  The greenhouse effect  Global warming  Air pollution

Air pollution 1. Air pollution is caused by the presence of pollutants in the air which are harmful to life and the environment. 2. Sources of pollution are as follows: a) Burning -

Rubbish

-

Forest

-

Solid waste

b) Factories and industries Burning of fossil fuels such as petroleum, diesel and gas in factories and power stations. Agricultural industries that use agrochemicals such as fertilizers, pesticides, insecticides and herbicides.

c) Motor vehicles -

Release harmful gases in car exhaust fumes.

3. Burning of fossil fuels produces gases such as sulphur dioxide and nitrogen dioxide. Burning of rubbish and emission of smoke and fumes from car exhausts and chimneys in factories produce carbon dioxide, carbon monoxide and soot (unburnt carbon particles).

4. Increase in carbon dioxide (a greenhouse gas) in the atmosphere will trap the Sun’s radiation and retain it as heat in the Earth’s atmosphere. This contributes to the greenhouse effect.

5. This will cause an increase in the Earth’s temperature.

Source of pollution: (a) Pollutant: Dust and soot -Cement factories, quarries, sawmills, burning of rubbish and motor vehicles. (b) Pollutant: Carbon monoxide, carbon dioxide, sulphur dioxide and nitrogen dioxide -Burning of fossil fuels and rubbish -Car exhaust fumes. (c) Pollutant: Lead -Car exhaust fumes which contain lead (d) Pollutant: Agrochemical substances -Activities of agricultural industry (e) Pollutant: Radioactive radiations -Nuclear power stations (f) Pollutant: Chlorofluorocarbon (CFC) -Aerosol and foam industries