Natural resources are resources supplied by nature that are used by humans. Air, water, soil, wildlife and forests are renewable natural resources, as long as humans do not overuse them. As for fossil fuels, they take millions of years to form naturally and cannot be replaced once they are used, thus they are known as non-renewable natural resources.
Deforestation
- Deforestation is the clearing of forests.
- Many forests are cleared to meet the increasing demands for land and materials such as wood.
- With modern technology, forests are being cleared at a much faster rate than they can be replaced.
- This leads to the loss of habitats.
- This causes soil erosion, where topsoil, the most fertile layer of the soil, to be washed away or eroded during heavy rain due to no protection as the trees are not tall enough or there are no trees at all.
- Eroded soil may be deposited in rivers and streams, thus resulting in flooding.
- When sunlight falls directly onto the soil, water will evaporate at a much faster rate from the soil, which then hardens, causing the land to become barren. Plants will not be able to grow in the soil. The destruction of land leading to desert-like conditions is called desertification. Consequently, habitats are lost and many species of organisms become extinct. Overgrazing by animals also lead to desertification because the plants cannot regenerate fast enough.
- Deforestation also causes climate changes. Rainwater that is retained and absorbed by the roots of tress is lost as water vapour during transpiration.
Uncontrolled fishing practices
- As humans catch fish for food, the increasing human population increases the demand for fish. Some species of fish have been caught in such large numbers that their populations have drastically decreased. These species are over fished.
- Modern fishing gear catches marine life indiscriminately, such that it does not distinguish between the targeted catch and and immature organisms or unwanted species, such as turtles, sharks and dolphins, which are unintentionally caught.
- Although these "accidental catches" are dumped back into the sea, they often die.
- Other methods of fishing also destroy the seabed and marine habitat.
- If fishing practices are not controlled, some species of fish will be caught faster than they can be replaces. Young fish that are caught will not have a chance to grow.
http://web.mit.edu/12.000/www/m2011/finalwebsite/graphics/intro/OVERFISHINGfromPEW.gifEutrophication
- Chemical fertilisers cotaining nitrates and phosphates are used to increase the yield of crops.
- However, overuseage of these fertilisers may lead to water pollution.
Biomagnification
- Refers to the increase in the concentration of a substance, such as the pesticide DDT, that occurs in the food chain as a consequence of food chain energetics and low (or non-existent) rate of excretion/degradation of the substance.
- Organisms feeing at higher levels in a foo chain can accumulate huge amounts of DDT from eating their prey. DDT may not be poisonous to large organisms in small amounts but may be harmful in larger amounts.
http://library.thinkquest.org/04oct/01590/pollution/culturaleutroph.jpg
http://www.pollutionissues.com/images/paz_01_img0027.jpg
No comments:
Post a Comment