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Ecology @ 5:43 AM
10) Discuss the impact of human activities on our ecosystem, highlighting issues on deforestation, over-fishing, eutrophication, biomagnification.
1)
Deforestation-Soil erosion
Deforestation is the clearing of forests. When the trees are removed, soil is exposed dierctly to the force of the rain. Topsoil, the most fertile layer of soil, gets washed away or eroded during heavy rain, espically when rain falls on steep slopes.
-Flooding
Eroded soil may be deposited in rivers and streams, blocking the flow of water, thus causing floods.-Desertification
Sunlight falls directly onto the soil. Water evaporates rapidly from the soil, which then hardens With the topsoil eroded, the land becomes barren. Plants cannot grow in the soil, Thus, organisms which depend directly or indirectly on plants for food will die off. This is known as desertification.-Climate changes
Rain water that is retained and absorbed by roots of trees is lost as water vapour during transpiration. The water vapour eventually condenses and falls as rain. When trees are cleared, the area becomes dry and warm thus, the annual rainfall decreases.2)
Over-fishingAs human populations increase, so does the demand for fish, thus over fishing i common. If the situation is not controlled, some species of fish are caught faster than they can be replaced. Young fish that are caught will not have a chance to reproduce. Hence, fish populations will decrease.3)
EutrophicationNitrates and phosphates present in the fertilizers are useful nutrients for the growth of algae and water plants. The enrichment of nutrients leads to rapid growth and multiplication of algae and water plants. Submerged algae and water plants die due to lack of sunlight. The dead bodies of the algae and water plants are decomposed by bacteria. Bacteria grow and multiply rapidly, using up oxygen in the water. Thus, other organisms and fish die due to a lack of oxygen.4)
BiomagnificationSome insectisides such at DDT are non-biodegradedable. These insectisides may be carried away into rivers, lakes, streams by rainwater when it is raining. Fish or animals may take in the polluted water. THe insectiside is stored in fatty tissue of the organism and will not be excreted. Organisms feeding at higher levels in the food chain will also get poisoned. And thus they will die and the population will decrease.
