EFFECTS OF DEFORESTATION
Soil erosion
-The leafy canopy of the trees in the rainforest protects the soil from the impact of falling rain.
-Rainwater is retained and absorbed by the roots of trees and gradually released into streams.
-Without trees, the soil is directly exposed to the force of rain. Topsoil is washed away or eroded during heavy rain.
soil erosion (picture from wikipedia)
Flooding
-Eroded soil may be deposited in rivers and streams, blocking the flow of water.
-The water levels in rivers rise rapidly causing flood.
flooding (picture from earth wikipedia)
Desertification
-When sunlight falls directly onto the soil, water evaporates rapidly from soil which then hardens.
-Plants cannot grow in the soil as the land becomes barren with the topsoil eroded.
-The destruction of land leading to desert-like conditions. Habitats are lost and many species of organisms become extinct.
desertification of land (picture from yahoo)
Climate changes
-Rainwater that is retained and absorbed by roots of trees is lost as water vapour during transpiration.
-The water vapour condenses and falls as rain.
-When trees are cleared, the area becomes dry and warm and annual rainfall decreases.
UNCONTROLLED FISHING PRACTICES
-Humans catch fish for food. As human population increases so does the demand for fish.
-Some species of fish have been caught in large numbers. Their population drastically decreased. (over-fished)
-Modern fishing gear does not distinguish between the targeted catch and immature organisms or unwanted species.
-shrimp or prawn trawlers drag large fishing nets along the seabed. Unwanted species are trapped
trawling (picture from yahoo)
-Scallop dredges scrape teh seabed, destroying coral reefs and organisms that live on seabed
dredging (picture form MSN)
EFFECTS OF UNCONTROLLED FISHING PRACTICES
-Some species of fish will be caught faster than they can be replaced. Young fish caught will not have a chance to grow and reproduce.
-Population will decrease. Other marine organisms that are unintentionally caught often die.
-Some species may become endangered or even extinct.
POLLUTION
-As human populations increase and technology advances, many products of technology is toxic.
-Toxic waste move into air and water, threatening lives of organisms
air pollution from WWII production (picture from wikipedia)
Sewage
-Untreated sewage may contain disease causing bacteria large amount of people may be affected with diseases if they got into drinking water.
-Bacteria grow and multiply rapidly using up all the oxygen causing death of fishes
-Bacteria that do not require oxygen breaks down the organic waste. Bad smelling gases (ammonia) is released durign the process.
sewage (picture yahoo)
Eutrophication
-Syndrome of ecosystem responsesto human activities that fertilize water bodies with nitrogen and phosphates, often leading to changes in animal and plant populations and degrations of water and habitat quality.
-Fertilisers that are not absorbed by crops will be washed away into rivers by rainwater.
-Submerged algae and plants die due to lack of sunlight. Dead bodies of algae and water plants are decomposed by bacteria which multiply and using up the oxygen in water.
-Other organisms such as fish die due to lack of oxygen.
fishes kill as result of eutrophication.Algal bloom in Australia(picture from encyclopedia of Earth)
Inorganic waste
-Industries dump large amounts of inorganic waste products (poisonous metals) into rivers
lnsecticides
-lnsecticides such as DDT (dichlorodiphenyltrichloroethane) are non-biodegradable. They cannot be broken down by micro-organisms. They remain in the soil
-lnsecticides are carried into streams rivers by rainwater and poison fish or animals.
-DDT accumulates in the bodies of consumers which result it to be passed along the food chain, increasing in concentration in the bodies of organisms along the trophic levels (bioamplification)
-Eventually the concentration of DDT in the top consumers accumulates to the extent that the top consumers suffer toxic effects due to bioaccumulation