OUR IMPACT ON THE ENVIRONMENT
How do we affect the ecosystem?
Natural resources are resources supplied by nature. Air, water, soil, forests and wildlife are renewable natural resources. This means they can be replaced in the ecosystem by natural cycles as long as humans do not overuse them. On the other hand, natural resources such as fossil fuels take millions of years to form naturally. Since their formation takes so long, they cannot be replaced once they are used, thus they are called non-renewable natural resources.
Humans are continually using and depleting the Earth's natural resources. This upsets the balance of nature and causes lasting damage to the environment. Since the environment damage caused is largely irreversible, human activities must be carefully planned and monitored to preserve and conserve the environment for the future.
Deforestation
The clearing of forests is known as deforestation.
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.
Why are forests cleared?
1. Land is needed for urban development, e.g. for building houses, roads and factories.
2. Land is needed for growing crops
3. Land is used for growing grassland for animal grazing
4. Firewood is a source of fuel
5. Wood is used as construction materials and is turned into pulp for making paper.
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EFFECTS OF DEFORESTATION
Figure 1. Deforestation
SOIL EROSION
Deforestation causes soil erosion. The leafy canopy of the trees protect the soil from the impact of falling rain. Rainwater is retained and absorbed by tree roots, and gradually released to the soil and then to nearby rivers, streams and lakes.
When trees are removed, the soil is directly exposed to the force of the rain. There are also no roots to bind the soil. The topsoil, the most fertile layer, is eroded (gets washed away) during heavy rains, especially if the rain falls on steep slopes. Soil erosion can lead to flooding. If too much topsoil and fertilizer filled soil makes its way into rivers, it negatively impacts the marine life. The fertilizer and nutrients found in the soil are used up by algae resulting in them mulptiplying uncontrollably. The algae numbers in such streams or lakes increase so much that they take up all the oxygen in the water, leading to eutrophication (depleting of oxygen) and the death of marine life.
Figure 2. Soil Erosion
FLOODING
Soil erosion due to deforestation can leaf to floods. The eroded soil may be deposited in river banks and streams, blocking the flow of water. The water levels in rivers rise rapidly, causing flooding.
Figure 3. Flooding in Houston
DESERTIFICATION
When forests are cleared, the leafy canopy of trees no longer exists, sunlight falls directly onto the soil. Water evaporates rapidly from the soil, causing it to harden. The land becomes barren ans plants cannot grow in the soil. The survival of organisms that depend directly or indirectly on plants for food are also threatened.
The destruction of land leading to desert like conditions is called desertification. Desertification results in habitats being lost and the extinction of many species of organisms.
Overgrazing by animals can also lead to desertification because the plants are not able to regenerate fast enough.
Figure 4. Desertification
CLIMATE CHANGES
Deforestation also causes climate changes. Rainwater that is retained and absorbed by the roots of trees is lost as water vapor during transpiration. The water vapor eventually condenses and falls as rain. When trees are cleared, there are fewer clouds, less transpiration and less rainfall. The area becomes dry and warm, and annual rainfall decreases.
Figure 5. Starving polar bear due to climate change
Uncontrolled fishing practices
Humans catch fish for food. As the human population increases, so does the demand for fish. Some species of fish have been caught in such large numbers that their populations have drastically decreases. It is said that these species are over-fished.
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Most modern fishing gear used in commercial fishing catches marine life indiscriminately. It does not distinguish between the targeted and non targeted cash (e.g. immature organisms or unwanted species). Some examples of harmful commercial fishing methods are:
- Drift nets are nets that are left freely in the seas. These nets trap almost everything in their path.
- Shrimp or prawn trawlers drag large fishing nets along the bottom of the sea (seabed), trapping marine life indiscriminately.
- Scallop dredges scrape the seabed, destroying coral reefs and organisms that live on the seabed.
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Marine life such as turtles, sharks and dolphins are often unintentionally caught using these fishing methods. Although these accidental catches are dumped back into the sea, they often do not survive.
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Another harmful fishing method, used to catch fish or pets, is called cyanide fishing. In this method, cyanide, a poison, is squirted into the water around coral reefs. The cyanide stuns reef fish and makes them unable to swim properly. The fishermen then capture the fish and sell them as pets. Explosives such as dynamite are also used to stun and catch reef fish. Both cyanide and explosives kill corals and other reef organisms.
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Effect of uncontrolled fishing practices
- Some species of fish will be caught faster than they can be replaced. Young fish are caught, and do not have a chance to reproduce. Eventually species will go endangered and then extinct.
Figure 6. Scallop Dredges
Figure 7. Drift Net
Figure 8. Trawler
Pollution
Pollution is the addition of substances to the environment that damage it, making it undesirable or unfit for life. Substance that cause pollution are called pollutants.
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Pollution threatens the lives of organisms in the ecosystem. Therefore, the sources of pollution need to be identified and methods need to be devised to prevent and reduce pollution.
Waste materials dumped into water bodies pollute the water and change the communities that live in such habitats.
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SEWAGE
Water-carried waste matter from home or industries is called sewage. Untreated sewage should not be discharged into rivers or lakes as it may contain disease-causing organisms such as bacteria. If these disease-causing organisms get into drinking water, they may affect a large number of people in the community with diseases. Cholera and typhoid are examples of water-bourne diseases caused by bacteria.
Untreated sewage contains phosphates and nitrates, which are nutrients for algae and water plants. This can lead to eutrophication.
SEWAGE TREATMENT VIA ENVIRONMENTAL BIOTECHNOLOGY
PROBLEMS CAUSED BY INORGANIC WASTE
1. Waste water containing poisonous metals is discharged into the water body.
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2. Poisonous metals are absorbed by the water plants in the water body.
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3. The water plants are eaten by fish
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4. Fish caught from the sea contain high concentrations of poisonous metals.
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5. Villagers who eat the fish are poisoned.
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*The process in which the concentration of a certain substance (in above case poisonous metals) continues to increase as one goes further up the food chain is called bioamplification or biomagnification.
Conservation
Conservation is the protection and preservation of natural resources in the environment
Biodiversity refers to the range of species that are present in a particular ecosystem.
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NEED FOR CONSERVATION?
- Conservation is necessary for the maintenance of Earth's biodiversity.
- Maintenance of a large gene pool is important as many plants and animals contain favorable genes. Through cross breeding, we can improve agricultural produce. Genes of different flora and fauna can be used in genetic engineering or to find the cure of a certain disease. Genes are everything!
- Conservation is important for scientific research. The study of wildlife provides useful information to humans. For example we learn about evolution through wildlife.
- For economic purposes like food, natural resources, and energy source.
- To maintain a stable and balanced ecosystem (this prevents disruptions of natural cycles, and also prevents global warming)
- to preserve natural scenery and wildlife for people to appreciate.
CONSERVATION MEASURES
- Keeping environment clean
- Managing use of Earth's natural resources in a sustainable way
- Protecting wildlife
- Control of human population
- Reforestation (NOTE: Forests and seas are major carbon sinks, they absorb the extra CO2 from the atmosphere and store them for an indefinite period of time. These carbon sinks are important as over time, they store CO2 as a source of energy in fossil fuels)
- Conservation of fishing grounds by - banning drift nets, small hole nets, trawlers, and dredges; regulating entry of ships into fishing grounds; limiting period of fishing; banning harvesting of fish in endangered species; raising endangered fish species in hatcheries and releasing them into fishing grounds where their populations are decreasing.