Any detrimental change in an ecosystem is called pollution. Human activities cause most kinds of pollution. There is a large human population. Their demands for good sand services are increasing. It increases pollution problems.

  1. Water population

There are many forms of water pollution. Industries generate toxic wastes, heat, and plastics. Some of these pollutants persist for centuries. Every household produces human wastes. The industrial and human wastes are disposed into ground water streams, lakes, and oceans. Their water becomes unfit for human consumption.

  1. Air pollution

Air pollution is also a serious problem. It has following affects:

(a)    Acid deposition or acid rain: Burning fossil fuels releases sulfur dioxide and nitrogen oxides. Sulfur dioxide and water combine to produce sulfuric acid. It falls as acid deposition (acid rain). Acid deposition lowers the pH of lakes.

(b)    Greenhouse effect: The burning of fuel produces carbon dioxide. It accumulates in the atmosphere. Thus it causes the greenhouse effect Carbon *dioxide forms a layer. This layer reflects solar radiation back to the earth. This reflection of solar radiation causes an increase in world temperature. This high temperature melts the polar ice caps. Thus ocean levels rises.

(c)    Depletion of ozone layer: The aerosol cans, air conditioners and refrigerators release chlorinated fluorocarbons. These compound causes depletion of the ozone layer. Ozone is an ultraviolet filter of the earth. Ultraviolet radiations cause skin cancer. Thus depletion of ozone layer increases the incidences of skin cancer.

( ) Biological magnification: The accumulation of matter in food webs is called biological magnification. Wastes and poisons enter into food webs. The organism of the highest trophic levels most severely suffers. Tiny amounts of a toxin incorporated into primary production. The herbivores eat primary production. Therefore, poison concentrates in the tissues of herbivores. Carnivores feed on herbivores. The poison becomes more concentrated in the carnivore. This problem becomes severe when the material is not biodegradable. All of this accumulation of poison is biological magnification.


Depletion of resources

The energy of ecosystem is used only once. Some quantity of energy is lost to outer space as heat. It is gone from the earth forever. Human populations are also wasting energy and other resources. Overgrazing and deforestation spread desserts. Humans exploit the tropical rain forests. May animal species live in these forests: The destruction of forests causes the extinction of many plant and animal species.

  1. Biodiversity

The variety of living organisms in an ecosystem is called biodiversity. The



exactnumber of species in the world is not known. The taxonomists have described about 1.4 million species. But taxonomists estimate that there are 4 to 31 million more species. Much of these species are unnoticed.

  1. Importance of the biodiversity
    re are following importance of biodiversity:

(i)      Forests hold back flood waters and recycle CO2 and nutrients.

(ii      Insects pollinate crops and control insect pests.

(iii The subterranean organisms promote soil fertility through decomposition.

(iv Many of these un-described species will provide new food crops. petroleum substitutes, new fibers and pharmaceuticals. All of these functions require large healthy populations

(v) Large populations promote the genetic diversity. This diversity is required for the survival of the species in the changing environmental. The genetic diversity is lost forever. The zoologists are trying to save endangered species. But they are able to save only a tiny portion of genetic pool.

  1. Causes of destruction of biodiversity

Th biodiversity is threatened all over the world. Acid rain, pollution, urban development, and agriculture are present everywhere. The expanding human populations destroy the habitat. It is the main threats to biological diversity. Humans are exploiting about 40% net primary production on the earth. They convert the natural areas into agricultural land. They destroy the native species. The loss of habitat destroys thousands of native plants and animals.

  1. Threatened natural areas.

Some of the most important threatened natural areas are tropical rain forests, coastal wetlands and coral reefs.

The tropical rain forests are most important forests. Tropical rain forests cover only 7% of surface of the earth land. But they contain more than 50% of the species of world. Tropical rain forests are destroyed rapidly. They are mostly destroyed for acricultural purpose. About 76000 km2 of these forests is cleared each year. Thus most tropical rain forests will disappear in this century. It is estimated about 17,500 rain forest species are lost each year. The soil of the tropical rain forest is thin and nutrient poor. Therefore, clearing of tropical rain forests gives little benefit.

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