Man is the most dominant and capable organism who can influence and alter his habitats. Various human activities have posed problems to other organisms in the same manner as the over dominance of a tiger in a forest would do to deer and zebras. Dominance of an organism in a habitat may be so detrimental as to wipe out other organisms that habitat. This can be visualized by imagining overgrowth of water hyacinth in a pond which makes the pond inhospitable for the existence of other organisms. In the succeeding paragraphs you will find various human activities that have depleted the quality of his habitat as well as those of other organisms.

Overpopulation, industrialization and urbanization have resulted in depletion and destruction of natural resources. Deterioration in the natural quality of the environment caused by physical, chemical or biological factors is known as pollution. In other wards, unfavourable alteration of our surroundings as a by-product of man’s action is pollution. There are three main types of pollution.

These are:

1. Air pollution, 2. Water pollution, 5. Soil pollution.

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To these, noise pollution, radioactive pollution, etc. can also be added.

All these types of pollution are caused by man or man’s activities. The environment is becoming more and more polluted day by day. The following human activities have disturbed the balance of nature:

Deforestation

Large scale cutting done of the fore3sts is called deforestation. The main reasons for deforestation are:

(a) Rapid increase in the population of human beings and their livestock.

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(b) Urbanization and human settlements, railway tracks, road and highways, establishment of new industries, educational institutions, recreational centers, etc.

(c) Cutting down of trees for obtaining fuel (firewood, charcoal) timber (construction of buildings, furnitures, boats, trucks, boxes), fodder for cattle, goats, sheep, industrial raw materials (plywood, paper, rubber) and other useful products (gum, resins, maple sugar, spices, cooking oils, medicinal plants, etc).

(d) Mining of ores, coal, mica, manganese, etc.

(e) Forest fires

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Some natural forces like landslides, earthquakes have also damaged the forest vegetation. It has been estimated that during 1959 to 1969, nearly 1.69 million hectares of forests have disappeared. Felling of trees in the Himalayan regions of Himachal Pradesh, North Bengal has been taking place on a very large scale in recent years.

Damage due to Deforestation:

Besides many economic uses, forests also maintain the natural water cycle. Forests maintain oxygen concentration in the environment and prevent soil erosion. Many adverse changes in the bi8osphere such as floods, famines, droughts, pollution are due to rapid deforestation. Forests also provide suitable habitat for many kinds of wildlife. It takes decades for a tree to grow to its full size, but just a few hours to cut it. Frequent droughts and floods in Uttar Pradesh and Bihar are due to erratic rainfall caused due to deforestation and soil erosion.

Relentless Killing of Animals

For various needs man kills and reduces the number of animals and plants. If the population of any type of animals gets reduced, it will have far-reaching consequences. For example, if the population of snakes is reduced, the population of rats in the farms will increase which will cause greater destruction of food grains.

Overexploitation of Habitats

Domestic sewage, industrial wastes, fertilizers, detergents, silt is being dumped in aquatic bodies which have changed the water quality to a great extent. Our great rivers like the Ganga and Godavari are becoming so polluted that their water is no longer suitable even for bathing purposes. A number of diseases like cholera, typhoid, dysentery diarrhea, jaundice, etc, are caused due to consumption of polluted water. Consumption of fish containing mercury may lead to irreversible brain damage or even death in man.

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The important sources of air pollution are smoke, exhaust gases from automobiles and industries, radioactive fall-out, biocides and pesticides photochemical smog etc. gases released from automobiles and factories contain carbon monoxide, oxides of sulphur and nitrogen, hydrocarbons, etc. these can cause respiratory problems, renal problems, high blood pressure, problems in nervous system etc. Many adverse effects like falling of leaves, degeneration of chlorophyll have been noticed in plants.

The excessive use of natural resources like water, air, minerals has resulted in serious problems. There has already been a crisis of petroleum and its products. From 1860 to 1960, the carbon dioxide content of air has gone up by 14%. The carbon dioxide of the atmosphere keeps the earth warm, much like the glass which keeps a greenhouse warm. This effect is\, therefore, called the greenhouse effect. The increase in carbon dioxide has intensified the greenhouse effect and has led to global warming, an increase in the average temperature of the earth. Excessive use of chemicals like CFC (chlorofluorocarbon) is reducing the ozone layer.

The ozone layer depletion will lead to severe damage to both plants and animals. The protective ozone layer prevents UV (ultraviolet) radiation from falling on the earth. Ultraviolet rays have harmful effects on human body. They cause skin cancer in human beings. Increase in the intensity of sound due to excessive use of automobiles, aircrafts, machine, etc. causes noise pollution’s the effects of radioactive fallouts can pass on to several generation. Many habitats throughout the world have been rendered b arre4n and inhospitable by man’s excessive exploitation.