Introduction
The term environment (which means surroundings) is viewed differentially by different environmentalists. It is defined as the sum total of all living (abiotic) and non-living (biotic) components.
In fact, environment creates favourable conditions for the existence and growth of living organisms. The environment has never been constant or static. It has been changing slowly, rapidly or drastically. All living organisms including human beings are affected by changes in the environment - the changes may be harmful or beneficial. It is well known that many species on the earth (which could not adapt with changing environment) vanished or are on the brink of extinction (vanishing) due to environmental changes or factors. A significant example is the extinction of dinosaurs due to hostile conditions of their environment. It is believed that the main cause of this was attributed to the newly appeared tiny primitive mammals, which ate the eggs of dinosaurs. Thus, for primitive mammals, the environment was favourable while for dinosaurs it was unfavourable.For past more than two decades, human beings have primarily been responsible for the changes in the environment. Some of these activities are as follows:
• Devastating forests by cutting trees for wood and bringing forest land under cultivation. This caused erosion of the soil. This activity has been going on from the past thousands of years.
• Killing the gentle animals for food and the fierce animals due to safety reasons.
• The industrial and scientific revolution in the recent past has a tremendous effect on the environment. This aspect is mainly responsible for polluting the water bodies with chemicals from industries, polluting the atmosphere by various poisonous and harmful gases discharged from industrial establishments including power plants using coal.
• A large number of episodes have affected the environment. The most important is the London Smog that killed about 4000 people in 1952, nuclear catastrophes including dropping of nuclear bombs on Hiroshima and Nagasaki and Bhopal gas tragedy. For a detailed discussion, see sec. 10.2.
To sum up, various changes in the environment have adversely affected the ecosystem as a whole. This aspect will be discussed subsequently (see sec. 2.7).
2.2