Tentatively, one can classify the environmental problems into five categories, with the provisions .that they are not mutually exclusive and that problems present in the lower-order categories are to be found also in higher-order categories. The categories are:
1. Environmental problems affecting human health, physiology, efficiency and general well being, such as environmental diseases, air and water pollution;
2. Environmental problems detracting from the habitation of an area, for example, hazardous waste and noise pollution;
3. Those endangering the optimum use of resources. Soil erosion, water logging, salinization and alkalinization fall in this category;
4. Those problems impinging on the normal functioning of an ecosystem, some of these being thermal pollution, disturbance or disruption of bio geological cycles, reduction of ecosystem diversity.
5. Environmental problems affecting the entire biosphere. Well-known examples are C02 build up, ozone depletion, loss of gene pool, and changes in radiation balance.
While it is evident that we use the environment and its resources to serve our many purposes, the fact of the matter is that because of ignorance, arrogance and defiance of the natural laws of the environment, the net result of the human occupancies of the Earth has been an environmental crisis of grave dimension.
It can, however, be said that in the last two and a half decades we have become increasingly aware of our environmental problems and realized the urgent need to protect, conserve, and manage our environment for sustainable development even as we move up the ladder of development.
This awareness may be related to both internal as well as external factors. Visible signs of environmental degradation, official concerns regarding undesirable effects of growth on the environment, experience of people directly affected by environmental crisis and their struggle to resist further onslaught on the environment and lastly intellectual articulation of the problems made us aware of the crucial role of the environment in the development process.
External factors that helped shape the changed perception were the United Nations Conference on the Human Environment and the preceding preparatory meeting at Founex in 1971. Global changes in terms of green house warming, depletion of the ozone layer, and radioactive fallout also drew our attention to the environment.
The branch of science concerned with plant and animal relationship with their environment is called ecology. Ecology is a very simple term. The term ecology is derived from Greek word “aikos” meaning ‘house, habitation or place of living’ and “logos” meaning study.
Ecology is a study of the relation of organisms to their surroundings. Nature exits in a very delicate balance.
It is a well-known fact that nature is controlled by the interdependence and interaction of all life forms between them and non-living world of rocks, water, soils, minerals, sun, heat, radiations and the course of changes going on in them.
The field of ecology deals with the influence of environmental factors on all the aspects of life such as morphology, physiology, growth, distribution behaviour and survival of organisms. The term ecology is the total relationship of an organism to both its organic and inorganic environments.