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Their formation requires millions of years which means to be beyond human scale of time. Also fruits, vegetables, meat, milk and milk products, wood, fibre, fodder, are renewable resources, as they can be generated again and again, as long as process of photosynthesis continues on this planet. The use of the natural resources is generally taken after some sort of manipulation or processing with the result that along with the main by-products, the pollutants or toxicants of various kinds are also produced. For example, forest fires produce fly ash, smoke and gases (mainly carbon monoxide); eruption of volcano produces ash and gases; micro-organisms release ammonia; swamps and marshes yield harmful gases, foul odour and from the desert, windblown dusts containing atmospheric particles are produced which impart harm to mankind in various ways. The basic requirements of human beings are food and water. They have direct as well as indirect concern with green plants which provide food of all kinds, shelter, materials, pulp, paper, fibre, cotton, herbal medicine etc. The green plants require inorganic carbon source (e.g. carbon dioxide), water mineral nutrients and light. All animals including man depend directly or indirectly for their food requirements on green plants. In such a situation, up-welling of agriculture, horticulture, tree plantation pasture, grass land, orchard, garden is indispensable need. Provision of water supply or availability of natural water in plenty is a parallel requirement. In addition to food and water, men also require, shelter, clothing, transportation, entertainment defence provision, medicine etc. which are generally called amenities of life. For fulfilling these sorts of requirements man needs both material and energy resources often in large quantities. Thus, the resources of importance to man today can be grouped as follows:

1. Fertile soil and sustainable agriculture

2. Livestock and fisheries

3. Fresh water provision (surface/underground)

4. Minerals and metals

5. Energy resources e.g., fossil fuels, natural gases

6. Forests and wildlife

7. Means of transportation

8. Equipment’s, weapons, arms and ammunitions for safety of life

In the present trend of mechanised agricultural system, extensive pursuit for industrialisation and urbanisation, adaptation of modern culture, various kinds of natural resources are tackled to suffice the needs, but unfortunately there is no escape from production of many kinds of pollutants as by-products. The ultimate result of manipulation of items of natural sources is of the same kind happening with man's activities with man-made resources.

Consumption of natural resources, whether at slow or fast rate, shall finally result in exhaustion of our non-renewable resources at some time in future. However, human skill is continuously working to explore suitable alternatives. As such, man can survive without many natural resources. Yet our greatest worry is the gradual deterioration in the quality of environment which has been damaging the resources of biological origin. These are renewable resources and it is these resources on which all life on this planet depends for food supplies. For a growing size of human population we need an ever rising quantity of food, fresh water and other materials. To accomplish the requirements, our natural sources have been mercilessly overexploited and this trend has led to deterioration in the quality of our environment. Unfortunately this situation has quality of our environment.