Systematic exploitation, modification and destruction of natural ecosystems began right from the time when man learned to use fire, domesticate animals and grow plants for food. Man’s interaction with his environment can be divided into three phases (Khoshoo, 1990). These are:
1. The phase of food gathering and hunting.
2. The phase of plant and animal domestication, pastoralism and settled agriculture.
3. The phase of science, technology and industrialization.
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Primitive man was essentially a part and parcel of natural environment. His basic requirements were limited to food and shelter – like all other animals. Food could be collected from surroundings while caves, bushes and trees were enough to provide shelter. For a major part of his existence since his appearance man lived a life of hunter and gatherer of food material. It was during the phase of domestication of animals and plants that he could harvest natural resources more effectively.
Necessity compelled him to clear natural vegetation to make room for his animals and plants. Natural ecosystems were modified, vegetation destroyed, flattened areas fenced off with stones, thorny bushes, logs etc. to accommodate his establishments, crops and grazing fields. By 10,000 B.C. small human establishments sprang up in fertile regions of the world.
It was around 4000 years before Christ, that man learned to extract copper and use the meta for making arms, tools or pans. Copper was the first metal to come into widespread use. It could be easily extracted from its ore as the extraction temperatures are lower.
Gradually other metals were discovered. The technology for extraction of iron was developed by about 1000 B.C., as extraction of iron from its ores requires a much higher temperature. Iron minerals are more abundant in nature as compared to those of copper but the absence of furnace capable of reducing iron oxides prevented the use of iron as common metal earlier. Use of metals conferred a tremendous advantage to the human society.
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It was, however, only by 17th century A.D. that technique to harden iron into steel by adding carbon was developed. With the appearance of steel and the use of mineral coal dug from earth the industrial revolution commenced in 17th century.
With an absolutely primitive state of technology for harvesting natural resources, a substantially higher yield could come only from expansion of agriculture and animal husbandry. There was plenty of room for this expansion. As human enterprises enlarged at the expense of natural ecosystems there was a slow but steady rise in world population to about 1 billion by 1800 A.D. With passage of time techniques of agriculture and animal husbandry were further refined.
However, it was largely an expanding crop-land and pastures which supported the enlarging human biomass from the time of Jesus the Christ to the beginning of Industrial Age. This expansion of agriculture and grazing fields modified natural ecosystems over a large area of land surface. Though many civilizations suffered the consequences of unscrupulous destruction of natural vegetation, yet all this made little impact on the global environment.
The situation changed with advancement of science and technology. After 1800 A.D., while the pressure of heavy mortality due to epidemics, diseases, natural calamities etc. was reduced, refined techniques of agriculture, animal husbandry, fruit cultivation etc. provided ample resources to human population to double itself within a span of about 130 years only. It was two billion by 1930 A.D.
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During the period which followed the Second World War, advancing frontiers of science and technology had made tremendous impact on human life style. While rapid deterioration of natural ecosystems continued, many new attributes were added to the human society which no longer remained an agriculture-based society. Some of these may be summarized as follows:
1. Replacement of muscle power (animal or man’s) with that of coal, petroleum and electricity. The use of coal and petroleum is responsible for bringing about subtle but perceptible changes in the chemistry of global environment.
2. Great strides in communication technology and transportation which enabled man to rush help wherever needed on earth’s surface saving millions of victims of flood, famine, war and other natural calamities.
3. Advances in medical sciences, use of antibiotics, immunization etc. raised average life expectancy by about 5 years per decade. Epidemics which razed villages after villages, taking a heavy toll of human and animal life disappeared altogether.
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4. Use of synthetic fertilizers, pesticides and improved seed varieties revolutionized agriculture, fruit production and animal husbandry, raising productivity high enough to match the exponentially rising global demands.
An obvious consequence of these changes was a rapid rise in human population which doubled itself within a span of 45 years only – from two billions in 1930 to about four billion in 1975. A population density of about 30 persons per sq. km. was attained by the year 1975 A.D. The world population now stands at about 5.5 billion with a population density of about 40 persons per sq. km. (1994 figures).