Present day population crisis is not only the problem of population size but mostly of its growth. Prior to 8000 BC the food gathering and hunting stage, the capacity of the earth to support was absolutely minimum; therefore their numbers were insignificant. The cultural stage of shifting agriculture is again of low sustaining stage. The first phenomenal growth of population was recorded on the dawn of river valley civilization. 110 Million population of 8000 BC increased to 200 million at IAD. Agricultural innovation development and progress during the three centuries from 1650 to 1950 was the main reason for five fold increase. (5000 million to 25000 million). This remarkable increase is attributed to improved standard of living like fall in death rate, improved medical aids, improved transportation and trade.
The natural increase of population is a product of the birth rate, the death rate and migration. Prior to 1800, higher percentage of increase had been recorded in present day developing world and not in the so called developed nations of today. Industrial revolution of eighteenth century was the dominant reason for rapid population growth in European countries and spread of European colonies in America and Australia originated the root of population increase. Population in 1987 has reached the mark of 5000 million, two fold increase within four decades. There were slight oscillations in the growth until the beginning of modern times.
The factors, which affect the growth of population, are natural factors, socioeconomic factors and demographic factors. The natural factors are caused by natural hazards like floods, droughts, volcanic eruption, earthquakes, cyclonic disasters. Whatever the developments man has achieved, his lack of or late understanding of consequences of his actions in ecosystem, are the basic reasons for present day natural calamities. Man is unable to defend fully against these incidences. The reduction in population numbers is the outcome of these events.
Socioeconomic factors include crop failure, over exploitation of resources, fall in production, spread of diseases due to pollution, wars and low standard of living. Their role in controlling population growth is as important as the increase when these are favorable. Population concentration in terms of agricultural density shows that there is a difference in growth rate between rice culture and wheat culture. Social habits such as discouraging the growth of female child, human sacrifices during the rituals and during 'sati' have influenced the population growth. It is strongly felt among the isolated tribal communities.
Demographic factors are birth rate, death rate, net reproductive rate, infant mortality and the longevity of life. The interaction of these factors indicates the changes in demographic cycle. The demographic transformation occurs in several steps. Initially the death rate declines rapidly causing a gap between deaths and births. This gap widens. Then the birth rate begins a sharp decline. Thus there are four hypothetical stages recognized. The regions are grouped according to their birth and death rates. The four stages are pre transitional, early transitional, late transitional and post transitional stages. Pre-transitional stage refers to high birth and death rates and the population is almost stationary. This is linked with the early agrarian communities or pre industrialized groups. The early transitional stage is marked by high birth rate and fast declining death rate. Death rate is declined due to improved standard of living, sanitation and medicines but sociological factors have caused high birth rate. This is the beginning of industrialization. The European countries till the early nineteenth century passed this phase. Most of the developing nations like Egypt, Uganda and Brazil mark this stage even today. Most of the Asiatic countries are in the passing phase of this stage. The late transitional stage is both declining birth and death rates. This is marked by controlled growth. Most of the developed nations of the present day world register less than the world average growth. The post transitional stage is the marking of declining stage of growth. The gap between birth rate and death rate is narrowed and is almost balanced. The population once again attain the stationary level. A few European countries like Belgium and Netherlands have reached this level of zero population growth. Before reaching the declining stage, the population growth has to be restored otherwise there results disappearance of mankind from the surface of the earth. The historical evidence of such incidents was the disappearance of Tasmanians and a few native Indians of mid west U.S.A.
Population problems due to uneven growth with the spatial variations may be grouped as those of over population and under population. Over population leads to fall in nutrition, low intake of calory, diseases (permanent) due to vitamin, protein and mineral deficiency in a country. Population pressure is felt in man's activities. Expansion of agricultural lands at the cost of ecosystem decay, over exploitation, of marine biotic resources because of increase in demand, crowdiness in living space, poor sanitary conditions, pollutants in air, land and water, unemployment, sickness and deaths are the outcome of overpopulation. Under population leads to under exploitation low standard of living, low levels of production techniques and economic backwardness.
International conferences on population growth and monitoring advocate the utmost necessity of population control. The concept of optimum population is widely advocated. The optimum condition of any country is the sustaining capacity of the prevailing ecosystem. Birth control, small family norms are the preventive measures undertaken. Few years back when China crossed one billion marks, they have adopted one child norm effectively. Its population growth rate is equal to that of some Europeans countries. The other Asiatic monsoon countries, developing nation in Africa are still facing the problems of over population. The low density parts of Canada, Siberia and Australia are experiencing under population stress.
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