With the abandonment of a hunting-gathering way of life and the rise of permanent settlements and eventually cities, the human population underwent dramatic growth. By the beginning of the Christian era it had reached 250 million, and by 1650, half a billion. Growth of population during 20th century was very rapid. In 1994 the total world population was estimated at about 5.
6 billion people. It increased by nearly 4 billion people during past 100 years. The most significant world trend is that death rates are currently falling in poor and rich countries alike, while birthrates remain high in most poor countries and low in most rich ones. Exceptions are the generally higher death rates of Africa and the high birthrates of the rich oil-producing countries. The most populous countries, in descending order, are China, India, the United States, Indonesia, Brazil, and Russia.
The U. S. population totalled about 260. 8 million in 1994.
In the 1990s about 4. 1 million children were born annually in the United States, and more than 2. 1 million persons died yearly. The greater number of births is due in part to a fertility rate that has increased by nearly 20 percent since the mid-1980s.
International immigration, both legal and illegal, is another major element in U. S. population growth. Legal immigration has recently amounted to about 1 million per year; illegal immigration is thought to be several hundred thousand. In China, the world’s most populous country, the 1994 population was estimated at nearly 1. 2 billion, more than double the 1953 census population of 584 million in mainland China.
China’s annual increase has been estimated at 1. 1 percent annually. India’s population of more than 911. 6 million people (1994 est. ) is increasing faster than that of China, and if present trends continue, it will soon catch up with or surpass China.
Since the disintegration of the USSR, Indonesia and Brazil are now the fourth and fifth most populous countries, with 1994 estimated populations of 199. 7 million and 155. 3 million, respectively. Sixth-ranked Russia has about 147. 8 million people (1994 est. ).
It has a negative natural increase rate of – 0. 2 percent, comparable to the low or negative rates found throughout Europe. The arithmetic is simple. Our oceans can supply a limited amount of fish. Farm production is limited by the amount of available land.
Once human demand for food, energy, and other materials exceeds sustainable levels, further increase in our population will mean that we each will get less and less and less. Not only will us humans suffer but so too will our earth. If all else were equal, more people would mean more of the activities that are causing environmental degradation. More people would mean greater energy consumption, more resource use, and more waste.
If the per capita impact on the environment were to remain constant (which in turn assumes consumption and activity patterns remains constant and environmental sensitivity to impacts is uniform), then population growth would have a direct relationship with environmental impact. Attainment of environmental goals is likely to fail if strategies to achieve them do not take into account changes in population size. A good example is air quality where efforts to reduce automobile emissions are offset by increases in the number of cars, which is in turn a function of the number of people in an affected area.Systems designed to accommodate waste streams may be overtaxed by population and plan for these changes will place responsible agencies in a crisis mode of operation with potentially disastrous consequences for the environment.Demand for many resources .