Before seventeenth century the world population increased very slowly i.e,it has been estimated that by 1650 the population had doubled since the year to about 500million.Over the following 200years the rate of increase was much faster ,so that by 1850 the population had more than doubled to 1200million.After that, the population growth accelerated so rapidly that people talked about a population “explosion”;in 1927 it reached the 2000million mark and by the year 2000,it had passed 6000 million. In 2003 the UN calculated that if the population continued to increase at the same rate, the global total would be somewhere between 10000 million and 14000 million by 2050, depending on how effectively family planning campaigns were carried out. It was also estimated, given the much lower birth rates in the developed world, that almost 90 per cent of the people would be living in the poorer countries.
During the 1980s the spread of HIV/AIDS reached pandemic proportions; most countries in the world were affected, but again it the poor nations of the Third World which suffered worst. The population growth of the nineteenth century helped to stimulate further economic development. There was a plentiful workforce and more people to buy goods, and this encouraged more investment and enterprise. Nor were there any great problems about feeding and educating these growing numbers because prosperity meant that the necessary resources were available. Later on, there were unexpected effects on the age structure of the population in the developed nations which was especially true in Europe where, because of the very low birth-rates and longer life expectancy, a growing proportion of the population was over 65.
The rapid population growth caused serious problems: some countries, like India, Pakistan and Bangladesh, became overcrowded and there was insufficient land to go round. This forced people to move into towns and cities, but these were already over-crowded and there were not enough houses or jobs for all the new arrivals. All areas of the world succeeded in increasing their food production during the late 1960s and 190s, thanks to what became known as the “green revolution. Scientists developed new strains of heavy cropping rice and wheat on short, fast-growing stems, helped by fertilizers and irrigation schemes. For a time, food supplies seemed to be well ahead of population growth.
In the USA crop yields increased three-fold between 1945 and 1995 and the Americans were able to export surplus crops to over a hundred countries. Third World governments were forced to spend their valuable cash to feed, house, and educate their growing populations. But these used resources which they would have preferred to spend on industrializing and modernizing their countries, and so their economic development was delayed.The general shortage of resources meant that the poorest countries also lacked sufficient cash to spend on health care. Health systems in many poorer countries were collapsing, and the situation was becoming worse because richer countries were reducing aid.