THE MENACE OF OVER-POPULATION

The essential fact about the population problem is well known. It is simply that world population is increasing at a rate with which food and other production may not be able to keep pace and will certainly not be able to overtake sufficiently to raise the standard of living in the underdeveloped countries. World population is thought to have increased by 1,000 million since 1800 - that is, by more than 60 per cent (Figure 1) - to raise the estimated total in 1956 to about 2,700 million, and the present rate of increase, which far exceeds the estimates of 25 years ago, is such as to conjure up visions of staggering numbers in the foreseeable future.

The total, now thought to be approaching 3,000 million, is not, of course, equally distributed in proportion to the land areas. Europe, including the U.S.S.R., is about averagely populated, Africa, North and South America and Oceania are under-populated and Asia is greatly over-populated (Figure 2 a, b). The rate of increase is also very uneven. Figure 3 shows birth-rates and death-rates since 1947 for four contrasting areas, the difference in the two rates representing natural increase. In Singapore a very high and almost static birth-rate, coupled with a rapid decline in the death-rate, is giving rise to serious alarm. Many other regions, such as Malaya, Ceylon and Mexico, are in the same position to a greater or lesser extent. In Japan a decline in the death-rate has been offset by a dramatic drop of nearly 50 per cent in the birth-rate brought about mainly by quasi-legalized abortion. In the United States a low and slightly declining death-rate has combined with a substantial and recently static birth-rate to give a formidable rate of natural increase. In Great Britain a death-rate which is not particularly low combines with a low birth-rate to give a very small rate of increase. Those Asian countries in which the rate of increase is still slow are being held back by a high death-rate rather than a low birth-rate, and the same applies to Africa. Unless steps are taken now, it is only a matter of time before the population explosion extends also to these areas.

The differing patterns of birth-rates and death-rates cause differences in the age structure of populations (Figure 4). A high death-rate and a high, static birth-rate mean that each age group comprises fewer people than the one before, giving the pyramidal 'profile' typical of India and many other countries today and of Great Britain a century ago. The same applies as a whole to South America, which demographically is essentially a country of the young. The profile for the United Kingdom, in which five years ago there were about as many people aged 40 to 45 as there were infants 0 to 5 years old, shows the effect of an erratic but overall decrease in the birth-rate over many years.

The explosive growth of world-population has not been caused by a sudden increase in human fertility, and probably owes little in any part of the world to an increase in birth-rate. It has been caused almost entirely by advances in the medical and ancillary sciences, and the consequent decrease of the death-rate in areas where the birth-rate remains high. This is of some biological interest. Nature takes as her motto that nothing succeeds like excess, and any living thing, including Man, if able to reproduce without restraint to the limit of its capacity, would soon inundate all parts of the world where it could exist. As it is, biological populations are kept severely in check by limiting factors, of which the most important are limitations of food supply, disease and enemies, and fluctuations in natural populations are determined by fluctuations in these limiting factors. Generally speaking relaxation of one factor, after a period of expansion, brings into operation one of the other two.

In the l00 years before the second World War, the expectation of life at birth in England and Wales rose from about 40 years to over 60 years - that is, one year every five years. In India the expectation of life at birth is about 40 years, and is said to be increasing by 2½ years every five years. Even if the birth-rate were at no more than replacement level, the increasing expectation of life would add enormously to the population of India. True, the expectation of life is not likely to increase indefinitely at the present velocity, but it has a very long way to go in many countries of the world. Even in the developed countries it has some way to go before everyone dies essentially of senility, and in the meantime increasing longevity will reinforce natural reproductivity. With present birth-rate and death-rate trends, the world is threatened with astronomical numbers of people. To quote from the preface of a United Nations report, The Future Growth of World Population (1958) : '. . . it took 200,000 years for the world's human population to reach 2,500 million; it will now take a mere 30 years to add another 2,000 million. With the present rate of increase, it can be calculated that in 600 years the number of human beings on Earth will be such that there will be only one square metre for each to live on. It goes without saying that this can never take place, something will happen to prevent it.' The human race will have to decide whether that 'something' is to be pleasant or unpleasant.

(A. S . Parkes from an article in The New Scientist )