An optimum population

Few would be so rash as to suggest an optimum world population. Most demographers would content themselves with the mere hope that human fecundity will keep within bounds. What bounds? Whose bounds? The bases for choice are many. In the individual they are highly subjective. At higher levels, they are nationalistic, ethnological, cultural or blatantly political. It would perhaps be a great step forward if these problems could be resolved in one particular territory where the economy has for many years been under close scrutiny, where agricultural productivity and land use are fairly accurately recorded and where the relationship between population density, on the one hand, and industrial production, education and the welfare services on the other have at least been studied in some detail if not completely elucidated. Such a country is Britain. In September 1969 the Institute of Biology organised in London a symposium on the 'Optimum Population of Britain'*. It was designed primarily as a platform for the expression of views rather than as a deliberate attempt to formulate a demographic policy. A diversity of views was expected-in fact sought and obtained. According to Miss]. H. Thompson, Great Britain was probably colonised in the wake of the last Ice Age. Population increase by invasion was a characteristic of the Stone and Iron Ages. The Dark Ages probably saw the end of immigration as a significant demographic factor although still important in a cultural, technologicalor political sense. In AD 1000 the population is believed to have been between I and 2 million rising to just under 4 million about the middle of the 14th century. The Black Death, in the course of a few years, cut the population by about a third. After some years delay, growth was resumed and in the middle of the t Sth century a major explosion began. It lasted for a century and a half. By 1900 the population of Great Britain stood at 37 million. By 1959 it was estimated at 54 million. One projection for 2000 put it at 70 million, revised in 1969 to 66 million (more recently 64 million). By some incredible coincidence, the excess of births over deaths is about equal to the number of illegitimate and unwanted legitimate children. The solution seems deceptively simple. But is it so simple? Even in a country where family planning and abortion for medical and medico-social reasons have official support, there are many socio-economic factors operating to maintain a marginally excessive birth rate. Is the food supply likely to be a limiting factor? The answer must ultimately be 'yes', if the population growth outstrips agricultural productivity. G. W. Cooke, in a detailed analysis of productivity trends, considers the possibility of feeding 54 million people (the estimated 1968 population) in the year 2000. He discusses confidently the likelihood of a considerably increased production of cereals and of livestock, envisages the possibility of growing most of the requirements in temperate fruit and vegetables but sees no hope for trebling the home production of sugar. However, in addition to declining to argue on the basis of a population of 66 million, he also reflects the misgivings of the economist Colin Clark about FAO dietary standards, which appear to place too much weight on Western-European diets. Clark has in

the end of immigration as a significant demographic factor although still important in a cultural, technologicalor political sense. In AD 1000 the population is believed to have been between I and 2 million rising to just under 4 million about the middle of the 14th century.
The Black Death, in the course of a few years, cut the population by about a third. After some years delay, growth was resumed and in the middle of the t Sth century a major explosion began. It lasted for a century and a half. By 1900 the population of Great Britain stood at 37 million. By 1959 it was estimated at 54 million. One projection for 2000 put it at 70 million, revised in 1969 to 66 million (more recently 64 million). By some incredible coincidence, the excess of births over deaths is about equal to the number of illegitimate and unwanted legitimate children. The solution seems deceptively simple. But is it so simple? Even in a country where family planning and abortion for medical and medico-social reasons have official support, there are many socio-economic factors operating to maintain a marginally excessive birth rate.
Is the food supply likely to be a limiting factor? The answer must ultimately be 'yes', if the population growth outstrips agricultural productivity. G. W. Cooke, in a detailed analysis of productivity trends, considers the possibility of feeding 54 million people (the estimated 1968 population) in the year 2000. He discusses confidently the likelihood of a considerably increased production of cereals and of livestock, envisages the possibility of growing most of the requirements in temperate fruit and vegetables but sees no hope for trebling the home production of sugar. However, in addition to declining to argue on the basis of a population of 66 million, he also reflects the misgivings of the economist Colin Clark about FAO dietary standards, which appear to place too much weight on Western-European diets. Clark has in 94 fact calculated that if British diets were based largely on cereals and vegetables, with some supplementation with animal products, these islands could support more than 100 million people without having to rely on much improvement in current yields.
Rising standards of living are a concomitant, if not a direct result, of increasing industrialisation. What does this mean in terms of pollution? More specifically, what effect will this pollution have on agriculture? Mellanby believes that pollution can be avoided at a price and that industry will be encouraged to make the necessary effort. Agriculture itself contributes to pollution, mainly through pesticides and the slurry effluent from intensive animal husbandry. The problem of pesticide pollution, Mellanby hopes, will be solved before the year 2000, even if conventional pesticides are still in use. He regards eutrophication-the enrichment of natural waters-as a more serious problem and one likely to be aggravated by intensification of agriculture.
The biological approach to the problem of human populations is frankly based on the population dynamics of animals, including insects. In some species, the food supply is clearly a limiting factor. In many birds, for instance, shortage of food during a severe winter may decimate the population. A parallel in man was suggested by Hutchinson in his address to the British Association for the Advancement of Science in 1966. Hutchinson concluded that population growth in Britain was related to agricultural production and attributes the severe effect of the Black Death to under-nourishment.
It would be surprising if, in the course of evolution, natural selection had not produced some regulatory mechanisms which prevented at least some species from over-exploiting their food supply and running the risk of extinction. Wynne Edwards and others have apparently identified such mechanisms, some of which restrict reproduction by affecting breeding behaviour with or without the intervention of changes in hormonal balance. Stress is undoubtedly a frequent concomitant of an increase in population intensity. In the Institute of Biology symposium, Southwood examines these views and leans towards the simplistic explanations. Regretably, parsimony takes precedence over elegance.
In this symposium an economist, Boreham, concludes that population change at the current British rate is irrelevant in economic terms and adds, gratuitously, that agriculture is in any case a declining industry. The sociologist Hawthorn finds less of a problem in population increase than in current population distribution. Claiming that the economic case for preserving farmland is weak, he readily finds land for recreation.
Put to the vote, 90% of the audience supported the view that "The optimum population of Britain had been exceeded". Perhaps this merely reflected the high proportion of biologists among the delegates; or perhaps it revealed an unease about more and more men seeking fewer and still fewer resources.
So much for Britain. What of the world as a whole? Decision and implementation may be difficult in one country; they appear well nigh impossible in a confused Babel of nations. FAO are wise to pay attention in the first instance to individual territories. An internationally integrated population policy-agreed or imposed-must come later. However difficult the problem, man must strive for a solution or, literally, perish in the attempt.