You were only half right, Mr Keynes

Solutions to population crises turn out to be surprisingly benign. Colin Tudge on an economist's blind spot

In advocating birth control for the working classes - that, plus a bracing dose of war, famines and pestilence - John Maynard Keynes, perhaps the greatest of 20th-century economists, was continuing a tradition that goes back to Thomas Malthus at the end of the 18th century: one which says we are doomed because there will soon be too many of us; and that the only way out is through suffering. In practice, Keynes and Malthus were half right: if we don't take population seriously, then the consequences could dwarf all previous horrors. But the second half of their argument is misguided. War, famine and pestilence emphatically are not the solutions. Indeed the only strategies of population control that are remotely liable to work are benign; far more benign than the policies now commonly practised in the world.

The statistics show how huge the problem is. According to the United Nations the population will reach 6 billion by 2000; Homo sapiens has long since broken the ecological law which says that "big, fierce animals are rare". More to the point: numbers are increasing by 1.6 per cent per year. That may seem modest; but because of the principle of compound interest, a population increasing at 1.6 per cent per year will double every 40 years. So at the present rate we would reach 12 billion by 2040, 24 billion by 2080, 48 billion by 2120, and about 100 billion within two centuries.

In the field of agriculture there aresome optimists who, over the past 25 years, have felt that a human population of about 15 or even 20 billion could be sustained - if we managed to triple the yields here and there, and correct economic imbalances. I know no one who thinks that 30 billion is sustainable. Yet such a figure could be reached in 100 years - within the lifetimes of millions of babies already lying in their cots. In short, something big has got to happen in the 21st century. Either there could be the most extraordinary collapse - for populations do not generally level out in anticipation of disaster, but only after disaster has occurred; or human beings have got to change their ways.

In principle - still dealing, for the minute, only in statistics - there are two ways to curtail population growth: increase the death rate, or reduce the birth rate. For some reason - perversity? - most people seem to have focused on the first of these: and hence Keynes's advocacy of war and pestilence. But in practice history shows that such measures do not work. After catastrophic set-backs, populations bounce back, provided the environment is not already too devastated. There have been baby booms after major wars, and after the Black Death of the 14th century. Ireland remains pro-natalist not expressly because it is Catholic, but because of the famine and emigrations of the 1840s; Catholic Italy, by contrast, has one of the lowest birth rates in Europe. In the poorest countries, where infant mortality is high, women have huge families in the hope that a few will live. But a biologist would observe that human beings reproductively speaking are 'K' strategists, like elephants and whales: our nature is to have only a few offspring, expecting that most will thrive. High infant mortality represents a system in biological disarray; not only inhumane, but hugely wasteful.

Curtailment of birth rate tends also to be presented in an unpleasant light: coercive vasectomies in 1970s India; the draconian one-child-per- family law of modern China. For such reasons population was not mentioned at all in the latest Indian elections, although no Indian can doubt its pertinence.

Yet the same demographic statistics that reveal the magnitude of our present plight also demonstrate that it can be solved. If couples produce an average of, say, 2.4 children, then human population will inexorably double every few decades. But if they average, say, 1.9 children - anything less than two - then overall population will stabilise within decades, and will eventually start to go down, leaving future generations to decide how small they would like human numbers to be.

So what inducements lead couples to have two children or fewer? History shows that the answers are: wealth, security, opportunity, fulfilment in areas other than child-bearing, and knowledge that any baby born has a good chance of reaching adulthood. People in affluent countries almost invariably have fewer children.

Wealth cannot be supplied instantly; but a reduction in infant mortality helps. In brutal terms, a succession of child deaths is a drain on resources. Security in this context mainly refers to old age; people should not need to have children just to be looked after. Perhaps the greatest contribution that could be made to humanity as a whole, and to the containment of human population in particular, is to ensure that everyone has a pension, from the Secretary General of the United Nations to the prostitutes of Nairobi. It's mundane; but the impact would be huge. Opportunity means access to family planning technology; Dr Malcolm Potts of the International Planned Parenthood Federation has spent much of his life talking to women in poor countries and believes that if only they had access to truly modern contraception, then the birth rate could be halved. For women in much of the world, too, motherhood is the only route to status; with careers, as opposed simply to toil, attitudes change. So nobody need be coerced; "enablement" is the politically correct term, and in this context is apt. Women in many of the most fecund countries would have fewer children of their own volition if only it was technically and socially possible to do so.

There is a case for some coercion, however. For, if population growth does come to a halt in the 21st century, it will be a huge volte face in human affairs: our numbers have been growing exponentially since the birth of large-scale agriculture, 10,000 years ago. The consequences of levelling out would cause angst among governments, industrialists, and trade unions. Reduction of babies combined with increased life expectancy skews the age distribution: soon there would be too many oldies and too few cut-price youngsters to do the work. In such circumstances, governments become pro-natalist and/or encourage immigration. But we will have to change our expectations - and perhaps here we might need coercion. Early retirement - or even retirement at 65 - may cease to be acceptable. A subsidiary but important task, then, is to make work more pleasant and more dignified.

In short, there is a bright light amid the dire statistics: no policy can work unless it is benign. If Keynes and others had seen this, 20th- century attitudes to population control could have been different - and so would our prospects for centuries to come.

The writer is a visiting Research Fellow at the London School of Economics.