Global Policy Forum

By James Meek

It will be a grey-haired world. There will be fewer Chinese, Europeans and Japanese, and more Africans, Indians and Americans. And at last, the planet will be getting a little less crowded. In the most sophisticated forecast so far of global population over the next hundred years, scientists say that by the end of the century, it will almost certainly be falling.

A team at Austria's International Institute for Applied Systems Analysis (IIASA) says the world population, now a little over 6bn, is likely to peak at about 9bn in 70 years time. By 2100, it will have gone down to 8.4bn, and will keep falling. "We do indeed now see the end of population growth on the horizon," said Wolfgang Lutz, head of the research project. "It's still rather distant, but it's likely to happen in this century, which gives a degree of optimism in struggling with sustainable development."

The new forecast underlines the extraordinary nature of the era that many of those alive today have experienced. "People who are now 40 or older have lived through a doubling of the human population," said Joel Cohen, Professor of Populations at Rockefeller and Colombia universities in the US. "This will be the only generation in human history to live through this. No one before the second half of the 20th century did, and, if we believe the UN and IIASA, no-one will again."

Different society

Dr Lutz, whose work is published in today's issue of the journal Nature, warned that the price to be paid for a shrinking world population was an increase in the number of elderly people in the world. "This doesn't come for free, but at the expense of a very significant ageing of the population, especially in western Europe and Japan," he said. "By the end of the century we may come close to 50% over-60s in these regions. It will be a very different looking society. "Will these elderly people be in good health? They probably will - healthy life expectancy is increasing as fast as life expectancy. The trouble is, social security systems are not changing to keep up."

The forecast by the IIASA, a non-governmental institute sponsored by scientists in Europe, Japan and the US, is not a total surprise, as the rate of world population growth has been slowing since 1968. But the most widely-quoted previous forecast, by the UN, predicted the population would flatten by 2100 at about 9bn. Dr Lutz's team believes there is a flaw in the UN forecast, namely the assumption that in prospering, developing countries, where birth rates are falling as women choose to have fewer babies, the rate won't fall below an average 2.1 children per woman - the rate required to keep a population stable.

In fact, the evidence from the real world suggests the birth rate will keep dropping way below two - as has happened already in many parts of western Europe. "There is strong agreement among population scientists that, eventually, developing countries will go down to the same levels of fertility as industrial countries today," said Dr Lutz. "Adults in countries like China are already having too few children to replace themselves." Population scientists use the word "fertility" to mean whether people actually have children, rather than whether they are medically capable of it or not.

Over the next century, despite the impact of diseases such as HIV, the IIASA predicts that more countries will go through "mortality transitions", when life expectancy increases, and then through "fertility transitions", when people choose to have fewer children. The forecast divides the world into 13 regions. In all but two - North and Latin America - the population is predicted to be falling by the end of the century. The biggest falls are in the China region, down from 1.4bn now to 1.25bn in 2100, and in Europe, from 813m to 607m. The population in the European part of the former USSR is falling sharply already; it is predicted to shrink by 18m to 218m in 2025, and to slump to 141m, a 40% depopulation, by 2100.

Other regions will have shrinking populations by 2100, but will still have many more people than they do today. Sub-Saharan Africa's population will be 1.5bn in 2100, compared to 611m now, and South Asia - including India and Pakistan - will by 2100 contain almost 2bn people, against 1.4bn now. "They will be stuck in misery," said Dr Lutz. "That's why the message of the end of population growth should not be considered as an end of population concern. For Africa and India, it's still a very great concern - people living in unhealthy conditions and poverty, which will be reinforced by further population growth."

Despite fears of continued poverty and bad health care, even the poorest countries are expected to see a big rise in the number of elderly. While Europe, Japan and the US can look forward to pensioner saturation, even in Sub-Saharan Africa, a fifth of the people will be of that age group. In India, it will be more than a third. "The beginning of the 21st century marks the end of the period of human history with more young people than old, and for the rest of human history, there are going to be more old people than young, unless there are some very major surprises," said Dr Cohen. "We are undergoing transitions unlike anything we've faced before."

Dr Lutz pointed out that, even now, half of western European voters are either of pensionable age or within a few years of getting their pension. He warned of potentially serious intergenerational political conflict ahead. "If this becomes a programme of political parties, it may well happen that all of a sudden a majority of people allowed to vote are in favour of higher pensions, and simply order the young to pay," he said. The IIASA stresses that its forecasts are given as percentage probabilities - an advance over UN forecast, but still not a certainty, with scientists juggling fiercely argued estimates of future life expectancy, mortality, fertility, and migration.

Economics, technological change, availability of food and water, diseases such as HIV and natural disasters can skew the forecasts. Besides, human behaviour is unpredictable: an earlier generation of demographers failed to foresee the 1970s western baby slump, the rapid rise in post-war life expectancy and the large numbers of the very old we see today. "It's not numbers. It has to do with equity. It's how we treat the quality of life for individuals. I think it will be easier for us to live on a planet that's attractive if we have lower population growth rather than higher," said Dr Cohen. "I would emphasise our lack of ability to predict the future ... this is not a machine. These are people making decisions when about whether to use contraception and whether to have children."

Key predictions from the global population forecast

• The world's population is likely to peak at 9bn in 2070. By 2100, it will be 8.4bn.

• North America (the US and Canada) will be one of only two regions in the world with a population still growing in 2100. It will have increased from 314m today to 454m, partly because first-generation immigrant families tend to have more children. The other expanding region is Latin America - forecast to increase from 515m to 934m.

• Despite disease, war and hunger, the population of Africa will grow from 784m today to 1.6bn in 2050. By 2100 it will be 1.8bn, although it will have begun to decline. By the end of the century more than a fifth of Africans will be over 60, more than in western Europe today.

• The China region (China and Hong Kong together with five smaller neighbouring nations) will see its population shrink significantly by 2100, from 1.4bn to 1.25bn. Because of its education programme, by 2020, when China is reaching its population peak of about 1.6bn, it will have more well-educated people than Europe and North America combined.

• India will overtake China as the world's most populous nation by 2020.

• Europe - including Turkey and the former Soviet Union west of the Urals - will see its population fall from 813m now to 607m in 2100: from 13% of the world's population to just 7%. Eastern countries such as Russia have already seen their populations fall; western Europe's is likely to peak in the next few decades.

• One 10th of the world's population is over 60. By 2100, that proportion will have risen to one-third.

• In 1950, there were thought to be three times as many Europeans as Africans. By 2100, the proportions will be reversed.

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