Crowded planet

10 Billion, by Stephen Emmott, Penguin, RRP£6.99, 208 pages

Population 10 Billion: The Coming Demographic Crisis and How to Survive It, by Danny Dorling, Constable, RRP£8.99, 448 pages

High-density accommodation in Hong Kong

Here we have two books with almost identical titles covering the same subject: the consequences of the world’s population rising towards 10bn. But they could hardly be more different in style, mood and content.

Stephen Emmott, head of computational science at Microsoft Research, has written a stark, simple and short warning about the coming catastrophe, which he feels is inevitable, resulting from human overpopulation and over-exploitation of the world’s resources. His concluding words, taken from a young scientific colleague’s answer to the question of what he would do in response to the current situation, encapsulate the book’s bleak pessimism: “Teach my son how to use a gun.”

By contrast, Danny Dorling, professor of geography at the University of Sheffield, brims with optimism. His Population 10 Billion wanders slowly and cheerfully down various demographic byways, showing on the way how human beings might overcome the pessimists’ predicted perils.

In 2011 the world’s population passed 7bn, according to the official United Nations estimate. The latest projections show it reaching 9.55bn in 2050 and 10.85bn in 2100, based on a medium fertility assumption. Emmott accepts without discussion that there will be at least 10bn of us on earth some time towards the end of this century. Dorling, in spite of his title, does not. “The more I have looked into this issue, the more I have seen that it is those who are most worried who write the most about population,” he says. “Perhaps this is natural, but there is very little contradicting opinion presented to the overarching thesis that population is a problem and that growth rates are too high.”

Dorling presents some sophisticated demographic analysis to suggest that population growth rates around the world, already in decline, will fall faster than the UN medium fertility model assumes. Indeed, he suggests that UN population specialists have raised their recent forecasts “because it became more politically expedient to increase them, to appear to be warning that the numbers of people might be getting out of control” – though he presents no evidence to back up this allegation.

The UN low-fertility model, which has received much less publicity, would see population peaking around 2050 at 8.34bn and then declining to 6.75bn by 2100. “That the first population fall without a disaster is coming is as near to a demographic certainty as it is possible to get,” Dorling writes. “Global average family size has never been so small and is falling rapidly. Already, across over half the peoples of the planet, it is now normal to have fewer than two children per woman.”

A related issue is immigration and the movement of people around the world. Emmott foresees richer countries coming to resemble fortresses, with militarised border controls to keep out the millions of people “who are on the move because their own country is no longer habitable, or has insufficient water or food, or is experiencing conflict over increasingly scarce resources”.

Dorling, on the other hand, sees a world of increasingly porous borders, where immigration controls fade away and wealthy countries with low fertility rates and declining populations welcome incomers from less fortunate regions. “Everywhere immigration is blamed for troubles while almost always heralding success,” he observes. Dorling also points out that such migration is good for slowing down global population growth, because on average people who move to rich countries have fewer children than if they had stayed put; they rapidly adopt the fertility rates of the places to which they move.

Of course, total population matters for the health of the planet and its inhabitants but what people do – how much and what they consume, and how they treat the earth – matters more. The planet might be able to sustain, say, 10bn living with wise restraint while 5bn with a modern western lifestyle would be beyond its long-term carrying capacity.

Dorling sees important indicators of human greed and environmental impact beginning to improve after decades of deterioration. In Britain total material consumption peaked in 2001, domestic water use peaked in 2003, and farmers have been using less fertiliser since the 1980s. The developed world “may have turned the corner towards a lower consumption economy” as it becomes wealthier and more populated.

For Emmott, however, everything continues to get worse. He writes vividly about the inputs of energy, water and materials needed to manufacture and transport the comforts of modern life. The figures for “hidden water” consumption are staggering. For instance it takes 3,000 litres of water to produce a beefburger, 9,000 litres to produce a chicken – and 27,000 to produce a kilo of chocolate.

“This should surely be something to think about while you’re curled up on the sofa eating [chocolate] in your pyjamas,” he writes. “But I have bad news about pyjamas. Because I’m afraid your cotton pyjamas take 9,000 litres of water to produce.” That passage exemplifies Emmott’s colloquial style. The book is based closely on the text of his Ten Billion show at London’s Royal Court Theatre last summer, a critical and popular success.

I do not believe that Emmott is quite as pessimistic as he seems on stage or in print. If he really did believe it was too late, he would not have devoted so much time and energy to trying to change people’s perceptions and behaviour. His message is ultimately that science and technology cannot avert a global catastrophe but radical social and political action – real action rather than token gestures – just might.

For a disapproving Dorling, Emmott “is the embodiment of angry pessimism”. But Dorling is just as keen to distance himself from “rational optimists” such as the science writer Matt Ridley, whose attitude he caricatures as “greed will prevail”. Dorling evidently feels the need for a label and describes himself as a “practical possibilist” in the mould of Hans Rosling, the Swedish professor of international health and development. “Looked at in a certain way, told with a certain kind of story in mind, it is possible to paint a picture that has a rosier, less optimistically combative and less pessimistically catastrophic ending than many presume,” he writes. “That is what a practical possibilist paints.”

But both “10 Billion” books, in their very different ways, make a valuable contribution to rekindling a discussion on global population that has waxed and waned in the two centuries since Thomas Robert Malthus first brought the issue to public attention. More scientists should follow Emmott and Dorling into the debate.

Clive Cookson is the FT’s science editor

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