Can the Planet Support 10 Billion People?
By JOEL E. COHEN, Published: October 23, 2011
How will countries feed and shelter populations that are expected to soar by century’s end?
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ONE week from today, the United Nations estimates, the world’s population will reach seven billion. Because censuses are infrequent and incomplete, no one knows the precise date — the Census Bureau puts it somewhere next March — but there can be no doubt that humanity is approaching a milestone.
The first billion people accumulated over a leisurely interval, from the origins of humans hundreds of thousands of years ago to the early 1800s. Adding the second took another 120 or so years. Then, in the last 50 years, humanity more than doubled, surging from three billion in 1959 to four billion in 1974, five billion in 1987 and six billion in 1998. This rate of population increase has no historical precedent.
Can the earth support seven billion now, and the three billion people who are expected to be added by the end of this century? Are the enormous increases in households, cities, material consumption and waste compatible with dignity, health, environmental quality and freedom from poverty?
For some in the West, the greatest challenge — because it is the least visible — is to shake off, at last, the view that large and growing numbers of people represent power and prosperity.
This view was fostered over millenniums, by the pronatalism of the Hebrew Bible, the Roman Empire, the Roman Catholic Church and Arab thinkers like Ibn Khaldun. Mercantilists of the 16th through the 18th centuries saw a growing population as increasing national wealth: more workers, more consumers, more soldiers. Enlarging the workforce depressed wages, increasing the economic surplus available to the king. “The number of the people makes the wealth of states,” said Frederick the Great.
In the late 19th and early 20th centuries, pronatalism acquired a specious scientific aura from social Darwinism and eugenics. Even today, some economists argue, incorrectly, that population growth is required for economic growth and that Africa is underpopulated.
This view made some sense for societies subject to catastrophic mortality from famines, plagues and wars. But it has outlived its usefulness now that human consumption, and pollution, loom large across the earth.
Today, while many people reject the equation of human numbers with power, it remains unpalatable, if not suicidal, for political leaders to admit that the United States and Europe do not need growing populations to prosper and be influential and that rich countries should reduce their rates of unintended pregnancy and help poor countries do likewise. With the globalization of work, the incentive for owners of capital today to ignore or not address rapid growth in the numbers of poor people remains as it was for the kings of yore: lower wages for workers at any level of skill offer a bigger economic surplus to be captured.
But just as pronatalism is unjustified, so are the dire — and discredited — prophecies of Thomas Malthus and his followers, who believed that soaring populations must lead to mass starvation.
In fact, the world is physically capable of feeding, sheltering and enriching many more people in the short term. Between 1820, at the dawn of the industrial age, and 2008, when the world economy entered recession, economic output per person increased elevenfold.
Life expectancy tripled in the last few thousand years, to a global average of nearly 70 years. The average number of children per woman fell worldwide to about 2.5 now from 5 in 1950. The world’s population is growing at 1.1 percent per year, half the peak rate in the 1960s. The slowing growth rate enables families and societies to focus on the well-being of their children rather than the quantity.
Nearly two-thirds of women under 50 who are married or in a union use some form of contraception, which saves the lives of mothers who would otherwise die in childbirth and avoids millions of abortions each year — an achievement that people who oppose and people who support the availability of legal abortions can both celebrate.
But there is plenty of bad news, too. Nearly half the world lives on $2 a day, or less. In China, the figure is 36 percent; in India, 76 percent. More than 800 million people live in slums. A similar number, mostly women, are illiterate.
Some 850 million to 925 million people experience food insecurity or chronic undernourishment. In much of Africa and South Asia, more than half the children are stunted (of low height for their age) as a result of chronic hunger. While the world produced 2.3 billion metric tons of cereal grains in 2009-10 — enough calories to sustain 9 to 11 billion people — only 46 percent of the grain went into human mouths. Domestic animals got 34 percent of the crop, and 19 percent went to industrial uses like biofuels, starches and plastics.
Of the 208 million pregnancies in 2008, about 86 million were unintended, and they resulted in 33 million unplanned births. And unintended births are not the whole problem. Contraceptives have been free since 2002 in Niger, where the total fertility rate — more than seven children per woman in mid-2010 — was the world’s highest. Women in Niger marry at a median age of 15.5, and married women and men reported in 2006 that they wanted an average of 8.8 and 12.6 children, respectively.
Human demands on the earth have grown enormously, though the atmosphere, the oceans and the continents are no bigger now than they were when humans evolved. Already, more than a billion people live without an adequate, renewable supply of fresh water.
Joel E. Cohen, a mathematical biologist and the head of the Laboratory of Populations at Rockefeller University and Columbia University, is the author of “How Many People Can the Earth Support?”