In an era of warming climates and cooling economies, Malthusian limits to growth look to be not just real but hard upon us. More people once meant more innovation. Now it just seems to mean less for each: Less water for cattle herders in the Horn of Africa. Less land for farmers from the Philippines to Guatemala. Less atmosphere to absorb the heat-trapping gases the global economy exhales. Less energy and food. And if the world's economy doesn't bounce back, fewer jobs.
This predicament brings back an old sore topic: human population and what, if anything, to do about it. Not that any immediate respite is possible. There are nearly 6.8 billion of us today and more on the way. To make a dent in these problems in the short term without throwing anyone overboard, we'll need to radically reduce individuals' footprint on the environment through improved technologies and, for the well-off, a downshift in lifestyle.
Raw population growth is worrisome enough. Rising consumption rates make it more so. As nations develop, their consumption – and its environmental harm – rises. The average American consumes many times the resources the average African does. Americans are just 4.5 percent of world population, but there are 1.2 billion people in industrialized countries. And another 2.4 billion people in China and India are clambering up the consumption ladder. Today's rapid growth in consumption on top of rapid population growth is a one-two punch that has the environment reeling.
One obvious need is to cut individual consumption rates – somehow. But until the world's population stops growing, there will be no end to the consumption squeeze. With the 9 billion people demographers project by 2050, even a global average lifestyle such as South Africa's could be unsustainable. Acting on both population and individual consumption consistently and simultaneously is the key to long-term environmental sustainability. For the sake of the poor, let alone the rest of the world, we'd be better off if population ended its growth soon and moved gradually to a level lower than today's.
For most of the public, slowing population means "population control," as in China. But the concept of "control" is, for good reason, anathema to most people. As it happens, it's actually more effective to address population based on our right to decide for ourselves if and when to have children. The basis for action is something that also makes sense for other reasons: Make unintended childbirth as rare as possible. The benefits ripple out from women's lives in particular to all of humanity and to nature.
The idea is hardly new. At a United Nations Conference in Cairo in 1994, almost all the world's nations agreed to reject population control and instead help every woman bear a child in good health when she wants one.
That approach, which powerfully supports reproductive liberty, might sound counterintuitive for shrinking population growth, like handing a teenager the keys to the family car without so much as a lecture. But the evidence suggests that what women want is not more children but more for the fewer children they can reliably raise to healthy adulthood. Left to their own devices, women collectively "control" population while acting on their own intentions. Governments can, and should, get out of the way, merely helping assure that family-planning services are safe, inexpensive, and available to those who seek them.
More than 200 million women in developing countries are sexually active without using effective contraception even though they do not want to be pregnant anytime soon, according to the Guttmacher Institute, a reproductive-health research group. The result: Some 80 million pregnancies around the world are unintended, a number similar (though not strictly comparable) to the one by which world population grows every year.
In the US, which spends about 17 cents per dollar of economic activity on healthcare, nearly half of all pregnancies is unintended. Yet in all nations in which a choice of contraceptives is available, backed up by safe abortion services, women have one or two children. Combine such services with education for girls and decent opportunities for women, and average global fertility would fall below two.
True, old-style population control seems at first glance to have helped slow population growth in China. But most of the drop in Chinese fertility occurred before the one-child policy went into effect in 1979, and given fertility trends elsewhere in Asia, it's likely the drop would have continued without coercion. Many developing countries – from Thailand to Colombia to Iran – have experienced comparable declines in family size by focusing on making schooling and family-planning services as accessible as possible.
With President Obama in the White House and Democrats dominant in Congress, the US government is at last supporting the kind of development abroad and reproductive health at home most likely to encourage slower population growth. Like nearly all other politicians, however, Mr. Obama doesn't talk about population or its connection to problems from health and education all the way to food, energy security, and climate change. The topic is still too sensitive, despite the recent upsurge in attention.
Bringing population back into the public conversation is risky, but people increasingly understand that the subject is only one part of most of today's problems and that "population control" can't really control population. Handing control of their lives and their bodies to women – the right thing to do for countless other reasons – can. There is no reason to fear the discussion.
Robert Engelman is vice president for programs at the Worldwatch Institute and is author of "More: Population, Nature, and What Women Want." A longer version of this essay first appeared in the magazine Scientific American.