Slate Magazine | Sept. 10, 2007
By Daniel Engber

Oh, if we all just disappeared. According to The World Without Us, Alan Weisman's strangely comforting vision of human annihilation, the Earth would be a lot better off. In his doomsday scenario, freshwater floods would course through the New York subway system, ailanthus roots would heave up sidewalks, and a parade of coyotes, bears, and deer would eventually trot across the George Washington Bridge and repopulate Manhattan. Nature lovers can take solace in the idea that the planet will thrive once we've finally destroyed ourselves with global warming. But Weisman takes the fantasy one step further: Let's not wait for climate change, he says. Let's start depopulating right now. 

Instead of burning down our numbers with oil and gas, we might follow the advice of the founder of the Voluntary Human Extinction Movement, who tells Weisman that everyone in the world should stop having kids all at once. Weisman isn't up for quite so drastic a measure, but he makes his own pitch, moderate in comparison: Let's cut the birth rate to one child per couple, for a few generations at least. The population would dwindle by about 5 billion people over the next century, he says, ensuring the habitability of the Earth for the 1.6 billion who remained. At that point, they could all reap the rewards of a more spacious planet, sharing in "the growing joy of watching the world daily become more wonderful." It seems like a notion from the fringe, but Weisman's book has become a mainstream best seller. Could population control be the next big thing in green culture?

Nine years ago, Bill McKibben was raked over the coals for making a similar proposal in his vasectomy memoir, Maybe One. ("It's the last remaining taboo thing to talk about," he said after it was published.) Maybe times have changed. As social policy, population control seems like an infringement on fundamental human rights. That's been the case in China, where mandatory birth planning has been a ghastly failure in both moral and practical terms. But these days, we tend to think of saving the environment in terms of personal choice, rather than government programs. We're obsessed with our green lifestyles—eating local, driving hybrids, paying off our excess carbon-dioxide emissions. From that perspective, voluntary familial extinction (or at least reduction) might not be such a bad idea. If you want to reduce your carbon footprint, cutting back on kids is the best choice you can possibly make.

What's the environmental cost of having a child? In the crudest terms, you've added another version of yourself into the world, which means you're potentially doubling your carbon-dioxide emissions over the total life of your family. That's a high estimate, since our kids won't spew as much greenhouse gas as we do—automobiles, appliances, light bulbs, and everything else will become more efficient in coming generations. But these marginal improvements aren't going to make our babies carbon-neutral. They'll just contribute to global warming at somewhat lower rates than we do.

Our other green lifestyle choices can't even begin to offset the cost of adding a brand-new CO2-emitter to the population. When I ran my own numbers through Al Gore's carbon calculator, I discovered that a switch to 100 percent wind and solar power would reduce my emissions by just 1.3 tons per year. That's not even enough to account for one quarter of today's average American. Meanwhile, I'd have to do quite a bit of driving around in a Hummer H3 to mimic the environmental impact of creating another version of me. Not to mention the fact that my children might eventually decide to have their own children, who would emit even more carbon dioxide down the line.

Critics of population-based environmentalism point out that the people most likely to cut back on their baby emissions are also the ones most likely to instill their children with green values. It's the Idiocracy argument: If all the eco-conscious Americans stopped having kids, their numbers would decline. But having fewer greenies around would be a net loss for the environment only if each greenie baby did more good for the planet than harm—i.e., if the value of his or her vote exceeded the costs of his or her CO2 emissions. (If that's true, environmentalists should have as many children as possible, to stuff the ballots for Dennis Kucinich.) It's also naive to assume our children will embrace our values just because we want them to; for all our preaching, we might end up with a generation of rebellious, gas-guzzling teenagers.

What about the global picture—do we know how much population growth will contribute to climate change over the next 100 years? According to U.N. projections, the world population is likely to increase by 2.5 billion people—to a total of 9.2 billion—by the year 2050. That won't necessarily drive an equivalent percent increase in CO2 emissions, since most of the growth will be confined to the developing world, where per capita emissions are at their lowest. But we can also expect to see significant growth in the United States, where individuals do the most damage to the environment.

Overall, the increase in population over the next century won't matter quite as much for climate change as the increase in global wealth, but it's still important. In general, a country's per-capita emissions rise as it becomes more prosperous, while its fertility rate declines. In other words, fewer babies are born, but each one emits more CO2. (That's why the economic boom in China will create a massive increase in greenhouse gas emissions even if its population remains stable.) In fact, the birth of every additional child in the developed world can have a major impact on the cost of keeping global warming in check. According to studies published over the last decade, this amounts to as much as $10,000 to $20,000 per baby. Policies that promote family planning—in the United States or elsewhere—might well be more efficient than other means to reduce CO2 emissions, like a Kyoto-inspired carbon tax.

Despite these findings, Earth-advocacy groups almost never raise the issue of family size, focusing instead on lifestyle choices with more modest environmental rewards. When a group of population-control advocates tried to take control of the Sierra Club in 2004, their anti-immigration policies were decried as racist and they were voted down. (Most of the population growth in the United States comes from immigrants, who are likely to broaden their carbon footprint once they've arrived.) Even the academics on the Intergovernmental Panel on Climate Change have shied away from direct references to population and global warming.

They have good reason to be squeamish. The anti-life implications of Weisman's book are likely to alienate some moderates, as well as any social conservatives who might otherwise be drifting green. There's already been a strong Christian backlash against the GOP defectors of the "Creation Care" movement, with their solar-powered churches and prayers over global warming. Right-wing religious groups accuse the evangelical environmentalists of being in league with tree-hugging abortionists.

Worries over population growth also give fodder to the climate-change skeptics, who are quick to reminisce over the ill-fated doomsday projections of Paul Ehrlich's The Population Bomb. Published in 1968 (just six years after Rachel Carson's Silent Spring), the book cited hockey-stick reproduction rates since the Industrial Revolution to predict an imminent global catastrophe. But dramatic improvements in agricultural technology provided enough food to forestall the crisis, and Ehrlich and his fellow Malthusians were discredited. To bring up overpopulation once again—now in the context of global warming rather than food shortages—invites the same counterargument: Science and innovation will save the day.

As a global solution for climate change, Weisman's depopulation plan may not have much of a chance. ("I knew in advance that I would touch some people's sensitive spots by bringing up the population issue," Weisman told Washington Post readers in an online chat, "but I did so because it's been missing too long from the discussion.") But that's no reason to neglect birth rates from the personal calculus of living green. With the rise of consumer-driven environmentalism, it may be that the McKibben moment has finally arrived. Whether it's eating vegetarian or wearing organic eye shadow, we're all shopping for absolution. We know that babies add more to global warming than anything else in our home. Isn't it time to cut back?