Quotes of the Day

As the director of the Central Intelligence Agency, Gen. Michael Hayden should have some insight on the biggest threats facing the U.S. But when Hayden recently described what he saw as the most troublesome trend over the next several decades, it wasn't terrorism or climate change. It was overpopulation in the poorest parts of the world. "By mid-century, the best estimates point to a world population of more than 9 billion," Hayden said in a speech at Kansas State University. "Most of that growth will occur in countries least able to sustain it." The sheer increase in population, Hayden argued, could fuel instability and extremism, not to mention worsening climate change and making food and fuel all the more scarce. Population is the essential multiplier for any number of human ills.

Back in the 1970s, Hayden's argument wouldn't have been surprising. That era, which saw the birth of the modern environmental movement (the first Earth Day was observed in 1970), was obsessed with the idea of global limits, that without drastic intervention, we were doomed to overpopulation. Books like Paul Erhlich's The Population Bomb warned that the Earth was reaching the end of its carrying capacity, and that within decades, hundreds of millions of people would starve to death. The only way to avoid this Malthusian fate was rigid population control, which many environmentalists were in favor of.

Fast-forward 30 years, however, and the situation has changed. The mass famines that Erhlich and others prophesized never happened, and while population growth has continued — an estimated 6.8 billion people now live on Earth — and on the whole, the world is better off today than it has ever been. A Green Revolution helped a growing planet feed itself, while the forces of globalization helped lift hundreds of millions in the developing world out of poverty, even as population continued to rise. As the years passed, overpopulation has dropped from the vocabulary of most environmentalists, partially due to the controversies that surrounded state-mandated birth control in countries like China, with its one-child policy. Though simple arithmetic will tell you that the bigger the global population becomes, the harder it will be to reduce greenhouse gas emissions, you rarely see the population connection made explicit in major environmental reports. "Environmentalists came to realize how complicated and sensitive this issue was," says Robert Engleman, vice-president for programs at the Worldwatch Institute, and the author of the new book More: Population, Nature and What Women Want. "People didn't want to tell their neighbors and friends how to have kids."

But now, the pendulum is shifting back. The sudden spike in both food and fuel prices is raising concerns that we may not be able to grow forever, that even with the best technological innovation, the planet may have limits. It's becoming increasingly clear that if we can't curb carbon emissions in a world of 6.8 billion, it may be impossible to do when there are 9 billion of us. And while population growth has slowed drastically in many countries in Western Europe and in Japan, where women are having fewer and fewer babies, it's still rising in much of the developed world — and for that matter, in the United States. "You really can't talk about the supply and demand imbalance that is sending energy and food prices up without acknowledging that we are adding 78 million people each year, the equivalent of a new Idaho every week," says Engleman.

The question remains though: what can we do about population? State-mandated birth control is essentially unfair — and a policy no American government would ever support. But in his new book, Engleman makes the argument that the government doesn't need to get involved. The key to limiting population growth, he says, is to give control over procreation to women. In society after society, even in countries where large families have always been the norm, when women take control over family size, birth rates shrink. "They don't have to be coerced," says Engleman. "This will happen as long as women are in charge."

I've seen this transition happen myself. In Japan, where I spent a year as a foreign correspondent, large families were once the norm, and women rarely worked. That's changed — and Japan's birth rate has plummeted — as women seek professional and personal fulfillment beyond having children. But that change has yet to occur in those parts of the developing world that are growing fastest, such as Uganda, where population is rising at 3.6%, the highest rate in the world. That's what Gen. Hayden is worried about — that bursting population will turn struggling nations like Uganda into basket cases, with political and environmental consequences for the rest of the world. For the U.S., the best option is vigorous foreign aid that helps make contraception safe, reliable and accessible in every country — too often women in the developing world who want to use contraception, can't get it. "The funding for contraception aid has been stagnant for decades," says Engleman. "Americans need to influence their government to get behind this." If we don't, we may find out very soon just what the limits of the Earth are. It's not just feminism to support population control — it's environmentalism.

• Bryan Walsh