But the question isn’t whether we will literally have enough space for more people—Kunzig points out that if 9 billion people were spread out around the habitable parts of the planet, the entire Earth would still have only half the population density of France.  Some time late in 2011—at least according to the people-crunchers at the U.N. Population Reference Bureau—humanity will reach a new demographic milestone with the birth of the 7th billion living person. Kunzig notes that global population has grown astoundingly fast during most of our lifetimes—while it took all of human history to around 1800 for the global population to reach 1 billion (a little Black Death here and there didn’t help), it will take a little more than 50 years for the world’s numbers to grow from 3 billion to 7 billion. With some 1.5 billion people already living on less than $1.25 a day, nearly 1 billion people hungry and the natural world already heavily damaged, are we on the path to destruction? The fear—from Malthus to Ehrlich—is that we won’t be able to support ourselves, that there won’t be enough food, water or energy to go around, as Kunzig wonders: 
 
 Many people are justifiably worried that Malthus will finally be proved right on a global scale—that the planet won’t be able to feed nine billion people. Think about it—in the future the developed world will lack young workers, and the developing world will have an excess of that resource. Ehrlich was right, though, that population would surge as medical science spared many lives. In the past, high fertility rates were the norm around the world, as women had to have large number of children to ensure that at least a few them would survive into adulthood. When child mortality declines, couples eventually have fewer children—but that transition usually takes a generation at the very least. So here’s the planet we could have in 2050: an overpopulated, overstressed developing world and an aging, economically stagnant developed world, with inequality even larger than it is today. More from TIME on population: 
 
 What Condoms Have to Do With Climate Change 
 
 Population: The Numbers Game A U.N. graph shows how fast population has grown, and where it might be headed: 
 
 That rapid increase is due to the demographic transition—and on the surface, it’s a sign of human progress. The U.S., Europe and other rich countries have already gone through the transition—in most well-off countries fertility is around or even well below the replacement rate of 2.1 children per woman—and it’s begun to happen in all but the poorest developing countries as well. We may, for example, says [population biologist Joel] Cohen, “see to it that all children are nourished well enough to learn in school and are educated well enough to solve the problems they will face as adults.” That would change the future significantly. Rwanda’s fertility rate also falls below the replacement level, but its population still rises to well over twice what it was before the genocide. Though its population continues to grow, China, home to a fifth of the world’s people, is already below replacement fertility and has been for nearly 20 years, thanks in part to the coercive one-child policy implemented in 1979; Chinese women, who were bearing an average of six children each as recently as 1965, are now having around 1.5. “Filling the family planning gap may be the most urgent item on the global agenda,” he writes, so if we don’t hold the world’s population to eight billion by reducing fertility, the death rate may increase instead. (That’s often still the case in extremely poor, heavily rural countries like Niger, where the average woman has seven children.) Those teeming slums seem to provoke a visceral disgust among the thinkers who worry most about population—like Paul Ehrlich, the author of The Population Bomb, whom Kunzig quotes: 
 
 I have understood the population explosion intellectually for a long time. I came to understand it emotionally one stinking hot night in Delhi a couple of years ago… The temperature was well over 100, and the air was a haze of dust and smoke. The streets seemed alive with people. People eating, people washing, people sleeping. People visiting, arguing, and screaming. People thrusting their hands through the taxi window, begging. People defecating and urinating. People clinging to buses. People herding animals. People, people, people, people. As Kunzig notes, that was written in 1966, when India only had 500 million people—today it has 1.2 billion, and it is projected to have over 1.7 billion by mid-century, which would make it the most heavily populated nation on Earth.
– Things to look forward to in 2011: all-natural Frito-Lay chips, a bunch of truly unnecessary movie sequels, and … the world’s 7 billionth living person. That lucky baby will arrive sometime next year, according to the UN Population Reference Bureau, writes Bryan Walsh for Time. The world’s 6 billionth living person was born just 11 years ago in Bosnia, and the population is expected to exceed 9 billion by the middle of the century. Can the planet really handle that? Robert Kunzig attempts to take on that question in a very lengthy National Geographic cover story (worth a read). Walsh picks out a few highlights: Kunzig calls out attention to the fact that it took nearly all of human history to get us to the 1 billion mark, but we're set to explode from 3 billion to 7 billion in about 50 years. By 2050, we'll be somewhere between 8 billion and 10.5 billion, according to the UN. Space isn't the issue. Kunzig notes that if 9 billion people were spread throughout Earth's habitable regions, the population density would be half of that in France. The potential problems: Not enough food, water, energy. And a lot of aging people. Writes Kunzig, "Fixating on population numbers is not the best way to confront the future. The number of people does matter, of course. But how people consume resources matters a lot more ... It’s too late to keep the new middle class of 2030 from being born; it’s not too late to change how they and the rest of us will produce and consume food and energy."