A numbers game.(FROM THE EDITOR)(Editorial)

At least since the days of Malthus, people have wondered when the planet will be too full of people. During the last several generations as the number of humans has grown exponentially and our use of resources has skyrocketed the question has taken on particular force. This place can feel intolerably crowded, and it seems only reasonable to ask: How many more souls can we possibly fit?

But I think that to wonder in 2009 when Earth will be overpopulated misses the point. It seems obvious to me at least that we are already well past full. The clearest proof of that are the 1.1 billion people who live without clean water, the more than 900 million people who are hungry, the 16,000 children who die every day from hunger-related causes.

Yes, I know that modern, chemical-based agriculture can grow enough food to feed 6.8 billion people and perhaps many more. But the fact that millions still die from filthy water or insufficient food just shows that we are grappling with political scarcity as much as ecological scarcity. And for those whose lives are all too nasty and short, the distinction doesn't matter one bit.

According to most projections, we will reach the 9 billion mark sometime around 2045 and then begin leveling off. I suppose that the planet can accommodate that many Homo sapiens. If we all lived modest lives as, say, farmers, pastoralists, and craftsmen and took good care of our ecological life-support systems, it just might work. But 9 billion of us can't live as Americans, or even like the slightly thriftier Europeans. There are simply not enough resources.

That fact is why discussions of population are so complicated: It's not ...