Too Many People?

Slate has a review of a new book called The World Without Us, by Alan Weisman. It ends enthusiastically and begins thusly:

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.

It is not a promising start for a review. “The world” cannot be better or worse off. “Better” or “worse” implies some way of defining “good” and “bad,” which the earth, not being a sentient being, is incapable of doing. We could ask whether the earth will be better or worse for human purposes; this would be a much more intelligent way to proceed. If we did so, we might still get to a question the author and the review tackle, namely whether there are too many people on the earth.

Are humans bad for the planet human species? Partly. In their consumption decisions they deprive others of resources, including others in future generations. Most of these transactions are correctly mediated by prices, so the benefits offset whatever costs are imposed. Some, of course, are not. The hysterical zero-populationist (or population-decline advocate, which Mr. Weisman may be) focuses on the effects of human choices on finite natural resources such as oil, and on warming of the earth, which changes the possibilities for future generations. The oil objection is easily dealth with. It is indeed a scarce resource, and if I use it you can't. But time is a scarce resource too, and if a scientist doesn't have enough time to cure cancer because he can't drive, that is a real cost. It is the function of the price system to weigh choices such as these. As for global warming, the things that generate it are the by-products of beneficial activities, which we would also be deprived of without the people whose activities are warming the earth; this suggests that the solution to these problems is to mitigate the costs (e.g., through anti-pollution laws), but to have the kids anyway so as to continue to reap the benefits.

And oh, what benefits they are! The Slate article obsesses about environmental costs, as if these were the only effects of humans on other humans. But humans, by entering into the market, bring huge benefits. Everyone they trade with reaps benefits from that trade. Humans create ideas that widen our horizons; they figure out ways to explore the universe; they invent the Internet; they write As You Like It and Beethoven’s Ninth; they climb Mt. Everest, just because it’s there. And they provide immense love and joy for their friends and loved ones. Do these benefits outweigh the costs from missing markets for polluted air and water? It is impossible to say for sure, but it seems likely. And Americans, inhabiting the most productive and one of the freest societies in the world, create these benefits disproportionately; they should perhaps be breeding faster than anyone.

The logic here suggests that if anything we have too few children. All of the problems other than pollution that the alleged overpopulation of humans is said to cause – malnutrition, taxing the water supply, etc. – are either in decline because of better economic policy and the fruits of human ingenuity or are solvable through good economic policy and the price system. So too climate change is amenable to remedies that are low-cost but that allow us to continue to achieve our goals and dreams.

The hatred of much of the current environmental movement for humanity itself is one of its most alarming aspects. In obsessing about only one kind of cost, they ignore all of the benefits that humans provide. So once you have settled down, get busy having children – you’ll be doing everyone else a favor.

Thanks to Steven Landsburg, to whom I owe some of the arguments in this piece.