In my experience, this meme shows up primarily among people who have studied biology, and who mistake human beings for Drosophila. Yes, under controlled conditions fruit fly populations will increase exponentially until they reach carrying capacity and crash. It’s a powerful image, and whenever an environmental issue comes up, there will be students of Drosophila, cultured bacteria and other life forms who tell us that, whatever we think the cause is, the real, underlying cause is overpopulation.
For the record, I think there are too many humans on the planet, and I hope population growth stabilizes quickly. There is certainly pressure on many natural resources because of our numbers, and we displace the habitats of other organisms in our zeal to maximize our exploitation of the planet. Besides, it would be nice to have more natural areas for solitude and recreation.
But this has little to do with climate change. The argument is essentially the same as in the previous post concerning economic growth.
We have to systematically reduce fossil fuel use until it hits zero by mid-century. Isn’t is obvious from simple arithmetic that the key variable has to be carbon consumption per capita and not the number of capita’s? Short of a mind-bending catastrophe, how can human population fall sufficiently over the coming decades to make a significant dent in greenhouse gas emissions?
In any case, humans aren’t fruit flies. Throughout history and what we know of prehistory we have regulated our reproduction in various ways. At this point, the majority of the world’s people live in societies that are at or near the final stage in the demographic transition—low death rate, low birth rate. There are still hundreds of millions that have yet to arrive, however, and of course they should be encouraged. The measures that have been shown to work are the extension of education and women’s rights, social welfare programs and economic growth, all of which are desirable in themselves. Stabilizing the world’s population at, say, eight rather than nine billion people would be a wonderful thing, but at best it could take us only about an eighth of the way toward reaching our carbon goals—and actually a lot less because demographic stabilization is way too slow.