From a reader:

Jonah,
I know you wonked as a population policy guy, and you have from time to time opined on the subject of population versus environmental capacity, resource scarcity etc. I think that you basic large point is a very good one –i.e. that people are intelligent actors and so trendline predictions are often wrong (ie. Europe DE-populationg etc), and that market mechanisms tend to take care of scarcity by disinsentivizing consumption and incentivizing finding alternates etc.
What I find frustrating is the tendancy, which you have shared sometimes, of conservatives to totally dismiss the environmentalist/ overpopulationists/ Malthusians claims without recognizing the true components or using very bad counter arguments. Specifically, it is seldom acknowledged that some of the things that seemed to specifically disprove Malthus’s population vs. arable land equation in history weren’t general phenomenon but one time off events. Population pressure and farm land shortage in Europe was relieved by the one time event of discovering a new continent with huge amounts of arable untilled land. Agricultural yields were doubled or whatever by discovery and exploitation of natural deposits of large but finite sources of organic fertilizer material –i.e. guano and then oil. Once those are used up, as guano already is, we can’t just use sand (unless you subscribe to a cold fusion techno magic deux-e-machina faith/ solution). Using these events as economic ‘proof’ that resources don’t run out is just silly. Just because my gambling addiction didn’t bankrupt my family because my rich uncle died and I inherited wealth just in time, is not proof that my gambling habit is sustainable in the future.
Another bad argument about population that your are guilty of sometimes tapping is the ‘vast open spaces’ one, and the related ‘but look at Holland (Japan, Singapore…). Just because x number of people can physically fit on y area of moon surface does not mean that the moon has carrying capacity for them (you know, the whole earth’s population could fit in east Texas thing), the important thing is the amount of land to grow food per person, the amount of land to grow plants to exchange their oxygen, filter their fresh water etc., and wide open desert doesn’t count as ‘available land’. Some economists say “but look at Holland (Japan, Singapore, Hong Kong, Manhattan…) to point out that more people equals more prosperity etc. But Manhattan requires a mostly empty, unpolluted, undeveloped majority of upstate NY to give it fresh water, and lots of Ohio and Idaho to feed it, so the idea that you could fill those places up like the island of Manhattan is silly.
Finally, the great weakness in the market argument is that some resources, like clean air and fresh water, are not demand flexible or substitutable, so using the fact that we don’t run out of copper because industry finds ways to do more with less, use other materials etc. is not a very good analogy to these items. And placing faith in ‘Star Trek’ solutions dependant on infinite energy from matter/antimatter reactions to create and change matter at a whim are not very good arguments either.
Anyway, I imagine you know these things, which is why I write. I wish you would write a thoughtful column on the subject that is less of a swipe at the hysterics and exaggerators on the other eco side and more an attempt to lay out the truth on the matter.