Bass Rock, covered in guano, off the east coast of Scotland. (photo attribution: “Bass Rock covered with guano” by John Lord is licensed under CC BY 2.0)

Thomas Malthus’s famous 1798 treatise on the dynamics of resource depletion and replenishment primarily concerned his home country of Great Britain, which constantly seemed mired in a population crisis. But he worried, too, about North America, which was lucky to lack many of the resource restrictions of an island. Of course, Malthus wrote in An Essay on the Principle of Population, the European-American population had doubled in a mere quarter-century — what was there in its way? And it would keep doing so…