(FORTUNE Magazine) – In a famous 1968 essay, ''The Tragedy of the Commons,'' philosopher, ecologist, and first-class gadfly Garrett Hardin explained to a then skeptical world why commonly owned economic resources must inevitably be overexploited. That insight was later tragically confirmed when the fall of the Berlin Wall laid bare the full extent of the eco-devastation wrought by the communist bloc economies. Now Hardin is back with another unsettling argument. In Living Within Limits: Ecology, Economics, and Population Taboos (Oxford Press, $25), he tries to burst the bubble of anyone who's overly optimistic about the planet's capacity to sustain human population growth -- and in his view that's a pretty big crowd. Hardin's hard-nosed position: Unless you believe excess earthlings can be exported to other planets -- a notion he finds risible -- population must be controlled. In recommending steps to avoid a crisis that he, like the 19th-century economist and population theorist Thomas Malthus, believes will generate only misery, Hardin is not afraid to be controversial. Advanced industrialized nations, he asserts, must soon pass measures limiting individual reproductive rights. These need not entail outright bans on excess births. Instead, he suggests, the government could pay teenage women to delay having children. Or it could grant every female child a sellable right to have no more than 2.1 children, the number required to maintain zero population growth. Those having more offspring would pay dearly for the privilege. Hardin also pours fuel on the fire of America's increasingly explosive debate over immigration policy. To avoid acting as a safety valve for the excess populations of developing nations unwilling to restrain birthrates, the industrial world, he insists, must clamp an even tighter lid on immigration. (Hardin, you will not be surprised to learn, lives in Southern California.) Despite a few odd digressions, such as an almost Ezra Pound-like rant against usury, Hardin's analysis is often witty and always provocative. The main problem is that like Malthus, he is insufficiently persuasive that a crisis is in the offing, or that if one is, technological progress will not be able to avert or ease it. At one point he tries to rebut the notion that a rising global standard of living will bring down fertility rates, only to admit that in some recent years the U.S. rate dipped enough to produce negative population growth -- without any draconian curtailment of reproductive freedom. So far, in short, no tragedy.