nother problem on the deadly-dozen list is invasive species. Invaders akin to the rats that helped wipe out Easter Island's palms now threaten even places we think of as ecologically robust: Diamond writes with great detail about the high cost to farmers of exotics like knapweed and leafy spurge in his beloved Montana. Rapidly growing populations, too, have bedeviled civilizations past, and we face the same kind of continued rise. Though fertility rates have fallen, the bulge of young people in the developing world means we will welcome several billion more brothers and sisters to this planet, and most of them will wish to live at something like the same high standard that we now enjoy. Their efforts to attain our comforts in turn mean that energy shortages, toxic chemical pollution, and global warming will become ever harder to contain. "People often ask, 'What is the single most important environmental/population problem facing the world today?' " Diamond writes. "Any of the dozen problems if unsolved would do us great harm, and because they all interact with each other, if we solved 11 of the problems but not the 12th, we would still be in trouble." Yikes.

But wait -- here's the upside, the anti-Easter Island. Diamond describes another South Pacific island, one I'd never heard of. On Tikopia, in about 1600 A.D., the natives decided to kill every pig on the island because the animals raided gardens, competed with humans for wild food, required 10 pounds of vegetables to produce one pound of pork, and had become an unsustainable luxury for kings. It was a good decision; the Tikopians are still going strong. By contrast, the Norse were disappearing from Greenland after 400 years of settlement at about the same time; one reason was that they would not switch from eating beef to eating blubber like their Inuit neighbors. Even though the cows were wreaking ecological and economic devastation comparable to that of Tikopia's pigs, they were too much a status symbol to surrender.

So are we Tikopia, or are we Greenland? We're neither, of course -- we're a planetary-scale civilization with endless feedback loops. On the one hand, we have technologies like the Internet to give us warnings that past societies didn't enjoy, and at least theoretically our markets can help us adjust to scarcities -- oil goes up in price, making the solar panel for your roof seem more desirable. On the other hand, those same communications technologies pulse with pictures of the good life, a life that, if pursued by nine billion people, would clearly overwhelm our planet.

If you want to be pessimistic, consider the SUV, which might be our equivalent of the Norse cow. On every logical count, it makes no sense for us to keep driving Explorers and Navigators; we should be switching to small hybrids as fast as we can. And yet for many people the sense of being American is deeply intertwined with an overpowered automobile, an oversize house, an overflowing plate. That, combined with the profits made by a small number of vested interests, has been enough to defeat almost every attempt at changing laws and regulations. And if that's our mass response, the actions of our elites are just as disconcerting: The defining characteristic of the first Bush administration, even more than the war in Iraq, was the ease with which it passed huge tax cuts for the rich, even though everyone knew those cuts would make the deficit much deeper. "Like Easter Island chiefs erecting ever larger statues, and like Anasazi elites treating themselves to necklaces of 2,000 turquoise beads, Maya kings sought to outdo each other with more and more impressive temples, covered with thicker and thicker plaster," Diamond notes. Making that plaster required wood, which in turn required the deforestation that helped trigger the Maya collapse. We don't know exactly what comparable imbalances we may be triggering, but the fact that we live in a world where the 500 richest people control more wealth than the three billion poorest feels fragile, feels unlikely to persist. Pick your deficit: trade, budget, carbon. We seem to be in a screw-the-future mood, and that's precisely the attitude that Diamond warns against. If it's nimble, adaptable, and pragmatic you want, America may not be your best case study.

I doubt, though, that this book will persuade many of the die-hard optimists, the cornucopians who firmly believe more people will mean more minds working on more solutions. They will note that Diamond is an intellectual companion of Paul Ehrlich, who sounded many of these same notes more than 30 years ago, albeit with less caution, in The Population Bomb, a book they now delight in dismissing as ludicrously pessimistic. In fact, the massive famines Ehrlich foresaw have not broken out. That book, however, along with the ceaseless campaigning of Ehrlich and other Cassandras, was important in mustering the resources to reduce fertility through education and contraception. "The reason that alarms proved false is often that they convinced us to adopt successful countermeasures," Diamond writes. With the enormous following and credibility that he gained with Guns, Germs, and Steel, there is at least the hope that he will manage something of the same trick here.