Mankind's Future: Dead as a You-Know-What

"ISLAND BIOGEOGRAPHY." IT doesn't exactly promise the intellectual seductions of such crossover science hits as, say, "chaos" or "a brief history of time." So when David Quammen assures us that island biogeography is a subject "fill of cheap thrills," we naturally figure he's trying to make up with hyperbole what his topic lacks in interest. But Quammen delivers. Song of the Dodo (702 pages. Scribners. $32.50) is as close as science writing gets to thrilling adventure yam. When Quammen isn't hiking the outback in search of the (almost certainly) extinct Tasmanian tiger, he's in the Indonesian jungle eluding a Komodo dragon that fancies a bite of his butt, scaling crumbling cliffs in pursuit of a Mauritius kestrel or getting jolted by insect bites that feel 'like a poppy seed shot from a cyclotron." The beasts hold up their end of the bargain, too: islands, not mainlands, have produced such outlandish creatures as kangaroos that climb trees and parrots that eat sheep.

But "Dodo" is also a sweetly, sadly elegiac book. Although it was island biogeography that revealed to Charles Darwin and Alfred Wallace how species are born, today this field tells us how, and when, they die. As logging roads slice up the Amazon and suburban sprawl chops up the American prairie, the world "has been hacked into pieces," Quammen writes. Those pieces are, from a biological standpoint, islands. And it is on islands that plants and animals are particularly vulnerable to extinction: of the birds that have become extinct in recent centuries (the dodo, the Guam flycatcher, the Mariana fruit dove, the Micronesian honeyeater, the passenger pigeon, the auk), 155 of 171 lived on islands. The story is the same for mammals and reptiles.

"Dodo" is at once chatty ("are you with me?") and erudite, with lucid explanations of evolutionary biology, of why both gigantism and dwarfism are common on islands, and of the relationship between the size of an island and the number of species it can support. This last, an equation of purely academic interest only 30 years ago, is now crucial to understanding why wildlife reserves cannot support a replica of the original ecosystem and why extinctions are rolling through even America's national parks.

Give Quammen, a journalist and former Rhodes scholar, credit for spurning the new-think "environmental optimism," now so trendy, which holds that since you can't see the air in Los Angeles so often, and since rivers don't catch fire, the environment is doing just fine. He dares use such unfashionable terms as "collapse" and cataclysm of extinction," and ever ventures the view that humans "probably won't survive long enough" to cause another round of extinctions: "The richness of Earth's ecosystems might recover ... within, oh, ten or twenty million years ... assuming Homo sapiens itself has meanwhile gone extinct too." In his crystal ball, sparrows, dandelions, rats and roaches inherit the Earth. "Dodo not only makes us believe; it makes us care.

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