THE SONG OF THE DODO

Island Biogeography in an Age of Extinctions. By David Quammen. Scribner: "Island biogeography is a new science concerned not only with islands but with the whole natural fabric of life. Because they are isolated and relatively small, islands can reduce animals and plants to rarity, and then chance factors -- a dry spell, brief infertility -- can end the species. Mankind has now carved up the entire earth into islands, David Quammen says, so we are looking at the possibility of the last extinction. That is his subject. But the performance is something else. Very seldom is science written like this. Mr. Quammen is not a professional environmentalist or a scientist. He is an accomplished essayist and a novelist and his book is a richly elaborated work of literary craftsmanship full of roaring adventures, madcap flights of imagination and people wilder than the animals they stalk with him. He is intelligent, playful and free of cant, so his bad news unaccountably uplifts us, making us rejoice in the ornery strangeness and amazing vitality of nature. Islands, even while they put species in danger, are, to use his words, the flywheels of evolution, and as he makes us see the giddy fecundity of nature he induces a smile again and again over our very fragility.

Slice up a fine Persian carpet into a few dozen neat rectangular pieces. The swatches may together occupy the same area as they did before. But your carpet no longer exists. You're left with a pile of worthless tatters and scraps. With this beguiling thought experiment, David Quammen begins ''The Song of the Dodo,'' his magnificent account of island biogeography -- a science that is not only about islands but about the whole fabric of the natural world. That fabric, the author warns, is unraveling, as once-unbroken expanses of woods, jungle and grassland, home to untold species of plant and animal life, are sliced up into industrial parks, housing developments, farms, parking lots, malls, roads. And maybe here and there a nature preserve.



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But a nature preserve, Mr. Quammen shows, is not nature in miniature, however much it might awe a human visitor, for in its isolation and limited extent, it functions as an island. And islands consign animal and plant species to extinction.

In 1598, Dutch explorers stopping in Mauritius, the small island 500 miles off the east coast of Madagascar, found a profusion of large-headed, big-butted flightless birds we call dodos and they called walckv<õ>gel. That's Dutch for ''disgusting bird,'' though they were not so disgusting that nobody would eat them. A pair of the 30-pound creatures could feed a whole ship's crew. ''We can imagine the shipboard menu,'' Mr. Quammen writes in one of the madcap imaginative flights to which he sometimes gives vent -- ''boiled dodo, roast dodo, pickled dodo, kippered dodo, dodo hash.'' Humans, though, weren't the dodo's only enemies. Later settlers brought pigs and monkeys to the island, and these may have devoured the eggs of the ground-nesting birds. In any case, ''the song of the dodo, if it had one, has been lost to human memory.'' In 1662 a Dutchman briefly marooned on the island gave the last credible eyewitness account of a living dodo.

The dodo is extinct. So are the tigers of Bali. And 45 species of bird on Barro Colorado Island. And hundreds of other island species. In the case of the dodos, humans played a major role. But that humans can be rapacious and shortsighted is not Mr. Quammen's point, at least not here. It's that dodos and other species met their end on islands. By one measure, he writes, ''an island bird faces about 50 times as great a likelihood of extinction as a mainland bird.''

Lapped by the waves, distant from the mainland, most islands are isolated and, relatively speaking, small. Strange, wonderful things happen on them. To Mr. Quammen, the delicious quirks of evolution on the Galpagos Islands, with their finches, iguanas and tortoises ''familiar to anyone who can find PBS with a remote control,'' are not unusual but, instead, ''prototypically ordinary.'' At one juncture, Mr. Quammen simply lists bizarre creatures native only to islands, ranging from a tree-climbing kangaroo on New Guinea to a rattle-less rattlesnake on Santa Catalina in the Gulf of California to a carnivorous parrot that preys on sheep in New Zealand. For two pages he goes on like that. ''Geographical isolation,'' he writes, ''is the flywheel of evolution.'' And islands have it.

But isolation endangers, too. Just as island species are more apt to take on bizarre, resplendent forms, they're also more apt to disappear. ''The evolution of strange species on islands,'' Mr. Quammen writes, ''casts light onto its dark double, which is the ultimate subject of this book: the extinction of species in a world that has been hacked into pieces.'' On the mainland, drought, disease or a glut of predators may kill many members of a species, but rarely all. Large populations, widely spread, absorb the damage. Ultimately, they bounce back. Sheer abundance gives species a better chance of long-term survival. But on islands? Well, if something goes wrong, it's big trouble. A new predator is introduced? A disease takes hold? Humans arrive? An island offers little margin for error. Numbers drop and, too frequently, the species edges into what Mr. Quammen calls ''the precondition to extinction'' -- rarity. Then chance takes over -- too few females in a few too many litters, an abnormally dry rainy season, and presto, extinction.

Mr. Quammen's subtitle is ''Island Biogeography in an Age of Extinctions.'' As the author and many scientists to whom he turns make clear, islands are the small stage on which can be seen portents of a larger tragedy. Islands represent what humankind is making out of the world, as great continental masses ecologically come to resemble South Pacific atolls, and so threaten extinction to species uncountable.

In the 16th century the Portuguese came to a 500,000-square-mile tract of unspoiled tropical forest along the Atlantic coast of Brazil, across high plains from the more famous Amazon rain forest. They started out by growing sugar cane. Settlements followed, then mining towns, and cleared fields for cattle grazing. And steel mills, which needed charcoal, which meant cutting down more forest. Then hydroelectric dams and highways and urban sprawl. Today only about 5 per cent of the original forest remains -- most of it, Mr. Quammen writes, ''in small strips and patches on hilltops, temporarily protected by inconvenience.''

Brown howler monkeys, masked titis and golden lion tamarins, among other primate species, still live in the region. But many are now endangered. When the Portuguese landed, perhaps 400,000 muriqui monkeys lived there. By 1972, their numbers had dropped to about 2,000, and by 1987, in one count, to 386 -- split into 11 scattered patches of forest. Portrayed on a map, they seem ''like a lonely little archipelago protruding above the ghost of Atlantis.''

Another soppy environmentalist tract, reeking of snail darters and spotted owls, earnest unto death? Well, to indulge in one of Mr. Quammen's own writerly mannerisms, let's stop right here for a moment to correct that misapprehension. A former Rhodes scholar, an award-winning essayist for Outside magazine and the author of two collections of articles and essays and of three novels, Mr. Quammen is, by trade, neither professional environmentalist nor scientist. He is a writer. And the book he has worked on for 10 years is intelligent, playful and refreshingly free of cant.

Yes, he revels in his tales of exotic species, he loves rolling their Latin names around on his tongue. Yes, he has a message. But he entertains us all the while, serving up an epic adventure of the mind and spirit. We join him as he gapes at giant tortoises in Mauritius, tracks komodo dragons in Indonesia, collects ants on an island off the coast of Baja California, surveys from the air the clear-cut rain forest of the Amazon. And we accompany him intellectually, too, through theories, conjectures and experiments of naturalists all the way back to Alfred Russel Wallace and Darwin himself.

Blemishes to the performance? A few. Why, one asks, his habitual use of four-letter words? In a thousand other contexts, such language might sound just right. But not here. In a book that otherwise achieves such harmony between feeling and intellect, word and idea, these small, errant intrusions sound jarring off-notes. Then, too, perhaps Mr. Quammen didn't have to pile up examples quite so high. Also, the book's 178 numbered sections, each a few pages long, end as cliffhangers a little too predictably. And sometimes -- as when he tells of getting mugged in Rio de Janeiro -- his personal adventures, however entertaining, don't quite fit the larger story.

Still, in Mr. Quammen's hands, the bad news of species extinction unaccountably uplifts. For it reminds us of nature's sheer, ornery diversity, and why it needs to be preserved. We share in the excitement of a new scientific discipline aborning. By book's end, we glean hints of hope that the future may not be entirely bleak.

''The Song of the Dodo'' follows no straight narrative line. It loops back on itself, develops themes, returns to them, plays them out in different ways. Repetitious? No, not unless you call Bach repetitious. Think of it, rather, as variations on an irresistible theme. You could, I suppose, pick it up anywhere, read 150 pages and come away with a good grasp of its main ideas. But then you might miss the komodo dragons tearing apart the goat in a staged feeding for tourists.

Here, in this richly elaborated work of a literary craftsman, we find rejoinder enough to the noisy claims of headline, hyperlink, computer icon and sound bite. Here is what a book can be. "