THE DIVERSITY OF LIFE By Edward O. Wilson. Illustrated. 424 pp. Cambridge, Mass.: The Belknap Press/ Harvard University Press. $29.95.
IN the Beatles cartoon "Yellow Submarine," there is a creature called the Vacuum Cleaner Monster, which sucks up everything in sight until it is the only thing left, and then it sucks itself up too. In the biological realm, this is a difficult trick to pull off. Most species that start destroying their own habitat simply manage to reduce their food supply, and so shrink in number before they can do further damage. The only species with real destructive powers are those whose adaptability and varied appetites allow them to switch to new food sources when they have exhausted old ones. Our planet does, however, house one species that takes adaptability and varied appetites to perilous extremes.
The central message of Edward O. Wilson's stirring new book, "The Diversity of Life," is that Homo sapiens is in imminent danger of precipitating a biological disaster to rival anything in evolutionary history. Mr. Wilson, the Frank B. Baird Jr. Professor of Science and the curator of entomology at the Museum of Comparative Zoology at Harvard University, is the doyen of American biology. Two decades ago he popularized the term "sociobiology," and generated a small industry of speculation about the biological basis of human nature. In this book he stops asking what biology does to humans, and asks instead what we humans are doing to biology.
The focus of his book is the extinction of species. As Mr. Wilson observes, other kinds of environmental damage can in principle be repaired, but a defunct species is gone forever. Not that the destruction of animal species by humans is a new phenomenon. For those who still believe there was a golden age of ecological harmony before our technological fall, Mr. Wilson produces strong evidence that prehistoric tribes killed off the mammoths, the moas and many other large animals.
STILL, the human population explosion of the late 20th century has lifted our destructiveness to altogether new levels. Our hunger for agricultural land and grazing pastures means that we are now wiping out not just individual animals, but whole ecosystems. As we chop down and burn primeval forests, we also suck species into oblivion -- now at the staggering rate, Mr. Wilson estimates, of 27,000 species per year, 74 a day, 3 every hour.
Even at this swift rate, though, it will take hundreds of years to exhaust the stock of species, so diverse are the creations of nature. No one knows exactly how many species currently exist. About 1.4 million are catalogued, of which insects constitute more than half, higher plants 250,000, birds 9,000 and mammals 4,000. But it is anybody's guess how many more species are still lurking in forest canopies and at the bottom of the oceans. Few biologists would put the figure at under 10 million, and some think it may be 10 times that.
"The Diversity of Life" is as much a celebration of this profusion as a warning of its imminent demise. Mr. Wilson, who is also the author of "On Human Nature" and "Sociobiology," writes urgently, as if to capture the kaleidoscope of nature before it breaks up into long-lost fragments. In the Amazon basin, he lists the lives hiding among the fallen trees and rotting branches: "basidiomycete fungi, slime molds, ponerine ants, scolytid beetles, bark lice, earwigs, embiopteran web spinners, zorapterans, entomobryomorph springtails, japygid diplu rans, schizomid arachnids, pseudoscorpions, real scorpions." The green conure parrot of Mexico, he tells us, provides a habitat for 30 species of feather mites, each of which lives on different parts of different feathers. In the forests of Costa Rica, he watches insects that eat the lichen that grows on the small trees that grow on the beds of orchids that grow on the big trees. Mr. Wilson even seems to delight in the cigar-shaped, half-meter-long cookie-cutter shark, whose habits were exposed in 1971: "It thrusts its maw into the bodies" of living porpoises and whales, he writes, and "twists to slice out five-centimeter-wide conical plugs of skin and flesh."
Interleaved with this catalogue of marvels is an introduction to macroevolutionary theory. In sharp contrast to the pleasingly simple laws that dictate developments within existing species, the forces that govern the proliferation of new species are complex and ill understood. Mr. Wilson is an excellent guide to the broad movements of evolution. He explains how each geographical setting has room for only a limited number of species, and how accidents of migration often determine which new species will take root. A species that arrives at an empty place, like the first finches on the Galapagos Islands, radiates into different niches and eventually divides into different species. This process, Mr. Wilson explains, has yielded a steady increase in the diversity of species since evolution began, an increase that has accelerated over the last 100 million years.