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Ringing a Biodiversity Alarm

AS has been seen with the recent controversy over vice-presidential candidate Al Gore's book "Earth in the Balance," some people (many, in fact) still doubt that the environment is in serious trouble. Global warming is an unproven theory, they say. Natural resources are plentiful enough to sustain growth and prosperity, and humanity is clever enough to engineer its domain if problems arise. And besides, what's a spotted owl more or less in the grand scheme when there are millions of species coming and go ing all the time?

For them - and for everyone - Edward O. Wilson's The Diversity of Life (Belknap/Harvard University Press, 424 pp., $29.95) is an answer to skepticism and complacency.

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Dr. Wilson is a professor of science at Harvard University who already has proven he can write, having won one Pulitzer Prize and shared another. He brings to mind the great novelist Vladimir Nabokov's instruction to his students at Cornell University that they must write "with the passion of the scientist and the precision of the artist." This seems to be a paradox, but not to writers like Wilson, who in this sense may be grouped with other great writers out of the scientific disciplines such as Loren E isely, Freeman Dyson, and Stephen Hawking.

Here, he demonstrates with passion and precision that Earth's biological diversity - its richness of species - is headed for major trouble. He shows how the current rate of extinctions is many times what should be normal for this stage of evolution, and why this could prove disastrous for our own species.

He bases his findings (which come out of four decades of research, much of it in the field) on science and his recommendations principally on economics. While there is a strong ethical element in his conclusion, he passes close to but does not linger long on religion or near-religions like the "Gaia" theory (which holds that Earth is one huge organism).

Some - especially those who favor "deep ecology" - may see this as a weakness. I see it as a strength to his work; while there is passion in his message, it is the precision of the science that mostly conveys it.

In the first half of "The Diversity of Life," Wilson walks readers through the history of the creation of species and ecosystems. He paints with words a vivid picture of life emerging and evolving on Earth. Patience may be required along the way as he explains some of this in considerable detail, but it is worth the trip.

Through this period of a half-billion years or so, there were five of what he calls "major extinction spasms," when biodiversity was sharply reduced because of natural events like climate change. Each time it took 10 million years or so to recover, but the number of species continued to increase.

Now, he says (and by "now" he means the relative blink of time since homo sapiens fully emerged), a sixth major extinction spasm is occurring. Whereas the normal "background" rate of extinction is 10 to 100 species a year, today "even with ... cautious parameters, selected in a biased manner to draw a maximally optimistic conclusion, the number of species doomed each year is 27,000. Each day it is 74, and each hour 3."

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Most of this has to do with the loss of ecosystems where species exist. The best known are the tropical rain forests, which make up 6 percent of the landmass but are home to more than half the world's 10 million to 100 million species. By the end of the 1980s, more than half the prehistoric amount of such forest cover had been destroyed. Such forests had been reduced to the equivalent of the contiguous 48 US states, and they were disappearing each year by an amount the size of Florida.

Wilson concludes that within the next 30 years (an instant of historic time) "a 20 percent extinction in total global diversity ... is a strong possibility...."

So what? the skeptic may ask, especially when most species (in Wilson's words) are "weeds and bugs." Part of the answer is that within those rapidly declining numbers (most of which have yet to be studied) are "keystone species," the loss of which can cause drastic changes to habitat communities.

"The loss of a keystone species is like a drill accidentally striking a powerline," he writes. "It causes lights to go out all over." Biodiversity is that which "holds the world steady," "the property that makes resilience possible." If organisms are disturbed too much, Wilson warns, the environment "will destabilize and turn lethal." For mankind, this means the risk of "catapulting ourselves into an alien environment."

In his concern about such losses and in his recommendations for how to avoid them, Wilson emphasizes the potential benefits to mankind that also may be lost - in particular, breakthroughs in medicine and food production that may never occur. But he also acknowledges that "wilderness has virtue unto itself and needs no extraneous justification."

This is an important book, one that should be on the short shelf of environmental works of anybody who believes the recent Earth Summit in Brazil should not be forgotten. And more so for those who already have started to forget.