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Environment : Life and Death in the Rain Forests : Species may be disappearing at a rate of more than one an hour. Alarmed conservationists have a new strategy for preservation.

Next week: Preserving the Amazon.


Al Gentry had no idea as he struggled toward the isolated Ecuadorean outcropping in 1982 that the name "Centinela Ridge" would become infamous in the literature of biology.

A botanist with the Missouri Botanical Garden, Gentry was on a field trip. And he was understandably excited when he discovered that the ridge at the base of the Andes nurtured more than 100 previously unknown species of plants.

Unfortunately, that's only part of the reason Centinela Ridge became a scientific cause celebre . The other part is that shortly after Gentry's find, the ridge was cleared by farmers, and nearly all those unique plants disappeared forever.

It's a story of destruction that has been repeated countless times since, throughout the tropics. Deforestation, population pressures and pollution in key parts of the world are combining into what British conservation consultant Norman Myers calls an "impending extinction spasm."

The World Wildlife Fund, a major conservation group, estimates that in 1970 species were becoming extinct at a rate of one a day. This year, biologists warn, the rate may be more than one an hour.

Not only has that increase alarmed conservationists; it has also fostered a whole new approach to the challenge of preserving the 1.4 million different types of plants, animals, bugs and other living things already identified by scientists, as well as the millions more species still believed to be lurking, undetected, on other Centinela Ridges.

There's always been a lot of nastiness in nature, of course, and species have come and gone since the world began without destroying the precariously balanced, wider communities of animals, plants and bacteria--or ecosystems--of which they were a part.

But for some 65 million years, extinctions through natural processes were remarkably low, an estimated rate of one species wiped out every 27 years. Man began to alter that rate about 15,000 to 35,000 years ago, scientists believe.

But what is happening now is of an entirely different order because of destruction of tropical forests and coral reefs which are home to a disproportionate share of the Earth's living species.

"If we continue the way we are going," said Jared Diamond, a UCLA physiologist and ecologist, "it is likely that more than half of all species will be extinct by the middle of the next century."

That prospect puts a different twist on one of the most urgent environmental questions facing world leaders. Until now, concerns about the tropical forests have mainly focused on the problem of global warming: Felled trees cannot absorb carbon dioxide, and when they're burned, or if they rot, they release it in great quantities, which may be adding to the greenhouse effect.

But conservationists increasingly point to another global threat from deforestation: the erosion of biodiversity, a term that simply refers to the wealth of life on Earth, the millions of organisms, the genes they hold and the ecosystems they help build and maintain.

While global warming is still a subject of much debate, biologists argue that species loss is both undeniable and a more immediate threat, not just to people in the tropics but to city dwellers in faraway countries who depend in ways they often don't realize on sometimes obscure life forms halfway around the globe.

The threat to this web of nature--and what that means to human survival itself--has galvanized the conservation movement as it heads into a new decade.

Major forest areas have already been virtually written off by some biologists. As much as 90% of Madagascar's forests are gone. Almost all of the forests in the Philippines have been destroyed or degraded, scientists say. The number of species lost in these two areas alone is considered to be enormous.

"The world is losing much more of its virgin tropical forests than had been thought," the World Resources Institute said in a report this summer. "This loss is occurring despite a surge of international concern to conserve the rain forests."

Using new data based on ground surveys of tropical forests, low-altitude photographs, satellite systems and side-looking radar, the resources institute concluded that deforestation is taking place 50% faster than the best previous scientific estimates showed.

The Brazilian Satellite Research Institute says that 8% of Amazon Basin rain forest has been destroyed, up from 5.8% announced last year. The new figure is the equivalent of a landmass about the size of Sweden.

In one sign of concern, experts on tropical ecosystems, agriculture and mining spent six days in Manaus, Brazil, last week for a "Forest 90" conference on ways to ease the adverse environmental impact of economic development.

"The losses have become so great, so rapid that we have to reorder our priorities," said Russell A. Mittermeier, president of Conservation International, in an interview. "We have to approach this with the same dedication, zeal and urgency we showed when we sent a man to the moon in the 1960s."

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