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November/December 2000
Rainforests and Mass Extinction

By Tim Keating


When I was in grade school, it was thought that Earth supported about a million species of unique life forms. Recently, however, I attended a conference on Biodiversity at the American Museum of Natural History that was the kickoff to the opening of their Biodiversity exhibit. There, I learned that it is now currently accepted that Earth supports at least 13 to 15 million species of life. This is the figure that was put forth at the conference by some of the world’s leading natural scientists. But recent studies show that even this figure is extremely conservative.

For example, one scientist, Terry Erwin, has conducted research on beetles in the rainforests of Peru. Dr. Erwin’s research points to a level of diversity of beetles in the world’s rainforests that surpasses the above figure for all species by a factor of two. Erwin found over a thousand species of beetles on a single rainforest tree, the vast majority of which had never before been catalogued by scientists. Moreover, Dr. Erwin found that the commonalty of beetle species on the trees dropped to as low as 20 percent among trees that were relatively near one another. In other words, on another tree just 50 meters away, over a thousand species were found, but about 80 percent of them were not the same as those on the first tree. Erwin repeated the method on a third tree and found the same results. This has led him to estimate that Earth supports 30 or even 100 million species of beetles alone!

Another speaker at the conference gave some early results of DNA testing of soil microbes from around the world. It used to be thought that soil organisms were similar worldwide since microbes can easily move from one location to another in water and even in water vapor, such as clouds. But preliminary studies are evaporating these old assumptions. In fact, it seems that the microbes account for the vast majority of Earth’s biodiversity, and that the medium and large flora and fauna actually comprise just a small percentage of Earth’s total species diversity.

In fact, the total number of species on Earth could be much higher than 100 million. We just don’t know. It could be 15 million or 150 million. It could be even higher than that.

A Tale of Numbers
For the sake of argument, let’s use the figure that is currently the best guess of a number of leading scientists—14 million species.

At the Biodiversity conference, Nigel Sizer, a biologist at the Missouri Botanical Gardens, gave this estimate: “At least half of Earth’s unique species of plants, animals and in-between are found in tropical rainforests.” This figure, too, is probably conservative, as current research (like that on microbes and beetles) points to a number that may be as high as 90 percent. But for now, let’s stick with Sizer’s estimate of 50 percent.

Government estimates put the rate of loss of tropical forests globally at 15 million hectares a year (a hectare is 2.47 acres—about the size of two and a half football fields), which is roughly two times the size of New York state. Figures for deforestation are notoriously underestimated. Governments are reluctant to present figures as they really are, because reports of the alarmingly rapid rate of deforestation can have negative repercussions—true reports of logging and deforestation can even affect multilateral loans, as recently happened in Indonesia.

The United Nations Food and Agriculture Organization and the International Timber Trade Organization are two groups that maintain and assess figures for deforestation. Both groups consider deforestation to be the total loss of tree cover. But numbers can be misleading. Tropical forest loss is actually much greater since heavy degradation can occur while some tree cover still remains. Such degradation is hard to observe in satellite images and is therefore mostly overlooked. Recent research that “ground-truthed” (that is, compared satellite images and estimates with on-the-ground observations) showed that estimates of rainforest loss should be at least doubled in areas where logging is occurring.

So, the real numbers are more like 20 to 25 million hectares a year: that’s one and a half to two acres of tropical forests disappearing every second of every minute of every day of the year.

Going, going...Gone?
Before the Spanish conquest of the Americas, rainforests once covered 15 percent of Earth’s entire land area. That area has been reduced to between six and seven percent due to the clearing and burning associated with the growth of civilization.

Nigel Sizer put it this way: “At the current rate of loss, Earth’s rainforests will have been totally wiped out (except for less accessible remnants and a few parks) within 50 years.” Some estimates forecast that the complete loss of rainforests will occur sooner than that—in as little as 35 years.

But let’s say that Earth’s rainforests will be gone in 50 years; and that there are 14 million species on Earth; and that half of all species are found in tropical rainforests. If we do the math, that means that seven million species may be extinct in 50 years. That’s 140,000 species becoming extinct every year; 383 species a day; 16 species an hour and a species going extinct every 3.75 seconds. And that’s just a conservative estimate.

The Time is...Now
We are right now in the midst of the greatest mass extinction of species the Earth has known in the last 65 million years—and perhaps the greatest mass extinction Earth has ever known.

A recent study has shown that mass extinction will last far into the future, and that it could take as long as 10 million years for even a semblance of diversity to recover. It is now widely accepted that roughly 65 million years ago, an asteroid collided with Earth, creating an upheaval that eventually led to the extinction of as much as 95 percent of all species on Earth. This catastrophe is said to have wiped out the dinosaurs and millions of other life forms. The fossil record also reveals four other mass extinctions in the history of life on Earth. But recent research has shown that the current mass extinction—this one perpetrated by humans we call ‘civilized’—may be happening at a faster rate than ever before.

Much of the destruction of rainforests—and thus the current rate of mass extinction—is the result of overconsumption of wood, paper, gold, aluminum, coffee, bananas, chocolate and other products. We all must reduce the demand for rainforest-destructive products. In part two of this article in next month’s Satya find out how we can end the demand for tropical woods in the U.S., slow the logging of tropical forests and thus slow the mass extinction of the species of the Earth.

Tim Keating is co-founder and Executive Director of Rainforest Relief, a New York-based organization that works through education and direct-action campaigns to reduce the demand for wood products and materials, which is driving the destruction of rainforests worldwide. For more information or to volunteer, contact: (718) 398-3760 or


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