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KNOXVILLE, Tenn. — Up to 30 percent of the animal species on earth will disappear in the next 50 years because their habitats are being destroyed, a University of Tennessee professor said Thursday.

 “Somewhere between 10 and 30 percent of all the animal species on the planet are the walking dead, based on the destruction that we have done now,” said Dr. Stuart Pimm of UT-Knoxville’s Department of Ecology and Evolutionary Biology.

 Pimm said destruction of forests resulting from human population growth is the primary factor contributing to species extinction.

 Birds provide a good example because they are common and most people know something about them, Pimm said.

 “Although birds are really quite robust, we will lose 5 percent of all bird species, or 500 species within the next 20 to 30 years,” Pimm said.

 “A smaller percentage of birds is actually threatened with extinction than any other group. If you look at fish, freshwater clams and other animals in the Mississippi River drainage, something like 45 percent of the species there are actually threatened with extinction.”

 Pimm and other researchers spent last year in western Kenya developing an updated basis for calculating the loss of species world-wide.

 The tropical forests in western Kenya and the region’s very high human population growth made the area an ideal model for the study, he said.

 “We picked tropical forests because most of the planets species are in places like forests rather than in deserts or frozen places like Antarctica,” Pimm said.

 Another factor in Kenya’s selection was the availability of old Royal Air Force photographs of the area for comparison with modern satellite imagery of the region.

 “We have a 50-year history of where the forests were and how fast they have been disappearing,” Pimm said. “We can go into the forests and see how many species have gone extinct and how many still survive.”

 Pimm presented his findings recently in Washington, D.C., at a forum sponsored by the National Academy of Sciences.

 There are philosophical and religious reasons to be concerned about the planet as well as the obvious economic and health reasons, Pimm said.

 All the world’s religions teach responsibility for the environment, with the Bible’s story of Noah building an ark for the animals one example, Pimm said.

 Economic benefits include tourism.

 “Biological diversity is enormously attractive to people,” Pimm said. “In our own backyard we have the Great Smoky Mountains National Park which attracts millions of visitors each year.” Health benefits would include taxol, a cancer drug derived from the bark of the ewe tree.

 “It’s a tree that until a few years ago everybody thought was worthless,” Pimm said. “Then we find in it this cancer drug with enormous potential — one that works in a way opposite most cancer drugs which slow the division of cancer cells.

 “But in taxol, nature has a trick. It speeds up the cell division, makes the cells divide too rapidly, so they die.”

 Nature still has many such tricks to teach, but with the extinction of every plant or animal there is the risk of losing important information forever, Pimm said.

 — Contact: Dr. Stuart Pimm (423-974-3065)