Asteroids destroying life on Earth are popular movie fare this summer, but

pollution and habitat destruction are killing species even faster than an

asteroid did millions of years ago, a UT ecologist recently said.

Daniel Simberloff, professor of Ecology and Evolutionary Biology, said

scientists believe a giant asteroid hit Earth more than 75 million years

ago, killing the dinosaurs in one of the largest mass extinctions in history.

"But geological records show that the extinction triggered by the

event occurred much slower than the rate at which species are disappearing

today," he said.

"From fossil evidence we know that many species persisted for centuries

after the meteorite hit," Simberloff said. "You can look at the

layer of the element Iridium that was left by the meteorite. Above that

layer are remains of species that survived and didn't die out for millions

of years. Today we are seeing this same volume of extinction happening in

every century or so."

Simberloff, who holds the Nancy Gore-Hunger Chair of Excellence in Environmental

Studies at UT-Knoxville, said the greatest mass extinction occurred in the

Permian era some 230 million years ago over a period of 5 million years.

"We are looking at something today that is incomparably faster than

that," Simberloff said. "The current rate of species extinction

is faster than four of the five great mass extinctions that have been studied,

and is at least equal to the fifth."

"Past mass extinctions did not affect some habitats or regions of

the globe, but the current one is affecting species everywhere in the world,"

Simberloff said.

Simberloff said in East Tennessee, some freshwater habitats now teeming

fish and other species are likely to be devoid of life in the next century.

"Freshwater habitats are in a lot of trouble," Simberloff said.

"The major rivers near Knoxville are all polluted. This is the norm

in the United States."

"We will be lucky if there are any wetlands, rivers, lakes and marshes

here 100 years from now that can support living organisms."

Simberloff participated in a recent survey by New York's Museum of Natural

History, in which 400 of the world's top scientists rated species extinction

as one of the world's gravest environmental problems.

Among the general public, however, barely half rated species loss as

a major threat.

"The problem is that we can't prove it. We are not there when the

last individual of a species disappears," Simberloff said. "There

are many species whose ranges and habitats are so poorly known that they

could easily go extinct without our knowing it for decades."

"But there are many indirect lines of evidence that in my mind all

point to the conclusion that we really are at the beginning of a period

of mass extinction."

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