Asteroids destroying life on Earth were 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 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
"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," said Simberloff. "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, said the greatest mass extinction occurred in
the Permian era some 230 million years ago over a period of 5 million
"We are looking at something today that is incomparably faster than that,"
said Simberloff. "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 in East Tennessee, some freshwater habitats now teeming
fish and other species are likely to be devoid of life in the next
"Freshwater habitats are in a lot of trouble," said Simberloff. "The major
rivers near Knoxville are all polluted. This is the norm in the United
"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
"The problem is that we can't prove it. We are not there when the last
individual of a species disappears," said Simberloff. "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 rate on rise
Published: Sat Aug 22, 1998 | Modified: Sat Aug 06, 2005 01:34 p.m.