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 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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