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| Extinction
is final |
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It
takes the Earth about 10 million years to recover
from the mass extinction of plant or animal species
-far longer than previously thought, two scientists
reported recently (March 2001). |
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| And it takes the
environment just as long to recover from the extinction
of even a few species, small events which nevertheless
rip holes in the biosphere that are impossible ever to
fully repair. |
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| When you lose a
species, that exact species is never coming back. You
can't recreate an animal.... extinction is final that
way," paleontologist Anne Weil, a research associate in
the Department of Biological Anthropology and Anatomy
at Duke University, said. What we were looking for is
the point at which entire ecosystems recover. The baseline
is an average of 10 million years." |
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| The study by Weil
and James Kirchner, an environmental scientist at the
University of California-Berkeley, comes amid predictions
that as much as half of all the Earth's species could
vanish over the next 50 to 100 years. Kirchner said the
study results, published in the current issue of Nature,
underlined the fact that humanity itself would be extinct
before anything resembling any of the vanishing species
is ever seen again on earth. |
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| "If we deplete Earth's
biological diversity, we will leave a biologically impoverished
planet, not only for our children and our children's children,
but for all the children of our species that there will
ever be," he said. The two scientists arrived at their
findings by comparing the extinction rate of fossil marine
organisms with their rate of evolution, or "origination,"
over 530 million years. Looking at some five major extinction
events, like the one that killed the dinosaurs 65 million
years ago, as well as smaller die-offs, they concluded
that the "lag" between extinction and revival of biodiversity
was much longer than had previously been believed, and
was remarkably consistent. |
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| "This is a very
exciting finding. What we found is a previously unrecognized
pattern in the fossil record," Weil said."The lag is evidence
of an evolutionary dynamic which wasn't suspected before,
and which we don't yet fully understand." Kirchner stressed
that their sobering findings do not necessarily mean that
the multitude of plants and animals currently endangered
by human activity are necessarily doomed for ever. |
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| "It's cause for
concern, and it's a cause for caution, but its not a cause
for depression," Kirchner said. "It is not preordained.
Whether it happens depends on the choices we make....We
can chose not to let it happen."But he added that the
speed with which fragile environments are being overrun
meant the choice would have to be made soon. Many species,
in fact, are disappearing from the Earth before human
scientists can even catalogue them, he said. "It has been
likened to burning down the library when you don't know
how many books are there, let alone what's written in
them," he said. |
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