North Carolina parakeet (Photo: Wikipedia) |
Eschenbach lectured an audience in California about the “Myth of Species Extinction,” more
specifically, the legend that humans have caused the disappearance of countless
birds and mammals with their existence and industrial activity.
A popular myth states that “we are in the sixth wave of
extinction,” said Eschenbach. It appears that life on Earth experienced five
mass extinctions due to natural disasters but some biologists are talking about
a sixth wave of extinction caused by humans. The top five extinctions are:
-
Ordovician-silurian extinction (small marine
organisms disappeared)
-
Devonian extinction (tropical marine species
died out)
-
Permian-triassic extinction (“largest mass
extinction which included many vertebrates”)
-
Triassic-jurassic extinction (“vertebrate
species on land allowed dinosaurs to flourish”)
-
Cretaceous-tertiary extinction
E.O. Wilson, a biologist from Harvard, said that there were
27,000 species going extinct each year for over twenty years at least, that’s
over half a million species. If that is so, “what are the species, where are
the corpses,” asked Eschenbach?
"We're in the end game all around the
world," said the Pulitzer-Prize winning biologist. E. O. Wilson, described
as “one of the world's most influential and eloquent thinkers on endangered
species issues,” said "’hot spots’ for biological diversity tend to be in
the same parts of the developing world where poverty has created ‘oppressed,
land-hungry people with no other place to go.’"
“In The Skeptical Environmentalist, statistician
Bjorn Lomborg has disputed Wilson's claim that 27,000 to 100,000 species are
becoming extinct every year.” http://news.nationalgeographic.com/news/2002/08/0809_wireowilson.html
Slender-billed grackle (photo: Wikipedia)
Eschenbach said that he decided to check the
causes of extinction looking at species-area relationships. An article in Nature stated that “species-area
relationships always overestimate extinction rates from habitat loss” and
admits that estimating extinction rates is still “highly uncertain because no
proven direct methods or reliable data exist for verifying extinctions.” But
somehow, “extinction from habitat loss is the signature conservation problem of
the twenty-first century.”
Atitlan grebe (photo: Wikipedia)
“The most widely used indirect method is to
estimate extinction rates by reversing the species-area accumulation curve,
extrapolating backwards to smaller areas to calculate expected species loss.
Estimates of extinction rates based on this method are almost always much
higher than those actually observed.” http://www.nature.com/nature/journal/v473/n7347/full/nature09985.html
Eschenbach looked first at the Red List which
“hypes the extinction” of birds. He then looked at the list from the American
Museum of Natural History (New York) which covers mammals. The problem was to
actually determine what constitutes an extinction, its taxonomy, specimens,
DNA, to show that they are a species, how we look for it, and the criteria for
extinction.
E. O. Wilson talked about extinctions due to
habitat loss each year, more specifically, loss of forests. Eschenbach found that
there were several waves of extinctions. There was a wave in the 1500s, one wave
in the 1700s, and a third wave into the 1800s and 1900s. Eschenbach discovered
that the number of birds and animals that had gone extinct in the last 500
years was actually 190, sixty-one mammals and 129 birds. So much for the infamous
Silent Spring, Rachel Carson’s book,
that started the green revolution against DDT and its eventual banning. Springs
are never silent in our forests; there are plenty of birds chirping year round.
He also found that, from these 190 species,
many island species had gone extinct from “introduced species.” When he
excluded those species, to his surprise, in the last 500 years there had been
only 9 species that had disappeared, 3 mammals and 6 birds.
Eschenbach enumerated the nine species that
had vanished and perhaps why they no longer exist:
1. An antelope hunted by European settlers around
the 1800s
2. Labrador duck (shooting and trapping,
overharvest of eggs)
3. Algerian gazelle (“extinction was assumed from
a single skin purchased in a market place in North Africa in 1894 and from an
adult male skull; we know nothing else about it”)
4. North Carolina parakeet (hunted to death
for food, for their prized feathers worn on hats; beekeepers also hunted the parakeets
because they ate bees)
5. Slender-billed grackle (lived in marshes
of Mexico that were drained; total destruction of habitat, any species would go
extinct from that)
6. Passenger pigeon (the most prolific birds
in the U.S.; extinct from extensive hunting and disease; we hunted them on a
large scale, “thousands were brought by trainloads to shoot them where they
roosted”)
7. Colombian grebe (predation by introduced
rainbow trout)
8. Atitlan Grebe (predation by the large-mouth
bass)
9. Cotton tail rabbit (“three specimens
collected in 1991 in a small area in Mexico, when they looked back, there were
none; nobody knows why they were extinct”)
Based on this record, the conclusion that can
be drawn is that when “European species met native species, native species usually
died.” Predation by another species is the number one cause of extinction. For
example, 95 percent of bird species on islands were killed by alien species. When
European species met with Australian species, there was a massive die-off but
it was a one-time event, said Eschenbach. Only one bird went extinct from
habitat destruction that can be pinpointed to draining a marsh. “Wilson said
that 39 extinctions a year occur from habitat loss,” added Eschenbach. Taking
his formula into account, we should have seen during “the last century over
1,000 extinctions.”
Eschenbach continued that Wilson explained
why his formula was not accurate at all – “50 years must pass before we know
that a species is extinct.” His second explanation was that “species don’t go
extinct immediately,” they may take up to 100 years to happen due to “exponential
decay.” The problem with that theory is that “we still should have seen 600
extinctions by now and we’ve seen none,” Eschenbach concluded.
Thanks for this post! Here's an article that backs it up:
ReplyDeletehttp://www.johnfgroom.com/essays/stateof2.php
Julian Simon and Aaron Wildavsky (my father) published a condensed version as an op-ed in the NY Times of May 13, 1993. For reasons unknown it does not appear on the Times' web site.
Thank you, Adam Wildavsky, for the link to your father's article.
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