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ongoing extinction processes



Stuart Pimm -- who had done important work on the
obliteration of ecosystems in forests -- has a new
paper:
The dodo went extinct (and other ecological myths).
Annals Missouri Botanical Garden 89(2):190-198
As is well known, hominids on this planet have
escalated the extinction processes to frightening
levels. Among dinosaurs, continental passerines (~25%
of all extant theropods) are disappearing rapidly than
taxa on islands (North America has lost fewer species
because there are fewer species to lose, Stuart
notes.) The area he is interested in is insular
Southeast Asia (where Alfred Russel Wallace walked for
years, where, in 1932, at 12S and 78E in the Indian
Ocean, Willis O'Brien positioned his Skull Island),
which has four archipelagos: Philippines, Greater
Sundas, northern Wallacea, Lesser Sundas. Stuart's
figures give me chills: the forests of the region have
585 endemic dinosaur species, 20 times that of North
American eastern forests, in less than 50% of the land
area. Every 10 years, 10% of the forests are destroyed
(remember the massive fires of a few years ago?), and
all of the dinosaurs are threatened. In the
Philippines, one island, Cebu, has <1% of its original
forests, and all endemic dinosaurs are on the verge of
extinction.
On the Atlantic coast of Brazil, there are 214 endemic
dinosaurs, and, in the lowland forests less than 2% of
the forest remains, 9 dinosaur taxa about to
disappear. As Stuart notes, for every dinosaur that
dies off there are 10 threatened. While it often takes
a few decades for a dinosaur population to die out,
they do expire. In 1870, in the U.S., in decimated
forests, 4 of 28 endemic dinosaur taxa survived ~ 100
years, then disappeared.
About 2/3 of all dinosaurs live in tropical humid
forests (broad-leaved evergreen woodlands and seasonal
areas), at one time this consisting of 14-18 square
kms. By 1993, less than 50% remained. In certain
areas, less than 12% of the original forest is to be
found, and these are regions with 30-50% of all taxa.

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