Huge Variance in Estimates of Number of Species

(p. D3) Scientists have named and cataloged 1.3 million species. How many more species there are left to discover is a question that has hovered like a cloud over the heads of taxonomists for two centuries.
“It’s astounding that we don’t know the most basic thing about life,” said Boris Worm, a marine biologist at Dalhousie University in Nova Scotia.
On Tuesday, Dr. Worm, Dr. Mora and their colleagues presented the latest estimate of how many species there are, based on a new method they have developed. They estimate there are 8.7 million species on the planet, plus or minus 1.3 million.
. . .
In recent decades, scientists have looked for better ways to determine how many species are left to find. In 1988, Robert May, an evolutionary biologist at the University of Oxford, observed that the diversity of land animals increases as they get smaller. He reasoned that we probably have found most of the species of big animals, like mammals and birds, so he used their diversity to calculate the diversity of smaller animals. He ended up with an estimate 10 to 50 million species of land animals.
Other estimates have ranged from as few as 3 million to as many as 100 million. Dr. Mora and his colleagues believed that all of these estimates were flawed in one way or another. Most seriously, there was no way to validate the methods used, to be sure they were reliable.

For the full story, see:
CARL ZIMMER. “How Many Species? A Study Says 8.7 Million, but It’s Tricky.” The New York Times (Tues., August 30, 2011): D3.
(Note: ellipsis added.)
(Note: the online version of the article is dated August 23 (sic), 2011.)

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