Earth May Be Home To 8.7M Species, Give Or Take A Million Or So

Aug 24, 2011

Figuring that one of the basic things we should know about the Earth is how many species of life we're surrounded by, a team of researchers has come up with a new estimate:

-- 8.7 million, "with a standard error of +/- 1.3 million."

Or, that is, somewhere between 7.4 million and 10 million. And so far, experts say, we've only discovered about 15 percent of them.

That's the word in a paper just published by PLOS Biology, a journal from the Public Library of Science.

One of the study's co-authors, Dalhousie University biology professor Boris Worm, tells The Associated Press that "we are really fairly ignorant of the complexity and colorfulness of this amazing planet. ... We need to expose more people to those wonders. It really makes you feel differently about this place we inhabit."

Now, if 85 percent of all species haven't been discovered, how did the scientists come up with their numbers?

The AP explains it this way: "Worm and Camilo Mora of the University of Hawaii used complex mathematical models and the pace of discoveries of not only species, but of higher classifications such as family to come up with their estimate."

As National Geographic points out, however, some scientists believe the researchers' reliance on "linear regression" instead of "ordinal regression" was a mistake. (Please, anyone who can explain those terms and what the argument is about, feel free to try to do so in the comments thread.)

Regardless, if the 8.7 million estimate is even close, "we could spend the next 400 or 500 years trying to document the species that actually inhabit our planet," Encyclopedia of Life executive director Erick Mata tells the AP.

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