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Millions of organisms unnamed as extinction accelerates, study says.



Various species of sea life found along the California coast (pictured).
Photographs by David Liittschwager, National Geographic


Traci Watson
for National Geographic News
Published August 24, 2011


Even after centuries of effort, some 86 percent of Earth's species have yet to be fully described, according to new study that predicts our planet is home to 8.7 million species.

That means scientists have cataloged less than 15 percent of species now alive—and current extinction rates mean many unknown organisms will wink out of existence before they can be recorded.

The study was driven by a simple question: "Are we within reach of finding all species, or are we way off?" said study co-author Boris Worm of Canada's Dalhousie University.

"The answer is, we are way off."



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Counting Earth's Millions

So far, some 1.2 million species are known to science. To calculate the percentage of unknown species, Worm and colleagues first had to answer one of the great questions of ecology: How many species live on the Earth?

Previous guesses ranged from three million all the way to a hundred million.

To gain a more precise answer, the authors examined the categories into which all species are grouped.

Scientists lump similar species together into a broader grouping called a genus, similar genera into a still broader category called a family, and so on, all the way up to a supercategory called a kingdom.

There are five kingdoms: animals, plants, fungi, chromists—including one-celled plants such as diatoms—and protozoa, or one-celled organisms.

Worm's team estimated the total number of genera, families, orders, classes, and phyla—a designation above class—in each kingdom. That's a relatively easy task, since the number of new examples in these categories has leveled off in recent decades.

By contrast, the number of newly discovered species continues to rise sharply.

Using complex statistics, Worm and colleagues used the number of genera, families, and so on to predict Earth's number of unknown species, and their calculations gave them a number: 8.7 million.

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Nature's Library Disappearing

Overall, formally categorizing a new organism is a lot more complicated than discovering one, study co-author Worm said. Scientists must compare their specimen to museum samples, analyze its DNA, and complete reams of paperwork.

"It's a long process," he said. Most scientists "will describe dozens of species in their lifetime, if they're really lucky."

Unfortunately, extinction rates have accelerated to ten to a hundred times their natural level, Worm added.

The information to be gained when new species are discovered "is nature's library, and we've only begun to decipher the first ten books," Worm said.

"We're throwing out entire books without having a look at them." -- http://news.nationalgeographic.com/

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