St. Louis ? Birds are becoming extinct faster than scientists had thought.

Conservationists now estimate that a species of birds vanishes every year. Previously, they believed the rate to be one species every four years.

And new research predicts that rate could leap to 10 species a year – an increase that could wipe out 12 percent of the nearly 10,000 known bird species by the end of this century.

“I think this represents a good, hard analytic look at the data on extinction in birds and reveals the problem to be considerably greater than previous estimates,” said Thomas Lovejoy, a tropical and conservation biologist and president of the Heinz Center for Science, Economics and the Environment in Washington.

“Basically, it means the conservation challenge is yet greater than many have appreciated – that is true for birds alone and is likely to be even more grave for some other forms of life,” he said.

A group of scientists that included conservationist Peter Raven, president of the Missouri Botanical Garden, revised the existing extinction estimate to take into account ongoing fossil discoveries of extinct species and missing birds not yet classified as extinct. The results of their study appear this week in the online early edition of the Proceedings of the National Academy of Sciences.

Since 1975, 20 species have gone extinct in the wild. But, the good news is that conservation efforts work, Raven said. “There would have been 25 more species gone extinct without the conservation efforts over the past 30 years,” he said.

“We depend entirely on other organisms for our continued life on Earth. We’re losing the sustainability of Earth,” said Raven, who is also the George Englemann professor of botany at Washington University. “It’s in all our art, our history, our legends. If you’re spiritual, you can ask: Do we have the right to kill off living things?”