The Red List has several categories, including extinct; extinct in the wild; and those threatened with extinction, including the critically endangered, endangered and vulnerable.
Jonathan Baillie, director of conservation programs for the Zoological Society of London, said that a sampling shows that 24% of all species of vertebrates -- animals with a backbone -- appear to face the threat of extinction.
Tracking the health and abundance of all species is too massive a job, Baillie said, but he suggested that such sampling might be tantamount to creating a Dow Jones industrial average index for the planet's biodiversity. In this case though, he said, "there's no $700-billion bailout on the horizon."
Holly Dublin, who leads the IUCN's species survival commission, said more details of the Red List would be unveiled in Barcelona this week as scientists and officials worked on plans to try to reverse the downward slide of so many species. For instance, she said, a clear picture of a species in trouble, along with information about its habitat, could discourage the World Bank from financing a development project that might imperil that species' existence.
Researchers have sought to make the IUCN's Red List the most trusted assessment of species vulnerability by accumulating the best scientific information without getting tied up in legal definitions or the politics of any particular nation. The Red List used to be published as a book, but it has grown so long -- now 44,838 species -- that it has evolved into an online catalog at www.iucn.org/redlist.
Still, these assessments are far from an exact science. The La Palma giant lizard was thought to have become extinct in the last 500 years, sometime after the Romans brought rats to the Canary Islands off the northwestern coast of Africa. But it was rediscovered last year, clinging to steep cliff faces out of reach of rats. It's now listed as critically endangered.
The assessment of marine mammals, the first completed since 1996, did not fully factor in the effects of global warming, the principal scientists said. The results of this study will be published this week in the journal Science.
The prospects for these animals may be worse than even the global numbers suggest, said Jan Schipper of Conservation International, who was the lead author of the Science paper. The problem is what he called a surprising lack of information about 836 mammal species.
"If you don't know where they are or how many there are, then it's hard to determine if they have viable populations or [are] threatened with extinction," Schipper said. Given this uncertainty, as many as 36% of land mammal species and 61% of whale, seal and other marine mammal species could be threatened with extinction.
--
ken.weiss@latimes.com
--
On latimes.com
Animals in danger
For photos of more than a dozen endangered mammals, go to latimes.com/world.
