Conservationists have taken the first detailed look at the world's mammals in more than a decade, and the news isn't good.
"Our results paint a bleak picture of the global status of mammals worldwide," the team led by Jan Schipper of the International Union for the Conservation of Nature in Gland, Switzerland, concluded.
"We estimate that one in four species is threatened with extinction and that the population of one in two is declining," the researchers said in a report to be published Friday in the journal Science. The findings were being released Monday at the IUCN meeting in Barcelona, Spain.
"I think the bottom line is, what kind of a world do you want to leave for your children," Andrew Smith, a professor in the Arizona State University School of Life Sciences, said in a telephone interview.
"How impoverished we would be if we lost 25% of the world's mammals," said Smith, one of more than 100 co-authors of the report.
"Within our lifetime hundreds of species could be lost as a result of our own actions, a frightening sign of what is happening to the ecosystems where they live," added Julia Marton-Lefevre, IUCN director general. "We must now set clear targets for the future to reverse this trend to ensure that our enduring legacy is not to wipe out many of our closest relatives."
The IUCN describes itself as the world's oldest and largest global environmental network. It is made up of more than 1,000 government and nongovernment organizations and almost 11,000 volunteer scientists in more than 160 countries. The research for the report took five years and involved more than 1,700 scientists around the world.
The report updates the IUCN's Red List of Threatened Species, which overall includes 44,838 species, of which 16,928 are threatened with extinction. Of these, 3,246 are in the highest category of threat, critically endangered, 4,770 are endangered and 8,912 are vulnerable to extinction. The IUCN estimated that 76 mammal species have gone extinct since 1500.
While the new report estimated that one-in-four mammals is threatened with extinction, the actual numbers listed were 1,141 out of 5,487 species. That comes out to 20.8%, closer to one in five.
However, the researchers noted that there were several hundred species about which they don't have enough data to classify. They believe that the lack of information about those animals indicates that they exist in such small numbers that many could be endangered, raising the total to 25% or higher, Smith explained.
Among the mammals particularly in danger are primates, used for bush meat in parts of Africa and facing major loss of habitat in Southeast Asia, Smith noted.
The report also notes unusually high threats to tapirs, hippos, bears, pigs and hogs, while among the less threatened are moles, opossums and free-tailed bats.
In general, larger mammals were found to be more threatened than smaller ones. Larger species tend to have lower population densities, grow more slowly and have larger home ranges.
For land species, habitat loss is a major threat across the tropics, including deforestation in the Americas, Africa and Asia. Hunting is having devastating effects in Asia, but African and South American species are also affected.
For marine mammals the major threat is accidental death, especially fisheries by-catch and vessel strike.
Climate change is also affecting sea ice dependent species such as polar bears and harp seals.
Even though most of the world has been explored, new mammal species continue to be discovered. This year's species total of 5,487 is up 19% since 1992.
Many newly discovered species are among those that are not well documented, living in regions in need of future research such as tropical forests in West Africa and Borneo. Marine mammals are not as well studied as land mammals and are more difficult to survey.
While it raises concerns, the new analysis isn't all bad news. It found about five percent of currently threatened mammals showing signs of recovery.
The black-footed ferret moved from extinct in the wild to endangered after a successful reintroduction by the U.S. Fish and Wildlife Service in eight western states from 1991-2008. Also, wild horses moved from extinct in the wild in 1996 to critically endangered this year after successful reintroductions started in Mongolia in the early 1990s.
In addition to raising concern about mammals, new additions to the IUCN Red List include:
• Indian tarantulas, sought by collectors and threatened by the international pet trade.
• The Rameshwaram parachute spider has been listed as critically endangered due to habitat loss.
• The squaretail coral grouper from the coral reefs of the Indo-Pacific has been listed as vulnerable because it has become a luxury food.
• In Costa Rica, Holdridge's toad moved from critically endangered to extinct, as it has not been seen since 1986 despite intensive surveys.
• La Palma giant lizard, found on the Canary Island of La Palma and thought to have become extinct in the last 500 years, was rediscovered last year and is now listed as critically endangered.
IUCN also said it is issuing a Sampled Red List Index, developed in collaboration with the Zoological Society of London. The index takes a random sample of species from a taxonomic group to calculate the trends in extinction risk within that group. It can be used to calculate trends much like an exit poll from a voting station.
Associated Press writer Daniel Woolls in Madrid, Spain, contributed to this report.