One in Four Mammals at Risk of Extinction

One in four of the world's 5,487 known mammal species face extinction, according to a new conservation "report card" unveiled today.

Marine mammals face even steeper odds, with one in three species at risk of disappearing, according to the study.

The assessment, done as part of the International Union for Conservation of Nature's (IUCN's) Red List of Threatened Species, took more than 1,700 experts from 130 countries five years to complete.

The report's findings were released today in conjunction with this week's IUCN meeting in Barcelona, Spain, and will appear later this week in the journal Science. "Our results paint a bleak picture of the global status of mammals worldwide," the study authors wrote.

(See photos of animals on the new list.)

Humans are mostly to blame, as habitat loss, pollution, and hunting continue to squeeze at-risk species.

Under Threat

The new report updates the last IUCN survey conducted in 1996 and adds 700 species not previously assessed.

"Perversely, the species that humans show greatest affinity toward—the largest mammals such as primates, big cats, and whales—are significantly more likely to be threatened with extinction," Barney Long, a biologist at the World Wildlife Fund in Washington, D.C., said in an email.

Some of the most threatened species are found in Asia, a region undergoing rapid human population and economic growth.

"This is leading to habitat loss due to agricultural expansion; development of infrastructure such as roads, which fragment critical landscapes; and increasing areas for industrial crops such as oil palm and pulp for paper," said Long, who helped create the new assessment.

Currently, 79 percent of Asia's primate species face extinction.