Tough times for mammals

Between a fifth and a generous third of the world’s mammal species now face the threat of extinction, according to the first comprehensive review since 1996.

Now 1,139 species rank in the most imperiled categories, the conservation monitoring organization IUCN reported October 6 at its World Conservation Congress in Barcelona, Spain.

Data from more than 1,700 experts went into this five-year review of the conservation status of all known wild mammals for the IUCN Red List of Threatened Species, the main global scorecard for extinction risk.

“All in all, a major event,” says Don Wilson, a mammal curator at the Smithsonian Institution in Washington, D.C. He has read a summary of the IUCN results to be published in Science October 10, and calls the study “by far the most extensive” analysis of mammal status so far.

IUCN reviewed mammals in 1996, but the world has changed since then, says one of the leaders of the effort, conservation ecologist Jan Schipper, who works with IUCN and Conservation International. Tasmanian devils, for example, have shifted from the category of least concern into the endangered category. Their population shrank some 60 percent during the last decade as a lethal, infectious face cancer spread through the species. And shrinking wetlands in Asia pushed the fishing cat out of a vulnerable ranking and into the endangered category.

Assessment methods have changed too. Taxonomy based on DNA has split some of the species listed in 1996 and lumped together others. Category definitions have changed too, but IUCN is working on a comparison between the new and the old reports, Schipper says.

“One of the things that surprised me the most was that there are still 836 species that are data-deficient,” Schipper says. Biologists may know mammals relatively well compared to other animal groups, but hundreds of mammals still remain so mysterious that the IUCN group couldn’t assess their conservation status.

If those mystery species are doing just fine, a situation Schipper considers improbable, then 21 percent of the currently known 5,487 mammal species face a serious threat of extinction. If all the little-known species turn out to be faltering, then that’s 36 percent of known mammals in trouble.

“We don’t want to say, ‘the sky is falling,’” Schipper says. The IUCN sets out quantitative criteria for the tally’s three worrisome categories of animals threatened with extinction: critically endangered, endangered and vulnerable. Even the least threatened among these, the vulnerable species, meet one of several thresholds, such as losing more than a third of their population during either a decade or over three generations.

In the new review, habitat loss or degradation ranks as the most widespread threat, grinding down the populations of some 40 percent of species studied. Hunting for food or medicinal use affects 17 percent of mammal species, the researchers say.

Mammals in the seas face a particularly troubled time, with about a third of the status-known species at risk of extinction. Their biggest problem is accidental death, such as dying in fishing gear set for other species or colliding with boats.

Not all the news is bad. Since the last assessment, reintroduction programs have moved black-footed ferrets from “extinct in the wild” to critically endangered — a step in the right direction.

“We have all known for a long time that things were not going well for threatened and endangered species,” Wilson says. But it’s “sobering indeed” to have such a massive effort document that more than a thousand species could disappear unless trends change.

Another Smithsonian mammal curator, Richard Thorington, says, “I am not greatly surprised, although the figures are higher than I had expected.”

Schipper says he hopes the report will inspire people to reduce their ecological footprints in their everyday lives, from grocery shopping to transportation, and to “just go out and get some face time with animals.”

This was only a report on wild species, he adds. Homo sapiens isn’t included, but IUCN does rank it — in the least threatened category.