BARCELONA, Spain — One in two mammal species on Earth are in decline and at least one in four are at risk of disappearing forever, according to a scientific survey released Monday and whose sponsors described the trend as an "extinction crisis" in the making.
"Mammals are declining faster than we thought," said Jan Schipper, lead author of a companion study being published this week in the journal Science.
The International Union for Conservation of Nature released the data compiled by 1,700 experts in 130 countries, adding that the numbers could be even worse given that data was lacking for hundreds of mammal species.
"The reality is that the number of threatened mammals could be as high as 36 percent," Schipper said in a statement released by the IUCN at a gathering in Barcelona.
"Our results paint a bleak picture of the global status of mammals worldwide," Schipper and his co-authors said in the study. "We estimate that one in four species is threatened with extinctionand that the population of one in two is declining."
"The situation is particularly serious for land mammals in Asia, through the combined effects of overharvesting and habitat loss," the experts wrote in their study, "and for marine species, victims of our increasingly intensive use of the oceans."
Mammals range in size from blue whales to Thailand's insect-sized bumblebee bat.
"I think the bottom line is, what kind of a world do you want to leave for your children," said Andrew Smith, a professor in the Arizona State University School of Life Sciences. "How impoverished we would be if we lost 25 percent of the world's mammals," said Smith, one of more than 100 co-authors of the companion study.
In South and Southeast Asia, 79 percent of primate species are threatened with extinction, the IUCN noted.
Habitat loss and degradation affect 40 percent of the world’s mammals, the IUCN added. "It is most extreme in Central and South America, West, East and Central Africa, Madagascar, and in South and Southeast Asia."
'A frightening sign'
More than half of the 1,141 threatened mammal species fall under "critically endangered" (188) or "endangered" (450) categories used for the 2008 "IUCN Red List of Threatened Species."
"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," IUCN Director Julia Marton-Lefevre said in the statement.
The Iberian lynx, with an adult population estimated at no more than 143, is among the critically endangered mammals. Its numbers have continued to decline due to earlier efforts by humans to eliminate its primary prey, the European rabbit.
Endangered mammals include the Tasmanian devil. The largest carnivorous marsupial in the world, it is the size of a small dog and found only on the Australian island state of Tasmania. It was moved from the "least concern" category after its numbers declined by more than 60 percent in 10 years due to a cancer that causes tumors around the mouth, eventually leading to death by starvation.
The fishing cat, found in Southeast Asia, moved from "vulnerable" to "endangered" due to habitat loss in wetlands.
"Over 45 percent of protected wetlands in Southeast Asia are considered threatened, including those that are home to this species," IUCN stated. "Clearance of coastal mangroves over the past decade has been rapid. The depletion of fish stocks from overfishing is likely to be a significant threat to this species which relies heavily on fish for its survival."
The Caspian seal also saw a downward trend — its numbers have declined by 90 percent in the last century due to unsustainable hunting and habitat degradation. "Since 2005 the number of pups born has plummeted by a catastrophic 60 percent to just 6,000-7,000," IUCN stated. "A low survival rate among pups has led researchers to fear there are barely enough breeding females to keep the population viable."
In addition, 29 species have been flagged as "critically endangered/possibly extinct."
Hopeful sign with African elephants
The IUCN noted that at least 76 mammals had gone extinct since 1500. "But the results also show conservation can bring species back from the brink of extinction, with five percent of currently threatened mammals showing signs of recovery in the wild," it added.
The study's authors urged governments and conservation groups to redouble protective efforts by using the Red List.
"More than simply reporting on the depressing status of the world's mammals, these Red List data can and should be used to inform strategies for addressing this crisis, for example to identify priority species and areas for conservation," the researchers concluded. "Despite a general deterioration in the status of mammals, our data also show that species recoveries are possible through targeted conservation efforts."
The 2008 Red List — which includes 44,838 species of wild fauna and flora, not just mammals — saw minor updates in recent years, but the version released Monday is the biggest revision since a 1996 Red List and includes marine mammals and many other species for the first time.
Under the new Red List, 16,928 species are considered 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.
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 percent since 1992.
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 percent, 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 percent or higher, Smith explained.
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.
Hopeful sign with African elephants
One hopeful story is that of the African elephant. Poaching for ivory and meat has long been a major threat, and populations across the continent declined by 25 percent from 1979 to 2007.
But the species actually improved on the Red List, going from "vulnerable" to "near threatened," because of recent conservation efforts — and population increases — in southern and eastern Africa.
Those efforts, the IUCN said, "have been of sufficient magnitude to outweigh any decreases that may be taking place elsewhere across their vast range."
In addition to raising concern about mammals, the IUCN highlighted the threats to other wildlife, including:
- Indian tarantulas, sought by collectors and threatened by the international pet trade.
- The Rameshwaram parachute spider, listed as critically endangered due to habitat loss.
- The squaretail coral grouper from the coral reefs of the Indo-Pacific, 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.
The Associated Press and Reuters contributed to this report.