BARCELONA, Oct. 6 — At least a quarter of the world’s wild mammal species are at risk of extinction, according to a comprehensive global survey released here Monday.
The new assessment — which took 1,700 experts in 130 countries five years to complete — paints “a bleak picture,” leaders of the project wrote in a paper being published in the journal Science. The overview, made public at the quadrennial World Conservation Congress of the International Union for Conservation of Nature (IUCN), covers all 5,487 wild species identified since 1500. It is the most thorough tally of land and marine mammals since 1996.
“Mammals are definitely declining, and the driving factors are habitat destruction and over-harvesting,” said Jan Schipper, the paper’s lead writer and the IUCN’s global mammals assessment coordinator. The researchers concluded that 25 percent of the mammal species for which they had sufficient data are threatened with extinction, but Schipper added that the figure could be as high as 36 percent because information on some species is so scarce.
Land and marine mammals face different threats, the scientists said, and large mammals are more vulnerable than small ones. For land species, habitat loss and hunting represent the greatest danger, while marine mammals are more threatened by unintentional killing by pollution, ship strikes and being caught in fishing nets.
While large species such as primates (including the Sumatran orangutan and red colobus monkeys in Africa) and ungulates (hoofed animals such as Africa’s Dama gazelle and the Malaysian tapir) may seem more physically imposing, the researchers wrote that these animals are more imperiled than smaller creatures such as rodents and bats because they “tend to have lower population densities, slower life histories, and larger home ranges, and are more likely to be hunted.”
Primates face some of the most intense pressures: According to the survey, 79 percent of primates in South and Southeast Asia are facing extinction.
Conservation International President Russell A. Mittermeier, one of the paper’s writers and a primate specialist, said animals in the region are being hit with “a triple whammy.”
“It’s not that surprising, given the high population pressures, the level of habitat destruction, and the fairly extreme hunting of primates for food and medicinal purposes,” he said in an interview. He added that some areas in Vietnam and Cambodia are facing “an empty forest syndrome,” as even once-populous species such as the crab-eating macaque, or temple monkey, are “actually getting vacuumed out of some areas where it was common.
In some cases, the scientists have a precise sense of how imperiled a species has become: There are 19 Hainan gibbons left in the wild on the island off China’s southeast coast, Mittermeier said, which actually counts as progress because there used to be just a dozen.
With others, including the beaked whale and the jaguar, researchers have a much vaguer idea of their numbers despite technological advances — such as satellite and radio tagging, camera tracking and satellite-based GPS (global positioning system) mapping. The authors of the assessment wrote that most land mammals occupy “areas smaller than the United Kingdom,” while “the range of most marine mammals is smaller than one-fifth of the Indian Ocean.”
The report on mammals came on the same day that the IUCN updated its “Red List” — a separate periodic survey of nearly 45,000 species of plants and animals — and concluded that 32 percent are threatened with extinction. Its scientists added 20 of the world’s 161 species of grouper to the list of those at risk of extinction, along with several tarantula species.
Jonathan Baillie, who directs conservation programs at the Zoological Society of London, said: “It’s a continual decline in all cases.”
Not all of the news was grim yesterday: IUCN officials said that the La Palma giant lizard, believed to be extinct for 500 years, was rediscovered last year in the Canary Islands and is now considered critically endangered.
The writers of the mammals assessment said the observed declines are not inevitable. “At least 5 percent of currently threatened species have stable or increasing populations,” they wrote, “which indicates that they are recovering from past threats.”
Said Mittermeier: “It comes down to protecting habitats effectively, through protected areas, and preventing hunting and other forms of exploitation.” As one example of how conservation can be effective, he noted that in areas where scientific researchers work, animals stand a much better chance of surviving. “Where you have a research presence, it’s as good or better than a guard force,” he said.
Schipper offered the model of the U.S. effort to bring back the black-footed ferret, which was essentially extinct on the North American prairie as of 1996. “Now it’s endangered, which, in this case, is a huge improvement,” he said. “When governments and scientists commit resources to a project, many species can be recovered.”
Monday’s reports come as researchers have been documenting effects of human-generated greenhouse gases. In a paper published Thursday in the journal Geophysical Research Letters, a team at the Monterey Bay Aquarium Research Institute found that ocean acidification spurred by carbon emissions will cause sound to travel farther underwater, because increasingly acidic seawater absorbs less low- and mid-frequency sound.
By 2050, the researchers predicted, sounds could travel as much as 70 percent farther in parts of the Atlantic Ocean and other areas, which may improve marine mammals’ ability to communicate but also increase background noise, which could prove disorienting.
“We understand the chemistry of the ocean is changing. The biological implications of that we really don’t know,” said ocean chemist Keith Hester, the lead writer. “The magnitude to which sound absorption will change, based mainly on human contribution, is really astounding.”
By Juliet Elperin, Washington Post Staff Writer, Tuesday, October 7, 2008; Page A13
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