Scientists work hard to avoid declaring a species extinct


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As a child in the 1980s, I was convinced that an ecological disaster was imminent. Scattered into my afternoon television programs were commercials about the dangers of soil erosion and acid rain. The scariest of all were ads showing some furry, wide-eyed primate, followed by the warning: “Extinction is forever.”

LonesomeGeorgeIt was an ominous warning for a kid who didn’t quite understand what “forever” meant. (My list of things that lasted forever at that time included tooth brushing and church.) But it got me wondering: How do they know a species is extinct? And who gets to make that call? Is there a Supreme Court for extinction out there?

Well, sort of. The International Union for Conservation of Nature’s Red List serves as the recognized authority on species population status. The group assigns conservation labels-“least concern,” “near threatened,” “vulnerable,” “endangered,” “critically endangered,” “extinct in the wild” and “extinct” – to the world’s wildlife. But the organization’s experts don’t like to think of themselves as arbiters of extinction.

“The main focus of the Red List is to stop species from going extinct – to identify species moving in that direction and to marshal resources to protect them,” says Craig Hilton Taylor, unit manager of the Red List. “But, by default, we became the standard international list for extinctions.”

The Red List has assigned monitoring responsibility to a series of conservation authorities. For example, there are 29 organizations tracking mammals, including one that handles anteaters, sloths and armadillos, one that surveys bat populations and two that catalogue elephants.

The mammals get the most attention, by far. One group, Birdlife International, handles the world’s birds even though there are twice as many known bird species (up to 10,000) as mammal species (fewer than 5,000).

These scientific authorities are supposed to conduct an assessment of all the animals in their purview at least every 10 years. But that’s a pretty tall order, and the program has a long way to go.

“There are between 1.8 and 2 billion described species worldwide,” notes Hilton Taylor. “We haven’t yet looked at 57,000 of them.”

So how do you count animals in the wild? It really depends on the creature. Some critically endangered birds, for example, are territorial. All it takes is binoculars and patience. For wide-ranging creatures, counting requires more creativity. Scientists use migration patterns and birthing habits to monitor certain whale species, for example. They conduct aerial photographic surveys of breeding waters, looking for newborns. Then they use data about what proportion survive to adulthood to calculate the health of the population.

For a species to get a Red List classification, conservation scientists must complete two surveys. The researchers submit a map of the species’s range, a list of its preferred habitats, the major threats against it and a projection of the population trend. Once a species is found to be threatened, the assessments become a regularly repeated process, with the Red List encouraging more-frequent surveys to monitor conservation progress.

There are no rigid criteria, such as the number of years since last sighting, for declaring a species extinct. But the Red List doesn’t make the decision lightly.

Consider the case of the Yangtze River dolphin, a long-beaked, nearly blind cetacean also known as the baiji, that inhabited about 1,000 linear miles of a single river in southeast China. While many believe there were thousands of specimens in the wild in the middle of the 20th century, a Chinese scientist completed the first formal population survey only in 1982. He estimated that there were around 400 individuals. On the basis of that survey, the dolphin was classified as endangered by a predecessor to the Red List in 1986.

That warning led to more surveys, which lowered the estimates. By the mid-1990s, scientists figured there were only 100 such dolphins remaining. In 1996, the Red List declared the species critically endangered.

Captive breeding was attempted, but six expeditions, each lasting more than two months, managed to net only a single female. She died trying to escape the breeding facility seven months later.

While several teams have gone looking for baiji, the last time anyone photographed the creature was in 2002. Boats have spent months cruising the river with binoculars and sonar equipment, and others have used hydrophones to pick up on the dolphin’s calls, without success.

Still, the Red List is holding off on declaring the Yangtze River dolphin extinct. The last official assessment was completed in 2008, and the group stuck with the “critically endangered” label, although it concedes that the baiji is possibly extinct. It will likely be years before extinction becomes official.

This kind of hesitation avoids the potential embarrassment of so-called “Lazarus species,” or species that have come back from the dead. For example, the La Palma giant lizard of the Canary Islands was classified as extinct in 2006, before a series of sightings and photographs elevated the creature to critically endangered status.

According to Hilton-Taylor, the official extinction declaration can sometimes cause the rediscovery of forgotten species. “Declaring a species extinct can be a bit of a challenge to some people,” he says, “and they set out to prove us wrong.”

Technology also occasionally proves conservation scientists wrong. For decades, researchers believed that Solitario Jorge, or Lonesome George, was the world’s last Pinta Island tortoise. He spends his days munching on greens in the Charles Darwin Research Station in the Galapagos Islands. But new genetic testing suggests that there may be a few other individuals on neighboring islands. Jorge hasn’t been in the mood to mate in captivity yet, but maybe he’s been waiting for the right girl.

These happy stories are relatively few. The Red List declared 473 species extinct in the first decade of this century, and only a handful of species have ever reappeared. Extinction may not always be forever, but it usually is.

Author: Brian Palmer | Source: The Washington Post [February 21, 2011]



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