Species Extinction Rates Grossly Overestimated

A group of researchers agrees that Earth is facing a mass extinction event, but they are daring to overturn dogma on how fast species are disappearing. The researchers say they have discovered why current estimates are overblown, and they recommend a different way to calculate the rates. "We need to go back to revisit ... how those numbers are derived," Fangliang He, of Sun Yat-sen University in Guangzhou, China, said in a press briefing with fellow study researcher Stephen Hubbell of the University of California at Los Angeles. It is very difficult to determine the number of species that are going extinct, since in most cases it's hard for researchers to know when the species is down to its last remaining individual. Most estimates are derived from the rate at which members of a species would be discovered during a survey of their habitat. Researchers estimate extinction rate by simply reversing this species discovery rate in its habitat: The more habitat you lose, the fewer species you'd expect to discover. To prove a species is extinct, however, one has to find the last remaining example of that animal. And Hubbell and He explain that the amount of habitat needed to find the last individual is much larger than the amount needed to find the first. In fact, the researchers mathematically prove in their paper that the habitat loss required for extinction is always larger, usually much larger — up to 160 percent — than the area required for discovery of a species. The study was published in the May 19 issue of the journal Nature...more