Species extinction rates 'overestimated by 160 pc'

London, May 19 (ANI): The most widely used method for estimating extinction rates, based on the species-area relationship (SAR), seems to be incorrect, after a new analysis found that these rates might have been overestimated by as much as 160 percent.

However, while the problem of species extinction caused by habitat loss is not as dire as many conservationists and scientists had believed, the global extinction crisis is real, said co-author Stephen Hubbell, a distinguished professor of ecology and evolutionary biology at UCLA.

"The methods currently in use to estimate extinction rates are erroneous, but we are losing habitat faster than at any time over the last 65 million years," said Hubbell, a tropical forest ecologist and a senior staff scientist at the Smithsonian Tropical Research Institute.

"The good news is that we are not in quite as serious trouble right now as people had thought, but that is no reason for complacency. I don't want this research to be misconstrued as saying we don't have anything to worry about when nothing is further from the truth," he added.

Hubbell, and lead author Prof Fangliang He from Sun Yat-sen University, China, said the existing mathematical models were fundamentally flawed.

"There is a forward version when we add species and a backward version when we lose species," said Hubbell.

"The species-area curve has been around for more than a century, but you can't just turn it around to calculate how many species should be left when the area is reduced; the area you need to sample to first locate a species is always less than the area you have to sample to eliminate the last member of the species," he added.

"The overestimates can be very substantial. The way people have defined 'extinction debt' (species that face certain extinction) by running the species-area curve backwards is incorrect, but we are not saying an extinction debt does not exist," he added.

There were predictions in the early 1980s that as many as half the species on Earth would be lost by 2000.

"Nothing like that has happened. However, the next mass extinction may be upon us or just around the corner. There have been five mass extinctions in the history of the Earth, and we could be entering the sixth mass extinction," said Hubbell.

The study is detailed in the current issue of Nature. (ANI)