Scientists with the University of California in Los Angeles (UCLA) announce the discovery of a fundamental flaw in the methods used to calculate the rate at which species go extinct. The implication this work has is suggesting that currently-accepted extinction rates are higher than in reality.These rates may in fact be overestimated by as much as 160 percent, the UCLA team reveals in a paper published in the May 19 online issue of the top scientific journal Nature. The team is however keen on explaining that the new data does not suggest the biodiversity loss crisis is not real.
What it does suggest is that the rate at which species are now lost is lower than biologists and conservationists initially calculated. At a global level, study coauthor Stephen Hubbell explains, the crisis is as real as it gets.
The expert, who holds an appointment as a distinguished professor of ecology and evolutionary biology at UCLA, says that “the methods currently in use to estimate extinction rates are erroneous.”
At the same time, “we are losing habitat faster than at any time over the last 65 million years,” he goes on to say. Hubbell is also a tropical forest ecologist and a senior staff scientist at the Smithsonian Tropical Research Institute (STRI).
“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 emphasizes.
Estimating extinction rates directly is notoriously difficult to do, since there is no actual method that is reliable enough to be taken into account. As such, experts have used a measure called the species-area relationship to conduct such investigations.
This approach takes into account the number of species in an ecosystem or a land area, and then estimates how this number will vary as the area increases in size. Experts can also predict how species numbers will decrease as more and more portions of the habitat are lost.
“There is a forward version when we add species and a backward version when we lose species. In the Nature paper, we show that this surrogate measure is fundamentally flawed,” the expert adds.
“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 adds.
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