Obviously there aren't many ways to directly know extinction rates and very few ways of even directly estimating extinction rates, so conservationists use an indirect estimation method (calibrate accordingly, as always) called a "species-area relationship." This method starts with the number of species found in a given area and then estimates how the number of species grows as the area expands. Then they reverse the calculations and attempt to estimate how many fewer species will remain when the amount of land decreases due to habitat loss.
As a result, there were predictions in the early 1980s that as many as half the species on Earth would be lost by 2000. A new estimation method by Stephen Hubbell, distinguished professor of ecology and evolutionary biology at UCLA and co-author of the Nature paper with lead author Fangliang He, a professor at China's Sun Yat-sen University in Guangzhou, seeks to make indirect estimation a bit more accurate and lead to less hysteria and, therefore, provide a better chance of real policy changes being made that can help.
"There is a forward version when we add species and a backward version when we lose species," Hubbell said. "In the Nature paper, we show that this surrogate measure is fundamentally flawed. 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.
"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."
How confident are they in their findings?
"100 percent," Hubbell said. "The mathematical proof is in our paper."
Their new mathematical proof addresses very large numbers of species and does not answer whether a particular species, such as the polar bear, is at risk of extinction.
That doesn't mean you can start throwing Starbuck's mugs out the car window. "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.
"We have bought a little more time with this discovery, but not a lot."
Take home message; don't get jaded by exaggerated claims of advocacy groups trying to raise money and think nothing should be done. Get out and enjoy nature, let scientists uncover any erroneous methods behind claims, and make sure you endorse real ways to protect nature so future generations can enjoy it also.
Citation: Fangliang He and Stephen P. Hubbell, 'Species–area relationships always overestimate extinction rates from habitat loss', Nature 473, 368–371 (19 May 2011) doi:10.1038/nature09985