Extinction rate theory creates ecological stir

PUBLISHED : Friday, 20 May, 2011, 12:00am
UPDATED : Friday, 20 May, 2011, 12:00am


A projected rate of extinctions of animals and plants this century may be less dramatic than feared because the most widely used scientific method could have exaggerated this by as much as 160 per cent, according to a study published in Nature yesterday.

The study, by Professor He Fangliang and Professor Stephen Hubbell, is causing a buzz in the ecological community.

The report also questions several high-profile reports, including a UN-led Millennium Ecosystem Assessment, which predicted extinctions would be at 1,000 to 10,000 times the current rates, and a study published in 2004 which estimated that up to 35 per cent of all plant and animal species could disappear by 2050.

He, an ecologist with both the University of Alberta in Canada and Guangzhou-based Sun Yat-sen University, said: 'Many previous estimates of extremely high extinction rates based on the use of SAR [species-area relationship] have not been observed.

'So, since 2003 we came up with the idea to find out why the SAR didn't work and whether there is any better way.'

The SAR method, the most widely used way to estimate extinction rates since the 1970s, has suggested the loss of 90 per cent of a habitat area means the loss of about half of the species in the area at the same time.

He said there was no field evidence or mathematical proof to support the method. He and Hubbell, an ecologist at the University of California at Los Angeles, explained a new way to use an old concept, called endemics-area relationship (EAR). Based on what they found, they wrote, 'extinctions caused by habitat loss require greater loss of habitat than previously thought'.

Even though the rates of species loss may be slower, He emphasised that habitat loss and a biodiversity crisis were still big problems.

'It is good news that the species extinction rates are not so high, but we are still in urgent need to find ways to save these plants and animals, which we believe the new method can help,' he said.

The report has received wide coverage and triggered debate among ecologists worldwide.

'We received many questions overnight, which is a much stronger response than we expected,' He said yesterday.

For example, Professor Stuart Pimm, a biologist at Duke University North Carolina, called the study 'total nonsense', and another scientist said he 'was desperately upset' that Nature had published it.

'But so far no one has questioned the mathematical proof we gave in the paper. It just seems like they don't like the tone and the results we cite in the report,' He said.

Other scientists said they needed time to evaluate the findings.

He said that to get a truer estimation for the rate of species loss, the EAR method required not only the size of the habitat that had lost species, but also specific data of the species in the area. He called on governments worldwide, including China, to invest more in data collection.

'To ... strengthen the science behind conservation planning, we need far better geographical data on endemism [the state of being unique to a location] and species distributions to improve forecasts of extinction rates,' the report said.

Spending most of his research time in China, He also strongly urged the central government to provide more support to scientists to collect ecological data, without which the country could not tell exactly how many species it had lost.