Scientist: Species going extinct slower

08:47, May 20, 2011      

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Scientists have been convinced for a long time that living species are going extinct at an alarmingly fast rate in the modern world.

While many are desperately trying to slow the losses, He Fangliang, a Chinese ecologist, is criticizing the current way of predicting how fast such losses will occur. His conclusions were published in the science magazine Nature on Thursday.

"A lot of factors such as deforestation, climate change and over-exploitation have led to an extreme rate of extinction," said He, who is an ecologist at Sun Yat-sen University in Guangzhou. "And the traditional method of predicting the rate of species loss is flawed."

The most common method of predicting extinction rates relies on what is known as the species-area curve, which is derived from the relationship that tends to exist between the size of a place and the number of species it contains.

In predicting how much extinction will result from the destruction of a certain amount of habitat, researchers often have recourse to the curve.

Using that traditional method, they have come to a general agreement that the Earth is losing its biodiversity at an extremely fast rate. Their calculations hold that species are disappearing 100 to 1,000 times faster than is normal, perhaps placing the Earth in a period of mass extinction.

The United Nations has said that rate will accelerate tenfold in coming centuries.

He's research casts doubt on those predictions. Working with Stephen Hubbell, a theoretical ecologist at the University of California, Los Angeles, He has proposed that the use of endemics-area curves, which take into account the distribution of species within a given space, might give scientists a better means of estimating extinction rates.

To compare the accuracy of the two mathematical models, they applied both of them to data drawn from studies of forest diversity in Asia, Africa and Latin America.

The upshot: The endemics-area curve produced results that corresponded closely with the data collected in the field, while the results stemming from the species-area curve greatly overshot the numbers drawn from the observed data.

"We can say that previous estimates should be divided roughly by 2.5," He said at a press conference in Guangzhou, capital of Guangdong province, on Wednesday.

"The traditional method has to be revised. It exaggerates the likelihood of extinction. That is not right."

As examples of the traditional method's tendency to produce exaggerations, he cited studies that had forecast the loss of 50 percent of all species by 2000 - a prediction that clearly has not come true.

The discrepancy often found between such predictions and reality is well known and has been attributed to "extinction debt", referring to the lapse of time that occurs from when a species is harmed through habitat destruction to when it is actually extinct.

"The 'extinction debt' is also flawed," He said. "Individuals of long-lived species may continue to reproduce or simply live on without reproducing."

Even so, He is far from denying that threats to biodiversity are becoming more common.

"The lower species loss rate does not mean we should be satisfied with our efforts to the protect the environment," he said.

He suggested that scientists should do more to ascertain how many species are in China and where they exist.

"China does not have fundamental data for animal and plant species," He said. "So it's hard for us to carry out effective measures to protect the environment if we don't know exactly where the species are and how many species there are in the country."

Source: China Daily
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