Extinctions often exaggerated: study

Despite that good news, the report also endorsed past findings that human activities are wrecking habitats from the tropics to the Arctic, threatening the worst losses of species since the dinosaurs.

“Our results must not lead to complacency about extinction due to habitat loss, which is a real and growing threat,” Fangliang He and Stephen Hubbell wrote. The study, based on a survey of birds in the United States and forests, suggested the most commonly used method can exaggerate losses by more than 160 per cent.

“The method has to be revised,” Hubbell, of the University of California, told a news conference. Scientists have long struggled to project extinctions as a rising human population shrinks habitats, for instance by felling forests to clear land for farms or cities. Pollution and global warming are also adding to threats.

The scientists stoked controversy by saying there was “reason to question” a UN-led
Millennium Ecosystem Assessment that projected future extinctions at 1,000 to 10,000 times current rates, and a 2004 study saying that 18 to 35 per cent of all species could be set on a path toward extinction by 2050.

Chris Thomas, the lead author of the latter study at the University of York in England, said he had published an update later in 2004 with a less severe extinction projection, broadly using techniques advocated in Wednesday’s report.

Climate change

Wednesday’s report did not question findings by the U.N. panel of climate scientists in 2007 — used by governments to guide climate policies — that said 20 to 30 per cent of species may be “at increased risk of extinction” as temperatures rise.