Scientists fine-tune extinction rate projections

The journal Nature recently reported that modern methods of measuring animal populations are too simple and often do not take into account the complexity of what influences species numbers. Professor Stephen Hubbell, from California, and Professor Fangliang He, from China, found that existing mathematical models for measurement were flawed: present figures overestimated rates by up to 160 percent, showing that calculations must be updated and made more accurate.

Nevertheless, Hubbell maintained although species extinction caused by habitat loss is not as dire a problem as initially believed, the global extinction crisis is still a real threat.

“We are not in quite as serious trouble right now as people had thought,” Hubbell told Smithsonian Science on May 18. “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.” He maintained, “Nothing is further from the truth.”

While there were predictions in the early 1980s that as many as half the species on Earth would be lost by the year 2000, Hubbell explained, “Nothing like that has happened. However, the next mass extinction may be upon us or just around the corner. There have been five mass extinctions in the history of the Earth, and we could be entering the sixth mass extinction.”

Probably the most authoritative global assessment of species status is the Red List of Threatened Species, which is published by the International Union for Conservation of Nature.

Jean Christophe Vie, IUCN’s species program deputy director, responded it was good that this was a clear effort to “get the science right,” but had reservations about how people would interpret it. He acknowledged to BBC News that he was worried about how the report could be used by those who were reluctant to take environmental issues seriously.

“We have explicit details in our guidelines that to estimate extinction is not something we should do,” said Vie. “For example, we know that species are not evenly distributed in ecosystems; habitat loss is not the only threat.” He added that the actual concern was “the rate of decline in populations.”

Addressing the issue, Hubbell cited a comparison: When a meteor struck the Earth some 65 million years ago, the Earth’s tree life was incinerated, and it took about 10 million years to fully recover and redevelop into continuous, flourishing forests. Hubbell said that the extinctions humans cause might be equally catastrophic, though in different ways.

“We need much better data on the distribution of life on Earth,” Hubbell said. “We need to rapidly increase our understanding of where species are on the planet. We need citizens to record their local biodiversity; there are not enough scientists to gather the information. We also need much deeper thought about how we can estimate the extinction rate properly to improve the science behind conservation planning.

“If you don’t know what you have,” Hubbell concludes, “it’s hard to conserve it.”

Photo: Wandering Skipper (Panoquina errans), a species that exists only in coastal salt marshes, with narrow requirements for life that make it vulnerable to extinction.