Time for a mass extinction metrics makeover

Researchers at Yale and Princeton say the scientific community sorely needs a new way to compare the cascading effects of ecosystem loss due to human-induced environmental change to major crises of the past. For too long, scientists have relied upon metrics that compare current rates of species loss with those characterizing mass extinctions in the distant past, according to Pincelli Hull , an assistant professor of Earth and planetary sciences at Yale, and Christopher Spalding, an astrophysicist at Princeton. The result has been projections of extinction rates in the next few decades that are on the order of a hundred times higher than anything observed in the last few million years of the fossil record. " The problem with using extinction rates this way is that their assessment is riddled with uncertainty," said Hull, who has conducted extensive research on mass extinctions of marine life in the ancient world. "We need a better thermometer for biodiversity crises." Furthermore, the researchers said, mass extinction predictions do not fully convey the severity of damage done to an ecosystem when species are depleted but not entirely wiped out. In a new study in the journal Proceedings of the Royal Society B, Spalding and Hull point out deep flaws in the way mass extinctions are being projected and propose a new model for assessing biodiversity loss. Part of the problem, they said, has to do with comparing extinctions found in the fossil record over millions of years with human-influenced extinctions from only the past century.