This story is also discussed on this week’s Nature Podcast.

A mathematical glitch means we’ve been massively underestimating how at risk endangered species are, according to a paper in this week’s Nature (paper, press coverage).

By failing to include random variations in individuals within a species, such as size and male-to-female sex ratios, risk estimates have been out by up to 100 times, say Brett Melbourne, of the University of Colorado at Boulder, and Alan Hasting, of the University of California, Davis. Which means animals like the Sumatran tiger could go extinct 100 times faster than we thought.

“This seems subtle and technical, but it turns out to be important,” Melbourne told AFP.

After developing new models that did incorporate some of the missing factors, Melbourne and Hastings confirmed them experimentally using a population of beetles in their lab.

“When we apply our new mathematical model to species extinction rates, it shows that things are worse than we thought,” says Melbourne (press release). “By accounting for random differences between individuals, extinction rates for endangered species can be orders of magnitude higher than conservation biologists have believed.”

This could have big implications for the IUCN, which manages the endangered species ‘red list’.

“We are certainly underestimating the number of species that are in danger of becoming extinct because there are around 1.8m described species and we’ve only been able to assess 41,000 of those,” says Craig Hilton-Taylor, of the IUCN (Guardian). “We are constantly looking at how we evaluate extinction risk, and it may be they have hit on something that can help us.”

Nancy Tcheou, who is acknowledged in the paper, says (of her acknowledgement), “I guess working in the beetle lab for more than a year kinda pays off… in addition to the fact that I’ve counted to 50 more times than countable. Just beetles. Yep.”