The northern hairy-nosed wombat, a burrowing marsupial native to Australia, is a critically endangered species—but according to Australian researchers, it may not be worth saving. A team from the University of Adelaide and James Cook University has developed a new index, called Species Ability to Forestall Extinction (SAFE), that takes current and minimum viable population sizes into account to determine if it’s just too expensive to save a particular animal. “SAFE is the best predictor yet of the vulnerability of mammal species to extinction,” says Corey Bradshaw, director of ecological modelling at Adelaide’s Environment Institute. Not all critically endangered species “are equal,” he says.
The northern hairy-nosed wombat might be a loser in this equation, but other species win. Based on this formula, conservationists should prioritize the Sumatran instead of the Javan rhinoceros, Bradshaw suggests: “The Sumatran rhino is more likely to be brought back from the brink of extinction based on its SAFE index.” Efforts to save endangered species are a bit like triage on the battlefield, these researchers argue, in which doctors have to make tough choices about who can, and can’t, be saved.