Australasian Science: Australia's authority on science since 1938

A New Test for Species Survival

By Stephen Luntz

A new test for the prospects of species survival could improve the targeting of conservation funds.

However, it has set the feral cat among the endangered pigeons, promoting practicality over emotion.

The International Union for Conservation of Nature publishes a Red List of Threatened species. This assesses the level of threat based on the decline in the number of individuals and the range over which the species exists in the wild.

However, Prof Corey Bradshaw of the University of Adelaide’s Environment Institute says this has some weaknesses. “A population may experience decline but have healthy subpopulations,” he argues. He also considers the time period over which the decline is measured as “arbitrary”.

As a collaborator in work demonstrating that most species need a population of around 5000 to maintain adequate genetic diversity (AS, Jan/Feb 2010, p.7), Bradshaw and colleagues have now established the Species Ability to Forestall Extinction (SAFE) index, comparing the number of living animals with the 5000 threshold.

“Our index shows that not all critically endangered species are equal. A combined approach – using the IUCN Red List threat categories together with the SAFE index – is more informative than the IUCN categories alone, and provides a good method for gauging the relative ‘safety’ of a species from extinction,” Bradshaw says.

After applying the SAFE index to 95 mammal species Bradshaw concluded that some species, such as the Javan rhinoceros, have very low long-term survival prospects. He suggests that money currently directed there might be better spent on the more numerous Sumatran rhinoceros. “Alternatively, conservationists with limited resources may want to channel their efforts on saving the tiger, a species that is at the ‘tipping point’ and could have a reasonable chance of survival.”

The idea of giving up on such popular species as the northern hairy-nosed wombat has attracted negative comment, although Bradshaw says that none has been directed at him. “This is not the whole story,” he agrees. “If you can get money to protect an area of habitat you might save 1000 species of insects while officially you are trying to conserve one mammal.”

Nevertheless, Bradshaw argues that we need to be realistic. “We are in a crisis, and in any crisis you need to drop luxuries. Is it moral to spend money trying to save one species that probably can’t be saved when that could be used to save hundreds of others?”