Conservation targets reassessed in the face of climate change



In the face of climate change, conservation biologists are setting minimum population size targets too low to prevent the extinction of endangered plants animals, according to an Australian study.

Research from scientists at the University of Adelaide in South Australia and Macquarie University in New South Wales has shown that populations of endangered species are unlikely to persist given current and predicted global climate change and habitat loss unless they number around 5,000 mature individuals or more.

"Conservation biologists routinely underestimate or ignore the number of animals or plants required to prevent extinction," said lead author Lochran Traill, from the University of Adelaide's Environment Institute.

"Often, they aim to maintain tens or hundreds of individuals, when thousands are actually needed. Our review found that populations smaller than about 5,000 had unacceptably high extinction rates. This suggests that many targets for conservation recovery are simply too small to do much good in the long run."

A long-standing idea in species restoration programs is the so-called '50/500' rule. This states that at least 50 adults are required to avoid the damaging effects of inbreeding, and 500 to avoid extinctions due to the inability to evolve to cope with environmental change.

"Our research suggests that the 50/500 rule is at least an order of magnitude too small to effectively stave off extinction," Traill said. "This does not necessarily imply that populations smaller than 5,000 are doomed. But it does highlight the challenge that small populations face in adapting to a rapidly changing world."

Team member Richard Frankham, from Macquarie University's Department of Biological Sciences, said: "Genetic diversity within populations allows them to evolve to cope with environmental change, and genetic loss equates to fragility in the face of such changes."

Conservation biologists worldwide are battling to prevent a mass extinction event in the face of a growing human population and its associated impact on the planet.

"The conservation management bar needs to be a lot higher," said Traill.

"However, we shouldn't necessarily give up on critically endangered species numbering a few hundred of individuals in the wild. Acceptance that more needs to be done if we are to stop 'managing for extinction' should force decision makers to be more explicit about what they are aiming for, and what they are willing to trade off, when allocating conservation funds."

The team's research findings were published earlier this month in the journal Biological Conservation.