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Thursday, April 7, 2011

SAFE (Species Ability to Forestall Extinction): a new method to predict how close species are to extinction

New method to measure threat of extinction could help conservationists prioritize

Researchers have developed a new method to predict how close species are to extinction. Dubbed SAFE (Species Ability to Forestall Extinction) the researchers believe the new tool, published in the Frontiers in Ecology and Environment, should help conservationists select which species to focus on saving and which, perhaps controversially, should be let go.

"The idea is fairly simple—it's the distance a population is (in terms of abundance) from its minimum viable population size. While we provide a formula for working this out, it's more than just a formula—we've shown that SAFE is the best predictor yet of the vulnerability of mammal species to extinction," co-author Professor Corey Bradshaw, Director of Ecological Modeling at the University of Adelaide's Environment Institute, says in a press release.

The authors say that the index is not necessarily meant to be a replacement to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species but a tool to use alongside. However, the SAFE index did prove to be a better predictor of extinction threat than another approach of looking at the percentage species' habitat loss.

"The SAFE index provides a more meaningful and fine-grained interpretation of the relative threat of species extinction than do the IUCN threat categories alone," the authors write.

Using rhinos as an example, Bradshaw explains: "our index shows that not all Critically Endangered species are equal […] For example, our studies show that practitioners of conservation triage may want to prioritize resources on the Sumatran rhinoceros instead of the Javan rhinoceros. Both species are Critically Endangered, but the Sumatran rhino is more likely to be brought back from the brink of extinction based on its SAFE index."

The SAFE index team analyzed 95 mammals species and found nearly 60% are close to a 'tipping point' that could push the species to extinction, while 25% are worse off and already close to extinction. Such analyses should allow conservationists a better tool to determine where to spend funds and time.

"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 reasonable chance of survival," Bradshaw says.

Clements RG, Bradshaw CJA, Brook BW, Laurance WF (2011) The SAFE. index: using a threshold population target to measure relative species threat. Frontiers in Ecology and the Environment doi:10.1890/100177.

The International Union for Conservation of Nature (IUCN) Red List is arguably the most popular measure of relative species threat, but its threat categories can be ambiguous (eg “Endangered” versus “Vulnerable”) and subjective, have weak quantification, and do not convey the threat status of species in relation to a minimum viable population target. We propose a heuristic measure that describes a “species’ ability to forestall extinction”, or the SAFE index. We compared the abilities of the SAFE index with those of another numerically explicit metric – percentage range loss – to predict IUCN threat categories using binary and ordinal logistic regression. Generalized linear models showed that the SAFE index was a better predictor of IUCN threat categories than was percentage range loss. We therefore advocate use of the SAFE index, possibly in conjunction with IUCN threat categories, because the former indicates the “distance from extinction” of a species, while implicitly incorporating population viability as a variable.

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