The SAFE index: using a threshold population target to measure relative species threat

Gopalasamy Clements, Corey Bradshaw, Barry Brook, William Laurance

    Research output: Contribution to journalArticlepeer-review

    27 Citations (Scopus)


    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 compare 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.

    Original languageEnglish
    Pages (from-to)521-525
    Number of pages5
    Issue number9
    Publication statusPublished - Nov 2011


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