Better SAFE than sorry

Abstract

[Extract] We welcome the debate that our proposed species' ability to forestall extinction (SAFE) index (Front Ecol Environ 2011; 9[9]: 521–525, this issue) has attracted from our peers (see previous letters by Akçakaya et al., Beissinger et al., and McCarthy et al.), because it has further emphasized the need for a more heuristic measure of species extinction threat. The main points of contention can be summarized as follows: (1) SAFE merely echoes the existing IUCN Red List categorization and is therefore redundant; (2) SAFE should not be proffered as a replacement for the Red List; (3) SAFE simplifies mathematically to a measure of a species' abundance and therefore provides no additional risk information; and (4) minimum viable population (MVP) size, on which SAFE is based, is species-specific and so a threshold abundance applied to all species cannot be used. We outline below why each of these arguments is unsupported.