The dilemma of accuracy in IUCN Red List categories, as exemplified by hawksbill turtles Eretmochelys imbricata

Since 1963 the International Union for Conservation of Nature (IUCN) Red List has provided the world with a credible and effective call to action for preventing species extinction. However, the criteria for assigning categories of threat (e.g. 'critically endangered,' 'endangered,' 'vulnerable'), particularly the 'decline criteria' (Criteria A), often exaggerate the real risks of extinction and are thus not accurate. This is exemplified here by hawksbill turtles Eretmochelys imbricata, but the problem is more widespread. There is an expectation by scientists that these accuracy problems will be rectified, yet this is by no means a minor adjustment for the Red List to make, because the Red List itself operates under significant constraints. The Red List is expected to meet the requirements of scientist and advocates, to be consistent with historical precedents, to pursue new directions at the biodiversity level, to meet the often conflicting views and values of diverse IUCN members, and still has to weather the stormy politics of conservation. Proposed changes to listing procedures would need to be scientifically justified, politically acceptable and as benign as possible to ongoing processes, such as biodiversity monitoring. The decline criteria are perhaps the most problematic, and these are examined in more detail here. A fundamental weakness is that they respond more to the challenge of reinstating historical abundance than to avoiding global extinction per se. This could potentially be overcome by using the current decline criteria to make an objective first stage determination based solely on decline (e.g. 'critically declined'), thereby overcoming almost all scientific objections concerning accuracy. A second-stage assessment could then examine the significance of that decline, in terms of allocating species to the existing extinction risk categories or retaining them as critically declined. There is an increasing conservation and humanitarian expectation that the IUCN, through the Red List, will become more involved with species that are critically declined but well-buffered against global extinction. To use global extinction as the gatekeeper to the IUCN's involvement in conservation issues today is difficult to justify. � Inter-Research 2008.