Sir

We welcome the recent announcement by the conservation partnership BirdLife International that they have launched a “global bid to try to confirm the continued existence of 47 species of bird that have not been seen for up to 184 years” (see http://go.nature.com/6Hc2Cn). But there are pitfalls, as the recent history of 'rediscoveries' has shown.

One of the species on BirdLife's target list is the ivory-billed woodpecker (Campephilus principalis), a bird that was prematurely alleged to have been rediscovered in 2005. This seemingly improbable reappearance provoked intense debate within the scientific community about the veracity of claimed sightings and, more generally, about what represents sufficient proof of continued existence (or extinction). Accusations of 'faith-based' ornithology resulted, increasing scepticism among politicians and policy-makers that conservation organizations are often too willing to put public relations before scientific rigour.

Many rediscoveries in the developing world are made by individuals or organizations from Europe or the United States, or are a direct result of Western-backed expeditions or initiatives. This wrongly reinforces the impression that only Western scientists are competent to find and save threatened species. In addition, high-profile rediscoveries can create an unexpected imperative for immediate action by hard-pressed national conservation organizations.

The international conservation community often seems to want it both ways, being unwilling to declare a species extinct but enthusiastically proclaiming the rediscovery of an 'extinct' species. This ambiguity is understandable — high biogeographic uncertainty can be generated both by the IUCN Red List requirements for 'exhaustive surveys' before a species is officially declared extinct, and by frequent taxonomic revisions that propel rarely seen subspecies to full species status. Rediscoveries are only meaningful if backed up by a self-sustaining population. Otherwise, conservationists are merely engaged in the sad task of documenting the prolonged demise of yet another species.

The genuine rediscovery of 'lost' species is a newsworthy event that helps bolster the pioneering, field-based credentials of conservation and draws attention to new sites worthy of increased protection. The combination of technology and improved access makes finding these species easier than ever. The real challenge is how to present rediscoveries to the public in a way that reflects their conservation significance and that will best encourage the support of future conservation efforts.