Action benefits from certainty: What certainty is there species are being lost and how can we improve it?
Evidence from the northern hemisphere and Australia shows that, although rates are variable spatially and taxonomically, there has been significant species extinction over the last 200 years within many vertebrate groups. Extinction rates have perhaps also been high in some invertebrate groups but there is surprisingly little evidence, especially in aquatic systems. This raises the question of whether aquatic invertebrates are particularly resilient or whether their occurrence has been so poorly documented that we are unaware of species being lost.
After a recent survey of the Western Australian wheatbelt, we predicted that about one-third of freshwater invertebrate species are at serious risk of regional extinction during the next 100 years as a result of salinization. In a contradictory result, we found no compelling evidence that any freshwater wheatbelt invertebrate species has become extinct during the past 200 years, despite substantial salinization having already occurred, and it could be argued that our prediction that one-third of species is at risk is alarmist.
Conservation planning must be based on information and currently is being driven by information from well-surveyed groups in which risk and decline can be domostrated. The pattern in these groups is unlikely to be representative of broader biodiversity. We urge the development of State or National databases, which extend beyond just specimen records and contain results of all survey work, to help address this imbalance. They are an essential conservation tool in the 21st century. With this tool available in the past we might have been able to document the loss of species from the wheatbelt, but it is much more certain that without it in the future we will never know in a 100 years whether our prediction of one-third species loss from the wheatbelt was right or wrong.