Aldabra banded snail  (Rachistia aldabra)

The last living specimen of the Aldabra banded snail was collected in 1997. Extensive searches for this species were conducted in many parts of Aldabra atoll in 2005 and 2006, but only shells were discovered, which were estimated to be five years old (2). Most of these remains therefore date the last living Aldabra banded snails to around 2000, meaning this snail is now most likely extinct (2).

With changes in habitat or food availability being ruled out as the cause of this extinction, (considerable changes have not been identified in either), the most likely cause is a change in climate (2), the most significant change on Aldabra atoll over the last 30 years (3). Throughout the 1980s and 1990s, there has been a decrease in rainfall, with increasingly prolonged dry periods (2).

Scientists have discovered that while adult land snails are well able to tolerate long periods of aestivation and dry conditions, juveniles suffer increased mortality and newly hatched snails do not survive aestivation (3). Thus, with an increase in long, dry periods, juvenile mortality would have risen, leaving an ageing population. As the old snails died naturally, the species would have slipped into extinction (2).

Now considered to be extinct, it is most likely too late for any conservation action for the Aldabra banded snail, but hopefully lessons can be learnt from the loss of this species. Its extinction highlights the complex challenges that may arise from climate change, and the wave of extinction that may hit biodiversity as climate change continues (2) (3).