Species that are adapted to live in cool headwater streams are globally threatened by climate change, as rising temperatures cause suitable habitats to retract. This long-term ‘press’ disturbance is exacerbated by increases in extreme climate events, which can pose an immediate threat to the persistence of vulnerable species. In early 2020 a series of extreme events combined – deep drought, record temperatures and widespread bushfires – imminently threatening the survival of a community of cold-water species in the upper Condamine and Border Rivers in Australia’s Murray-Darling Basin. These river blackfish (Gadopsis marmoratus), mountain galaxias (Galaxias olidus) and spiny crayfish (Euastacus sulcatus) populations in the north of the Basin are extremely restricted and fragmented. Raised water temperature or poor water quality caused by cessation of flow, loss of riparian vegetation or bushfire runoff could have led to the permanent loss of local populations, leading to regional scale decline. The potential for natural repopulation is extremely limited by the species’ movement behaviours and natural and artificial barriers. Intervention was required in order to offset potential impacts.
A series of actions were undertaken in response to the extreme climate events in an effort to preserve these species: salvage of wild fish, development of captive holding practices, and reintroduction. In addition, ongoing monitoring of environmental conditions, surveying distributions post-disturbance, and community awareness-raising are helping to support longer-term conservation of these species and their habitat. However, the threats remain. Lessons learned will help to inform future emergency responses.