Estimating the Impacts of Future Extreme Heat on Dryland Threatened Mammals: An Australian Case Study.

Extreme heat is an escalating threat to biodiversity, with dryland ecosystems particularly vulnerable. Using Australia's dryland mammals as a model system, we present a framework comparing baseline and future heat envelopes for 36 threatened species to quantify future heat exposure, identify potential refugia and evaluate the suitability of translocation sites. We conducted a systematic review to assess our understanding of these species' thermal ecology. Our analyses identified eight species (22%) as high risk (three rodents, two dasyurids, one bat, one wombat and one macropod), for which their current distributions are projected to substantially exceed both current and historical heat envelopes. Rodents were overrepresented as high-risk species while bats and dasyurids were underrepresented, whereas body size, range extent and conservation status did not predict heat risk. High-risk species typically had narrow heat envelopes and have contracted to regions near their historical thermal maxima. High-risk species had rarely been translocated (50% of species), with only one moved to a site projected to remain within its historical thermal maximum under all climate futures. Most moderate-risk species (12 of 14; 86%) have been translocated, but > 60% of translocation sites are projected to exceed current thermal maxima. Our review revealed substantial knowledge gaps, with ten species (28%) entirely absent from the thermal literature, and high-risk species (mean = 1.4 studies) being less represented than moderate- and low-risk species (mean = 4.7 and 6.3 respectively). Research was biased toward behavioural and physiological responses, while critical subjects such as in situ responses, functional traits and direct evidence of heat-related consequences were limited and are urgently needed to guide adaptive management. Conservation in drylands must prioritise protection of thermal refugia, improved land condition and integrate climate projections in long-term planning. Our combined framework provides a globally relevant screening tool to identify heat-vulnerable species and direct conservation management priorities.