Assessing the global vulnerability of dryland birds to heatwaves

As global average surface temperature increases, extreme climatic events such as heatwaves are becoming more frequent and intense, which can drive biodiversity responses such as rapid population declines and/or shifts in species distributions. However, extreme climatic events are largely ignored in conservation plans. Birds are known to be susceptible to heatwaves, especially in dryland ecosystems. Understanding which birds are most vulnerable to heatwaves, and where these birds occur, can offer a scientific basis for adaptive management and conservation. We assessed the relative vulnerability of 1,194 dryland bird species to heatwaves using a trait-based approach. 886 bird species are estimated to be vulnerable to heatwaves (169 highly vulnerable, 8 extremely vulnerable). 91.2% (808/886) of bird species identified as vulnerable to heatwave impacts are currently considered non-threatened by the IUCN, which suggests that many species will likely become newly threatened with intensifying climate change. We identified the top three hotspot areas of vulnerable species in Australia (206 species), Southern Africa (124 species) and Eastern Africa (99 species,). Populations of vulnerable species recorded in the Living Planet Database were found to be declining significantly faster than those of non-vulnerable species (p = 0.044) after heatwaves occurred. In contrast, no significant difference in population trends between vulnerable and non-vulnerable species was detected when no heatwave occurred (p = 0.66). This suggests that our framework can correctly identify vulnerable species, and that heatwaves are already impacting the population trends of these vulnerable species. Our findings will help prioritize heatwave-vulnerable birds in dryland ecosystems in risk mitigation and adaptation management as the frequency of heatwaves accelerates in the coming decades.