Patrice Pottier , Michael R. Kearney, Nicholas C. Wu , Alex R. Gunderson, Julie E. Rej, A. Nayelli Rivera-Villanueva, Pietro Pollo, Samantha Burke, Szymon Marian Drobniak, Shinichi Nakagawa

Amphibians are the most threatened vertebrates, yet their resilience to rising temperatures remains poorly understood. This is primarily because knowledge of thermal tolerance is taxonomically and geographically biased, compromising global climate vulnerability assessments. Here, we employed a novel data imputation approach to predict the heat tolerance of 60% of amphibian species and assessed their vulnerability to daily temperature variation in thermal refugia. We found 198 out of 5203 species are currently exposed to overheating events in shaded terrestrial conditions. Despite accounting for heat tolerance plasticity, a 4°C global temperature increase would create a step-change in impact severity, pushing 9.4% of species beyond their physiological limits. In the Southern Hemisphere, tropical species encounter disproportionally more overheating events, while in the Northern Hemisphere, non-tropical species are more susceptible. Our findings challenge evidence for latitudinal gradients in overheating risk and underscore the importance of considering climatic variability in vulnerability assessments. Notably, our conservative estimates assume access to shaded microenvironments, implying that global warming’s impacts on amphibians may exceed our projections. Our microclimate-explicit analyses also demonstrate how the availability of vegetation and water bodies is critical in buffering amphibians during heat waves. Immediate action is needed to preserve and manage these microhabitat features.