A user's guide for understanding reptile and amphibian hydroregulation and climate change impacts.

Human impacts on ecosystems have intensified variation in water variability for terrestrial life, thus challenging the maintenance of water balance, or hydroregulation. The accelerated development and accessibility of technologies and computational models over the past decade have enabled researchers to predict changes in animal hydroregulation and environmental water with greater spatial and temporal precision. Focusing on reptiles and amphibians, we discuss current methods, limitations and advances for quantifying ecologically relevant metrics of environmental water stressors and organismal responses to both acute and long-term water stress that are applicable for conservation and management. We also highlight approaches that integrate environmental water data with an organism's water balance and physiological, behavioural and life history traits to predict the limits of species' responses and assess their vulnerability to climate change. Finally, we outline promising future directions and opportunities in hydroregulation studies with a conservation focus, including broader inferences about acclimation responses, linking gene expression to functional changes, and exploring inter- and transgenerational plasticity and adaptive evolution. Advances in these fields will facilitate more accurate assessments of species' capacities and the limits of hydroregulation in response to a more variable and unpredictable future climate.