Global exposure risk of frogs to increasing environmental dryness

Species exposed to prolonged drying are at risk of population declines or extinctions. A key missing element for assessments of climate change risk is the sensitivity of species to water loss and their microhabitat preference, or ecotype, as both dictate the risk of environmental drying. Here, we identified globally where water-sensitive ectotherms, i.e. anurans, are at risk to increasing aridity and drought, examined which ecotypes are more sensitive to water loss from 238 species, and estimated how behavioural activity is impacted by future drought and warming scenarios through biophysical models. Under an intermediate and high emission scenario, 6.6 and 33.5% of areas occupied by anurans will increase to arid-like conditions, and 15.4 and 36.1% are at risk of exposure to a combination of increasing drought intensity, frequency, and duration by 2080¬–2100, respectively. Critically, increasing arid-like conditions will increase water loss rates and anurans in dry regions will almost double the water loss rates under a high emission scenario. Biophysical models showed that during the warmest quarter of the year, the combination of drought and warming reduced an anuran’s potential activity by 17.9% relative to the current conditions compared to warming alone which reduced potential activity by 8%. Our results exemplify the widespread exposure risk of environmental drying for anurans, posing a serious challenge for the lives of water-sensitive species beyond the effects of temperature alone.