Speaker: Dylan Hogan

Title: The global freshwater resource costs of climate change accounting for agricultural land use

Abstract: The rapid decline of many freshwater resource stocks threatens global food supplies and the stability of agricultural markets. Anthropogenic climate change is likely to exacerbate freshwater scarcity in many regions of the globe, both directly through changing natural recharge of aquifers and surface reservoirs and indirectly through changing how people and crops use available water resources in agricultural landscapes. In this paper, we provide the first globally-comprehensive and empirically-derived estimates of the impacts of climate change on local water availability, accounting for endogenous adaptive responses in agricultural landscapes. On average across the world, we find that in the short-run, temperature days beyond 35°C, relative to 20°C, reduce water storage by 0.2 cm. However, this global average effect masks important heterogeneity across agricultural land uses—rainfed and irrigated agriculture increase the temperature sensitivity of freshwater storage by about 50% and 150%, respectively. These impacts are mediated in the long-run, as hydrologic and socioeconomic forces adjust to increased heat exposure and resulting water loss. In a second step, we estimate long-run responses of water storage to temperature and rainfall, using these estimates in combination with an ensemble of climate models to project the impacts of historical and future climate change on freshwater resources across the globe.