Modeling Impacts of Environmental Change on Ecosystem Services across the

Climate model projections suggest that there will be considerable increases in temperature and variability in precipitation across the conterminous United States during the next 100 years. These changes in climate coupled with changes in land use and increases in human population will likely have a significant effect on water resources, carbon fluxes, biodiversity, and the services they provide. As society reacts to changing environmental conditions, the adaptation and mitigation strategies for one ecosystem service could come at the expense of another. It is critical that planning tools be developed to evaluate these tradeoffs between ecosystem services so that sound management decisions may be made in the face of climate, economic, and demographic change. This paper presents the Water Supply Stress Index–Carbon & Biodiversity model (WaSSI-CB) and demonstrates its potential for predicting changes in water supply and demand, carbon dynamics, and potential biodiversity under multiple stresses. The core of WaSSI-CB is a water balance model (WaSSI) that is sensitive to land cover and climate and operates on a monthly time step at the 8-digit hydrologic unit code (HUC) watershed scale across the conterminous United States. Annual U.S. Geological Survey water demand estimates are adjusted for population, disaggregated to the monthly scale, and compared to groundwater and surface water supply to assess water supply stress. Gross ecosystem productivity, ecosystem respiration, and net ecosystem carbon exchange are estimated using actual evapotranspiration. Similarly, potential biodiversity of reptiles, birds, amphibians, mammals, vertebrates, and tree distribution and abundance are estimated as a function of evapotranspiration. We show how th