Historic ecological literature suggests that regional ecosystem evapotranspiration, productivity, and biodiversity distributions are tightly coupled.  Climate has direct influences on rainfall distribution and evapotranspiration, therefore climate change and variability are likely to alter ecosystem productivity, water use and biodiversity patterns.  This study attempts to develop an integrated model that examines the trade-offs among water, carbon, and biodiversity at a large scale.  We developed a water supply stress index-carbon and biodiversity (WaSSI-CB) model by integrating published literature on water-carbon relations, global eddy flux data, landcover/land use, and climate and population dynamics data.

Results/Conclusions

The long term average gross primary productivity (GPP) and net ecosystem exchange of CO₂ (NEE) were estimated as 7.6Pg C/m3/yr and -0.79 Pg C/m2/yr.  The southeastern U.S. appears to be the major carbon sink due to warm climate and a large forests area.  Simulation results compared favorably with USGS streamflow data for water yield and MODIS-based GPP and NEE estimates.  This study indicates that continental scale ecosystem productivity (GEP) can be reasonably estimated with a water-centered model.  We conclude that quantifying the water balance is critical to accurately predicting the effects of climate change on carbon balances and biodiversity. The modeling frame work can be used by researchers who concern broader biosphere-atmospheric interactions.