Interactions of future climate, carbon dioxide, and ozone change crop and forest productivity and water use

The demand for agricultural and forest yield will continually increase as populations grow, though it is unclear how agricultural and forested ecosystem productivity and water use will respond to the interactions of changing climate, carbon dioxide and ozone. In ecosystems essential to resource production, it is critical to understand how productivity and water use will respond to these future changes. Previous research suggests that future climate and ozone can each decrease crop and timber yield and water use efficiency, while future carbon dioxide might increase yield and improve water use efficiency. However, the change in agricultural and forest water use and yield in response to the interactions among these variables has not yet been determined. We use the Community Land Model (CLM) to determine how changes in agricultural and timber water use and yield in response to the interactions of all three variables (climate, carbon dioxide, and ozone). Preliminary results suggest that future ozone and climate decrease forest and grain yield. However, carbon dioxide concentrations increase forest and grain yield, offsetting the decreases. Future climate increases evapotranspiration in all regions more than the decreases caused by carbon dioxide and ozone. The interactions of climate, carbon dioxide, and ozone decrease water use efficiency, with climate having the largest impact. These results demonstrate that, to maintain agricultural and forest productivity in the future, the demand for irrigation will increase.