Assessment of Climate Change Impact on Eastern Washington Agriculture

An assessment of the potential impact of climate change and the concurrent increase of atmospheric carbon dioxide (CO2) concentration on eastern Washington State agriculture was conducted. Climate projections from four selected general circulation models (GCM) were chosen to evaluate impacts for the periods 20102039, 2030-2059 and 2070-2099, identified as 2020, 2040, and 2080 scenarios, respectively. All climate projections reflect a warming future climate, but the individual GCMs vary with respect to precipitation changes – some models reflect wetter conditions and some drier. The assessment included the crops with larger economic value for the state at selected representative locations: irrigated apples at Sunnyside; irrigated potatoes at Othello; dryland wheat at Pullman (high precipitation), Saint John (intermediate precipitation), and Lind and Odessa (low precipitation). To evaluate crop performance, a cropping system simulation model (CropSyst) was utilized using historical (19752005) and future climate sequences, including simulations with and without concurrent elevation of atmospheric CO2 concentration as given by the IPCC A1B CO2 emission projection. Crops were assumed to receive adequate water (irrigated crops) and nutrient supply and possible negative impacts from pests and diseases were not accounted for. Simulation results project that the impact of climate change on selected but economically significant crops in eastern Washington will be generally mild in the short term (i.e., next two decades), but increasingly detrimental with time (potential yield losses reaching 25% for some crops by the end of the century). However, the projected CO2 elevation is expected to provide significant mitigation of climate change effects, and in fact result in yield gains for some crops. Yields of winter wheat, without CO2 effect, are projected to increase 2% to 8% for the 2020 scenario, tending to decline with further warming in high precipitation locations, but continue increasing to reach a 12% gain by the 2080s in low precipitation locations. With CO2 elevation, winter wheat yields are projected to increase by 15% for the 2020 scenario, with larger increases later in the century. Spring wheat yields are projected not to change for the 2020 scenario, and decline 10% to 15% (2040), and 20% to 26% (2080) without CO2 effect. However, earlier planting combined with CO2 elevation is projected to increase yields by 16% for the 2020 scenario. 1 Department of Biological Systems Engineering, Washington State University, Pullman, Washington 2 Tree Fruit Research and Extension Center, Washington State University, Wenatchee, Washington 3 Irrigated Agricultural Research and Extension Center, Washington State University, Prosser, Washington 4 USDA-ARS at WSU IAREC, Prosser, Washington 5 Center for Sustaining Ag & Nat Res, Washington State University, Wenatchee, Washington 5: Agriculture CHAPTER 5: Agriculture 191 Yields of irrigated potatoes are projected to decline 9%, 15%, and 22% for the 2020, 2040, and 2080 scenarios, respectively, but these losses are significantly smaller (2 to 3%) with CO2 elevation. Varieties with a longer duration of green leaf area, combined with elevated CO2, could potentially result in yield gains of 15%. However, reductions of tuber quality are a concern under warmer conditions. Apple yields are projected to decline 1%, 3%, and 4% for the 2020, 2040, and 2080 scenarios, respectively, but with projected yields increasing 6% (2020), 9% (2040), and 16% (2080) with CO2 effect. Growers will need to adapt management to benefit from possible yield increases while maintaining fruit quality standards. Lack of good representation of the frequency and persistence of extreme temperature and precipitation events in current climate projections, which could adversely affect crop yields, and the extent to which the beneficial effects of elevated CO2 on future crop productivity will be expressed are sources of some uncertainty to the projections in this study.