Photo by Chad Kruger. The Sunshine Farm in Chelan, Wa.
Yields for dryland crops like winter and spring wheat look good, while irrigated corn and potatoes will be down.
That’s the forecast through the year 2030 from a group of WSU researchers, who are working to assess future growing conditions under climate change for 40 types of crops in the Columbia River Basin.
As part of a project funded through the Washington State Department of Ecology and the United States Department of Agriculture, the researchers developed a forecast for water supply and demand in 2030 and assessed how future economic and environmental conditions, including water scarcity, will affect agricultural productivity.
While future precipitation projections are uncertain, more robust warming projections will mean that more precipitation will occur as rain and snow will melt earlier in the season, so that less water will be available for crop irrigation in the late summer months.
To better understand how crop yields will be affected by climate change, Jennifer Adam, a civil and environmental engineering assistant professor, worked closely with her colleagues, including Claudio Stöckle in the Department of Biological Systems Engineering, Chad Kruger with the Center for Sustaining Agriculture and Natural Resources, and Michael Brady in the School of Economics. Kirti Rajagopalan, a graduate student in the Department of Civil and Environmental Engineering, also worked on the project. The researchers integrated three computer modeling programs, bringing together climate predictions, water management scenarios, and economics to better understand water supplies, demand for irrigation, unmet demand, and future crop yields.
“There are several competing factors that have positive and negative impacts,” Adam says. “Our science is teasing out the effects.”
The researchers found that dryland crops, like winter wheat and spring wheat, will be positively affected, at least in the next 20 years, as atmospheric carbon dioxide levels rise due to anthropogenic activities, such as burning fossil fuels. The increased carbon dioxide allows the plants to use water and sunshine more efficiently.
“The direct impact of more carbon dioxide benefits some types of plants,” says Adam.
Other crops that will also grow better in a warmer Northwest are alfalfa, hay, and timothy grass. Warmer temperatures will affect all of the crops negatively, but warmer temperatures can be outweighed by higher carbon dioxide levels.
As temperatures continue to rise, however, the negative effects of warmer temperatures may eventually have a larger negative impact, says Adam.
“It’s non-linear,” she says. “Crop productivity impacts are positive at first, but at some point, warming results in negative impacts.”
At the same time, irrigated crops in Washington, such as potatoes and corn, should see lower yields by 2030, says Adam. While increased carbon dioxide levels might help the crops grow better, warmer temperatures and insufficient water supplies will outweigh any possible positive effects.
For their models, the researchers use “mechanistic” models, which are based on simple physics and computer programming to predict future climate impacts. The models use fundamental scientific principles, like the conservation of mass and energy, to predict what will happen as the climate drives change.
The model is complicated because it has to include all the physical factors, such as evaporation, transpiration, snow pack, and soil moisture just to get a predicted number for stream flow, for example.
“It is a very compelling computing challenge,” she said. “But the whole point is to integrate and to get a better understanding of land use and our natural ecosystems.”