Effect of warming temperatures on US wheat yields

Abstract

Climate change is expected to increase future temperatures, potentially resulting in reduced crop production in many key production regions. Research quantifying the complex relationship between weather variables and wheat yields is rapidly growing, and recent advances have used a variety of model specifications that differ in how temperature data are included in the statistical yield equation. A unique data set that combines Kansas wheat variety field trial outcomes for 1985-2013 with location-specific weather data is used to analyze the effect of weather on wheat yield using regression analysis. Our results indicate that the effect of temperature exposure varies across the September−May growing season. The largest drivers of yield loss are freezing temperatures in the Fall and extreme heat events in the Spring. We also find that the overall effect of warming on yields is negative, even after accounting for the benefits of reduced exposure to freezing temperatures. Our analysis indicates that there exists a tradeoff between average (mean) yield and ability to resist extreme heat across varieties. More-recently released varieties are less able to resist heat than older lines. Our results also indicate that warming effects would be partially offset by increased rainfall in the Spring. Finally, we find that the method used to construct measures of temperature exposure matters for both the predictive performance of the regression model and the forecasted warming impacts on yields.agriculture | climate change | global warming | wheat | yield T he potential impact of global warming and climate change on socioeconomic outcomes has become an important and growing area of scientific study and evaluation. Separate lines of study include quantifying the likely impact of climatic change on measures of civil conflict (1-5) and agricultural land values, profitability, and/or production efficiency (6-22). Both lines of literature continue to measure, discuss, and debate the effects of warming temperature. An issue that has received much attention in both sets of literature is how best to quantify exposure to extreme temperatures. This is an important concern, as many studies rely on historical spatial and temporal variations in weather outcomes to identify the effects of weather extremes. If these historical extremes are not measured correctly, estimates of their impacts will not be credibly identified, thereby raising doubts regarding any climate change projections based on these impacts.Here we use regression analysis to estimate wheat yields as a function of observed weather variables and forecast yield impacts under a variety of weather scenarios. Our main findings are as follows. First, the effect of temperature exposure varies across the September−May growing season, with the biggest drivers of yield loss being freezing temperatures in the Fall and extreme heat in the Spring. Second, the net effect of warming on yields is negative, even after accounting for the benefits of reduced exposure to freezing temperatures. Thir...

Disaggregating sorghum yield reductions under warming scenarios exposes narrow genetic diversity in US breeding programs

“…We find that an additional DD above 33°C is associated with a 1.3% yield reduction (SI Appendix, Table S4). This extreme heat threshold is above ones identified for corn (29°C) and soybeans (30°C) but similar to ones identified for cotton (32°C), rice (33°C), and wheat (34°C) (20)(21)(22).…”

“…As discussed in ref. 22, the management practices for the Kansas field trials vary by location and year and are considered "best management practices" as they are designed to eliminate all yield-reducing factors such as nutrient deficiencies or toxicities, damage from insect pests and disease, and competition from weeds. These optimal growing practices potentially differ from the production practices of actual farmers, who base management decisions on profitability.…”

Vulnerability of grain crops and croplands in the Midwest to climatic variability and adaptation strategies

“…These projections for wheat are similar to the 5.3% yield reduction per 1°C observed in Australia by Innes et al (2015) using a combination of experimental results coupled with simulation models. Tack et al (2015), using historical yield trials and meteorological data for Kansas, found a combination of freezing and warming impacts were responsible for yield variations. They observed a 40% reduction in wheat yields with a 4°C temperature increase and that newer varieties were less able to resist heat stress above 34°C than older varieties.…”

Indicators of climate change in agricultural systems

“…Warming temperatures decreased USA wheat yields as observed by Tack et al (2015) using historical yield trials and meteorological data for Kansas. They used a combination of freezing and warming impacts in their regression model to evaluate yield trends and variation among years.…”