Muons penetrate much further than X-rays, they do essentially zero damage, and they are provided for free by the cosmos.
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Edited by Maureen L. Cropper, University of Maryland, College Park, MD, and approved April 20, 2015 (received for review August 7, 2014)
Significance
This study provides insights for wheat breeding efforts, public policy, and agricultural decision making related to climate change. Our findings provide opportunities for the international wheat breeding community to intensify research efforts to increase resistance to heat stress during focused developmental stages. These efforts could result in net positive warming effects since reduced exposure to freeze was found to be a yield-enhancing benefit of warming. Our results indicate that advancements in heat resistance could come at the expense of higher average yields, and that there is currently limited scope for producer adaptation through alternative variety selection. Our results also suggest that irrigation could help mitigate the effects of warming, which has implications for policies focused on the conservation of increasingly scarce water resources.
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.
Footnotes
- ↵1To whom correspondence should be addressed. Email: tack{at}agecon.msstate.edu.
Author contributions: J.T., A.B., and L.L.N. designed research; J.T. and A.B. performed research; J.T. and A.B. contributed new reagents/analytic tools; J.T. and A.B. analyzed data; and J.T., A.B., and L.L.N. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1415181112/-/DCSupplemental.
Warming effects on US wheat yields
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