Davis, California, USA
May 15, 2017
A wheat field in Provence, France, is almost ready for harvest. (republica/getty images photo)
- Weather and yield data span 1950 to 2015
- Flexible model considers temperature extremes, not just averages
- Possible rainfall increases wouldn’t make up for warmer temperatures
Climate change will likely cause wheat and barley yields to decline by 17 to 33 percent by the end of the century, predicts a new statistical model developed by researchers at the University of California, Davis, and Cornell University.
The study, based on 65 years of weather records and wheat and barley yield data from France, provides some of the first evidence of the negative effects of warming on wheat and barley yields in Western Europe. The findings are reported online in the journal Environmental Research Letters.
The study is of particular importance because wheat is the most widely grown crop in the world and, along with rice, one of the top two sources of calories for human consumption.
“This is not to be interpreted as saying that yield will decrease regardless of any technological improvements that may be made in the future,” said co-author Matthew Gammans, a UC Davis graduate student working with Professor Pierre Mérel in the Department of Agricultural and Resource Economics.
“It does suggest, however, that climate change will lessen the rate of any yield improvements that will be achieved by technological advances,” Gammans said.
New statistical model for climate impacts
The new model, developed by Gammans, Mérel and Cornell economist Ariel Ortiz-Bobea, is one of the first flexible statistical models applied to wheat and other cereal crops. Model flexibility, allowing for extremely high or low temperatures to have very different effects than the average temperature, is important in understanding the true effects of temperatures on yields. This model was developed from data spanning 1950 to 2015.
The newly published study focused on three major crops: winter wheat, winter barley and spring barley, all of which are primarily watered by rainfall, rather than being irrigated. The winter crops are planted in the fall, lying dormant through the winter and then growing during spring and summer. Spring barley is planted in spring and grows through summer.
Key predictions
Based on the historical weather and yield data, the new model predicted that by the end of the century:
- Under the most severe warming scenario, yield declines will be 21 percent in winter wheat, 17.3 percent in winter barley and 33.6 percent in spring barley.
- The negative impacts of increased heat during climate warming won’t be offset by a decrease in extreme cold temperatures during winter.
- Possible increases in rainfall would help mitigate the effects of heat stress but would not be sufficient to offset the negative impacts of warming temperatures.
The model did predict that if technological improvements continue on their current trajectory, they could offset most of the negative effects of climate change. Such improvements could include new heat-tolerant crop varieties and improved farming methods.
“We now want to explore what role adaptation to climate change will play in mitigating negative impacts on yields of wheat, barley and other cereal grains,” Gammans said.
Agricultural data for this study was made available by the French Ministry of Agriculture.
Reference
Negative impacts of climate change on cereal yields: statistical evidence from France
Matthew Gammans, Pierre Mérel and Ariel Ortiz-Bobea
ublished 5 May 2017 • © 2017 IOP Publishing Ltd
Environmental Research Letters, Volume 12, Number 5
Abstract
In several world regions, climate change is predicted to negatively affect crop productivity. The recent statistical yield literature emphasizes the importance of flexibly accounting for the distribution of growing-season temperature to better represent the effects of warming on crop yields. We estimate a flexible statistical yield model using a long panel from France to investigate the impacts of temperature and precipitation changes on wheat and barley yields. Winter varieties appear sensitive to extreme cold after planting. All yields respond negatively to an increase in spring–summer temperatures and are a decreasing function of precipitation about historical precipitation levels. Crop yields are predicted to be negatively affected by climate change under a wide range of climate models and emissions scenarios. Under warming scenario RCP8.5 and holding growing areas and technology constant, our model ensemble predicts a 21.0% decline in winter wheat yield, a 17.3% decline in winter barley yield, and a 33.6% decline in spring barley yield by the end of the century. Uncertainty from climate projections dominates uncertainty from the statistical model. Finally, our model predicts that continuing technology trends would counterbalance most of the effects of climate change.
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