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Global Crop Yield Response to Extreme Heat Stress under Multiple Climate Change Futures Delphine Deryng*,1,2, Declan Conway2, Navin Ramankutty3, Jeff Price1 and Rachel Warren1 *[email protected] 1Tyndall Centre for Climate Change, University of East Anglia, Norwich, UK; 2Grantham Research Institute on Climate Change & the Environment, London School of Economics and Political Science, London, UK; 3Liu Institute for Global Issues, University of British Columbia, Vancouver, Canada Figure 3 Global average yield trends simulated by PEGASUS under all 4 RCPs x 18 GCMs ensemble for maize, spring wheat and soybean. Thick lines represent median value across each set of simulations. Full lines are for simulations including both CO 2 fertilization effect and HSA (CC). Dotted lines are for simulations not taking into account HSA (CCw/o HSA) and dashed lines are for simulations with no CO2 fertilization effects (CCw/o CO2). Grey areas represent the range of global average yield estimates in the case of CC simulations. Context Extreme heat stress during the crop reproductive period (crop anthesis) can be critical for crop productivity. Projected changes in the frequency and severity of extreme climatic events are expected to negatively impact crop yields and global food production. This study applies the global crop model PEGASUS to quantify, for the first time at the global scale, impacts of extreme heat stress at anthesis (HSA) on maize, spring wheat and soybean yields resulting from 72 climate change scenarios for the 21st century. Figure 4 Boxplots of Y(%) simulated for RCP 8.5 x 18 GCMs for the 2080s relative to the 1980s among different income-level countries as defined by the World Bank: high income (HI), medium high income (MHI), medium low income (MLI) and low income (ML) levels for maize, spring wheat and soybean. The bottom and top of the box are lower and upper quartiles, respectively, the band near the middle of the box is the median value across each set of simulations, and the cross is the mean value. Figure 2 Barplots showing netproduction (left side) and relative change in production (right side) for RCP 8.5 by the 2080s among top-five producing countries for maize, spring wheat and soybean. The top of the bar stands for median value and whiskers show range for each data. Dashed red lines on the left plots show current level of production, circa the year 2000. Production is estimated using present-day harvested area.nd near the middle of the box is the median value across each set of simulations, and the cross is the mean value. Citation: Deryng et al. (2014) Global crop yield response to extreme heat stress under multiple climate change futures. Environmental Research Letters 9, 034011 (13pp) Heatwaves could threaten food crops, study warns Extreme temperatures could hit key crops such as maize, wheat and soybean if climate change not addressed Our results show that maize yields are expected to be negatively affected by climate change, while the impacts on wheat and soybean are generally positive, unless CO2 fertilisation effects have been overestimated. However, extreme heat stress reinforced by ‘business-as- usual’ reduces the beneficial effects considerably in wheat and soybean. A quarter of the positive impact on soybean production would be lost - while the benefit to wheat would be cut by 52% . Some of the largest areas likely to be affected by heatwaves are also important crop production, one example being the North American corn belt. Climate mitigation policy would help reduce risks of serious negative impacts on maize worldwide and reduce risks of extreme heat stress that threaten global crop production. © 2014 Guardian News Global impacts across different RCPs Impacts on top-5 crop producing countries Negative impacts of extreme heat-stress in all income economies Figure 1 Left: Maps of median Y(%) across the 18 GCMs ensemble for RCP 8.5 in the 2080s relative to the1980s for maize, spring wheat and soybean. Right: Maps of corresponding heat-stress index, representing intensity of crop yield reduction caused by extreme temperatures during the crop reproductive preiod. -100 -50 0 50 100 0 0.2 0.4 0.6 0.8 1 Heat-stress index Maize Soybean Spring Wheat % Yield
