Future warming increases probability of globally synchronized maize production shocks

• Published in: Proceedings of the National Academy of Sciences - PNAS 2018-06, Vol.115 (26), p.6644-6649
• Main Authors: Tigchelaar, Michelle, Battisti, David S., Naylor, Rosamond L., Ray, Deepak K.
• Format: Article
• Language: English
• Subjects: Breeding; Climate; Climate change; Climate variability; Coefficient of variation; Commerce; Consumers; Corn; Crop production; Crop yield; Edible Grain - economics; Edible Grain - growth & development; Edible Grain - supply & distribution; Exports; Food; Food security; Food Supply - economics; Food Supply - statistics & numerical data; Forecasting; Global temperatures; Global Warming; Grain; Heat tolerance; Hot Temperature; Humans; Marketing; Physical Sciences; Plant Breeding; Poverty; Probability; Social Sciences; Stability; Temperature effects; Temperature tolerance; Volatility; Vulnerable Populations; Zea mays - growth & development
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1718031115

Meeting the global food demand of roughly 10 billion people by the middle of the 21st century will become increasingly challenging as the Earth’s climate continues to warm. Earlier studies suggest that once the optimum growing temperature is exceeded, mean crop yields decline and the variability of yield increases even if interannual climate variability remains unchanged. Here, we use global datasets of maize production and climate variability combined with future temperature projections to quantify how yield variability will change in the world’s major maize-producing and -exporting countries under 2 °C and 4 °C of global warming. We find that as the global mean temperature increases, absent changes in temperature variability or breeding gains in heat tolerance, the coefficient of variation (CV) of maize yields increases almost everywhere to values much larger than present-day values. This higher CV is due both to an increase in the SD of yields and a decrease in mean yields. For the top four maize-exporting countries, which account for 87% of global maize exports, the probability that they have simultaneous production losses greater than 10% in any given year is presently virtually zero, but it increases to 7% under 2 °C warming and 86% under 4 °C warming. Our results portend rising instability in global grain trade and international grain prices, affecting especially the ∼800 million people living in extreme poverty who are most vulnerable to food price spikes. They also underscore the urgency of investments in breeding for heat tolerance.