Spatial Patterns of Crop Yield Change by Emitted Pollutant.

Field measurements and modeling have examined how temperature, precipitation, and exposure to carbon dioxide (CO) and ozone affect major staple crops around the world. Most prior studies, however, have incorporated only a subset of these influences. Here we examine how emissions of each individual pollutant driving changes in these four factors affect present-day yields of wheat, maize (corn), and rice worldwide. Our statistical modeling indicates that for the global mean, climate and composition changes have decreased wheat and maize yields substantially whereas rice yields have increased. Well-mixed greenhouse gasses drive most of the impacts, though aerosol-induced cooling can be important, particularly for more polluted area including India and China. Maize yield losses are most strongly attributable to methane emissions (via both temperature and ozone). In tropical areas, wheat yield losses are primarily driven by CO (via temperature), whereas in temperate zones other well-mixed greenhouse gases dominate. Rice yields increase in tropical countries due to a larger impact from CO fertilization plus aerosol-induced cooling than losses due to CO-induced warming and impacts of non-CO gasses, whereas there are net losses in temperate zones driven largely by methane and other non-CO gasses. Though further work is needed, particularly on the effects of aerosol changes and on nutritional impacts, these results suggest that crop yields over coming decades will be strongly influenced by changes in non-CO greenhouse gasses, ozone precursors, and aerosols and that these should be taking into account in plant-level models and when examining linkages between climate change mitigation and sustainable development.