Estimating Market Implications from Corn and Soybean Yields Under Climate Change in the United States

The United States is one of the largest producers and exporters of corn and soybeans globally partly because of yields that are among the highest in the world. However, a changing climate could affect these yields, which could ultimately affect production and the availability of products for export. In this report, the authors estimate that U.S. corn yields could increase 3.1 percent and soybean yields could decrease 3.0 percent in 2036 relative to 2016, based on climate projections. These results are driven primarily by the increased frequency of periods of extreme heat and declines in precipitation in counties east of the 100th meridian part of the United States. These estimates are then used in a simulation model to explore the market implications from these yield projections, and those results indicate that these yield changes could affect U.S. production and ultimately trade. The estimated growth in U.S. corn yields increases corn production that could ultimately affect the amount of corn the United States has available to export. Holding yields in other countries fixed, the model indicates that U.S. corn exports increase 0.36 percent (the equivalent of $63 million). The decline in soybean yields decreases production, leading to a 1.17-percent drop in U.S. exports (the equivalent of $319 million) based on 2016 exports.美国是全球最大的玉米与大豆生产国及出口国之一，这在一定程度上得益于其位居全球前列的单产（yield）水平。然而，气候变化或对这类单产造成冲击，进而最终波及相关作物的总产量及可供出口的产品供应量。本报告中，研究团队基于气候预测（climate projections）估算得出：相较于2016年，到2036年美国玉米单产将提升3.1%，大豆单产则将下降3.0%。上述结果主要由美国西经100度经线（100th meridian）以东县域内极端高温时段频次增加及降水（precipitation）减少所主导。随后，研究团队将上述估算结果代入模拟模型，以探究单产预测变化所带来的市场影响，结果显示，单产变动可能会对美国的总产量及最终贸易格局产生影响。美国玉米单产的预计增长将推高玉米总产量，进而最终影响美国可供出口的玉米供应量。在其他国家单产保持不变的假设前提下，模型显示美国玉米出口量将增长0.36%，对应金额约为6300万美元。大豆单产下降则会拉低总产量，基于2016年的出口规模计算，美国大豆出口量将下滑1.17%，对应金额约为3.19亿美元。