Agriculture, bioenergy, and water implications of constrained cereal trade and climate change impacts

and Brazil results). Note that the Middle East region defined here covers not just large oil-pro- ducers but spans diverse countries from the eastern Mediterranean to the Persian Gulf (S2 Table in S1 File). Also, among the four regions, only Brazil has sugarcane ethanol production, while the three others have corn ethanol production, a cereal crop-based ethanol that is more directly affected by the cereal trade constraints. Although sugarcane is not a cereal crop, sugar- cane ethanol production and consumption are indirectly impacted by the global zero cereal import dependency. For discussion on the results of sugarcane ethanol across scenarios, please refer to SI. Ethanol results (both corn and sugarcane) across all GCAM regions are also shown in S7 and S8 Figs in S1 File. The following results are based on Tables 1 and 2 for the USA and Middle East, respectively. Non-cereal crop production, consumption, and trade. The effect of ID on USA non-cereal production is also negative as the effect on USA cereal production, though very small (<0.6%). This is due to two competing drivers. First, the relatively low cereal prices lead to an increase Table 1. Summary of key variable results in 2050 for the USA. The numbers in the parentheses indicate the percent change compared to RF. Numbers are rounded. Mt —Million tons. Key Variable of RF ID CC IC Import dependency ratio Cereals -23% 0% -21% 0% Production (Mt) Cereals 523 461 (-11.8%) 467 (-10.6%) 416 (-20.4%) Non-Cereals 348 346 (-0.6%) 343 (-1.5%) 340 (-2.3%)

All Crops 871 808 (-7.3%) 811 (-7.0%) 756 (-13.2%) Consumption (Mt) Cereals 424 461 (8.9%) 385 (-9.0%) 416 (-1.8%) Non-Cereals 324 306 (-5.2%) 340 (4.9%) 324 (0.0%) All Crops 747 767 (2.8%) 726 (-3.0%) 740 (-1.0%) Exports (Mt) Cereals 113 22 (-80.9%) 98 (-13.3%) 22 (-80.8%) Non-Cereals 110 123 (11.9%) 97 (-11.7%) 109 (-1.5%) All Crops 224 145 (-35.2%) 196 (-12.5%) 130 (-41.7%) Imports (Mt) Cereals 14 22 (53.7%) 16 (15.6%) 22 (54.7%) Non-Cereals 86 83 (-3.0%) 94 (10.4%) 92 (7.6%) All Crops 100 105 (5.0%) 111 (11.1%) 114 (14.2%) Net Trade Revenue (billion 2015$) Cereals 31.5 1.75 (-94.5%) 27.9 (-11.2%) 1.71 (-94.6%) Non-Cereals 12.7 19.8 (55.5%) 3.6 (-71.8%) 10.3 (-19.4%) All Crops 44.2 21.5 (-51.3%) 31.5 (-28.7%) 12.0 (-72.9%) Crop Producers’ Revenue (billion 2015$) Cereals 155 128 (-17.8%) 150 (-3.4%) 125 (-19.3%) Non-Cereals 200 198 (-1.1%) 208 (3.9%) 205 (2.4%) All Crops 356 326 (-8.4%) 358 (0.7%) 331 (-7.1%) Caloric Consumption (Kcal/cap/day) Cereals 1048 1075 (2.5%) 1044 (-0.4%) 1070 (2.1%) Non-Cereals 2701 2682 (-0.7%) 2687 (-0.5%) 2668 (-1.2%) Staples* 1142 1142 (0.0%) 1141 (0.0%) 1141 (0.0%) All Food 3749 3756 (0.2%) 3731 (-0.5%) 3738 (-0.3%) Food Expenditures as a share of GDP All Food 0.31% 0.30% 0.34% 0.33% Irrigation Water Consumption (km3) Cereals 42.4 36.2 (-14.5%) 37.7 (-11.1%) 32.5 (-23.3%) Non-Cereals 37.0 36.7 (-0.7%) 41.3 (11.7%) 41.0 (10.9%) All Crops 79.4 72.9 (-8.1%) 79.0 (-0.5%) 73.5 (-7.4%)

Ethanol Production (EJ) Corn 1.28 1.42 (10.4%) 1.05 (-18.1%) 1.15 (-10.0%) Corn Consumption for Ethanol (Mt) 143 158 (10.4%) 117 (-18.1%) 129 (-10.0%) Share of Corn Consumption for Ethanol 41.0% 42.5% 38.4% 39.9% *Staples include cereals as well as roots and tubers in our model. https://doi.org/10.1371/journal.pone.0291577.t001 PLOS ONE Agriculture, bioenergy, and water implications of constrained cereal trade and climate change impacts PLOS ONE | https://doi.org/10.1371/journal.pone.0291577 September 15, 2023 11 / 18