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

The combined effects of changes in quantity and price will impact other measures of well- being, including trade revenue, producer’s revenue, and consumer’s food expenditure. The direction of these impacts, and the extent to which climate change or trade perturbations impact regions are dependent on whether regions are net importers or exporters and how the yields of their major crops are expected to be affected by climate change. Net trade revenue and producer revenue. As a major cereal exporter in RF, USA experiences a decrease in net export revenue from cereals in ID, while increasing export revenue from non-cereal crops. The net effect of ID on total crop export revenue is negative, resulting in a roughly 50% loss relative to RF. In CC, trade revenue decreases for both cereal and non-cereal crops, but the total loss, roughly 30%, is smaller than that in ID. The combined effects in IC are large, with a loss in trade revenue of nearly 75%. In ID, the Middle East shows a 94% reduction in cereal net import expenditures. However, these are partially offset by increased trade expenditures for non-cereal crops, with a total reduction in crop trade expenditures of 42%. In CC, the revenue changes are very small, with slightly increased crop trade expenditures. In IC, changes in trade revenue are dominated by the effects of the cereal import dependency constraints. The effects of the import dependency constraint on USA producer revenue from cereals (-18%) are directionally the same as trade revenue (-94%), though only one-fifth as large.

While non-cereal trade revenue increases in ID, producer revenue from no-cereal crops has a slight decrease. In CC, USA cereal producer revenue decreases slightly, while total producer revenue increases slightly, driven by increased prices for non-cereal crops. As with trade reve- nues, the results in IC are similar to ID, as the trade perturbations is the dominant effect. In the Middle East, producer revenues from cereal crops increase in ID, CC, and IC, where reve- nues also increase for non-cereal crop producers. Caloric consumption and food expenditure. We also show caloric consumption from cereal, non-cereal, and staple foods, a category that includes cereals as well as roots and tubers. The category of staple foods provides relatively inexpensive, but often less nutritious calories than non-staples. The overall effects of trade perturbations on staple caloric consumption are small, less than 0.5% for both regions and all scenarios, where changes in cereal caloric consumption are offset by changes in other staple foods, reaching a net zero change in staple consumption. However, changes in prices also result in changes in non-staple consumption. The Middle East has reductions in total calories in CC, driven by reductions in non-staple consumption. The USA has a slight increase in total caloric consumption in ID, but decreases in CC and IC. Like producers, consumers are affected by the net impact of changes in both quantity and price. One measure of well-being is the food expenditure share of income (measured as

regional crop prices times food consumption, as a share of GDP). In the Middle East the food expenditure share increases due to both the trade perturbations and climate change, while in the USA it decreases in ID but increases in CC and IC. Overall, consumers in most cereal importing regions (in RF) are paying more for food in all scenarios than in RF. In scenarios where crop producer revenues decrease while food expenditures increase, the producers, who are also food consumers, would be financially worse off. However, in scenarios where crop producers’ revenues increase, the net effect is ambiguous for producers, as they have both higher revenues and higher food expenditures. Water consumption. In the water sector, the distribution of irrigation water consumption changes significantly, decreasing roughly 8% in the USA and increasing 21% in the Middle East due to the impact of cereal import dependency constraints. In the USA, irrigation water for non-cereal crops decreases slightly, associated with the decrease in non-cereal crop pro- duction in ID. In the Middle East, irrigation water consumption for both cereal and non- cereal crops increases, due to the need to intensify production in ID. In CC, irrigation water 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 13 / 18