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

systems could be affected by changes in trade patterns and how those results could be miti- gated or amplified with the effects on crop yields due to a simultaneously changing climate. Our findings show that the global trade quantity of cereals decreases to almost half of the base- line quantity under the effects of global zero cereal import dependency across all regions, with much lower decreases in cereal production and consumption. Although the overall impact of this constraint is larger than climate change on cereal production and consumption, climate change has an important role in some regions such as the USA. The import dependency constraints for cereals will also affect production, consumption, and trade of non-cereal crops indirectly. Reducing import dependence will reduce regions’ domestic agriculture system sensitivity to fluctuations in the international agricultural supply chains. However, such changes increase the countries’ susceptibility to domestic shocks, such as drought or floods. These constraints also have the potential to negatively impact measures of economic well-being, including trade and producer revenues as well as food expenditures. Changes in domestic production due to import dependency constraints will also impact the level of agricultural inputs, such as land and water, potentially accelerating the scarcity in regional resources. Climate change impacts on agricultural yields will also influence these measures. In some cases, climate change and import dependency constraints slightly amplify each other, as in total irrigation water con-

sumption in the Middle East, which increases by 21% and 0.7% under ID and CC, respectively, but 22% under IC. In addition to the implications of the trade perturbations and climate change to agriculture, bioenergy, and water outcomes, there may be other potential far-reaching multi-sector out- comes that are not evaluated directly here and could be of interest in future studies. For exam- ple, the effects on ecosystems are not included in this study, while other studies have shown that agricultural trade may be positively correlated with deforestation [35–37]. This could also have an impact on ecosystem carbon storage, net emissions, and biodiversity [38]. For another example, industries involved in the production and distribution of agricultural inputs, such as seeds, fertilizers, pesticides, and machinery, may experience changes in demand and profits if farmers modify their crop choices or adjust their production practices in response to the trade perturbations and climate change. As shown by a previous study, international agricultural trade can significantly redistribute the global phosphorus (P) cycle, particularly due to con- sumption of P fertilizers [39]. A third example is the effect on the overall energy market and alternative energy investment options due to the fluctuations in biofuel production, a poten- tially important energy source in the future [40–42]. Synergies and tradeoffs were revealed as we systematically alter trade patterns and climate. While reducing import dependency could potentially lower the risk in situations of supply

chain disruptions, other region-specific costs and benefits differ across sectoral outcomes and the effects of climate change alter the relative changes. Further, in the real world, the relative impact of trade perturbations and climate change may differ depending on specific constraints and effects of climate change that are not modeled here. For instance, regional import depen- dency constraints may not be as extreme as those modeled in this study, where different regions would likely implement varying levels of import dependency extents for varying bas- kets of different agricultural commodities. The climate change impacts used here represent long-term averages of climate impacts on crop yields under a single climate model’s represen- tation of future change. The effects of inter-annual variability in weather shocks, such as droughts or floods, are likely to have sharper impacts on regional production than long-term climate averages, potentially changing the relative effects of disruption from supply chains compared to the disruption from domestic production losses. Thus, the real-world implica- tions will depend on which and to what degree countries act to reduce import dependency to combat uncertainty from supply chain disruptions and the local effects of climate change. 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 15 / 18