Current food trade helps mitigate future climate change impacts in lower-income nations

expected to experience yield losses, has a strong aggravating impact on Japan, Central Ameri- can countries, and a few Caribbean islands. These regions rely on the USA for over 50% of their calorie supply (indicated by the size of the bubbles in S6 Fig). In contrast, Argentina, Aus- tralia, and Canada mitigate impacts for most of the countries that depend on them (except for Malaysia and Peru in the case of Argentina, and Ecuador in the case of Canada). We also find certain countries are heavily dependent on multiple mega-exporters for a substantial portion of their calorie supply, which can either significantly aggravate or mitigate climate impacts (S7 Fig and S3 Text). Additionally, we examine the role of mega-exporters separately for wheat, maize, and rice, finding that their impact transmission varies across these three crops (S4 Text; S8–S10 Figs). Discussion Transforming food systems to be resilient to supply disruptions from climate change requires resilience-building at multiple scales–at the farm scale by employing climate-resilient agricul- ture practices [34–36], but also at the national scale by managing reserves and trade portfolios [12]. In this paper, we examined how imports mediate the climate impacts on national food supply. We found that under 2˚C future warming, imports largely mitigate impacts on food supply for low- and low medium income countries. For example, the climate impact on food supply is mitigated for Sudan when imports are incorporated into impact assessment. This is

due to its high import dependence on Australia and Germany (mega-exporters), both of which have projected increases in wheat production under future climate change. On the contrary, imports aggravate climate impacts for Japan as a result of its high dependence on the USA, a mega-exporter expected to face negative climate impacts. Our findings are consistent with an alternative definition of national consumption which does not exclude exports as it is considered to be within a nation’s control, for example, through an export embargo (S5 Text; S11 Fig). While our results consist of multiple sources of uncertainties, we evaluated one source of uncertainty based on the variation in impact esti- mates (20th and 80th percentile) across the sixty climate-crop model impact estimates. We find a larger variation in our climate impact estimates across these confidence intervals for a given degree of warming, compared to variation across the degrees of warming for a particular confi- dence interval (S3 Fig); these results reflect the findings of other studies that variation in yields simulated by different crop and climate models (which define our confidence intervals) for any given level of warming are greater than variation due to levels of warming [24, 37]. Our analysis examined climate impacts on calorie availability. But economic considerations may add further complexity to this picture. The economic status of countries, geographic dis- tribution of climate impacts on crop yields, and the geographic structure of the global trade

network determines winners and losers from increased global prices caused by natural or human-made production shocks [19]. High-income countries are generally better positioned to withstand price shocks from supply disruptions. More importantly, a rise in global prices benefits exporters of that commodity and hurt importers through changing “terms of trade” [19]. For example, supply disruptions from the ongoing Ukraine-Russia war, along with vari- ous compounding challenges, benefited other exporters (for example, wheat farmers of the USA) while import dependent (especially low and lower middle-income) countries battled high food prices to procure sufficient food [38]. Thus, it is critical to consider risks from both the availability and accessibility of food to design effective policies against food supply disrup- tions. This emphasizes the need for import-dependent countries to find a good balance between improving domestic food production capacity and diversifying their import portfolios to become more resilient to climate change. However, the capacities of countries to do so PLOS ONE Current food trade helps mitigate future climate change impacts in lower-income nations PLOS ONE | https://doi.org/10.1371/journal.pone.0314722 January 3, 2025 11 / 16