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

climate change for many countries–it aggravates the impact for 63 countries (1.3 billion peo- ple), but mitigates it for 81 countries (2.8 billion people). For example, Saudi Arabia experi- ences a –23% domestic production impact under 2˚C warming, but this decreases to a consumption impact of –4.7%. In contrast, imports worsen climate impacts for Canada (– 5.7% domestic production impact worsens to –6.9% consumption impact). Finally, for the most populous countries, China and India, consumption impacts are comparable to domestic impacts owing to their low import dependence for the three crops. We find that the effect of trade in mitigating climate impacts is muted under lower warming (S3 Fig). Under +1˚C warming, the number of countries for which trade mitigates climate impacts reduces to 66 (2.3 billion people exposed) and aggravates increases to 78 (1.5 billion people exposed). Cross-border effects vary considerably by crop and countries Our decomposition results show that the factors determining cross-border effects vary consid- erably by crop and countries (Fig 2). The cross-border effect is interpreted as the impact on an average calorie of food consumed by a certain country compared with impact on a calorie of food produced for domestic-use by the same country. Positive values suggest impact on an average calorie consumed is less than impact on average tonne produced. Overall, beneficial cross-border effects are highest for wheat, both in magnitude and in terms of number of coun-

tries. Over 70% of countries have positive cross-border effects for wheat, with only a few (18 out of 161) having negative effects larger than 2%. The cross-border effects for maize are oppo- site to wheat. Most countries (except thirty-seven) have detrimental cross-border effects with over one third of large magnitude (greater than 2%). For rice, the cross-border effects are low in magnitude. We decompose the cross-border effect into import dependence and the difference between import and production impacts (see methods section). We find the import dependence is highest for wheat, with most African and South Asian countries highly reliant on wheat imports. Both maize and rice have smaller import dependence compared to wheat (S2 Text). For import dependent countries, the difference between import and domestic production impact drives the cross-border effect (Eq 11; Fig 2). With wheat, cross-border effects are largely positive for South Asian countries (Malaysia, Indonesia, Vietnam) due to a positive difference between import and domestic production impacts. Whereas, some east African countries (Uganda, Tanzania, Kenya) and east Asian countries (Japan, North and South Korea) have similar import dependence but find a negative difference between import and domestic production impacts. In the case of maize, for which yields of wheat, maize, and rice to future warming) (x-axis, S4 Fig) to the consumption impact on calorie supply i.e., climate impacts on both domestic and overseas supplying regions (y-axis, S4 Fig). Positive impact values suggest more

calories are projected to be available because of warming and negative impact values suggest fewer calories are projected to be available. Climate impact is aggravated when consumption impact increases the detrimental effect (lower loss to higher loss or gain to loss) or decrease the beneficial effect of climate change (from higher gain to lower gain) on the total calorie supply i.e., consumption impact is worse than domestic impact. Climate impact is mitigated if the opposite is the case, i.e., consumption impact decreases the detrimental impact (higher loss to lower loss) or increase the beneficial impact (lower gain to higher gain or loss to gain) on the total calorie supply. No effect on climate impact is considered when domestic impact and consumption impact are close to each other, where close is defined based on the lowest 5th percentile of the shortest distance between each point on the plot and the 1:1 line. The color of the data points corresponds to the World Bank income classification for the corresponding year and the size of the data points are scaled to 2010 national populations. Top panel (inset): We show the percentage of countries under each income class for which climate impacts are aggravated, mitigated, and shows no change under consumption impact. Bottom panel: The map shows the countries for which climate impact is mitigated (blue), aggravated (orange), and has no effect (white) on food supply for the three crops aggregated. For countries in gray, the impact estimates are

not included. The map is generated using R version 4.2.1 and shapefiles sourced from the NaturalEarth project (naturalearthdata.com). https://doi.org/10.1371/journal.pone.0314722.g001 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 7 / 16