Global cereal trade under relaxed geopolitical frictions: distance-prioritized reallocation and implications for transport costs and CO2 emissions

Introduction Amid rising concerns over the fragility of global cereal supply chains under geopolitical tensions, infrastructure underutilization, and decarbonization pressures, this study examines how counterfactual reallocation can reshape the cost-emissions profile of international cereal logistics under transparent allocation rules. Methods The analysis combines bilateral cereal trade data with dyadic conflict information from the Uppsala Conflict Data Program (UCDP) to identify politically tense links during non-war periods. Missing route-mode freight costs are imputed using mode-specific regression models. A distance-prioritized, capacity-constrained sequential allocation rule then reallocates trade flows toward geographically proximate feasible partners subject to export-capacity and import-demand constraints, under a counterfactual benchmark of relaxed geopolitical frictions. Results Under this benchmark, 76 bilateral links that are inactive in the observed baseline receive positive trade volume. Aggregate transport work falls from 1.91 to 1.40 trillion ton-km, while system-wide emissions decline by approximately 21 to 70%, depending on the mode-assignment rule. Belt and Road Initiative corridors show larger proportional emissions reductions than the global average, whereas conflict-linked corridors experience distributional shifts in which their shares of system-wide costs and emissions can rise even when total emissions decline. Discussion The findings are best interpreted as scenario benchmarks that clarify how distance compression, modal composition, and corridor-level burden shifting jointly shape the efficiency and sustainability of global cereal logistics under relaxed geopolitical frictions.