Agricultural trade externalizes belowground ecosystem loss to climate-stressed exporting nations

International agricultural trade redistributes environmental burdens across borders, yet one cost remains unquantified: the loss of belowground ecosystem multifunctionality (BEMF) in producing nations, and the degree to which climate warming amplifies it. We provide the first global quantification of trade-embodied BEMF loss, coupling 15 soil biological and biogeochemical indicators with the FABIO multi-regional input-output framework (155 matched exporting nations, 123 commodity sectors) and CMIP6 projections under three emissions scenarios to 2100. International trade embodies 14.7% of global cropland BEMF production. Thermally stressed exporters (mean annual temperature > 16.4°C) sustain 37% lower per-hectare BEMF than climatically stable exporters, yet direct a larger share of their production into trade (18.1% vs 10.8%), so supply chains draw disproportionately on the most ecologically depleted regions. Export-driven hotspots concentrate in Brazil, Sudan, India, and Eswatini, with the Brazil-to-China soybean corridor the single largest transfer. Projected global BEMF declines range from 6.2% under low emissions to 14.5% under high emissions by 2100, with the steepest zonal loss (23.8%) in currently cooler regions sitting on the steep portion of the temperature-BEMF curve. The ecological cost of an agricultural import therefore depends not only on what or how much is traded, but on where and under what thermal conditions it is grown. We argue for integrating belowground indicators into consumption-based accounting and applying a Climate Exacerbation Factor within climate-adjusted supply chain governance aligned with the Kunming-Montreal Global Biodiversity Framework.