Targeted opportunities to mitigate water scarcity, inequality, and inequity embedded in international food trade for vulnerable countries.

International food trade reshapes regional water scarcity through virtual water transfers (VWT), influencing water use equality and equity. This study examines eight populous yet impoverished countries in Africa and Asia, representing 30 % of the global poor population and contributing 20 % to agricultural VWT. Despite their significant role, these countries have been understudied due to a lack of data or attention. By integrating multiple datasets and models, we assess how international food trade impacts water scarcity, inequality, and inequity within these countries and identify the driving factors. Our findings reveal varied outcomes: Uganda and Ethiopia benefit from reduced water scarcity (∼40 % and ∼7 %) and improved equality and equity (∼90 % and ∼68 %), while India and Pakistan face exacerbated scarcity (∼4 % and ∼2 %) and widening inequality and inequity (∼4 % and ∼7 %). The effects are largely driven by critical trade flows of staple and cash crops like rice, sugar cane, and cotton among developing countries, propelled by comparative advantages in agricultural production, econo-geography, food demand, and water endowment between importers and exporters. Addressing these water challenges involves diversifying import channels to reduce reliance on detrimental trade flows, such as India's rice exports to Iran, while promoting beneficial flows, like Bangladesh's cotton imports from India, through trade agreements. Additionally, implementing pro-poor water policies (e.g., providing water subsidies) and water-saving techniques (e.g., adopting drip irrigation) is crucial, though caution is needed to avoid unintendedly marginalizing vulnerable groups through large-scale water projects.