Trade Imbalance and Environmental Cost of China-Vietnam Agricultural Trade from the Perspective of Cross-border Virtual Water Flows

Against the background of deepening RCEP regional integration and increasingly frequent bilateral agricultural trade between China and Vietnam, the resource and environmental externalities brought by cross-border agricultural trade have become a key constraint on the green and sustainable development of bilateral trade. Traditional trade research mostly focuses on economic scale, trade efficiency and tariff barrier effects, while ignoring the implicit water resource transfer and environmental cost imbalance behind agricultural commodity circulation. From the perspective of cross-border virtual water flows, this study takes the panel data of 28 subdivided agricultural product categories between China and Vietnam from 2015 to 2024 as the research sample, systematically measures the virtual water trade flow, structural imbalance characteristics and embodied environmental costs of bilateral agricultural trade, and constructs a multi-scenario simulation framework of collaborative water-saving policies. The results show that China-Vietnam agricultural trade presents a significant virtual water trade imbalance: China has long been a net importer of agricultural virtual water from Vietnam, and tropical characteristic agricultural products and aquatic products are the core carriers of cross-border virtual water transfer. In terms of environmental costs, the bilateral agricultural trade leads to asymmetric water resource pressure transfer, and Vietnam bears higher gray water environmental pollution costs due to large-scale agricultural product export, forming a “trade-economic gain and environmental cost mismatch” dilemma. Scenario simulation results indicate that single water-saving regulation has limited improvement effects on virtual water imbalance, while collaborative policies combining trade structure optimization, graded virtual water quota management and green trade supervision can effectively reduce bilateral agricultural virtual water waste and narrow the asymmetric environmental cost gap. This study expands the research perspective of green bilateral agricultural trade, clarifies the spatial-temporal evolution characteristics and environmental externality mechanism of cross-border virtual water flows, and provides empirical evidence and policy enlightenment for China and Vietnam to build a collaborative water-saving trade mechanism, balance trade benefits and water resource environmental costs, and promote the green upgrading of regional agricultural trade under the RCEP framework.