Impact of Belt and Road Initiative trade facilitation on biofouling-mediated species spread risk

The spread risk of non-indigenous species (NIS) is a major concern for coastal ecosystems, particularly via biofouling, as it is not mandatorily regulated in most regions. Trade policies can influence the NIS spread risk by changing shipping activities. The Belt and Road Initiative (BRI) trade facilitation policy aims to enhance trade activities, but its impact on biofouling-mediated NIS spread risk, primarily driven by reduced port residence times and changes in trade-driven shipping traffic, remains unclear. Here, we integrate a computable general equilibrium model with a higher-order NIS spread risk assessment model to evaluate how BRI trade facilitation influences biofouling-mediated NIS spread risk. Our findings show that trade facilitation does not necessarily increase NIS spread risk, as shorter port residence times generally exert a dominant mitigating effect. Consequently, overall NIS spread risk declines in most countries, with increases observed in only five cases. At the bilateral level, 85% of country pairs experience a net reduction in NIS spread risk. Importantly, changes in trade volumes and NIS spread risk do not align for most countries, with over 80% of countries decoupling risk changes from trade growth, leading to positive economic and environmental outcomes. These results highlight that trade facilitation does not necessarily exacerbate risks when accompanied by improvements in port operational efficiency. Policymakers should prioritize reducing port residence times as an effective risk mitigation strategy in the context of trade development. Countries experiencing increased risks should incorporate targeted measures, such as optimizing trade structures and strengthening vessel inspections, into their trade policies.