Troubled waters – Where is the bridge? Confronting marine plastic pollution from international watercourses

A considerable volume of marine plastic pollution derives from watercourses, and many of the world's largest and most heavily polluted watercourses are international. In spite of the clear factual link between the utilization and protection of international watercourses and marine plastic pollution there is hardly any interaction between the legal sub‐fields of international water law and marine environmental law. This lack of interaction also reflects the absence of a global treaty, or even a shared global understanding, of the environmental threat from plastic pollution and the universal responsibility this generates also for landlocked States. This article investigates the possibilities for more integrated measures to prevent pollution of international watercourses and oceans, and argues that regimes within international water law and marine environmental law must cooperate to create awareness of the plastic pollution risk from watercourses and take steps to harmonize their legal rules and policies to contribute to the control and mitigation of marine plastic pollution. Regional coordination, such as improved cooperation between the regional seas organizations and river basin organizations, could provide a tool to better address transboundary sources of plastic. Potentially, such developments could be adopted to control marine plastic pollution from the most heavily polluted international watercourses.