Plastics at sea: Treaty design for a global solution to marine plastic pollution

Treaty design is a key determinant of success for environmental regulatory regimes. Well-designed treaties incentivise participation, reward compliance and deter non-compliance among the parties to the agreement. The design process can also positively affect interactions between states and help shift national perspectives and interests during negotiations. Based on treaty design evaluations of the Montreal and Kyoto Protocols, a review of existing measures to curb plastics at sea, and expert interviews, this study identifies seven treaty design elements likely to improve the success of a future legally binding mechanism to address marine plastic pollution. These include: a) the adoption of a principle of common but differentiated responsibilities; b) an adequate scope considering land- and sea-based sources, as well as chemical additives and all stages of the lifecycle of plastics; c) issue-linkage to international plastics trade; d) a financial mechanism to support implementation measures; e) built-in flexibility to adapt to changes; f) effective monitoring, reporting and review procedures; and g) enforcement through incentivising compliance and deterring non-compliance. Developed out of an inclusive treaty negotiation process, these elements can help overcome current governance challenges regarding the elimination of marine plastic pollution.