Plastic pollution is a planetary threat, affecting nearly every marine and freshwater ecosystem globally. In response, multilevel mitigation strategies are being adopted but with a lack of quantitative assessment of how such strategies reduce plastic emissions. We assessed the impact of three broad management strategies, plastic waste reduction, waste management, and environmental recovery, at different levels of effort to estimate plastic emissions to 2030 for 173 countries. We estimate that 19 to 23 million metric tons, or 11%, of plastic waste generated globally in 2016 entered aquatic ecosystems. Considering the ambitious commitments currently set by governments, annual emissions may reach up to 53 million metric tons per year by 2030. To reduce emissions to a level well below this prediction, extraordinary efforts to transform the global plastics economy are needed.

Marine plastic pollution has emerged as one of the most pressing environmental challenges of our time. Although there has been a surge in global investment for implementing interventions to mitigate plastic pollution, there has been little attention given to the cost of these interventions. We developed a decision support framework to identify the economic, social, and ecological costs and benefits of plastic pollution interventions for different sectors and stakeholders. We calculated net cost as a function of six cost and benefit categories with the following equation: cost of implementing an intervention (direct, indirect, and nonmonetary costs) minus recovered costs and benefits (monetary and nonmonetary) produced by the interventions. We applied our framework to two quantitative case studies (a solid waste management plan and a trash interceptor) and four comparative case studies, evaluating the costs of beach cleanups and waste-to-energy plants in various contexts, to identify factors that influence the costs of plastic pollution interventions. The socioeconomic context of implementation, the spatial scale of implementation, and the time scale of evaluation all influence costs and the distribution of costs across stakeholders. Our framework provides an approach to estimate and compare the costs of a range of interventions across sociopolitical and economic contexts.

Ensuring the security of ocean ecosystems that provide food and livelihood benefits from seafood systems requires significant investment in improving the sustainability of fisheries and aquaculture production at scale. Seafood certification and ratings systems have established strong benchmarks for sustainability, but markets need to incentivize sustainability throughout the value chain and at relevant ecological scales in order to generate meaningful conservation impacts and support lasting on-the-water stewardship efforts. Here, we propose that market-based approaches and ecosystem-based governance initiatives can be integrated to improve the sustainability of seafood production systems using a jurisdictional approach. Jurisdictional approaches are place-based initiatives deployed in key commodity producing regions to drive sustainability through aligned incentives among government, market, and producer actors. To explore the applicability of this approach in seafood, we first identify key mismatches in existing certification and ratings schemes that stymie the effectiveness of market-based approaches to drive ecosystem-scale impacts. Subsequently we identify the differentiated incentives for sustainability among producers, supply chain companies, and governments-drawing evidence from research and practice. Based on this analysis, we review the potential for jurisdictional approaches to align actors' incentives for sustainability at the scale of entire production geographies, bringing market-based approaches and governance improvements together to achieve conservation outcomes.

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Coastal communities, Indigenous peoples, and small-scale fishers are intimately connected with the ocean. Yet, these historically and structurally marginalized groups often bear a disproportionate distribution of coastal and marine harms, and are culturally and politically excluded from marine decision-making. In response, calls for blue justice are emerging. Here, we review key perspectives, new developments, and gaps in the emerging blue justice scholarship. We also synthesize existing case studies of blue injustices and review some of the many successful examples of grassroots resistance efforts to help define what blue justice entails. We aim to help centre the knowledge, strength, and agency of coastal communities responding to blue injustice. Ultimately, concerted efforts are needed by all to support and empower coastal communities to reject blue injustices and to achieve their diverse aspirations for blue justice.