A mess of plastic: It is not clear what strategies will be most effective in mitigating harm from the global problem of plastic pollution. Borrelle et al. and Lau et al. discuss possible solutions and their impacts. Both groups found that substantial reductions in plastic-waste generation can be made in the coming decades with immediate, concerted, and vigorous action, but even in the best case scenario, huge quantities of plastic will still accumulate in the environment. Science , this issue p. 1515 , p. 1455

The ecological and societal impacts of plastics production, use, and waste are a complex global challenge. Management strategies to mitigate the impacts of plastics, such as recycling, waste-to-energy, and replacement with alternative materials have impacts of their own. Achieving long-term sustainability of plastics use therefore requires considering the externalized impacts of such management strategies. Here, we assessed the literature on the most common plastic waste management strategies to identify their impacts in relation to the sustainable development goals. We reviewed impacts of bans, levies, and taxes; alternative products; recycling; waste-to-energy; plastic recovery; and extended producer responsibility. Our analysis identified a total of 259 measured impacts of plastic waste mitigation strategies, from 113 papers. Ninety-three impacts were negative, 104 were positive, 11 were neutral, and 51 depended on the context of implementation. Consideration of the impacts of both plastic materials and management strategies is necessary to avoid perverse outcomes of plastic pollution mitigation efforts.

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.

Plastic ingestion has been documented in nearly 1,300 marine species, including every seabird family, marine mammal family, and sea turtle species. Acute mortality, due to obstruction, perforation, or torsion of the gastrointestinal (GI) tract, has been confirmed via necropsy in all three taxa; however, quantitative risk assessment for macroplastic ingestion poses unique challenges, with risk more dependent on probability of discrete events involving diverse plastic types rather than cumulative exposure models (e.g., LC ₅₀ ). We model mortality risk associated with macroplastic ingestion in seabirds, marine mammals, and sea turtles, using data from more than 10,000 necropsies reported in the academic literature and stranding network databases. Employing an adapted Weibull Accelerated Failure Time model, we assess the relationship between the GI load (pieces and volume/animal length) of different plastic types—hard, soft, rubber, or fishing debris—and likelihood of plastic-induced mortality. Overall, 35% of seabirds, 12% of marine mammals, and 47% of sea turtles ingested plastic, and 1.6%, 0.7%, and 4.4% died from plastic, respectively. When modeling plastic together, a 90% chance of mortality was associated with 23 pieces (0.098 cm ³ /cm) in seabirds, 29 pieces (39.89 cm ³ /cm) in marine mammals, and 405 pieces (5.52 cm ³ /cm) in sea turtles (377 for juveniles). The plastic types that posed the greatest risks were rubber for seabirds, soft plastics and fishing debris for marine mammals, and hard and soft plastics for sea turtles. This research furthers scientific understanding of the likelihood of mortality from plastic ingestion and can inform monitoring, risk assessments, and management frameworks.