Improving the Source-to-Sea approach for marine litter in Brazil

Combating marine litter pollution is a major challenge nowadays, and it is also one of the targets proposed by the Sustainable Development Goal 14. It is estimated that 8 million tons of plastic waste enter the ocean each year. And Brazil is the 16th leading contributor to this kind of pollution. This study draws a panorama of marine litter in Brazil under the Source-to-Sea approach, in four steps: (I) assessing the current research network, existing knowledge, and coupling between science and policy-relevant concerns; (II) analyzing solutions proposed by the literature on macrolitter in Brazil and evaluating their alignment with upstream approaches; (III) understanding the potentialities and limitations of subnational estimates of litter leakage to the environment; and (IV) identifying hotspots of leak-prone plastic waste (LPW) generation and leakage to the ocean. To map studies and research groups, we performed a systematic mapping of scientific articles on macrolitter in Brazil. To analyze solutions proposed by the literature, we compared solutions to the Waste Hierarchy, Sustainable Supply Chain Management, and Source-to-Sea approaches. To systematize parameters for modeling litter leakage to the environment, we performed a mapping of specialized literature and study of parameters, followed by data prospection for Brazilian municipalities and evaluation of data usability. To map hotspots of LPW generation and leakage to the ocean, we correlated sociodemographic data with solid waste and water network information; using data for all 5570 Brazilian municipalities and prioritizing data sources with better usability. The present study found 189 articles on marine litter in Brazil, of which 59 were focused on macrolitter. Macrolitter studies were mostly episodic and fragmented, and they adopted a variety of sampling collection and processing strategies. Moreover, studies were not well linked to policy-relevant concerns and the research network was not well-integrated. While most articles proposed solutions for marine litter (71.2%), few studies urged changes in the production chain and patterns of waste generation (10.2%), which are essential under the source-to-sea approach. Based on various links of the production-consumption-discard-pollution chain, we systematized solutions and proposed a Marine Litter Hierarchy. Furthermore, we identified 51 parameters that can be used to estimate litter leakage to the environment, including socio-economic, environmental, and sanitation information that well represents subnational particularities. For Brazil, only 29.4% of these parameters were linked to data sources with great or good usability, a fact that exposes the difficulties of performing estimates without access to good quality data. We also estimated that Brazil has potential to generate 3.44 million tons of LPW a year. We indicated the hotspots of greater potential LPW generation and leakage to the ocean, at the level of municipalities and watersheds, highlighting the Guanabara Bay, Patos Lagoon and Amazon, São Francisco and Tocantins rivers as main hotspots of litter entry into the ocean. Produced information provides a baseline for future studies, supports prevention and mitigation measures, and subsidizes plans for monitoring marine litter and managing solid waste, thus supporting the attainment of local, national, and international agendas to prevent and mitigate marine litter.