Tracing Plastic Pathways: A Global Perspective on Its Fate and Transport Along River Corridors

Plastic pollution threatens the health of humans and aquatic and terrestrial ecosystems worldwide. Addressing this threat with effective strategies and solutions requires a clear understanding of the processes that control the fate and transport of mismanaged plastics at various scales, from watersheds to regions and even continents. River corridors serve as dominant pathways and traps for mismanaged plastic generated within the landscape, which eventually reaches the ocean. In this work, we examine the main sources of plastic pollution globally and share findings from a new flow and transport model for plastic waste in riverine environments. Our results show that only about 0.25% of the mismanaged plastic entering rivers since the 1950s is expected to reach the ocean by 2100, with most plastic being stored in freshwater ecosystems. Patterns of plastic buildup and how long it stays depend heavily on (i) topology and geometry of the river network and (ii) the position and trapping efficiency of flow regulation structures, especially large dams. Our model highlights the crucial role of rivers as significant sinks for plastic waste and emphasizes the importance of targeted remediation strategies that consider river network structure and human-made controls when designing interventions and sampling plans. These measures can help maximize benefits and set realistic expectations.