The plastic cycle: a watershed-scale model of plastic pools and fluxes

Research on plastics in global ecosystems is rapidly evolving. Oceans have been the primary focus of studies to date, whereas rivers are generally considered little more than conduits of plastics to marine ecosystems. Within a watershed, however, plastics of all sizes are retained, transformed, and even extracted via freshwater use or litter cleanup. As such, plastic litter in terrestrial and freshwater ecosystems is an important but underappreciated component of global plastic pollution. To gain a holistic perspective, we developed a conceptual model that synthesizes all sources, fluxes, and fates for plastics in a watershed, including containment (ie disposed in landfill), non-containment (ie persists as environmental pollution), mineralization, export to oceans, atmospheric interactions, and freshwater extraction. We used this model of the plastic cycle to illustrate which components have received the most scientific attention and to reveal overlooked pathways. Our main objective is for this framework to inform future research, offer a new perspective to adapt management across diverse waste governance scenarios, and improve global models of plastic litter.

Automated summary

Research on plastics in global ecosystems is rapidly evolving, with oceans being the primary focus and land and freshwater ecosystems often overlooked. A conceptual model was developed to synthesize the sources, fluxes, and fates of plastics in a watershed, highlighting both the components receiving the most attention and the pathways that have been overlooked.