Halting plastic flows into oceans by 2050 may not stop…

Halting new marine plastic inputs by 2050 is the core objective of the Osaka Blue Ocean Vision, which was shared and endorsed alongside the G20 Implementation Framework for Actions on Marine Plastic Litter. However, stopping new plastic inputs will not remove existing marine debris, which can gradually fragment into microplastics that are difficult and costly to remove. Source reduction must therefore be accompanied by cleanup of legacy plastic debris.

To investigate this, professor Takuro Uehara of the College of Policy Science at Ritsumeikan University in Japan collaborated with Dr. Mateo Cordier of Université de Versailles-Saint-Quentin-en-Yvelines—Université Paris-Saclay in France and Laurent Lebreton of The Ocean Cleanup in the Netherlands.

They developed a system dynamics model examining the physical and economic effort required to address initially buoyant marine plastic debris by 2050. Their findings were published in the journal Communications Earth & Environment .

The model simulates the transport, degradation and cleanup of macroplastics and their breakdown into microplastics across shoreline, coastal and offshore zones.

"The framework is designed to look at marine plastic pollution as a dynamic problem rather than a one-time cleanup challenge," Uehara said.

"By linking plastic inputs, the movement and breakdown of debris, cleanup timing and location, and the associated costs, it allows us to explore which combinations of prevention and cleanup could be both environmentally effective and economically realistic. This provides a basis for more informed decisions about where and when cleanup efforts should be prioritized."

Testing cleanup against source reduction

The model followed the transport and degradation of macroplastics and their breakdown into microplastics across shorelines, coastal waters and offshore areas. The researchers tested seven scenarios combining different pathways for reducing plastic inputs with different approaches to cleanup.

In scenarios aimed at stopping plastic at its source, inputs were progressively reduced from 2026 until reaching zero by 2050. The model then compared cleanup strategies to assess how the timing and intensity of these measures could influence the amount of plastic remaining in the ocean.

Legacy plastic persists after prevention

The modeling showed that halting plastic inputs by 2050 could reduce the cumulative amount of plastic entering the ocean between 1950 and 2050 by 51.4% compared with the business-as-usual (BAU) scenario. However, stopping new inputs alone did not resolve the legacy of plastic already in the ocean. Without cleanup, microplastics were projected to make up 58.4% of accumulated plastic by 2050.

Cleanup without source reduction was also insufficient. For example, delayed cleanup under BAU resulted in approximately 10,319 kt of microplastics remaining in the ocean by 2050, compared with 10,146 kt under source reduction combined with delayed cleanup. All cleanup scenarios focused on removing macroplastics, leaving microplastics unaddressed.

Among the full-cleanup strategies combined with source reduction, accelerated cleanup resulted in the least plastic debris remaining by 2050. Under Scenario 4, which combined source reduction with delayed cleanup, approximately 10,168 kt of plastic remained by 2050. This decreased to 8,824 kt under constant cleanup and 7,312 kt under accelerated cleanup.

Earlier cleanup limits fragmentation

The findings highlight the importance of timing when initiating marine plastic cleanups. Accelerating the removal of legacy plastic while concentrations are still high is the most ecologically effective strategy. Early intervention prevents larger items from fragmenting into microplastics , which current large-scale technologies cannot recover efficiently.

However, faster cleanup is associated with substantially higher costs. Delaying full cleanup costs an estimated average of €1.0 billion annually, whereas accelerating cleanup between 2026 and 2050 drives costs up to €3.4 billion per year. Offshore operations are more expensive than shoreline cleanup. Furthermore, as cleanup operations deplete plastic concentrations, the unit cost increases over time.

Cleanup cannot replace prevention

The study was motivated in part by the scale of the marine plastic problem and the lack of research examining whether the physical and financial effort needed to address it would be feasible. Uehara said, "The scale of marine pollution demands more than just better cleanup strategies. Relying on massive recovery efforts to balance out unchecked plastic waste is a structurally unsustainable solution."

Preventing plastic waste from entering the environment must remain a priority. Upstream measures, including cutting plastic production, curbing consumption, improving waste collection and upgrading recycling infrastructure, are essential. Industries also play an important role and must reevaluate traditional manufacturing limits, targeting sustainable levels of plastic production.

Overall, the findings suggest that stopping plastic at its source and addressing legacy debris are complementary strategies.

While halting new inputs by 2050 is essential, earlier removal of legacy macroplastics can reduce the amount of plastic available to fragment into microplastics, although substantial microplastic accumulation is still projected. The results therefore highlight the need to combine source reduction with strategically targeted cleanup while considering the financial and environmental costs of different approaches.