Overseas plastic on Australian beaches set to rise

The Ocean Cleanup has published new modelling forecasting that plastic washing up on Australian beaches from overseas will rise from 440 tonnes in 2020 to about 850 tonnes a year by 2050 without intervention. The findings identify foreign river pollution as the main source of the increase.

The research is based on what the non-profit calls its Global River Model, which estimates plastic emissions from more than 200,000 watersheds and links them to an ocean dispersal model. It uses ocean circulation and wind data to track where debris ends up. The organisation evaluated the preliminary data against more than 440 field observations from over 40 rivers worldwide, including scientific studies, monitoring camera data, and measurements from its own river interception systems.

The analysis identifies Southeast Asia as the largest source of overseas plastic reaching Australia, contributing 170 tonnes, with Indonesia alone accounting for more than 110 tonnes. Island nations contribute a further 140 tonnes, with trade winds carrying debris towards the coasts of Queensland, New South Wales, and Victoria.

Other flows come from farther afield. South America contributes 90 tonnes and Africa 40 tonnes, according to the modelling, with plastic travelling across the Southern Ocean and neighbouring basins before reaching Australian shores.

The findings distinguish between imported marine debris and Australia's domestic litter problem. While the model estimates Australia's own rivers contribute 7 tonnes a year, separate CSIRO research found national coastal debris density fell 39 per cent over the decade to 2023, alongside a 16 per cent increase in surveyed areas with no debris.

That contrast suggests local clean-up and waste efforts have reduced Australian-sourced debris, while plastic entering the sea elsewhere is making up a growing share of what reaches the country's coastline. The Ocean Cleanup also pointed to earlier research it co-authored with the University of Western Australia and Minderoo Foundation, which found concentrations of plastic pieces per square kilometre in Ashmore Reef Marine Park comparable to those in the Great Pacific Garbage Patch.

Policy scenarios

The organisation modelled three scenarios for 2050 based on policy pathways aligned with the OECD Global Plastics Outlook. Under a business-as-usual scenario, overseas plastic reaching Australia would rise to around 850 tonnes a year.

Under a regional ambition scenario, in which wealthier countries move faster and adopt stronger measures, the total would reach more than 570 tonnes. Under a global ambition scenario based on rapid, coordinated action, the figure would fall to around 300 tonnes.

The scenarios are intended to show how interventions in upstream countries could affect the amount of plastic landing on Australian beaches. The model can also estimate reductions linked to improved waste collection in specific countries, the group said.

Boyan Slat, Founder & CEO of The Ocean Cleanup, said: "Australians are doing a great job of cleaning up their own coastline, but none of that local effort can prevent the arrival of plastic from rivers in other countries. This is the share of plastic pollution that is growing the fastest, and so it is the share that makes the most sense to target.

"This problem is solvable and with ambitious public and private partnerships we can accelerate action in Southeast Asia. This includes leveraging Australian and Pacific expertise in science, technology, and the circular economy, alongside funding streams, to accelerate action in Southeast Asia, where much of the region's plastic emissions originate."

Cross-border flows

The study adds to a growing body of work examining how marine plastic travels across national boundaries, raising questions for governments about how to direct funding and cooperation. For Australia, the figures indicate that a significant share of coastal debris may increasingly depend on waste management systems, river controls, and collection efforts beyond its borders.

Laurent Lebreton, Head of Research at The Ocean Cleanup, said: "We've known for years that plastic crosses borders; what this model adds is the arithmetic. We can now estimate how much less plastic lands on an Australian beach if a particular country upstream improves its waste collection, which means funding decisions can be argued on numbers.

"The future state of Australian beaches in 2050 can be determined now. Through collective national and regional action across Asia and the Pacific, we can all have clean beaches and safeguard our marine environments for people to enjoy in the future."

The Ocean Cleanup has collected more than 62 million kilograms of trash from aquatic ecosystems worldwide and now operates in 13 countries with a team of about 200 people.