An ocean-focused technology non-profit, founded by an 18-year-old aerospace engineering university dropout, has released new modelling that traces plastic from over 200,000 river watersheds around the world to Australian beaches.
The non-profit is The Ocean Cleanup, which Boyan Slat founded in 2013 to rid the world's oceans of plastic. Its new forecast shows that, without further action, the overseas plastic washing onto Australian beaches will almost double by 2050, from 440 tonnes in 2020 to around 850 tonnes a year.
That figure comes from the organisation's “Global River Model” report, which estimates how much plastic each of those watersheds sends downstream, then follows it on ocean currents and winds to the beach where it lands.
To ensure the numbers hold up, The Ocean Cleanup tested the model against over 440 field observations from over 40 rivers globally, given the transboundary nature of the issue. Those observations include data from AI-powered river monitoring cameras, plastic flux measurements published in scientific literature, and readings from the Interceptors it uses to catch plastic in rivers before it reaches the sea.
Laurent Lebreton, The Ocean Cleanup's Head of Research, wrote the research, drawing on over 20 years in numerical modelling and physical oceanography. He said the model's value lies in the maths.
“We've known for years that plastic crosses borders; what this model adds is the arithmetic,” Lebreton said. “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.”
Indonesia leads a 440-tonne inflow
Speaking to the numbers, they show that most of that plastic comes from Australia's neighbours.
The model traces 170 tonnes of the 2020 total to Southeast Asia, with Indonesia alone contributing over 110 tonnes. Island nations add a further 140 tonnes, because limited waste-management capacity lets plastic escape to sea, where prevailing trade winds carry it to the beaches of Queensland, New South Wales, and Victoria.
The rest arrives from even further afield, with 90 tonnes crossing the Southern Ocean and neighbouring basins from South America and 40 tonnes from Africa.
Australia's own rivers, by comparison, add just 7 tonnes a year. With CSIRO research recording a 39 percent decrease in coastal debris around Australian coastal cities and local beaches getting cleaner, the bulk of the problem now arrives from offshore.
This is why Slat is adamant that Australia’s local problem requires effort that is focussed regionally.
“Australians are doing a great job of cleaning up their own coastline,” he said. “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.”
From a teenage dive to a $500 million river program
Slat's interest in ocean plastic began underwater.
He was 16, scuba diving in Greece, when he realised he was swimming past more plastic bags than fish. So in 2012 he took that image to a TEDx stage with a plan to rid the oceans of plastic using technology.
When the video went viral, he walked away from his aerospace engineering degree to build it.
The Ocean Cleanup launched the following year, and by 2014 its 20-year-old founder was accepting the United Nations Champion of the Earth award. Today the organisation employs approximately 200 people across 13 countries, and it reports that it had pulled over 62 million kilograms of rubbish out of rivers and oceans by September 2026.
In rivers, The Ocean Cleanup’s main tool is the Interceptor, a family of machines built around the fact that no two rivers share the same width, depth, or flow. The most advanced of them, the Interceptor Original, runs on solar power and uses an autonomous conveyor to lift rubbish out of the water and into onboard storage.
Scaling that technology takes money, and The Ocean Cleanup is fully reliant on donations from individuals, corporations, governments, and institutions.
In March 2026, donors to the Audacious Project committed about $174 million to its 30 Cities Program, which aims to cut up to a third of the world's river plastic emissions by 2030. The organisation has costed the program at about $500 million, which leaves most of the bill still to be raised.
The Global River Model now gives its much-needed funders a way to see what their money would change on Australian beaches.
850 tonnes or 300: Australia’s choice for 2050
How much those funders could change depends on what happens upstream, according to Lebreton’s research.
The Ocean Cleanup ran its model through three policy scenarios to 2050, consistent with the OECD's Global Plastics Outlook.
If the world stays on its current trajectory, overseas plastic reaching Australia climbs to around 850 tonnes a year. Strong policies from wealthier countries, on the other hand, would hold it to just over 570 tonnes. But rapid, globally-coordinated action could reverse the trend, pulling the figure back to around 300 tonnes.
That leaves about 550 tonnes a year between the best and worst of those futures, and Lebreton said the choice between them is being made now.
“The future state of Australian beaches in 2050 can be determined now,” Lebreton said.
“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.”
For Slat, closing that gap is where Australia comes in.
“This problem is solvable and with ambitious public and private partnerships we can accelerate action in Southeast Asia,” he said.
“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.”
A worthy effort if it means Australia can keep its cherished beaches clean.