Roughly 9.1 million tonnes of plastic waste will head from land to sea this year alone in 192 coastal countries worldwide.

The latest study published this week in Science from researchers at the University of Georgia and the National Center for Ecological Analysis and Synthesis put a startling figure to a mounting environmental problem many have become familiar with in the past decade – the huge volume of plastic waste in the world’s waterways.

Now there’s a working scale for the mounting crisis. Jenna Jambeck, an environmental engineering professor at the University of Georgia and lead author of the report, argued people living within 50 kilometres of the coastline in these coastal countries are responsible for generating more than 275 million tonnes of plastic trash every year.

Of that, between 4.8 million and 12.7 million tonnes of plastic flow into the Atlantic, Pacific and Indian oceans, as well as to the Black and Mediterranean seas.

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“It was hard to wrap my head around that number,” said Jambeck of the eight-million-tonne average estimate the study uses. “I think envisioning it is challenging.”

Converting eight million tonnes into something people can comprehend, Jambeck calculated that the total input of plastic into the oceans every year is equivalent to encountering five retail shopping bags full of plastic trash for every foot of coastline. “When I did that conversion, I was shocked by the number,” she said.

The study is the first of its kind to attach a volume to the amount of waste flowing into the world’s oceans annually. Before that, Jambeck said, researchers could only rely on a 1975 estimate of the total volume of plastic intentionally introduced to the seas, whereas her study also analyses unintentional plastic flow. 

People living within 50 km of the coastline in coastal countries are responsible for generating more than 275 million tonnes of plastic trash every year.

It took three and a half years to complete the report and the flurry of media interest in the story has caught Jambeck slightly off guard. We were supposed to speak Wednesday afternoon, but an apologetic email told me she was waylaid by a TV interview with CBS News. When A\J finally caught up with Jambeck Wednesday evening on the phone from the American Association for the Advancement of Science conference in San Jose, she was near ready to collapse. “I think I’ve pretty much spoken to every major media outlet that I can think of,” she said with a laugh.

Part of the reason so much plastic waste is entering the oceans is inadequate management of waste worldwide mixed with old-fashioned litter. "This mismanaged waste goes uncaptured, meaning that it then becomes available to enter marine environments,” she said.

Once in the ocean, sea turtles, sea birds and whales have been known to ingest the plastic, which tends to fragment into smaller pieces over time. These micro-plastics easily make their way throughout the food chain.

A May 2012 report from Scripps Institution of Oceanography at University of California San Diego found the massive influx of plastic was changing marine habitats in profound ways. While some organisms, like water striders, have found the plastic flotsam a useful place to lay their eggs, fish species at intermediate ocean depths in the North Pacific Ocean ingest roughly 12,000 to 24,000 tonnes of plastic annually.

Many of the coastal countries studied have no formal waste management systems in place. However, it’s still possible to help reduce the volume of single-use plastic people generate.

"We need to prevent plastic from entering the oceans in the first place through better waste management, more reuse and recycling, better product design, and material substitution," said Roland Geyer, co-author of the report and an associate professor at University of California Santa Barbara’s Bren School of Environmental Science & Management.

Yet beyond these broad suggestions for improvement, Jambeck’s study won’t make specific policy recommendations. People react passionately to waste management because how we deal and think about waste has strong social and cultural ties, she told me.

“The way we [improve waste processing] is probably going to look very different from the way another country will,” she said.

Part of the reason so much plastic waste is entering the oceans is inadequate management of waste worldwide mixed with old-fashioned litter. 

And even in places that do adequately process waste, the volume of plastic generated per person is astounding. In the United States alone, the average American generates roughly five pounds of trash each day, with approximately 13 per cent of that being plastic. Researchers suggest the average volume of plastic making its way into the ocean every year is equivalent to all the plastic produced worldwide in 1961.

Once that plastic enters the ocean, it’s almost impossible to remove. "Large-scale removal of plastic marine debris is not going to be cost-effective and quite likely simply unfeasible," Geyer said.

A December 2014 paper published in PLOS One led by Marcus Eriksen from the Five Gyres Institute in Los Angeles argued that the total plastic in the world’s oceans is broken into more than five trillion pieces. This makes it “economically and ecologically prohibitive, if not completely impractical, to recover,” he argued.

“The sea surface is likely not the ultimate sink for plastic pollution,” Eriksen writes in his report. Sequestering the plastic in sediment after it settles is the next best removal option, he notes. But on its way to being interred in sediment the plastic pieces will cause “a myriad of biological impacts along the way.”

Kara Lavender Law from the Sea Education Association (and another co-author of the Jambeck report) said in a release that organizations like hers are only finding a small portion of the waste generated floating on the surface – between 6,350 and 245,000 tonnes of the eight million tonnes of plastic waste Jambeck believes are making it to the oceans and seas annually.

"This paper gives us a sense of just how much we're missing and how much we need to find in the ocean to get to the total,” Law said. “Right now, we're mainly collecting numbers on plastic that floats. There is a lot of plastic sitting on the bottom of the ocean and on beaches worldwide."

Andrew Reeves is the Editor-in-Chief of Alternatives Journal. Overrun, his book about Asian carp in North America, will be published in Spring 2019 by ECW Press. His work has also appeared in the Globe & MailSpacing and Corporate Knights. Follow him on Twitter.

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