Beyond simply piling up along the coast, discarded plastics that end up in the ocean could also be a major source of greenhouse gas emissions, according to a study by a Canadian-led team of researchers from the University of Hawaii.
The team, which is led by Quebec native Sarah-Jeanne Royer, has garnered international attention ever since their findings were published in the American scientific journal PLOS ONE last week.
Royer said the researchers found that some types of common plastics emit greenhouse gases when they degrade, and that the phenomenon is intensified by sun exposure.
"Aided by solar radiation, the plastic will degrade and become microplastic, and the more the plastic breaks down into smaller pieces, the more it will produce greenhouse gases," the oceanographer told The Canadian Press in a phone interview.
"If we look at the last 70 years, all the plastic that has been produced is currently being degraded in the environment and producing greenhouse gases. So the longer we wait, the more (greenhouse gases) will increase exponentially."
Royer said the research is based on low-density polyethylene plastic that is found in food packaging or storage bags, as well as the plastic rings that hold soft drinks or beer cans.
Some 90 per cent of the debris discovered along the Hawaiian coast comes either from the fishing industry or from Asia, and washes up on the Pacific island due to ocean currents, she said.
"In Asia, they no longer have places to put waste and an incredibly high number of garbage will end up along the coast," she said.
"Afterward, the high tide arrives and brings all this waste to the ocean."
The Quebec-born oceanographer, who was previously based in Brazil, said she left that country to join the Hawaii team in 2015 after it made its first discovery.
The work has drawn the attention of California Gov. Jerry Brown, who invited her to discuss her findings at the next global climate action summit in San Diego in September, which will include discussions on ocean protection.
It's unclear whether the results of the American study will interest Donald Trump's administration, who left June's G7 summit meeting in Quebec without signing an agreement to reduce plastic waste in oceans, as did Japan.
It also doesn't appear to interest members of the plastic industry, who Royer says have thus far refused to co-operate with her team.
"It was extremely difficult to communicate with them, and eventually they all told me they didn't want to answer my questions or communicate with me," she said, adding that she doubts her research comes as a surprise to the industry's big players.
"In my opinion, the plastic industries know (the effects of plastic) very well and don't want to share it."
Despite the rebuff, the Quebec native appears to have joined forces with some strong allies.
For the last three years, she's been collaborating with NGOs such as Greenpeace and the Leonardo DiCaprio Foundation in order to keep the public informed on the latest research into ocean pollution.
CORRECTION: Aug. 6, 2018: An earlier version of this story misidentified the name of the journal that published the study about plastics and greenhouse gases as Plot One. The correct name is PLOS ONE.
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