The majority of the plastic waste washing up on a tiny island in the middle of the South Atlantic consists of bottles from Asia which have likely been dumped by ships, according to research.
The results of the study—which were published in the Proceedings of the National Academy of Sciences—question the widely held assumption that most plastic debris at sea comes from land-based sources, the authors say.
Many islands in the open ocean are bombarded with plastic waste, especially those located near the Earth’s major ocean gyres—vast systems of rotating currents—where floating debris accumulates.
To understand more about the source of this debris, a team led by Peter Ryan from the University of Cape Town, South Africa, examined the plastic ending up on the rocky shores of Inaccessible Island—a remote, uninhabited dot of land halfway between Argentina and South Africa which is located near the major South Atlantic gyre.
The authors visited the island in 1984, 2009 and 2018, finding that plastic drink bottles were the type of debris which had experienced the fastest growth rate on its shores, increasing by 15 percent every year, compared with seven percent for other types of debris.
The authors say that in the 1980s, two-thirds of the bottles on the island had drifted from South America more than 1,800 miles away. But by 2009, the situation had changed with most of the bottles coming from Asia.
And after examining more than 2,500 plastic bottles and other containers which had accumulated on the island’s coast over a 72-day monitoring period, they concluded that, currently, 73 percent of accumulated bottles and 83 percent of newly arrived bottles come from Asia, with most originating in China.
The team found that 90 percent of the bottles identified during the monitoring period had been manufactured in the last two years, according to their date stamps. This indicates that the debris likely did not drift over from Asia—which would usually take between three and five years.
This finding—alongside the rapid growth of Asian cargo vessels in the Atlantic—led the researchers to conclude that, instead, plastic bottles are likely being dumped by Asian merchant ships (mostly from China) in contravention of the International Convention for the Prevention of Pollution from Ships regulations.
“It’s inescapable that it’s from ships, and it’s not coming from land,” Ryan told AFP, noting that many of the bottles had been crushed, as is customary on board cargo ships to save space. “A certain sector of the merchant fleet seems to be doing that, and it seems to be largely an Asian one.”
Plastic which originates from land-based sources makes its way into the oceans via rivers, often as a result of inadequate waste management.
“For example, litter due to unavailable waste collection gets washed down drains on streets entering rivers that carry these plastic debris to sea,” Richard Alan Gross, from Rensselaer Polytechnic Institute, told Newsweek.
“Other entry routes include illegal dumping directly into or nearby waterways, blowing off landfill sites, accidental and inevitable discharges of plastics during activities such as construction, manufacturing, farming, washing our clothes and via waste-water treatment plants,” he said.
However, nautical activities including shipping, recreational activities, fishing and aqua-farming also contribute to the amount of plastic waste in the ocean.
It is generally assumed that around 80 percent of the plastic waste in the oceans originates from land-based sources. However, the researchers say there is “little direct evidence” for this idea, arguing that the latest results cast doubt on the assumption.
In fact, oceanographer Laurent Lebreton from The Ocean Cleanup organization said that the 80-percent figure that is often quoted does not apply to the high seas.
“Everyone talks about saving the oceans by stopping using plastic bags, straws and single use packaging. That’s important, but when we head out on the ocean, that’s not necessarily what we find,” he told AFP, noting that pollution from ships is “under-appreciated.”