Study: Inaccessible Island’s plastic trash comes from ships
It’s called Inaccessible Island for a reason. This small volcanic island in the South Atlantic Ocean lies between the African and South American continents in the middle of the sea, a rocky and forbidding spot that’s part of the UK’s overseas territory of St. Helena, Ascension and Tristan da Cunha.
The remote island isn’t just inaccessible but also uninhabited except for wildlife, and it’s been on the UNESCO list of World Heritage Sites since 1995. So when a group of scientists wanted to know how the plastic swirling around Inaccessible Island got there, they investigated and discovered that the plastic likely is getting tossed from passing ships, primarily from Asia.
Those scientists, led by Peter Ryan of the FitzPatrick Institute of African Ornithology at the University of Cape Town, published their findings on Monday in the Proceedings of the National Academy of the Sciences (PNAS). A bird enthusiast who is no stranger to Inaccessible Island, Ryan has studied the impacts of plastic ingestion on seabirds and the broader concern of how ocean plastic is impacting marine ecosystems.
That’s especially true on the island and its cliffs and beaches. It has a comparatively high load of debris and the waste washing up on its western shores has been observed since 1984. A lot of the plastic pollution comes in the form of discarded water bottles, the presence of which is growing at 15 percent per year while the presence of other kinds of debris increases at 7 percent.
Last year, Ryan and his team examined 2,580 plastic bottles and containers, which accounted for a third of all the debris they encountered. They also looked at another 174 bottles that washed up as they monitored the coast across a 72-day period and think they’ve discovered a few clues.
First was the oldest item they found. It was a polyethylene (PE) container made in 1971. The common plastic is manufactured in different forms and this sturdy high-density PE survived nearly 50 years, which is troubling in its own right when evaluating plastic garbage and its future impacts. Yet what Ryan and his team learned was that most of the items they found were drink bottles made from a different plastic.
“Of the bottles that washed up during our survey, 90 percent were date-stamped within two years of stranding,” the PNAS article notes. That’s important, because if the plastic bottles had drifted to the island from Asia solely because of weather and waves, the scientists say it would have taken longer.
But why Asia?
The next clue came from the historic patterns of plastic pollution on Inaccessible Island. In the 1980s, about two-thirds of the plastic bottles that washed up were from South America, driven by winds from the west before coming to rest on the island after a 3,000-kilometer journey. By 2009, South America was eclipsed by Asia as the source of the bottles.
By the time the 2018 research was completed, Asian bottles – most of them made in China – accounted for 83 percent of all of the newly arrived bottles, and nearly three-quarters of the overall total collected and studied.
“The rapid growth in Asian debris, mainly from China, coupled with the recent manufacture of these items, indicates that ships are responsible for most of the bottles floating in the central South Atlantic Ocean,” the researchers concluded – and, they added, that’s a violation of international rules for pollution from ships.