By this time, the proliferation of plastics in the world's oceans is old news. You've probably heard of the Great Pacific Garbage Patch, a trash vortex in which ocean currents converge to collect all kinds of marine debris — mostly plastic, which doesn't biodegrade — into a stagnant trash slurry that can't support sea life.
But a new study published in the Proceedings of the National Academy of Sciences finds that trash isn't only found swirling in ocean gyres, or littering the beaches of densely-populated areas. According to the research, some of the most remote islands on the planet are covered in our plastic trash. At least one island — the unpopulated Henderson Island — is littered with the highest density of plastic trash than any other place we know about. And for an idea of just how remote and un-humaned Henderson, which is in the U.K.'s Pitcairn Islands territory, is, consider that it's 120 miles (193 km) from the nearest human settlement and more 3,100 miles (5,000 kilometers) from the nearest major city.
Because Henderson Island has no people living on it, it only gets visits from human researchers every five to 10 years. However, during the most recent visit to the atoll in 2015, University of Tasmania researcher Dr. Jennifer Lavers was astounded to find Henderson Island littered with 671 items of plastic debris per square meter, which comes out to about 62 pieces of plastic debris per square foot. She calculated a total of 17.6 tons (15.9 metric tons) of trash on the beaches of an island measuring just 10,600 acres (4,308 hectares) — most of it not even visible in photographs because it is buried under sand.
"Far from being the pristine 'deserted island' that people might imagine of such a remote place, Henderson Island is a shocking but typical example of how plastic debris is affecting the environment on a global scale, said Lavers, a research scientist at University of Tasmania's Institute for Marine & Antarctic Studies, in a press release.
This UNESCO World Heritage Site, prized for an ecology supposedly "practically untouched by human presence," is situated near the center of the South Pacific Gyre, where it collects trash from local fishing outfits as well as distant Asia and South America via ocean currents. The research team estimates at least 3,570 new pieces of litter wash up on a single Henderson Island beach each day. In fact, Lavers thinks they might actually have underestimated the amount of trash on the island:
"It's likely that our data actually underestimates the true amount of debris on Henderson Island," she says, "as we were only able to sample pieces bigger than two millimetres down to a depth of 10 centimetres, and we were unable to sample along cliffs and rocky coastline."
So trash keeps finding its way to Henderson Island, as Lavers' video below shows, and tampering with what might otherwise be great habitat for sea turtles, birds and invertebrates.
"Plastic debris is an entanglement and ingestion hazard for many species, creates a physical barrier on beaches to animals such as sea turtles, and lowers the diversity of shoreline invertebrates," said Lavers. "Research has shown that more than 200 species are known to be at risk from eating plastic, and 55 percent of the world's seabirds, including two species found on Henderson Island, are at risk from marine debris."