In the last decade, beach cleanups have grown into a global phenomenon, with volunteers gathering at regular intervals for the Sisyphean task of cleaning up plastic trash. Now, new research on a remote Australian island chain suggests that beach cleanups can inadvertently mask the full scale of plastic pollution, much of which lies below the sand’s surface.
The look at isolated islands also provides a disturbing glimpse of what beaches in populated places might look like if they were never cleaned up and plastic simply accumulated year upon year, breaking down ultimately into smaller and smaller pieces: microplastics.
The Ocean Conservancy began conducting beach cleanups on a single Texas beach in 1986. It now directs such operations in more than 100 countries that over the decades have collected some 300 million pounds of trash.
What that trash collection can’t retrieve, however, are the microplastics in the sand beneath the surface. No one is sure how much is embedded, how quickly it amasses or to what effect.
“Sadly, the situation on the Cocos Islands is not unique,” Jennifer Lavers, a research marine scientist at the University of Tasmania in Australia, says in a paper published May 16 in Scientific Reports.
“With 2,000 oceanic islands worldwide, and thousands of new plastic items washing up on remote beaches every day, cleanups cannot keep pace. In the absence of rapid and meaningful change … marine plastic mitigation will remain a perpetual game of catch-up,” she writes.
More than 80 percent of the 8 million tons of plastic trash that end up in the world’s oceans every year originates on land. But remote, uninhabited or sparsely populated islands offer scientists a unique window into the consequences of global waste and its movement around the world because little or none of it is generated locally.
The Cocos (Keeling) Island group, an isolated chain of 27 small atolls in the Indian Ocean 1,300 miles northwest of Australia, is home to fewer than 600 people. Almost everyone lives on the two largest islands. Essentially all of the trash that ends up on Cocos beaches is carried by ocean currents and washes ashore.
The islands are advertised as “Australia’s last unspoilt paradise.” Levers and her team arrived in 2017 to take samples of beach trash from 25 beaches on seven islands. They collected wood, glass, metal and plastic from the surface areas of beaches and the overgrown areas directly behind beaches where waste that washes ashore also accumulates. They also collected microparticles buried about four inches below the surface. Ninety-five percent of the materials were plastics.
Based on the sampling, Lavers estimated that the string of islands contained 414 million pieces of debris, weighing 238 tons. Microparticles buried in the sand comprised 93 percent of the estimated count.
“What you can see on the surface is the absolute tip of the iceberg,” Lavers says. “What is actually there is completely hidden from view.”
Among the larger items, 25 percent included straws, plastic bags, toothbrushes, and shoes. Only 2 percent of the beach trash was fishing gear, evidence that most of the fishing around the islands is small-scale and not industrial, Lavers says.
The finding that the majority of the Cocos beach plastics are microplastics embedded in sand is a logical outcome, given how plastics break down into smaller and smaller pieces as they are exposed to sunlight and wave action, said Kara Lavender Law, a research oceanographer at the Sea Education Association in Woods Hole, Massachusetts,
“I’m glad people are doing this kind of field work to look in more detail about the kind of debris, including the sizes found on beaches and how,” she says. “We don’t know the full extent of contamination of beaches.”
Nearly a decade ago, scientists in Hawaii found that microplastics embedded in beach sand made it easier for water to flow through the sediment, which in turn affected how fast sand dries out. As microplastics accumulated, they acted as an insulator, preventing heat from reaching deeper layers of beach, affecting the temperature of sand. That in turn had affected the sex of turtle hatchlings, which is determined by the temperature of eggs during incubation.
“Colder nest temperatures mean longer incubation times and can shift the sex ratio of turtles, with more males being born,” says Steven Colbert, a marine scientist at the University of Hawaii, one of the authors of the 2011 study.
Lavers says the Cocos research—along with her 2017 study of plastic trash on isolated Henderson Island in the South Pacific’s Pitcairn Islands, where she found the world’s highest density of plastic pollution—provide a new platform to move this kind of beach research forward.
“This is the million-dollar question: What does plastic do to the functionality of beach sediment? You can’t keep adding to the beach and not have it change,” she says. “At some point, it will change the temperature of the beach, the chemistry of the beach, how the beach absorbs or evaporates water. All of these things will be altered and all of the animals that live on the beach will be affected.”
Lavers, the last scientist to visit Henderson, plans a 16-day return trip to the uninhabited island to collect data on temperature, humidity, and water content. She leaves June 1.
George Leonard, the Ocean Conservancy’s chief scientist, said he is dubious of the idea that California beaches might look similar to the Cocos beaches if California beach cleanups stopped.
“You can’t make that leap,” he says. “Habitats are different. The oceanography is different. But the fact that plastic goes to places untouched by humans and leaves such a ghastly footprint of our plastics obsession is pretty terrifying. It’s a call for a global effort.”