Nowhere is safe from plastic. A tiny South Pacific island 5000 kilometres from the nearest human occupation has the highest density of washed-up plastic rubbish known anywhere in the world.
Henderson Island is an uninhabited, 5-kilometre-wide speck of land halfway between Australia and South America. A recent expedition led by Jennifer Lavers at the University of Tasmania in Australia found 38 million items of rubbish weighing a total of 18 tonnes spread across its beaches.
Until recently, a major build-up of marine plastic was thought to mainly affect the North Pacific Ocean, where a swirling current called the North Pacific Gyre traps floating debris to form the Great Pacific Garbage Patch.
But in 2013, a similar garbage patch was reported in the South Pacific. This patch is also delineated by a circular current, called the South Pacific Gyre. Water sampling in the region found up to 400,000 plastic particles per square kilometre, which is close to the density in the North Pacific garbage patch.
Lavers and her colleagues have now found that Henderson Island, which sits on the western edge of the South Pacific Gyre, acts like a sink for this floating garbage patch. Its beaches are carpeted with an average of 239 items of rubbish per square metre – the highest density recorded in the world. Of these items, 99.8 per cent are plastic.
Most are fragments of plastic, but common intact goods include plastic cutlery, bottles, bags, pens, straws, cigarette lighters, razors and toothbrushes, as well as fishing equipment such as buoys, nets and lines.
Blast from the past
Labels on some items reveal that a handful come from Asia and Europe, but most come from South America. This is probably because the South Pacific Gyre sweeps up the west coast of the continent.
The worn condition of the rubbish indicates that it is decades-old, says Lavers. This is reinforced by the types of items discovered, like toy soldiers that were popular in the 1970s.
The dynamics of the South Pacific Gyre are still poorly understood, but research suggests that Henderson Island sits in an area of the current where rubbish that has cycled round for a long time is spat out, Lavers says. This could explain why the rubbish is old, and why the island is so coated in debris, she says. “It’s also very rarely visited, so there are no clean-ups.”
The pile-up threatens marine animals including fish, turtles and seabirds. They can ingest the plastic detritus or become ensnared in it, and turtles find it hard to lay eggs in the polluted sand.
The solution is two-pronged: produce less plastic and prevent existing plastic from spreading in waterways, Lavers says. Annual global plastic production has increased from 2 to 300 million tonnes since the 1950s and continues to rise, she says. “The faster we can cut it down the better.”
Plastic ocean pollution should be considered a similar level of threat to the health of oceans and humanity as climate change, Lavers says. “Like climate change, it has a legacy effect,” she says. “You put carbon dioxide into the atmosphere or plastic in the oceans and both will stick around.”
Journal reference: PNAS, DOI: 10.1073/pnas.1619818114