Henderson Island in the Pitcairn Islands, about halfway between New Zealand and Chile, is roughly 10 kilometres long and three kilometres wide.
That means the estimated 38 million pieces of trash on its shores makes it the site of the highest concentration of trash recorded anywhere in the world.
“The sheer volume of plastic on Henderson Island was something that I had not seen before in all my travels and it is really quite remarkable in all the wrong ways,” says Jennifer Lavers, research scientist at the University of Tasmania and lead author of the study published in the Proceedings of the National Academy of Sciences.
“There were all these everyday consumer items that we use and dispose of without even hesitating for a moment, things like toothbrushes, cigarette lighters, razors, bottle caps, items that absolutely shouldn’t have been in the middle of nowhere.”
Lavers found the build-up of trash has to do with the island’s proximity to a vortex of ocean currents called a gyre, one of which is found in each of the world’s five major ocean basins.
“What they are is basically a combination of wind and wave patterns that create something like a large-scale vortex and essentially what it does is trap plastic and concentrate it in these hotspots where the density becomes much higher than the surrounding areas,” she says. “Henderson has the unfortunate luck to be on the western boundary of the South Pacific gyre and so it’s likely that much of the plastic came from that gyre.”
A way to visualise a global problem
While scientists know plastic is accumulating in these gyres, it is not easy visualise or measure, meaning the new study helps demonstrate how plastic moves in the oceans.
“What is particularly worrying about the Henderson Island story is just how much plastic there is on such a remote and what we thought was a very pristine place,” says Erik van Sebille, an oceanographer at Utrecht University in the Netherlands, who adds the study contributes to our understanding of how plastic accumulates.
“In Europe, the US and Asia, where we think that have much cleaner beaches, a lot of that might have to do with the fact that we just keep cleaning them,” he explains. “We might be fooling ourselves a bit by thinking there is not that much plastic. If you leave a coastline alone for a while, more and more plastic would accumulate.”
The researchers were also able to trace the origins of certain pieces of plastic to their countries of manufacture, which considered with the activity of gyres, presents a picture of how global trade contributes to the problem.
“As an oceanographer, I finding it very unlikely and almost unimaginable that something would float all the way from Germany to the South Pacific,” says van Sebille. “This shows us our global consumer society is so interconnected that even if something is made in Germany, it can very well end up in Australia, in South America or on one of the other islands in the South Pacific, which are much more likely to be the source of plastic in this case.”
Plastic in the ocean is about more than clean-up
Part of Lavers’s three and a half months of research on the island involved cleaning up part of the beach only to find some 13,300 new pieces of plastic washed onto the beaches every day.
“That begs the question, what would be the purpose of cleaning it up if a month, two months, three months down the road, you would be right back where you started,” she says.
What really needs to happen, Lavers suggests, is that plastic must be prevented from making its way into the ocean in the first place.
“It requires broad, sweeping behavioural change on behalf of each and every one of us to rethink how and when it’s right to use plastic.”
Current knowledge suggests the plastic visible on Henderson Island is just a drop in the ocean, compared with the 10 trillion pieces of plastic scientists believe to be in the gyres and elsewhere.
The study also points out that the nearly 18 tonnes of plastic thought to be on Henderson Island amounts to what is produced around the world every two seconds.