The overwhelming majority of the debris — an estimated 1.8 trillion pieces — are plastic fragments and fibers smaller than 5 millimeters. They’re mostly the result of larger items breaking down in the elements.
But those pieces make up less than 10 percent of the total weight of the garbage patch. Nearly half of the mass comes from fishing nets and line lost or jettisoned by trawlers, which clump together and collect other floating trash along the way. The trash is spread over an area about 1.6 million square kilometers — roughly 1,300 by 1,300 km (800 by 800 miles) — with the bulk of it concentrated toward the center.
The findings, published March 22 in the research journal Scientific Reports, were based on surface sampling and aerial surveys conducted over a 14-month period in 2015 and 2016, as well as computer modeling. The new estimate is four to 16 times bigger than previous calculations, including one Lebreton produced himself. But he said earlier studies were conducted from the surface and likely underestimated the amount of large debris.
“We said, ‘Instead of trying to observe large debris from observers on vessels, let’s try to fly above it and get pictures and come back with a more precise estimate of the large debris,’ ” he said.
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And some of the larger items, like crates or bottles, appear to be durable. Sweeps of the water turned up debris that dated back decades — a crate from 1977, a hardhat from 1989, the back of a Nintendo Gameboy from 1995. Lebreton said the study couldn’t determine precisely how long those items had been floating around, but “You can tell it’s spent some time in the water, because it’s degraded.”
The patch is growing as up to eight million tons of plastic washes into the world’s oceans a year, the United Nations estimates. That plastic is a hazard to marine life: Fish and other sea creatures can mistake the indigestible polymers for food, while hazardous chemicals can latch onto plastics and accumulate up the food chain when they’re consumed.
Lebreton said he hopes the findings will help convince people to take action to reduce their consumption of plastic, particularly those items that are discarded after a single use.
“I’m not saying we should move away from plastics,” Lebreton said. “I don’t think that is going to happen, because plastic is very useful in many applications. But I think there are some plastics that could actually not be there in the first place, and single-use plastic is definitely one of them … if you buy something, open the package and just throw it away, those are the type of things that end up in the ocean very quickly.”