After a yacht captain stumbled across the Great Pacific Garbage Patch in the late 1990s, scientists soon began finding similar patches of plastic waste in oceans around the world. They've since identified at least five, each fed by currents that carry plastic bags, bottles and other trash into vast vortices of seawater known as gyres.

Since most plastic isn't biodegradable, this trash keeps swirling around for years, often crumbling into smaller pieces but refusing to fully break down. Much like carbon dioxide emissions — which linger stubbornly in the sky as they fuel climate change — garbage patches have come to symbolize the effects of man-made pollution run amok.

And now, thanks to a new study by Australian scientists, we have a clearer picture of just how amok all this pelagic plastic really is. Using GPS-equipped drifter buoys to model the travels of maritime trash, researchers at Australia's Center of Excellence for Climate System Science report a sobering discovery: Even if no plastic waste entered the oceans after today, Earth's garbage patches would still continue growing for hundreds of years, both because of plastic's longevity and its long transit time to the gyres.

"These patches are not going away," says lead author Erik van Sebille, an oceanographer at the University of New South Wales, in a video statement about the study. "The garbage patches will stay there for at least the next thousand years."

Despite a name that makes them sound like seafaring landfills, garbage patches are actually nebulous and low-profile, consisting mostly of small plastic bits floating below the surface. And while that may seem less dramatic, the diffuse nature of garbage patches makes them more nefarious and harder to deal with, van Sebille points out.

"If you sail through these areas, you will not see big lumps of plastics or rubber duckies or things like that," he says in a press release. "The sun and interaction with the ocean breaks the plastics down into very small pellets that are almost invisible to the naked eye. However, these plastics even at this small size do affect ecosystems — fish and albatross swallow these plastics, while phytoplankton can use the floating pellets to stay buoyant and float near the surface, where they grow best.

"Plastic is also the canary in the coal mine," he adds. "Poisonous chemicals, [which] are much more hazardous to the ecology, ride the currents in the same way and are actually absorbed by the plastic pellets."

ocean gyres

The five major ocean gyres, where currents cause floating plastic to accumulate. (Illustration: NOAA)

Not only will the five biggest, best-known garbage patches continue growing for centuries, but the researchers also say a sixth one is in the offing. "Interestingly, our research suggests a smaller sixth garbage patch may form within the Arctic Circle in the Barents Sea," van Sebille says, "although we don't expect that to appear for another 50 years."

The buoys also helped the researchers determine that garbage patches are surprisingly cosmopolitan, containing plastic not just from nearby coastlines, but from around the world. "This means that garbage from any country can end up in any one of these garbage patches," van Sebille says. "This tells us that no single country is responsible. Ocean garbage is an international problem that requires an international solution."

But if cutting off their plastic supply won't stop the patches' growth for at least 1,000 years, what kind of international solution is possible? Van Sebille admits the task is daunting, and says any cleanup efforts would be futile. Instead, he suggests focusing on ways to improve the garbage patches' diet. "There's really no solution for getting the plastic out of the ocean. It's too small, too diverse, too thin to get out there with a ship and pick it up," he says. "Of course, the way to go then would be to make plastics that do break down, plastics that even if they get into the ocean, don't really have the time to accumulate in these garbage patches, because they will just disintegrate."

As big and fast-growing as garbage patches are, however, they're still just one symptom of a broader problem. For the next stage of his research, van Sebille plans to study the dynamics of plastic waste closer to coastlines. "Clearly, by the amount of plastic found on beaches, not all of it ends up in the gyres to form garbage patches in the deep ocean," he says. "We need to find out what happens to the plastics closer to land, where most fishing occurs, and what effect that has on the environment around our coasts."

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