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The best places to pick up ocean plastic aren’t the big garbage patches

The best places to put plastic collectors are areas where the most plastic is moving through, not the places where the most plastic ends up.
February 2, 2016

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The prevailing approach to the ocean plastic problem seems intuitive: if you see a bunch of garbage, pick it up. And the trash isn’t hard to find. A lot of microplastic pollution ends up trapped and floating around in large circular currents called gyres. The most dramatic of these is the vast Pacific Garbage Patch, a conglomeration of plastic that covers a stretch of ocean between Hawaii and California more than twice the size of the United Kingdom.

But according to a new analysis, cleaning up the Garbage Patch isn’t the most efficient way to get the most plastic out of the ocean, nor is it the best way to minimize plastic’s harm to marine life.

The best places to put plastic collectors are areas where the most plastic is moving through, not the places where the most plastic ends up, researchers found. Oceanographer Erik van Sebille and undergraduate physics student Peter Sherman, both at Imperial College London, used data on ocean currents and waste-management practices in different countries to simulate the entry and circulation of plastic in the oceans from 2015 to 2025. They then identified a set of locations for 29 trash clean-up devices that would result in removal of 31 percent of the ocean’s microplastics by 2025. In contrast, putting all of the collectors into the Pacific Garbage Patch would reduce plastic in the oceans by only 17 percent.

The analysis assumed that each collector would capture 45 percent of the plastic bits passing through its vicinity. This is based on a previous study by an organization known as The Ocean Cleanup, which is developing the devices.

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The researchers also considered where to put the collectors in order to minimize harm to marine life from plastics. To do this, they mapped net primary productivity in the oceans, which indicates the growth of microscopic floating plants called phytoplankton. Because phytoplankton form the base of the marine food chain, they reasoned, areas with high net primary productivity are likely to be rich in ocean life in general.

To maximize plastic removal and minimize harm to marine life, they determined that most of the plastic collectors be placed near coastlines—especially off China and in the Indonesian archipelago, because a lot of plastic in the oceans comes from East Asia.

Despite the impressive plastic removal stats generated by the researchers’ model, the total mass of microplastics on the ocean surface would still increase by four percent by 2025, even with the plastic collectors going full-time. That’s because we’re producing ever greater amounts of the stuff, and the more plastic we make, the more of it ends up in the sea.

Source: Sherman P and van Sebille E. Modeling marine surface microplastic transport to assess optimal removal locations. Environmental Research Letters. 2016.
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