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Humans are putting 8 million metric tons of plastic in the oceans — annually

Debris from urban activities and runoff accumulates at the edge of Lake Michigan. (Courtesy Jenna Jambeck/University of Georgia)

Late last  year we learned that, thanks to human beings, the oceans are carrying at least 5 trillion pieces of floating plastic — or nearly 700 pieces per human alive on the planet. In weight, that’s some 250,000 tons of the stuff.

But new research suggests that even that haul is probably a serious underestimate. In a paper published this week in the journal Science, Jenna Jambeck of the University of Georgia and a group of colleagues tried to estimate the total amount of plastic going into the oceans annually from 192 coastal countries, whose total population is 6.4 billion. People in these countries within 50 kilometers of the coast, the study estimates, produced 99.5 million metric tons of plastic waste in 2010 — and 31.9 of those million tons, the study estimates, were in some way mismanaged.

Thus, the authors calculate, each year about 4.8 million to 12.7 million metric tons of plastic are entering the oceans — for a midpoint figure of around 8 million metric tons. This is vastly higher than the number cited above — and moreover, it’s an annual number.

“It’s much larger than what they’re finding in the water,” says Jambeck. “But of course, as you know, they only can count what they find, and they only can find where they look.”

Here’s an infographic, courtesy of the researchers, that takes you through the process of measuring global plastic production, refining the estimate down to plastic waste in coastal regions, and then eventually estimating how much plastic winds up in the oceans (and how much we measure at the surface):

So what does 8 million metric tons of plastic actually mean? And is there any way to state such a gigantic figure in human terms?

“It’s five bags filled with plastic for every foot of coastline in the world,” says Jambeck.

So, why is so much of this stuff getting into the ocean? The reason, the paper asserts, boils down to a massive global waste management problem. The countries estimated to have the greatest mismanagement issues for plastic waste tend to be developing nations — China, Indonesia, the Philippines, Vietnam — with large and growing coastal populations, where waste management hasn’t kept pace with the population explosion.

“Sixteen of the top 20 producers are middle-income countries, where fast economic growth is likely occurring but waste management infrastructure is lacking,” notes the paper.

In other words, this is not just a lot of plastic bags getting swept up by wind and deposited at sea. “You have, from the random plastic bag blows to … they pretty much dispose of it right there on the coastline, right there on the bank of a river,” says Jambeck. “That’s the variability that you might find.”

The United States comes in 20th on the global plastic dumping list. While this country does have advanced waste processing, it also has a very large coastal population. (The top 20 countries contribute 83 percent of the world’s total mismanaged plastic, the study estimates.)

Ocean plastic has many consequences. It can kill fish and birds through entrainment or strangulation and can also be ingested by marine creatures and enter into the food chain, where it may have many unknown effects.

This is not a new issue to the global plastics industry. A group of plastics associations from various countries recently released a declaration on the matter, outlining a number of potential solutions to the problem and noting that “plastics do not belong in the world’s oceans and should not be littered — plastics should be responsibly used, reused, recycled and finally recovered for their energy value.”

The Science paper also has a forward projection: The plastic problem is expected to get worse.  By 2025, U.S. mismanaged plastic waste is expected to grow by 22 percent, and in the five biggest countries for the problem, it’s expected to double.

“We will not reach a global ‘peak waste’ before 2100,” notes the paper.