Garbage in the ocean is a big problem, but until now we didn't know how big. A study published today in Science drops a rough but still astounding estimate: 8 million metric tons per year. That's 20 to 2000 times more than what experts had estimated.

Until now, a lot of our information about how much plastic ends up in the ocean was from sources that had gone out of date. For example, a standard estimate that you hear a lot is that 0.1 percent of all plastic makes it into the open waters. But that number comes from a National Academy of Sciences report written in the 1970s. A lot has changed since then.


This new Science study is a still a rough estimate, but it incorporates up-to-date data.

So how did the researchers determine that we're dumping 8 million metric tons of plastic into the oceans every year?

First they used World Bank data to calculate how much plastic waste was being generated along a 50 kilometer (or 31 mile) coastal strip in 192 countries along the oceans. Then, they built a statistical model estimating the level of waste mismanagement in each country based on their economic status and region of the world. (The statistic model extrapolated from 80 countries for which waste management data was available.) As one final touch, they factored in a littering rate of 2 percent for everyone.

The most important number is the global one, but the study also includes a country by country breakdown. It's no surprise that developing countries with fast-growing economies are at the top of the list.


Here's the weird part. Last year, scientists sailed around the world looking for ocean plastic, only to find one percent of what they expected. Ninety-nine percent of ocean plastic was missing. Keep in mind, that is 99 percent by 1970s estimates. By this new estimate, it would be closer to 99.9 percent. So where has it gone?


You've probably heard of the Great Pacific Garbage Patch, which is a swirling gyre of tiny pieces of plastic. Based on new evidence, it now appears that the vast majority of plastic has either sunk to the bottom of the ocean or is floating somewhere in the water column beneath the surface. We're only just beginning to understand the depth of our ocean plastic problem. [Science]


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