How Much Plastic Debris Moves from Land to Sea?

Nations need to improve their waste management strategies to "turn off the tap" of plastic flowing into the world's oceans.
The new study identifies the 20 countries that contribute the most plastic to the world's oceans.

SAN JOSE — About eight million tons of plastic waste wound up in the world's oceans in 2010, and researchers warn that the cumulative amount could increase more than tenfold in the next decade unless the international community improves its waste management practices.

Jenna Jambeck from the University of Georgia, along with colleagues from the United States and Australia, studied the sources of ocean-bound plastic around the world and developed models to estimate countries' annual contributions. They suggest that coastal countries generated close to 275 million tons of plastic waste in 2010 — and that 4.8 to 12.7 million tons of that plastic made its way to the oceans.

Until now, researchers did not have a firm grasp of the amount of plastic that makes its way from land to sea each year. The new study identifies the major sources of ocean-bound plastic and lists the 20 countries, from China to the United States, that contribute the most.

These findings are published in the 13 February issue of Science.

"One of our major findings is that the amount of plastic entering the ocean from plastic waste generated on land is 20 to 2,000 times larger than estimates of the amount of plastic floating at the sea surface, globally," said co-author Kara Lavender Law from the Sea Education Association in Woods Hole, in a press briefing held at the 2015 AAAS Annual Meeting.

"We ultimately want to know how this contaminant is affecting the ocean, and marine life, in particular," she said. "Not only sea turtles, whales, and seabirds but also animals at the base of the food web, all the way up to what we call 'seafood.'"

"Our estimate of eight million metric tons going into the oceans in 2010 is equivalent to five grocery bags filled with plastic for every foot of coastline in the world," said Jambeck. "This annual input increases each year, so our estimate for 2015 is about 9.1 million metric tons."

"In 2025, the annual input would be about twice the 2010 input, or 10 bags full of plastic per foot of coastline," she continued. "So the cumulative input by 2025 would equal 155 million metric tons."

The researchers combined data on solid waste from 192 different coastal countries with factors such as population density and economic status. They found that uncaptured waste — trash that is littered or lost from waste management systems — was the biggest source of ocean-bound plastic debris in the world.

"Our mismanaged waste is a function of both inadequate management — open dumping, for example — and litter," explained Jambeck. "This mismanaged waste goes uncaptured, meaning that it then becomes available to enter marine environments."

According to the researchers' models, a country's population size and the quality of its waste management systems largely determines the amount of such mismanaged waste that it generates. In order to prevent the amount of plastic debris that reaches the oceans from increasing by a full order of magnitude over the next decade, Jambeck and her colleagues suggest that nations around the world need to reduce their overall waste and adopt better management strategies.

"We need to make sure that we are collecting and capturing solid waste and plastic around the world," emphasized Jambeck. "Second to this is what we do with it...If we at least capture it, it's not going to go into the oceans."

"Solutions will require a combination of local and global efforts," she explained. "They need to be culturally appropriate and sensitive to social and economic concerns. But a shift in how we manage waste could provide jobs and opportunities for economic innovation, and it could improve the living conditions and health of millions of people."

“The ocean is a very difficult place to work,” said Law. “My feeling is that we are far better off trying to stop the input into the ocean. Even if we could go out and collect all these little bits of micro-plastic, we are not going to solve the problem unless we turn off the tap.”