Plastic ocean

In 2010, about eight million tonnes (mt) of plastic waste ended up in the oceans of the world, according to a report supported by Ocean Conservancy and published in the latest issue of Science by Jenna Jambeck of the University of Georgia in Athens, along with United States and Australian scientists. Warning that the cumulative amount could increase more than tenfold in the next decade, they have called for improved waste management practices the world over.

The researchers studied the sources of ocean-bound plastic around the world and developed models to estimate their annual contributions. They said that coastal countries generated close to 275 mt of plastic waste in 2010, of which 4.8-12.7 mt made its way to the oceans. While it was known that a considerable amount of plastic waste does end up in the oceans every year, researchers did not have an estimate of the quantity. This study has not only put a number to it but also identified the major sources of it around the world. It has listed 20 countries—from China to the U.S.—that contribute the most.

The estimate of 8 mt of plastic waste is equivalent to five grocery bags filled with plastic for every foot of coastline in the world, according to Jenna Jambeck. Given that this annual input increases each year, their estimate for 2015 is about 9.1 mt. And the researchers estimate that in 2025, the annual input would be about twice the 2010 input, which means that the cumulative input by 2025 would equal 155 mt.

In their modelling, 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,” Jenna Jambeck says. According to the researchers’ models, a country’s population size and the quality of its waste management systems largely determine the amount of such mismanaged waste that it generates which goes uncaptured and enters the marine environment.