Research reveals that rivers deliver up to 4 million metric tons of plastic debris to the sea every year, with up to 95% coming from just 10 of them.

We are drowning the sea in plastic. The numbers are staggering and predictions dire: We dump the equivalent of a garbage truck full of plastic into the ocean every minute, plastic that has a life expectancy of thousands of years in the ocean. Some 700 species of marine wildlife are estimated to have ingested plastic; plastic will be found in 99 percent of seabirds by 2050. The encyclopedia of horrors centered around ocean plastic is epic.

Questions about the source and amounts of ocean plastic have been vexing conservationists for years, and maybe even more so is the question of how to stem the prodigious flow. But now a new study may offer some clues.

The researchers found that just 10 rivers may be responsible for dumping almost four million metric tons of plastic into the ocean every year. And thus, targeting those rivers could have a dramatic impact on reducing marine pollution.

The research – conducted by scientists from the Helmholtz Centre for Environmental Research and the Weihenstephan-Triesdorf University of Applied Science – brings to light the importance of better management of upstream systems to reduce the significant proportion of plastic transferred via rivers, notes Tim Wallace at Cosmos Magazine.

Previous research concluded that 1.15 to 2.41 million metric tons of plastic waste entered the ocean by way of rivers for a global total of 67 percent coming from 20 polluting rivers. By using a larger data set and separating particles by size, the new study found that rivers contribute even more: Between 410,000 and 4 million metric tons of ocean plastic a year, with 88 to 95 percent coming from only 10 polluting rivers.

The ten rivers are:

In East Asia:

Yangtze

Yellow

Hai He

Pearl

Amur

Mekong

In South Asia:

Indus

Ganges Delta

In Africa:

Niger

Nile

And while this may all seem like rather dismal news, the (relative) bright side is tangible. Given that so much of the pollution is coming from just a few sources, managing that waste could have a big impact. The authors conclude: “Reducing plastic loads by 50% in the 10 top-ranked rivers would reduce the total river-based load to the sea by 45%.” Which would prove challenging in and of itself, but at least knowing where to aim some effort is a good start.