Researches from The Ocean Cleanup published the first estimate of plastic emissions from rivers into the world’s oceans on June 7. In a piece for Nature Communications, researchers calculated that rivers annually transport between 1.15 and 2.41 million metric tons of plastic waste into our oceans.
"Two-thirds of this input comes from the 20 most polluting rivers, most of which are located on the Asian continent," writes The Ocean Cleanup in a press release. "The distribution of plastic in the oceans can only be mapped if the main sources of plastic pollution are known. By pinpointing these sources, The Ocean Cleanup can target the best possible locations in the ocean for the deployment of its cleanup systems. Additionally, knowledge about the sources of plastic pollution can aid prevention efforts.
"It is commonly accepted that most plastic found in the oceans originates from land-based sources. It is also well known that rivers play a particularly important role in transporting mismanaged plastic waste from land into the ocean. Until now, however, researchers had quantified neither the total amount of plastic flowing out of the world’s rivers, nor how much plastic is emitted by each individual river. With today’s study, this information is now available."
Researchers created a model for the study using global geospatial information on population density, waste management, topography, hydrography, and the locations of dams. Of the 40,760 ocean-bound rivers studied, just 20 are responsible for two-thirds of the global plastic input. The model also shows that plastic input from rivers is highly correlated with drainage of debris from the river banks and creeks leading into main waterways, and that this river-to-ocean input therefore varies per season. Researchers concluded that three quarters of the plastic released annually enters the oceans between May and October.
In a statement, Boyan Slat, Founder and CEO of The Ocean Cleanup said: “We’re pleased to see how many initiatives have been taken in the past few years to raise awareness of the ocean pollution problem. However, for our work in the deep ocean to succeed in the long run, it’s crucial that governments and other organizations speed up their efforts to mitigate the sources of the problem we aim to resolve. The results of this latest study can assist with those efforts.”