Thousands of rivers, including smaller ones, are responsible for most of the plastic pollution worldwide, a study has shown.
Previously, researchers believed that 10 large rivers – such as the Yangtze in China – were responsible for the bulk of plastic pollution.
But in fact, 1,000 rivers (1% of all rivers worldwide) carry most of the plastic to the sea.
The research means that areas like tropical islands are likely to be among the worst polluters, the researchers say.
The study by the non-profit The Ocean Cleanup used measurements and modelling to work out that 1,000 rivers worldwide are behind 80% of plastic emissions.
The number is 100 times more than the 10 rivers that were previously thought to be responsible for most of the pollution.
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Boyan Slat, Founder and CEO of The Ocean Cleanup, said: "While the plastic problem may seem daunting in scale, this updated understanding of where plastic becomes ocean plastic will allow for a much more targeted intervention.
"As we see huge differences in pollution levels across the globe, these results could help to rapidly increase the speed of solving the problem. We will use this new data as a guide for our cleanup activities, and we hope others will too."
The researchers say that factors such as rainfall and distances to the sea have not been taken into account in previous research.
The research means that tropical islands are major plastic polluters, the researchers say.
The researchers write: "The study shows that tropical islands are areas with relatively high probability due to their abundant rainfall, short distances from land-based sources to rivers (of which there tend to be many on these islands), and much shorter distances to oceans than big continental rivers.
"These new factors lead to evident concentrations of riverine plastic pollution in many countries, including the Philippines, Indonesia, Malaysia, Dominican Republic, and throughout Central America, while large continental countries such as China and India are still high on the list as well.
"Conversely, regions with a relatively low probability of becoming problem areas are land-locked countries, arid areas with little wind, or those behind thick forests.
"Low probability is caused by the much longer travel distances that the plastic needs to cover, with increased chances of the trash somehow being trapped underway, combined with a limited driving force through slower moving rivers.
"Examples of regions with low polluting numbers are Central Africa and Western China."
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