Notably absent from the debris was plastic from nations with lots of plastic pollution in their rivers. This was surprising, says Egger, because rivers are thought to be the source of most ocean plastic. Instead, most of the garbage-patch plastic seemed to have been dumped into the ocean directly by passing ships.This suggests that “plastic emitted from land tends to accumulate along coastal areas, while plastic lost at sea has a high chance of accumulating in ocean garbage patches”, Egger says. The combination of the new results and the finding that fishing nets make up a large proportion of the debris indicates that fishing — spearheaded by the five countries and territories identified in the study — is the main source of plastic in the North Pacific garbage patch.

Every 60 seconds the equivalent of a lorry-load of plastic enters the global ocean. Where does it end up? Right now, researchers simply don’t know. But in a bid to help find out, an ESA-led project developed floating transmitters whose passage can be tracked over time, helping in turn to guide a sophisticated software model of marine plastic litter accumulation.