Millions of tonnes of plastic is trapped along the world’s coastlines and will eventually find its way into the ocean, according to new research.
And even if we stop dumping it today, the amount of plastic in the marine environment will continue to grow because our shorelines are working like a holding facility for plastic already on its way to sea.
That’s the grim finding from modelling carried out for the Netherlands-based Ocean Cleanup Foundation and reported in the journal Scientific Reports.
The researchers wanted to find an explanation for the huge discrepancy between the volume of plastic that is estimated to have found its way into the ocean, and the amount that is floating on its surface.
Most estimates put the quantity of floating plastic at more than 250,000 tonnes. That’s a lot, but only a tiny fraction of the tens of millions of tonnes of plastic believed to have been released into the ocean since the 1950s.
About two-thirds of all that plastic has a density lower than sea water, and thus should be floating. It isn’t.
That gap has usually been attributed to the breakdown of macroplastics (bits more than five millimetres long) into microplastics, which do not float. In other words, it has been assumed that the missing plastic has gone under, perhaps down to the ocean bed and into the ecosystem.