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According to new research, millions of tons of plastic are trapped along the world's shores and will eventually end up in the ocean.
And even if we stop rejecting it today, the amount of plastic in the marine environment will continue to grow as our shores function as a plastic storage facility en route to the sea.
This is the gloomy finding from modeling done for the Ocean Cleanup Foundation in the Netherlands and reported in the newspaper Scientific reports.
The researchers wanted to find an explanation for the enormous difference between the volume of plastic that would have entered the ocean and the amount floating on the surface.
Most estimates point to a quantity of floating plastic greater than 250,000 tonnes. That's a lot, but only a tiny fraction of the tens of millions of tons of plastic that would have been dumped in the ocean since the 1950s.
About two-thirds of this plastic has a lower density than that of seawater and so should float. This is not the case.
This difference has generally been attributed to the decomposition of macroplastics (pieces more than five millimeters long) into microplastics, which do not float. In other words, it was assumed that the missing plastic had been deposited, perhaps to the bottom of the ocean and into the ecosystem.
That would be bad enough.
More recent work analyzing materials collected on the surface of the ocean, however, shows a more complicated picture. Much of the recovered floating plastic was decades old, suggesting that the degradation process takes much too long to take into account the missing tonnes.
The Foundation has therefore used field research data to model the likelihood of debris stuck in coastal environments rather than going to sea. This can happen if plastic mixes with other materials or because wind and ocean currents.
The researchers claim that their model supports the theory that plastic floating near the shore is taken up by the landmass and trapped in sediment until it is finally released and that it floats – or breaks down into microplastics.
Their modeling estimates that 66.8% of all floating plastic released into the marine environment since the 1950s is stored on the shores of the world as stranded, deposited or buried debris. This would represent between 46.7 and 126.4 million tons of plastic.
Another third of all marine plastics can already be broken down into microplastics. Disturbingly, the model predicts that most of today's microplastic contamination comes from materials dating back to the 1990s and earlier – such huge amounts of newer plastics have not even begun to decompose.
As for the future, the Foundation has incorporated different models into its model to determine what this vast plastic storage on the coastline could mean in the future.
If we continue to unload plastic as we have done so far, the amount floating on the surface could quadruple by 2050 and up to 231.6 million tons will have polluted the ocean as microplastics .
The situation is better if we stop discarding plastic in the ocean from 2020 onwards. In this scenario, the volume of floating plastic would drop to 59% of its current levels. But the amount of microplastics in the ocean is expected to more than double by 2050 as materials already trapped in the environment degrade.
The problem will be with us for decades, the researchers write.
"Mitigating microplastic pollution in the global ocean requires two major components: (1) significantly reduce plastic pollution emissions in the coming years and (2) actively participate in environmental plastic waste disposal operations. to reduce the future generation of secondary microplastics.
"Without proper handling and management of accumulated plastic waste, the legacy of the last 70 years of the disposable society will continue through the generation of ever-smaller synthetic polymer fragments in soils, ecosystems, and more." fresh water and finally the ocean. "
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