Figures for the volume of waste plastics in the world’s oceans are constantly being revised upward. For some, this suggests that even the most sophisticated technologies are neither able to measure the onslaught nor rid the world’s waters of rubbish that ranges from casually discarded drinks bottles to fishing nets.

But it is not only the horror stories about the extent of the pollution that are startling. More troublesome can be the way the growing problem is presented, as shown by a Dutch study published in August by the journal Geoscience Nature.

Though it may sound like a contradiction, the general conclusion of the research presented ahead of the next round of talks in November for the highly anticipated UN global plastics treaty is that “there is far less plastic littering the oceans than scientists previously thought.”

This sounds like good news, especially with pieces bigger than 25 mm constituting over 95% of plastics floating in the ocean, but it is the much less visible volume of microplastics – those less than 5 mm in length – that clouds the calculation as well as the extent of the danger to the ecosystem.

While bigger pieces are easier to remove, Erik van Sebille, co-author of the study by the University of Utrecht, said there is no effective way of removing microplastics, which underlines the challenge of ocean cleanup efforts. 

Of the estimated more than 25 mn t of plastics waste in the oceans, 250,000 t – one-tenth – floats on the surface, and another 3 mn t lurks largely unseen just below, according to the scientists’ 3D model developed with an impressive amount of observational data and measurements taken from surface water, beaches, and the deep ocean from 1980 to 2020.

As a side note, the research team added that although less plastics now finds its way to the ocean every year than previously thought, with around about 500,000 t stemming largely from coastlines and fishing activity, the weight of the addition to the existing load generally leads to new problems.

Less could sound like progress, but the litter will likely remain in place for much longer than previously believed, the Dutch model predicted.

“This means that if insufficient action is taken, it will take longer than hoped until the effects of measures to combat plastic waste will be visible,” said study leader Mikael Kaandorp.

Without further reduction and clean-up, the lingering plastics litter could double within two decades, he warned. It is already killing more than 1 mn seabirds and 100,000 marine mammals each year according to the United Nations Environment Programme (UNEP).

The focus of the marine litter problem up to now has been on the mitigation of ocean pollution. New international research however shows that concentrations of microplastics in lakes are even more daunting.

Analysing the findings of samples from 38 natural and manmade lakes in 23 countries, researchers writing in the magazine Nature stressed that action to clean up microplastics pollution in lakes as well as oceans is necessary to save the global ecosystem.

Stunningly, the magazine quotes university professor Hans-Peter Grossart of Germany’s Leibnitz Institute of Freshwater Econology and Inland Fisheries (IGB, Berlin; www.igb-berlin.de/en), who participated in the study, as saying that more microplastics were found in inland waters near population centres than in the North Pacific Subtropical Gyre.

In all the inland waterways examined, a large share of microplastic particles exceeding 0.25 mm were found, for the most part polyester, polyethylene, and polypropylene. As swimwear is often made of fibres based on those three polymers, the researchers surmised that more than half of the pollution could be coming from bathers.