A recent claim that there will be more plastic than fish in the sea by 2050 was intended to highlight a pollution crisis in the oceans. The problem really does exist, but do the figures hold water, or is there something fishy going on?
The prediction was made by the Ellen MacArthur Foundation and the World Economic Forum, in a report called The New Plastics Economy, which looks at the amount of plastic that ends up in the sea.
It got a lot of coverage in the press, including the Guardian, the Washington Post and the Daily Telegraph, among others.
One of the big headlines from the report was that if we continue dumping plastic in the sea at the present rate, measured by weight, there will be more plastic than fish by 2050.
This raises two questions: how do you measure the plastic, and how do you count the fish?
The report acknowledges that it is difficult to be precise. For the plastics, it refers back to a study led by Prof Jenna Jambeck of the University of Georgia, published last year. She tried to carry out a global census of plastic pollution and to estimate how much ends up in the ocean. Her study looks at estimates for total waste in all non-landlocked countries, and then estimates how much of that waste is likely to be plastic, how much of it is recycled, and so on.
But to estimate how much of this plastic then ends up in the sea, the study examines just one area – San Francisco Bay. “If that’s not representative of the rest of the globe then you can see the potential for large deviations in this calculation,” says Prof Callum Roberts from the University of York.
What the Ellen MacArthur Foundation report does is to take Jambeck’s research, which makes predictions only up until 2025, and project it forwards to 2050. So how much plastic will there be in 2050?
Surprisingly, for such an important number, this is not spelled out in the report, though it is implied there will be a total of 750 million tonnes of plastic in the ocean by then.