Verdict: Broadly correct on both sets of figures, but both figures are based on long-term forecasts. Omits any mention of a significant third factor.
A popular media claim is… “By 2050, the oceans will contain more plastic by weight than fish”, a claim most often based on the publicity for the advocacy documentary film A Plastic Ocean (2016).
Cleaning up the world’s oceans is a very worthy aim, one I support and have blogged about here. But I’m always suspicious when leftists glom onto such concerns, often in a bid to make crude political points by blaming the oil companies / capitalism / fat guzzlers of beefburgers and sodas, and as a means of boosting the general level of alarmism around their other issues.
Therefore I looked to see if the movie had been publicly fact-checked. I couldn’t find anything in that line, so I fact-checked just this one main ‘headline’ claim about 2050. It traces back to an Ellen MacArthur Foundation report, “The New Plastics Economy” written 2015 for the World Economic Forum and published in mid January 2016. The report comes in two public variants, The New Plastics Economy : Rethinking the future of plastics (36 pages), and a 120-page “extended version of this report, with additional chapters and appendices”.
I search both reports for “2050” claims, and then tracked these through to their endnotes and references. The reports assumes an… “annual growth in leakage flows of plastics into the ocean of 5% up to 2025” and 3.5% per year thereafter through to 2050. Given likely economic and population growth levels to 2050, that seems a fairly sensible broad estimate, even when one factors in things like public pressure, new technologies, and better management at all levels of production and recycling.
In the first version of the report, the endnotes on page 29 give the sources for the 2050 plastics/fish claim. The footnotes are the same in both versions. Note the disclaimer at the end of endnote 25…
“The stock of fish is assumed to stay constant between 2015 and 2050” at “an estimated 812 million tonnes (S. Jennings et al., Global-scale predictions of community and ecosystem properties from simple ecological theory (Proceedings of the Royal Society, 2008).”
This is broadly in line with the latest scientific consensus, as summarised in this recent paper in Food Security journal…
“A consensus has emerged in the literature that the doom-and-gloom rhetoric that had driven the discussion surrounding the state of marine fisheries in the late 2000s (Garcia and Grainger 2005; Caddy and Seijo 2005) was exaggerated (Grafton et al. 2010; Hilborn 2010) and that although the situation remains concerning in respect to many stocks, we are not likely to face the global collapse that had been announced by some biologists (e.g., Myers and Worm 2003; Worm et al. 2006; Pauly 2009). Instead, the downward trend of overfished stocks may have been reined in (Fig. 4). Reflecting this, most of the projections proposed in the recent literature estimate that the global fisheries’ landings are likely to be stable in the short to medium term. The OECD-FAO model for instance estimates that capture [i.e. wild] fisheries will be 5% higher by 2024 than it is was in 2013, that is, around 96 Mt (OECD-FAO 2013) while the World Bank-FAO-IFPRI model estimates that this will be around 93 Mt in 2030. These figures are at a global scale”.
Which indicates that, broadly, the headline claim that “By 2050, the oceans will contain more plastic by weight than fish” is correct in terms of its two inputs.
However, the claim omits a third factor. The report appears to assume constant ever-increasing accumulation of plastics,1 without degredation by plastic-eating and oil-munching ocean microbes. My search of the full report for “biodegradation” found only discussion of the man-made production of deliberately biodegradable items (i.e.: possible eco-friendly replacements for the plastic packaging used for potato chips, kebab meals, soda bottles and suchlike). The report appears to have no mention at all of natural ocean biodegradation (decomposition) of marine microplastics in the open ocean. To be more certain I hadn’t missed such a mention, I then further searched the report for “microbial”, “microbes”, “microorganisms” and “bacterial”. Nothing relevant was found. This omission seems a curious one for such an in-depth report to such a high-level group.
Thus it appears that the widely-heard claim that “By 2050, the oceans will contain more plastic by weight than fish” rests on two broadly valid estimates — that leakage of plastics into the oceans grows marginally each year to 2050, and that global wild fish stocks will remain broadly stable to 2050. However, it seems to me that those who wish to sustain this 2050 claim in future must also address the rate at which ocean microplastics are being “cleaned up” [backup PDF] by naturally occurring microscopic ocean life.
1. The specific volumes for the claim are that the ocean currently has an estimated 150 million tonnes of plastic debris and microplastics in it, with 8 million tonnes newly added each year. And that by 2025 there will be 1 tonne of ocean plastics for every 3 tonne of fish (meaning: 270 Mt), and that by 2050 fish and plastics will be equal (meaning: 812 Mt each). ‘Accumulation without biodegradation’ thus appears to be implicit in the forecast.