Sophie Cook

In the 65 years between 1950 and 2015, the world cumulatively produced nearly 8 billion tonnes of plastic (Ritchie and Roser, 2018). Mismanaged plastic waste now permeates our rivers and oceans, threatening the health and stability of critical ecosystems. The California-born ‘Ocean Cleanup’ project is starting to make headway into tackling this constantly expanding pile of anthropogenic marine detritus.

It is estimated that the surface waters of our oceans contain 5 trillion plastic particles (Erikson et al., 2014). Global circulation and ocean currents chorale this debris into foci at the centre of sub-tropical gyres, from which they cannot escape. Five such gyres exist – the largest of which has come to be known as ‘The Great Pacific Garbage Patch’ (GPGP). Found halfway between California and Hawaii, it is not actually a solid ‘garbage island’, but a vast area of ocean where a huge amount of plastic waste is concentrated.

Make-up of the Great Pacific Garbage Patch

The GPGP covers an area of 1.6 million square kilometres, equivalent to three times the size of France (Lebreton et al., 2018). Of the 5 trillion plastic particles in our oceans’ surface waters, it’s thought that more than 1.8 trillion are found here (Ocean Cleanup, 2022). Weighing in at a total of 80,000 tonnes, it is roughly equivalent to the weight of 500 jumbo jets. The distribution of plastic in the GPGP is not uniform: it’s density gradually increases towards the centre where there are hundreds of kilograms of plastic per square kilometre (Figure 1).

Environmental impact

The GPGP has huge implications for both marine ecosystems and human health. The variety of plastic types and sizes found in the GPGP present different challenges. By mass, 46% of the GPGP is made up of fishing gear including nets, ropes, and lines (Ocean Cleanup, 2022). These ‘ghost nets’ are perilous traps which regularly ensnare both marine life and seabirds. Furthermore, researchers found that in the upper few metres of the GPGP, there is 180 times more plastic debris than common prey species. This makes it far too easy for surface feeders such as seabirds and turtles to mistake plastic for food. Sea turtles caught in and around the GPGP were found to have diets consisting of up to 74% plastic by dry weight (Ocean Cleanup, 2022). In addition to the plastic itself, 84% of plastic samples were found to contain at least one bio-accumulative toxin (Chen et al., 2017). The bioaccumulation of microplastics and their associated toxins up the food chain is a major concern: not only for marine ecosystems, but for the fish and shellfish on our own dinner plates. Moreover, once larger plastics have broken down into microplastics (through the action of sun exposure and waves), they can infiltrate far down the water column, becoming much more of a challenge to remove (Kooi et al., 2015). Another emerging problem is the coastal species found living on 90% of plastic debris in the GPGP. These coastal animals are living far from their natural habitats out on the high seas and are fuelling concerns that ocean plastic is facilitating the spread of invasive species around the globe (Haram et al., 2021).

Source of the problem

Each year, between 1.15 to 2.41 million tonnes of plastic drain out of rivers and into our oceans (Lebreton et al., 2017). In total, 80% of ocean plastics originate from terrestrial sources, while the remaining 20% come from marine activities like fishing. It is estimated that Asia accounts for 81% of global plastic inputs into the ocean (Ritchie, 2021). This does not mean that Asia is consuming more plastic than other continents, but that their management strategies for disposing of plastic waste are not as efficient. Moreover, many Western countries export their recyclable plastic waste to Asian countries for processing, thereby also exporting their responsibility for managing that waste. Although this provides a valuable source of income for many developing countries, some have recently announced bans on further waste imports as their capacity to deal with the mounting piles of often impure plastic have become untenable (BBC, 2019). However, these import bans will not change the fact that the improvement of waste management systems across the developing world is critical to reducing ocean plastic pollution.

The Ocean Cleanup project

The Ocean Cleanup began as a research expedition: to quantify the scale of the problem posed by the GPGP. After collecting huge amounts of data, they have now moved into their ‘cleanup’ phase, which involves a large barrage system capable of collecting vast quantities of plastic quickly and efficiently. The first prototype was tested in the North Sea in 2016, and in October last year, they launched ‘System 002’ into the North Pacific (Ocean Cleanup, 2021). Over 47 days of operation, ‘System 002’ removed 40,000 kilos of plastic, and the expedition is informing the design of the new and scaled-up ‘System 003’. The project is also targeting rivers as the primary source of ocean plastic. Research found that 1000 rivers are responsible for 80% of global riverine plastic emissions into the ocean (Meijer et al., 2021). The Ocean Cleanup have therefore developed and deployed solar-powered ‘Interceptors’ to autonomously extract floating river debris to prevent it from reaching the ocean and the GPGP. There are currently eight ‘Interceptors’ working in the field, and at full capacity, each can remove 50,000 kilograms of plastic each day from the world’s most polluted rivers (Ocean Cleanup, 2022(b)). By the start of 2021, the Ocean Cleanup had removed nearly 500 tonnes of plastic from oceans and rivers, and they plan to continue scaling up in size and efficiency (Ocean Cleanup, 2021).

The need for systemic solutions

The United Nations estimates that the environmental damage to marine ecosystems caused by ocean plastics totals around $13 billion US dollars (UN, 2014). It is estimated that by 2050, there will be more plastic in the ocean than fish (Ellen McArthur Foundation, 2016). Fishing line takes 600 years to fully biodegrade; plastic bottles take 450 years. This problem is not going to go away, even if we stopped producing plastic tomorrow. We need to take active steps to rectify the sheer volume of plastic already expelled into our oceans. Organisations like the Ocean Cleanup project are unusual as not only are they tackling the downstream problem (i.e., clearing up ocean plastic), but they are simultaneously tackling the upstream source of the issue issue through their work in key rivers around the world. Of course, this work needs to be partnered with efforts to improve plastic waste management, especially in Asia. We will never solve our global commons problems by only dealing with their symptoms, but we must systemically address their cause if we are to affect meaningful change.

References:

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Chen, et al. (2017), Pollutants in Plastics within the North Pacific Subtropical Gyre. Environmental Science and Technology 52, no. 2: 446-456, http://doi.org/10.1021/acs.est.7b04682 ↩

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Erikson M., et al., (2014). Plastic Pollution in the World’s Oceans: More than 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea. PLoS One 10;9(12):e111913. doi: 10.1371/journal.pone.0111913

Haram et al. (2021). Emergence of a neopelagic community through the establishment of coastal species on the high seas. Nat Commun 12, 6885. https://doi.org/10.1038/s41467-021-27188-6

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Lebreton, et al. (2017). River plastic emissions to the world’s oceans. Nature Communications 8, no. 15611, http://doi.org/10.1038/ncomms15611 ↩

Lebreton, et al. (2018). Evidence that the Great Pacific Garbage Patch is rapidly accumulating plastic. Scientific Reports 8, no. 4666, https://doi.org/10.1038/s41598-018-22939-w ↩

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