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Marine Litter

Vital Graphics


Estimates of the open ocean surface stock of plastic

debris have been steadily rising from 7,000–35,000 tonnes

(Cózar et al., 2014) to 66,000 tonnes (Eriksen et al., 2014),

and to 93,000–236,000 tonnes (van Sebille et al., 2015).

The variation is mainly explained by differences in data

standardization and methods used to scale up to global

loads. Including floating particles larger than 200 mm, not

considered in the figures above, would add a minimum of

203,000 additional tonnes to these estimates (Eriksen et al.,

2014). Even using the highest of these figures, plastic debris

represents only about 1 per cent of the 34 million tonnes of

plastic waste estimated to be floating in the open ocean.

Several explanations are put forward to account

for the mismatch of about 99 per cent between the

above generic calculation of the amounts of buoyant

plastic in the open ocean and the amounts so far

estimated through direct measurement, extrapolation

and modelling (Cózar et al., 2014; Eriksen et al., 2014;

van Sebille et al., 2015). This could be due to transfer

mechanisms that are hard to measure, such as shoreline

deposition, decreased buoyancy due to fouling, uptake

by biota and excretion through sinking faecal pellets,

degradation, and high-energy oceanographic events

leading to massive transportation from surface coastal

areas to the deep open ocean. It has also been pointed

out that the methods used so far to measure floating

plastics do not capture the largest or the smallest items,

thus leading to concentration underestimates.

In summary, it is very important to note that while a lot of

attention has been paid to the accumulation and potential

impacts of plastics on the surface of the open seas, and

solutions for its clean-up, this accounts for only about 1

per cent of the plastics estimated to have been released

into the ocean. The other 99 per cent has received much

less attention and, even if we improve the methods for

determining the distribution of plastics in open ocean

waters (i.e. at the surface or through the whole water

column), these calculations indicate that less than 30

per cent of plastic debris “resides” in open ocean water.

The remaining nearly 70 per cent – accumulated where

sensitive ecosystems and many important economic

activities are found – has been overlooked. The focus

needs to be broadened to include risk assessment and

clean-up operations in these areas.

86 million tonnes Total plastic estimated to have ended up in the sea 1 29 million tonnes 3 23 million tonnes 2 34 million tonnes 210 000 - 439 000 4 tonnes 50 000 tonnes/year Annual input from maritime activities* Coastline and sea oor Coastline and sea oor * Latest estimates available are from the 1970s Coastal ocean waters Coastal ocean waters Open ocean waters Open ocean waters Floating on the open ocean surface Floating on the sea surface = 100 000 tonnes Plastic mass Sources: GRID-Arendal own calculations, each source is indicated in the notes 1 Calculated as 1.4% of all the plastics produced since the 1950s. From Jang et al., 2015 Notes: 2 Lebreton et al., 2012 3 Assuming 66% of the plastic is buoyant. From Jambeck et al., 2015 4 From Cózar et al., 2014; Eriksen et al., 2014; van Sebille, 2015 Howmuch plastic is estimated to be in the oceans and where it may be Floating plastic, just the tip of the iceberg 26.8% 0.5% 33.7% 39%