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Marine Litter
Vital Graphics
COMPARTMENTS AND STOCKS
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%