From rivers to the sea — the pathways and the outcome

What's the problem?

Tracing marine litter back to the rivers is the logical solution. It means studying the whole riverine system — from water catchments in cities to meandering creeks, major rivers and artificial structures (e.g. canals, weirs and dams) that make up Europe’s complex waterways. It also means gathering better data on similar networks outside Europe.

Limited monitoring, weak data and uncertain analyses continue to hamper the study of marine litter sources and pathways, making informed policy and action harder to implement. Two positive signs are the EU zero pollution package putting forward new monitoring requirements for microplastics in wastewater, and the United Nations Environment Programme providing new guidance for monitoring and assessing plastic in freshwater systems. Both provide a baseline for evaluating riverine emissions in the future.

We have to go upstream — to rivers — to understand the marine litter problem

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How does litter reach the sea?

Rivers carry litter to the seas, where it continues to accumulate. Because we have limited information about the true extent of riverine litter, the Eionet ETC report uses estimations from two recent studies: González-Fernández et al. (2021) and Meijer et al. (2021).

On average, 626 million ‘floating items’ are discharged into European seas every year. However, estimates vary from a conservative estimate of 307 million items to a top-end estimate of 925 million items.

Nonetheless, it is clear that two hotspots bear the brunt of nearly 90% of riverine floating litter in Europe. The Mediterranean Sea is receiving the largest share — more than one third of the total floating litter discharged by the rivers modelled. With almost two-thirds, river mouths in the Black Sea contribute the largest share relative to the number of emission points.

Spatial distribution of floating macrolitter inputs to the sea from Europe

Source: González-Fernández et al. (2021).

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Where are Europe's marine litter hotspots?

In contrast to our limited knowledge of riverine pathways, we have robust data about the extent of litter in the marine environment. In the Eionet ETC report, the EEA demonstrates the use of prototype Marine Litter Assessment Tool (MALT), which is used to identify ‘problem areas’ and ‘non-problem areas’ on Europe’s coasts. Only about 25% of coastal areas assessed have ‘non-problem area’ status.

The status of Europe’s seas

Note: For a more detailed explanation of the counting, coverage and analysis carried out using MALT, please consult the Eionet ETC report Marine litter in Europe: an integrated assessment from source to sea.

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EEA efforts to identify and classify major ‘problem areas’ and compare them with ‘non-problem areas’ in Europe’s marine environment reveal a number of noteworthy hotspots. Evaluations are based on the assessment of sea floor litter, beach litter and floating microlitter data from 2010 to 2021 in different locations.

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Although the area assessed in the Mediterranean region appears small, the data set on coastal pollution is comprehensive and geographically well-distributed. With 75% of the assessed area of Europe’s regional seas considered polluted, their current state is very concerning. 

What do regional differences reflect?

Comparing the average amounts of plastic packaging and small non-packaging plastic items (PPSI) recorded on the beaches of the four European regional seas, the Baltic Sea has the least amount of marine litter, followed by the North-east Atlantic Ocean. The Mediterranean Sea and Black Sea are the most polluted. These variations reflect regional differences in the estimates of both mismanaged plastic packaging and PPSI waste in coastal regions, and in the modelled riverine discharges of floating macrolitter (González-Fernández et al., 2021).

There is a correlation between poorer waste management and greater riverine litter on the one hand, and the amount of litter on European coasts on the other

Sources: (ETC/ICM, 2022a); González-Fernández et al. (2021); (ETC/ICM, 2022b).

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Without radical and coordinated action from all levels of government and without individual behavioural changes, marine litter will continue to pose a threat to marine life and human health — and to key economic sectors that depend on coastal and maritime environments.