Litter travels from land to sea

It is often difficult to identify the origin of litter that ends up in the sea. Similar-looking debris can come from entirely different places, either nearby or far away. The litter may also have changed so much during its journey or time in the sea that it can no longer be traced.

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Littering is most intense in population centers, where there are many people and various activities. However, the main sources of marine litter vary greatly by region. A key factor is the type of litter-generating activities practiced in each area and how direct the pathways to the sea are.

Most litter comes from land

Litter collected from Finnish beaches between 2012 and 2018 has been classified based on their most likely sources. According to the analysis, the largest contributors to litter were tourism and beach users. Other significant sources included boating and shipping, as well as construction.

At sea, in addition to water traffic, the main sources of litter emissions are fishing and aquaculture. While land-based litter requires a pathway to reach the sea, any litter released at sea ends up directly in the marine environment.

Transport of litter

Litter reaches the sea primarily through various waterways. Rivers, streams, and ditches are significant transport routes for debris. In coastal cities especially, stormwater plays a major role in marine littering, as untreated stormwater can carry street litter directly into the sea.

Wind and air currents also transport especially lightweight and small litter. Micro litter can also enter the sea through wastewater discharges from treatment plants or when sewage sludge is used, for example, in landscaping.

At sea, the journey of litter continues. Certain plastics and other lightweight debris can travel long distances with currents or sea ice.