Marine litter, also known as marine debris, comprises wastes which have been released into oceans, seas, lakes and rivers or other waterways either by deliberate or accidental act. These wastes are any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment. It is the result of human neglect and inadequate waste management practices.
Marine litter adversely affects marine ecosystems. It has environmental, health and safety impacts on marine mammals, seabirds, turtles and fish. Debris which sinks to the ocean bottom adversely affects coral systems and interferes with sea floor life.
Marine litter is a global problem. It does not respect national boundaries or territories. Litter and debris produced in one country or region will often end up elsewhere.
The main land-based sources are:
The main ocean/sea-based sources are:
The Nature of the Problem
Marine litter comprises an enormous variety and number of anthropogenic items including plastic pellets, plastic bags, buoys, rope, bottles, cans, fishing lines and nets and even medical wastes. The contents of the estimated 10,000 containers are lost at sea every year from container ships also add to the problem.
There is no accurate data on the type and amount of marine litter and debris. Nor is there any substantiated data on the numbers of marine mammals, seabirds, fish or corals affected by such debris.
Some reports are described as marine litter surveys but most are actually surveys, or clean-ups, of beach and coastal litter. These give only a partial picture and only some of the litter will end up at sea.
Accurate measurement is probably impossible because it would have to measure debris entering from rivers, storm sewers, beaches, dumping at sea, industrial activity and many other sources.
However, the EU has estimated that in the North Sea, half of all marine debris comes from ships. A group of UN experts has estimated that globally, up to 80% of marine litter arises from land. The US Academy of Sciences has suggested that there is as much as 6.4 million tonnes of marine debris dumped annually.
A number of studies support the view that the majority of surface marine litter – possibly of the order of 75% - is plastics-related and includes pellet, products and fragments. As plastics are usually lighter than water, they float on the surface and so are very apparent.
Glass, metals and even wood litter tends to sink to the bottom of the ocean, sea, lake or river and so is less noticeable and is only found if bottom surveys are conducted.
Once waterborne, debris becomes mobile, sometimes ending up in the middle of oceanic gyres where currents are weakest. The so-called Great Pacific Garbage Patch is the largest and best known. Some claim it covers a vast area containing at least three million tonnes of plastics, some that it is the size of Texas, others that it is smaller than Texas.
Controlling Marine Litter
There are many monitoring programmes around the world which provide some information on the types, quantities and distribution of marine litter and debris, identifying sources and increasing public awareness of the problems and issues.
The United Nations and some governments have a range of measures to prevent further accumulations and to clean up existing accumulations on beaches and in the oceans and seas, including:
In addition, many national and regional governments impose higher standards on waste management and landfilling.
The Honolulu Strategy, agreed at the 2011 5th International Marine Debris Conference, is particularly noteworthy. Representatives of 38 countries agreed a commitment to reduce the amount and impact of both land- and sea-based sources of marine debris and the amount and impact of marine debris on shorelines and beaches aimed at stopping marine pollution by 2030.
The Rio+20 Conference committed to "take actions to reduce the incidence and impacts of such pollution in marine ecosystems in part by implementing the Honolulu Strategy. At the same time, the EU Marine Strategy Framework Directive sets out to ensure a "good environmental status in Europe’s seas by 2020”.
It has been suggested that marine litter reduction targets should be set. This however is impractical as ocean currents and seasonal factors make comparisons over time unreliable and in any case, the composition of marine litter will vary widely from place to place.”
Recognising that plastics debris is the major component of marine litter and debris, plastics industry organisations from 47 countries around the world signed up in 2011 to a "Joint Declaration for Solutions to Marine Litter”. More have signed up since.
This sets out actions by the plastics industry and, as a result, by late 2012 there were more than 140 projects around the world underway or planned to prevent plastics marine litter. These included preventing plastics pellet loss from manufacturing units, from transport and from distribution systems.