According to the United Nations Environment Programme marine debris is any persistent, manufactured or processed solid material discarded, disposed of or abandoned in the marine and coastal environment. Of the 120 marine mammal species listed on the IUCN Red List 54% are known to have been entangled in or have ingested plastic debris, according to the Global Environment Facility's report, Marine Debris: Defining a Global Environmental Challenge. Evidence of harmful effects of plastic on wildlife is mostly restricted to observations on individual specimens that have become entangled in or have ingested plastic debris. Plastic debris has also been implicated in the transport of non-native invasive species which can raft considerable distances on floating debris. Physical effects, such as entanglement of seals and other animals in drift plastic, increases with the size and complexity of the debris and potential chemical effects are likely to increase with a reduction in the size of plastic particles.
A good part of the marine debris from land-based sources results from unsustainable production, consumption, and poor waste management. Increased development, urbanization, and consumerism lead to increases in the use of disposable and non-degradable products and packaging, which results in increased generation of solid waste. Poor management or mishandling of waste materials creates the foundation for land-based sources of marine debris. The sources and movement pathways for plastic in the marine environment are in the publication Plastic Debris in the Ocean: UNEP Yearbook 2011.
Large quantities of debris can now be found in the most remote places of the ocean, and persist almost indefinitely in the environment. Dr. Melanie Bergmann from the Alfred Wegener Institute for Polar and Marine Research reports that biologists have recorded increasing amounts of plastic litter in the Arctic deep sea.Their studies confirm that the amount of marine debris lying on the seabed, mostly plastic, has doubled today compared to ten years ago.