Sources, distribution and fate of marine debris

CSIRO led a three-year, world-leading survey of marine debris in Australian waters to help protect ecosystems and wildlife.

The Challenge

Plastic and other marine debris are a major environmental concern

Marine debris is a globally recognised environmental issue of increasing concern.

Examining marine debris on the beach

Marine ecosystems worldwide are affected by human-made refuse, much of which is plastic.

Marine debris comes from both land and sea-based sources and can travel immense distances. It can pose a navigation hazard, smother coral reefs, transport invasive species and negatively affect tourism. It also injures and kills wildlife, has the potential to transport chemical contaminants, and may pose a threat to human health.

Our Response

Building and sharing knowledge on marine debris impact

CSIRO has completed a survey of sites approximately every 100 km along the Australian coastline. This body of work represents the largest scale, integrated, rigorous data to have been collected anywhere in the world aimed at addressing the marine debris issue.

Parts of this research engaged with thousands of students, teachers and Shell employees and has reached more than one million Australians, helping to educate them about, and increase their understanding of, the problems of marine debris.

The Results

Sources, distribution, and ultimate fate of marine debris

We found that within Australia, approximately three-quarters of the rubbish along the coast is plastic. Most is from Australian sources, not from overseas, with debris concentrated near urban centres. In coastal and offshore waters, most floating debris is plastic. The density of plastic ranges from a few thousand pieces of plastic per square kilometre to more than 40,000 pieces of plastic per square kilometre. Debris is more highly concentrated around major cities, suggesting local sources.

Exposure of marine wildlife to debris

Litter impacts wildlife directly through entanglement and ingestion and indirectly through chemical affects. As the quantity of debris increases in the marine environment, so does the likelihood of impacts from debris to marine animals. Plastic production rates are intensifying, and the volume of refuse humans release into marine systems is growing at an exponential rate. Even toothpaste and personal care products can have plastic microbeads in them. These microplastics can be mistakenly eaten by a range of marine species.

Effect on marine wildlife populations

Globally, approximately one third of marine turtles have likely ingested debris, and this has increased since plastic production began in the 1950s. Most items eaten by turtles are plastic and positively buoyant. Smaller oceanic turtles are more likely to ingest debris than coastal foragers; herbivores are more likely to ingest debris than carnivorous species; oceanic leatherback turtles and green turtles are at the greatest risk of ingested marine debris effects; and benthic turtles show a strong selectivity for soft, clear plastic that resembles natural prey such as jellyfish.

Around the world, nearly half of all seabird species are likely to ingest debris. Birds eat everything from balloons to glow sticks, industrial plastic pellets, hard bits of plastic, foam, metal hooks and fishing line. CSIRO researchers and colleagues found that 43 per cent of short-tailed shearwaters have plastic in their gut. Young birds were more likely to ingest debris and ate more pieces of debris than adult birds. A global hotspot for seabird impacts exists in the Tasman Sea south of Australia. CSIRO predicts that plastics ingestion in seabirds may reach 95 per cent of all species by 2050, taking into account the steady increase of plastics production.

Seabirds, turtles, whales, dolphins, dugongs, fish, crabs and crocodiles and numerous other species are killed and maimed through entanglement. We estimate that between 5,000 and 15,000 turtles have been killed in the Gulf of Carpentaria after becoming ensnared by derelict fishing nets, mostly originating from overseas. For pinnipeds in Victoria, the majority of seal entanglements involved plastic twine or rope, and seals become entangled in green items more than in any other colour. In general, young seals are entangled in greater numbers than adults.

What you can do

Together, we can contribute to the improved understanding of the types, amounts and sources of debris that arrives on Australia's coastline. Visit the online national marine debris database.

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