Ten rivers carry 90 per cent of plastic found in Earth’s oceans
GERMANY: Ninety per cent of the plastic entering the ocean comes from just 10 rivers, a study has found.
Two of the rivers, the Nile and the Niger, are in Africa, and the other eight are in Asia: the Yangtze, Yellow, Haihe, Pearl, Mekong, Amur, Ganges and Indus.
They are responsible for such a high percentage of plastic pollution because they are some of the world’s longest rivers, have huge populations living alongside them and are in countries that tend to have poor controls on waste, according to the Helmholtz Centre for Environmental Research in Germany.
Tackling the sources of the pollution along these rivers would be the most effective way of reducing the overall problem of plastic in the ocean, suggests the study published in the journal Environmental Science & Technology.
The greatest source of pollution is China’s Yangtze River, which carries up to 1.5 million tonnes of plastic into the ocean every year. The Thames, by contrast, transports 18 tonnes of plastic annually into the sea.
The paper was based on analysis of previous studies of plastic pollution that involved 79 sampling sites along 57 rivers. The authors found the quantity of plastic per cubic metre of water was significantly higher in large rivers than small ones.
Christian Schmidt, lead author of the report, said: ‘‘Halving the plastic input from the catchment areas of these rivers would be a major success. To achieve this, it will be necessary to improve waste management and raise public awareness of the issue.’’
The researchers plan to study how long plastic debris takes to reach the sea once it gets into a river. Schmidt said it was important to know this to devise effective methods of trapping and removing the plastic.
The Ocean Cleanup group in the Netherlands hopes to deploy floating barriers to clean up giant patches of plastic waste in the deep ocean and similar technology could be used in the mouth of rivers. Other potential solutions include floating bins which suck rubbish from the sea. One type, called a Seabin and capable of collecting 1.5kg of waste a day, is being tested in Portsmouth harbour.
However, marine scientists say the best solution is to prevent plastic waste from getting into rivers in the first place.
A study in June also found that a small proportion of rivers accounted for most of the plastic pollution, but the results were not as extreme as those produced by the Helmholtz Centre.
The earlier study, published in Nature Communications, concluded that two thirds of the plastic that enters the ocean from rivers comes from 20 rivers.
Brendan Godley, professor of conservation science at the University of Exeter, said that the results should not be used as an excuse to drop proposals for more or better controls on plastic waste in the UK.
‘‘A lot of the rubbish on British beaches is coming from British maritime activities and poor waste governance in Britain.
‘‘It is not all from far away and it can’t all be blamed on other people.
‘‘If we in Europe made a big difference to the way we managed and used plastic we would have less plastic in our seas. But it is true that a small proportion of rivers are responsible for most of the plastic tipping out - it might not be ten rivers but it could be 20.’’
A United Nations resolution, agreed unanimously last week, called for greater action ‘‘to prevent and significantly reduce marine pollution of all kinds’’ by 2025.