90 Percent

“Every year, millions of tonnes of plastic debris ends up in the sea – a global environmental problem with unforeseeable ecological consequences. The path taken by plastic to reach the sea must be elucidated before it will be possible to reduce the volume of plastic input. To date, there was only little information available on this. It has now been followed up by an interdisciplinary research team who were able to show that plastic debris is primarily carried into the sea by large rivers.

Honnery-Rachel

“In the meantime, minute plastic particles can be found in the water in virtually every sea and river. This constitutes a serious and growing global environmental problem. There are enormous quantities of input each year and plastic weathers only very slowly. Marine life can be harmed by the tiny plastic particles floating in the water. One example of how this happens is when fish, seabirds or marine mammals mistake the particles for food and consume them. “It is still impossible to foresee the ecological consequences of this. One thing is certain, however: this situation cannot continue,” says Dr. Christian Schmidt, a hydrogeologist at the UFZ. “But as it is impossible to clean up the plastic debris that is already in the oceans, we must take precautions and reduce the input of plastic quickly and efficiently.”

“However, in order to take practical measures to reduce plastic input, it will be necessary to answer the initial questions: Where does all the plastic come from anyhow? And how does it get into the sea? Schmidt and his team addressed these questions in a study that recently appeared in the current issue of “Environmental Science & Technology” journal. For this purpose, the researchers analysed various scientific studies that examined the plastic load – that is the quantity of plastic carried by the water – in rivers. They converted the results of the studies into mutually comparable datasets and determined the ratio of these figures to the quantity of waste that is not disposed of properly in the respective catchment area. “We were able to demonstrate that there is a definite correlation in this respect,” says Schmidt. “The more waste there is in a catchment area that is not disposed of properly, the more plastic ultimately ends up in the river and takes this route to the sea.” In this context, large rivers obviously play a particularly large role – not only because they also carry a comparatively large volume of waste on account of their larger discharge. Schmidt says, “the concentrations of plastic, i.e. the quantity of plastic per cubic metre of water are significantly higher in large rivers than small ones. The plastic loads consequently increase at a disproportionately higher rate than the size of the river.”

“The researchers have also calculated that the ten river systems with the highest plastic loads (eight of them are in Asia and two in Africa) – areas in which hundreds of millions of people live, in some cases – are responsible for around 90 percent of the global input of plastic into the sea. “Halving the plastic input from the catchment areas of these rivers would already be a major success”, says Schmidt. “To achieve this, it will be necessary to improve the waste management and raise public awareness for the issue. We hope that our study will make a contribution to a positive development so that the plastic problem in our oceans can be curbed in the long run.”

Text: Rivers carry plastic debris into the sea

Pic: Rachel Honnery, ‘…researching marine plastics and their role as kipple’.

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Surface Trawls

“Publication of the garbage patch study coincided with a new report from Britain, Foresight Future of the Sea, that found plastic pollution in the ocean could triple by 2050 unless a “major response” is mounted to prevent plastic from reaching the ocean. The report declared plastic pollution to be one of the main environmental threats to the seas, along with sea-level rise and warming oceans.

“The study included two aerial surveys in October of 2016 that took 7,000 images, and 652 ocean surface trawls conducted in July, August, and September of 2015 by 18 vessels.

“The surface trawls also filled in the rest of the story.

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“Fifty plastic items collected had a readable production date: One from 1977, seven from the 1980s, 17 from the 1990s, 24 from the 2000s, and one from 2010. Researchers also found 386 objects with recognizable words or sentences in nine different languages.

“The writing on a third of the objects was Japanese and another third was Chinese. The country of production was readable on 41 objects, showing they were manufactured in 12 different nations.

“The study also concluded that plastic pollution is “increasing exponentially and at a faster rate than in surrounding waters.” Others are not as confident that the conclusion indicates a dramatic change in distribution of marine debris. Much of the world’s marine debris is believed to lie in the coastal regions, not in the middle of oceans.

“Leonard says he was impressed with the scope of the study. “It’s strong science,” he says. “But at the same time, in this field, the harder we look, the more plastic we find.”

Text: The Great Pacific Garbage Patch Isn’t What You Think it Is, National Geographic