Rivers are the main conduits for human litter transferred from land to the ocean. A new study shows that European countries release more than 600 million floating macrolitter items (> 2.5 cm) to the ocean in a single year. The team behind this study is composed of 22 institutions from 12 different countries and includes Italian researchers from CNR. The team demonstrated that plastic is the principal litter material observed in rivers across Europe.
Eight out of 10 litter items are made of plastic, including single-use plastics such as bottles, packaging (like food wrappers), and bags. Almost 40% of the floating litter are pieces of plastic (fragments of larger items), meaning many plastic items begin to fragment in the river basins before reaching the ocean. Turkey, a Eurasian upper-middle-income economy, is the top contributor (17%) in the list of countries included in the study. More importantly, high-income economies share 64% of the total annual litter loading, including Italy, UK, Spain, and Greece in the top five contributors.
“Our assessment demonstrates that countries with supposedly the best waste management strategies are not able to stop plastic pollution from reaching their waterways and, eventually, their seas” says Daniel González, researcher at the University of Cádiz (UCA) and lead author of the study.
“This is happening in a scenario where high-income economies are relieving pressure on their systems by exporting plastic to third countries”, adds Andrés Cózar, co-author of the study and head of the UCA Marine Litter Lab (www.marinelitterlab.eu). Following China’s restriction of plastic imports in 2017, Turkey has emerged as one of the world’s largest export destination’s for European plastic waste. Recently, NGOs have reported that an important part of the UK’s plastic waste exports is being dumped and burned in Turkey, rather than recycled. High-income economies show the largest plastic waste generation per capita, and the export is a common pathway for their low-quality plastic waste.
“Given the incapacity of high-income economies to deal with their own plastic waste, mitigation strategies should mainly be oriented towards reducing plastic consumption and avoiding waste generation”, Daniel says. Why do large rivers deliver less litter to the ocean than small ones? In Europe, around 70% of the annual litter loading is channelled through numerous “small” coastal basins (i.e., catchment areas smaller than 100 km2).
The authors explain this finding based on two arguments. Firstly, the 32 European and Eurasian countries considered in the study include litter inputs from 23,000 of these small coastal basins, related to small rivers, streams, and intermittent torrents that are activated by storm waters. The plastic emission from basins smaller than 100 km2, many of them highly populated, has not been considered in previous models.
“Unlike suggested to date, our data show that plastic emitted to the ocean is an issue beyond a limited number of largely polluted rivers and low-income economies”, Daniel explains. Secondly, field measurements show that large rivers are less efficient in transferring floating macrolitter to the ocean than small basins.
The study is based on the world´s largest database on riverine floating macrolitter input to the ocean. More than 700 field monitoring datasets were collected in 42 rivers from 11 countries across Europe, from large rivers (like Danube, Rhône, Vistula, and Douro) to very small streams. Large European rivers are highly regulated, disrupting their natural flow. ‘The Danube River has more than 700 dams and weirs in its main tributaries, enduring macrolitter transport downstream to the coast” Daniel adds. “Large quantities of plastic most likely remain trapped upstream of dams, beached on riverbanks or entangled in the vegetation, waiting to be fragmented before continuing their journey to the ocean in the form of small pieces and microplastics, Andrés points out. The demonstrated mobility and persistence of plastic litter calls for actions focused on reducing the leakage at source.
Reference: González-Fernández, D., Cózar, A., Hanke, G., Viejo, J., Morales-Caselles, C., et al., 2021. Floating macrolitter leaked from Europe to the ocean. Nature Sustainability, doi.org/10.1038/s41893-021-00722-6
Forte S. Teresa - Pozzuolo di Lerici
19032, Lerici (SP)