Until a few years ago, scientists believed that the main cause of the accumulation of plastic waste in the seas and oceans was attributable to a rather limited number of rivers, about twenty, almost all located in Asia.
This belief stemmed from a study that concluded in 2017 that 90% of plastic waste in the seas was caused by the Nile, the Amazon, the Yangtze River, and about two dozen smaller rivers. Efforts were largely focused on cleaning up these rivers, ignoring the fact that the problem was much larger.
Over 1,000 rivers are responsible for polluting seas and oceans
A 2021 research published by Science Advances has in fact overturned these results and it has been understood that There are more than 1,000 waterways that are most responsible for the presence of plastics and microplastics in the seas. A much more complex scenario, which makes it equally difficult to find effective solutions in the short term. The 2021 research was more in-depth than the previous one: the analysis covered over 1,600 rivers, considering factors that had previously been ignored, such as the type of land, the effects of rainfall, proximity to population centers and so on.
This study also highlighted another aspect that was previously poorly taken into consideration, namely the fact that Not all waste in rivers reaches the sea. There are rivers that “host” various types of garbage for decades.
This evidence therefore underlines the fact that rivers that carry waste to the seas and oceans are much more than previously thought and in many cases they are minor rivers. The latter are concentrated in various areas of Asia (such as Malaysia and the Philippines) but also in Central America. Furthermore, not all waste reaches the sea, making the waters of the rivers themselves highly polluted.
Possible solutions
What is being done to solve the problem? The research conducted in 2021 was funded by The Ocean Cleanup the NGO founded by the Dutch entrepreneur Boyan Slat, committed to cleaning the Pacific Ocean from waste thanks to Inceptor, a kind of “garbage eating” machine. This is certainly a noteworthy project but we reiterate that it is not enough: to really solve the problem at the root we need to shift the focus from the raw material to the education of people. The general public opinion and what is mainly spread by the media is that the problem is plastic itself, when in fact it is a precious material, which can have multiple lives, if disposed of and recycled correctly. The problem is not plastic but the fact that it is poured into rivers, seas and soils.
The Italian situation: the Po
In Italy, fortunately, the health of our rivers is much better than in other countries. Recently, an in-depth analysis conducted by the Po River District Authority in collaboration with La Sapienza University of Rome, Arpa Daphne and AIPo has highlighted that the amount of microplastics in the waters of the Po is much lower than previously thought and does not reach critical levels.
To put it in numbers, the number of microplastics per unit of volume in the Po varies between 2.06 and 8.22, while in the Seine in France it is between 9.6 and 63.9 (2019 Alligant research), Oujiang, Minjiang in China between 100-4100 (2019 Zhao research), the Thames in Great Britain stands at values of 14.2-24.8 (2020 Rowley research), Clyde, Bega and Hunter estuary in Australia 98-1032 (2019 Hitchcock & Mitrovic research), as can be learned from the website UNIONPLAST's Right Collection.
This news is certainly reassuring but it should not make us lower our guard: on the contrary, it is essential to continue to analyze in depth the causes and consequences of river pollution to find increasingly efficient solutions. A key role is in informing and educating people: greater efforts must be made to ensure that everyone is more aware of the risks deriving from pollution and to prepare resources that favor separate waste collection and waste disposal.
