When the summer celebrations on the Isar are over, tons of rubbish are often left behind. Garbage collectors have to collect around 4,000 kilograms on the beaches in Munich on summer weekends. Even they don’t find everything that was simply thrown away. Thousands of cigarette butts, small plastic or aluminum foils, but also bottle caps remain between the pebbles on the beach or drift down the Isar. “The smaller the garbage, the bigger the problem,” says Frank Meissner, a board member at the Isar fishermen in Munich. The problem is called microplastics and microwaste.
The Isar fishermen, who are considered the Munich nature conservation association, have now investigated the problem and collected 108 kilograms of micro-waste within three hours in a Ramadama campaign with almost one hundred members on the Isar bed under the Thalkirchner bridge. In previous years, the Isar fishermen had already collected rubbish on and in the Isar and salvaged junk bikes and e-scooters, among other things. But this time they have concentrated on collecting beer mats, cigarette filters, packaging and tin cans with magnetic lifters, garbage tongs and wooden tweezers. Because these are the biggest sources of microplastics, which first collect in the river and later in the sea. “The source of all the waste in the oceans is often the rubbish on our doorstep, or in this case on the banks of the Isar,” says Meißner.
As is well known, the Isar flows into the Danube, which flows to the Black Sea. Four years ago, researchers at the University of Bayreuth found that the amount of microplastics in the Isar between Baierbrunn in the south of the city and a measuring point north of it has increased tenfold. At that time, the scientists could not explain where the massive entry came from. In addition, it was not clear in the study, which was considered to be the largest worldwide on the subject of microplastics, in which period the samples were taken. At that time, however, it was almost impossible that the microplastic came from the tire abrasion of thousands of cars that drive over the bridges in Munich every day. It is more likely that it is party rubbish that was carelessly left lying on the bank or even thrown into the Isar.
Bags of rubbish that often take hundreds of years to decompose in nature.
(Photo: Leonhard Simon)
And it is precisely this garbage that is particularly problematic. According to various studies by the Federal Environment Agency, the German Alpine Association and the United States Meteorological and Oceanographic Administration, NOAA, it takes 200 to 400 years for an aluminum-coated tetrapack to decompose, and some plastic drink holders for six-packs also up to 400 years. According to calculations, a beer can takes about 200 years to dissolve. A PET plastic bottle could lie in the landscape for up to 500 years.
Cigarette butts, on the other hand, appear harmless and take two to seven years to decompose. However, each butt pollutes about 40 liters of water and harms organisms such as fish, birds and insects. According to the Isar fishermen, bottle caps take between 80 and 200 years to decompose. In addition, they are coated with plastic on the inside and paint on the outside. Klaus Betlejewski, board member of the Isar fishermen, says about the Ramadama campaign: “We clean up our Isar because we don’t give nature the rest.”
Researchers from the University of Bayreuth, led by Professor Christian Laforsch, and scientists from the Technical University of Munich, who have examined not only the Isar but also the Danube and other rivers in southern and western Germany for microplastics, want to publish further research results this year. They are apparently also investigating the question of why so much microplastic collects in the river in the Munich area and drifts towards the Danube.