Researching waste in German rivers

Scientists are well aware of how just how polluted the German seaside is. But less-known is how much garbage ends up in the sea via rivers.

To close this knowledge gap, thousands of students aged 10 to 16 have worked together with scientists from the north German research lab Kieler Forschungswerkstatt.

Over the last two years, the children and teenagers, from 300 different schools, applied scientific methods to collect trash in and along rivers, documenting their findings along the way.

Scientists have now analyzed the data, which represents the largest study of waste in German rivers to date. The results are alarming, says teacher and scientist Katrin Kruse, and paint a different picture than most Germans have of their environment.

DW spoke with Kruse, who works at the Kieler Forschungswerkstatt and at a German high school where she supervised the project "Plastikpiraten," or plastic pirates.

DW: What's the state of German rivers?

Katrin Kruse: They are not as tidy and clean as one would like to think. Our results debunk the myth that Germany isn't responsible for the garbage in the oceans. We are responsible - because trash in rivers ends up at the seaside. It doesn't matter whether you live in Schleswig-Holstein [a state in northern Germany bordering the North Sea and the Baltic Sea] or in Bavaria [a state in southern Germany]. 

How much trash did the students find in the rivers?

The students collected in total 10,897 pieces of rubbish in an area of 16,611 square meters on the riverbanks. Let's illustrate it like this: If you imagine a classroom of 50 square meters, this would mean that 33 garbage pieces would be lying on the floor.

We are still analyzing how much microplastic is in the rivers. The students collected more than 200 samples; we have evaluated 50 of them. What we can tell so far is that half of these samples contain microplastics — around five plastic particles per cubic meter.

This doesn't sound like a lot. But the Rhine River, for example, sends 2,900 cubic meters of water per second into the North Sea. If you extrapolate our findings, this would mean that 14,500 pieces of microplastic ends up in the ocean — per second. That's an entirely different scale.

It does sound like a lot of garbage. Were you and the students surprised by the results?

My colleagues and I at the Kieler Forschungswerkstatt have been researching plastic waste in the ocean for the last five years. A while ago, sperm whales were stranded on the shores of the North Sea, and they had a lot of plastic waste in their stomachs. We are increasingly aware that in Germany, a lot of garbage ends up in our oceans.

But for the students, this was totally new. They usually think that we don't have this problem in Germany. Our streets, riverbanks and beaches get regularly cleaned.

But our results painted a different picture. The students were very alarmed by how much garbage they found – especially how much plastic. I think that the research will leave a lasting impression on them.

"Plastic pirates" is a citizen science project. How did the students and scientists work together?

The students learned scientific methods in the classroom and then went out to the rivers to apply them. They documented everything and took photos. Then, they uploaded their results to a website, where they could compare their findings with the findings of their peers from other schools.

The students sent their microplastic samples to the Kieler Forschungswerkstatt. Based on these samples and the uploaded photos, the scientists could double-check the results. This step is critical in citizen science projects in order to guarantee the quality of the data.

In all, 5,500 teenagers participated in the scientific study. This is simply amazing if you consider how long a small group of researchers would have taken to collect this amount of data. The students did a great job.

What was the feedback from the students?

They were totally thrilled that they were taken seriously by scientists, and that they could work as scientists themselves. On the other hand, they were also shocked to see how much garbage they collected. One group even witnessed how animals were entangled in plastic waste and or were eating trash.

We hope that students learn from this experience and change their habits. That they don't litter. That they go home and tell their parents they don't want to buy products packed in plastic anymore.

Will the plastic pirate project continue?

We would very much like to continue it. The project was part of the Science Year Seas and Oceans that ended in 2017 [an initiative by the German Education Ministry]. So we need to see how to finance it further. We are positive we can continue, since we collected such a huge amount of data that is significant for Germany and for the rest of the world. The students also said they would like to continue. They are very motivated to do their bit against garbage in the oceans.

Katrin Kruse is a biology and chemistry teacher at the Selma Lagerlöf high school in the northern German town of Ahrensburg. She is also a scientist at the Leibniz Institute for Science and Mathematics Education, conducting research into citizen science projects around microplastics.

The interview was conducted by Katharina Wecker and has been translated from its original German.