Lifelines in a state of war

When you hear news reports such as the recent evacuations in Berlin after a bomb was found in the Spree River, what are your first thoughts?

Nicolas Wiese: We had an event very close to where the bomb was found that day and we wondered if it would have to be cancelled. Such events generally amaze me because of how dangerous bombs can still be, even many decades after they were dropped.

Claudia van Hasselt: I am always shocked by how long we have to deal with the consequences of wars that still affect our everyday lives. Bombs are weapons that, in addition to their mechanical dimension, cause problems primarily in chemical terms, such as phosphorus leaking from ammunition remnants in the Baltic Sea.

Christian Wolter: Finding ammunition remnants has also become part of everyday life on the Oder River. The area was a front line for such a long time that explosive ordnance still has to be cleared whenever houses are built near the riverbank or groynes are constructed in the river. The main problem is containers of explosive ordnance rotting in the water and leaking dangerous substances.

Oleksandra Shumilova: It strikes me again that the past of war remains particularly present in rivers. Sunken, unexploded mines can move and end up in areas that were previously safe. For example, there are cases in the Western Balkans where people are injured by mines left behind after the war in the former Yugoslavia 30 years ago.

Mr Wolter, do you come across any traces of past wars while working on the Oder and Spree rivers?

Christian Wolter: Not just like that, you have to look for them. During the Oder flood in 1997, weapons and ammunition were washed out in places where the summer dyke had broken. This area of the national park is now in the core zone and is closed to visitors because clearing it would be too costly. When we monitored the construction of the parallel construction near Reitwein between 2017 and 2019 from a fish ecology perspective, the explosive ordnance disposal team was on site and identified over 1,500 suspected items. While there were a few bombs and grenades, most of the items that set off the metal detectors were stones from the rockfill that came from mines near Aue.

Ms Shumilova, why is it still difficult to detect the consequences of war in rivers?

Oleksandra Shumilova: My research focuses on the impacts of the ongoing conflict in Ukraine on rivers and water infrastructure. There, due to the danger of drone attacks or landmine explosions, it is often too risky for us to take samples. That is why we frequently resort to remote sensing and mathematical modelling.

What parallels do you see when you compare past wars with today's wars?

Oleksandra Shumilova: Warfare today is very different from 80 years ago – drones and missiles are mainly used for attacks, while ground operations are relatively limited. However, the similarity is that rivers play role as frontlines, while dams of large reservoirs are used as weapons of war. Damaged dams, for example, prevent troops from crossing rivers. This already happened during the Second World War on the Dnipro, when the dam of the Dnipro hydroelectric power station was attacked several times. And it happened again in 2023, when the dam of the Kakhovka reservoir broke and many other dams on other rivers were also damaged.

The Kakhovka reservoir has run dry following the destruction of the dam. According to media reports, trees are growing in the area of the former reservoir. Is this a sign that nature is returning?

Oleksandra Shumilova: The ecosystem is re-establishing rapidly, which is one of the main arguments used by environmental activists against rebuilding the reservoir. However, as our study published in the journal Science in 2025 shows, the sediments of the former reservoir bed contain thousands of tonnes of heavy metals that accumulated at the bottom of the reservoir during its operation. These sediments formed a huge "toxic sponge" that has now been exposed. Currently, we do not know how much of these heavy metals are being absorbed by vegetation. We therefore propose erecting some temporary barriers to prevent the remobilisation and transport of pollutants from areas that are particularly prone to flooding due to seasonal floods and rainfall.

What other long-term consequences can we expect after the war ends?

Oleksandra Shumilova: The impacts of wars on rivers are associated with the long-lasting legacies of toxic pollution from sunken military munition containing heavy metals, explosives, fuel and other toxic components. Over time, these substances can be released into the aquatic environment when munitions corrode, affecting organisms and becoming incorporated into food chains. There are also many indirect effects on freshwater ecosystems. I would like to highlight the ongoing conflict in eastern Ukraine – the Donbass region – which began in 2014. The region was known for its mining industry. After many mines were closed down, the rising mine water had to be pumped out to prevent flooding. Attacks on the energy infrastructure interrupted this process, and many mines were flooded. This has led to the contamination of surface water and groundwater. There may be further consequences of which we are not yet aware of, given that the mines are located underground.

Christian Wolter: The accumulation of certain pollutants such as heavy metals and PCBs in the food web can cause widespread problems in war zones. But destruction also present opportunities: for example, if ecologically harmful infrastructure is destroyed in floodplains, it can be rebuilt elsewhere to minimise damage.

Claudia van Hasselt: I find this aspect particularly exciting, that opportunities are opening up for nature to reclaim "lost" areas. Take the Oder, for example. As a border river, it was never really suitable for commercial navigation anyway.

Christian Wolter: I think the point about the changed or reduced economic use of river ecosystems is important. We have demonstrated in numerous studies what leads to the degradation of water bodies. However, rivers have the ability to regenerate. It would be interesting, for instance, to remove the groynes from the Oder and see how the river forms its new bed.

What do you expect?

Christian Wolter: The river would erode laterally. In the case of the Oder, the material moved by the river is mainly sand. The Oder would flatten out and form more sandbanks. It would also develop a wider bed with a multitude of channels, and areas with different flow velocities would emerge.

So, measures that appear to be economically necessary, such as straightening and deepening rivers for inland navigation, actually harm the river and the people living alongside it?

Christian Wolter: Yes. Straightening rivers causes the water to flow faster. This artificially deepens them, meaning that when the water level is low, more groundwater flows into the river, making the surrounding landscapes drier.

Oleksandra Shumilova: Rivers and river landscapes are dynamic and constantly changing – due to human influence, as well as extreme events such as military conflicts, but also floods and droughts. These changes influence whether people stay in a region or settle elsewhere. This has an impact not only locally, but also globally. We are working on new approaches to better predict how ecosystems re-establish  after such events, and how knowledge obtained from studying floodplain ecosystems in Europe can be transferred to understand recovery of nature in Ukraine after military impacts.

Ms van Hasselt, Mr Wiese, in your work you translate partly invisible phenomena into images, sound and vibration. How do you artistically capture the image of the ‘damaged river’?

Claudia van Hasselt: A good example is the Gleiwitz Canal, a tributary of the Oder River where fish deaths occur repeatedly. We made sound and underwater video recordings there. There was a distinct smell of chemicals, and the pollution of the water was immediately apparent. In the sound recordings, we could clearly hear insects' activities underwater and in the sediment. Subsequent analysis showed that these frequencies corresponded exactly to those amplified by salinity, mainly high frequencies. We use these recordings in our work.

Nicolas Wiese: The damage to the water was also visually apparent when compared to ‘healthy’ water. Visibility was very low and the water was brownish-green in colour. We captured and depicted this artistically in OderHive, another joint project with IGB: we used the video recordings to highlight the differences between healthy and unhealthy rivers. In doing so, we created an immersive experience for the audience, who were surrounded by underwater sounds, textures and visuals.

Wars also leave their mark on the those involved in acts of war. Ms van Hasselt, you have compared documents from then and now. What did you find?

Claudia van Hasselt: An existential fear is always expressed in them. For example, in the Shukow bunker, we found quotes from Russian officers who were lying there in fear towards the end of the Second World War. This is understandable because, at the end of armed conflicts, the aim is always to cause as much destruction as possible. I also find it interesting that war reporting is universal. We compared reports on acts of war from different centuries, from Caesar's 'Bellum Gallicum' to the present day. When written accounts are stripped of contemporary data such as places and numbers, we found that the choice of words is always the same. We don't evolve; we don't learn.

Nicolas Wiese: ... also because language shapes collective thinking and actively influences it. Warlike language creates the awareness of being at war – not only that, it mobilises people. It creates a warlike state of mind.

In your project 'PEACES so far', you specifically address the question of how rivers can be made visible as victims, while also serving as places of regeneration and understanding. An excerpt from your work will be on display at Berlin Science Week. What can visitors expect?

Claudia van Hasselt: For example, there will be recordings from floodplains, including sounds recorded underground. We also work with vibrations and want to explore the topic in a more associative way to show: What does it sound like when a bomb falls into the water, and what is it like in the moments that follow? The impact creates a zone in which sound cannot be transmitted – similar to the area beneath the waves of the sea. This creates complete silence for a brief moment. What impact does this have on life forms in the water, particularly in areas where rivers repeatedly become combat zones?

Christian Wolter: Such strong shock waves can cause barotrauma in fish, meaning their swim bladders can rupture, damaging their eyes and organs. The effects depend on the size of the explosive charge, reaching up to 390 metres with 55 kg of TNT, for example.

Claudia van Hasselt: Another aspect of our project concerns how communities organise themselves along rivers that often cross national borders. While there are transnational communities in most border areas, this is less common on the Oder River. Why is that? To what extent can this be explained by the legacy of the Second World War? For example, there are no bridges at all over long distances on the section between Hohenwutzen and Schwedt. Does this reflect the lack of exchange, even during the East German era? How can a community be established here? The way the river is managed, particularly following the fish kill in 2022, is also intriguing: in Poland, there are numerous NGOs along the riverbanks, whereas in Germany, political pressure is more prevalent. We are building a transnational network with the aim of forming an Oder community. There are many individual initiatives, but they are only partially networked.

Nicolas Wiese: That's why we always seek to engage in dialogue with visitors at our events. We've already had positive experiences of this at OderHive. It's important to show the people living by the river that we are taking their concerns seriously, because most of them know more about 'their' river than we do.

What specifically do you want to convey at Science Week?

Claudia van Hasselt: For Nicolas and me as FrauVonDa//, art is a mediator between science and society. It can translate things into a more accessible language, albeit a simplified one. Take the universality of rivers as weapons, for example. People tell us that our work has given them an understanding of the Oder and a connection to the ecosystem, even though they have never visited the river. That's what we're all about: making content transferable to as many people's environments as possible. We are driven by the idea of combining emotion and cognition, and of making science a sensory experience, thereby making it accessible to as many people as possible.

What is the most important thing we should learn from the stories of the rivers?

Nicolas Wiese: That we cannot continue with economisation. Using rivers as borders or lines of defence is also fundamentally abusive.

Christian Wolter: Geologically, we know the history of rivers...

Claudia van Hasselt: ... and that's why the question actually needs to be asked the other way around: human history has played out alongside rivers ...

Christian Wolter: ... and we are still deeply dependent on rivers, even if most people are not aware of this. We must prioritise rivers in our conservation efforts because without them, we will not achieve any climate or biodiversity goals. If river systems continue to be damaged – whether by wars, construction or nutrient inputs – their ecosystems will collapse. Freshwater resources are scarce on our planet, and rivers are where they come together. They provide everything necessary for life.

~

The interview was conducted by Wiebke Peters.

People

Dr Oleksandra Shumilova is an ecologist who works as a postdoctoral researcher at IGB in Berlin. Her research focuses on the dynamics, functioning and services of river systems. She is particularly interested in the geomorphology, hydraulics and biodiversity of rivers and their floodplains, the ecosystem ecology of intermittent rivers, and issues relating to water infrastructure during and after armed conflicts. Since the outbreak of war in Ukraine, she has been intensively studying the impact on water resources – a topic that is close to her heart both professionally and personally, as she comes from Mykolaiv, a city in southern Ukraine, that has been severly affected by water supply issues since the outbreak of the war in 2022.

Dr Christian Wolter studied at Humboldt-Universität zu Berlin. He is a fish ecologist who primarily researches fish communities in rivers. He investigates the harmful effects of human influences such as hydropower and shipping on fish, and how renaturation measures can help to protect river fish. At IGB, he heads the Research Group on River Revitalisation. Since 1998, he and his team have been fishing the Oder at least three times a year for research purposes, both in the middle of the river and along the banks. Consequently, he is very familiar with the dynamic development of fish stocks in the Oder. 

Claudia van Hasselt and Nicolas Wiese lead FrauVonDa//, an intermedia ensemble for new music. Since 2013, the group has been creating transdisciplinary works at the intersection of art, science and society. Their projects explore the unheard and unseen – often without words, but in many languages – creating multisensory experiences that appeal to both the emotional and intellectual senses. Addressing pressing social and environmental issues, FrauVonDa// blends artistic expression with research-based openness, always inviting active audience participation. Transcending boundaries between genres, disciplines and geographies, the ensemble works respectfully and sensitively, drawing on a wide range of artistic skills. They cooperate with an international network of scientists, historians, musicians, activists and curious minds from the general public. At the heart of their work is the vision of an inclusive, interactive community that embraces diverse perspectives and sensory experiences – locally rooted, globally connected.