Leipzig's floodplain suffering from chronic disease
Environmental Ministry of Saxony and City of Leipzig agree on measures to improve state of Leipzig’s floodplain forest
Leipzig. Leipzig’s floodplain forest is one of the largest of its kind in Central Europe. But the floodplain is currently under huge pressure – as a result not only of drought and climate change but also of human intervention. These stressors as well as revitalization measures for the large urban forest were discussed during a visit to Leipzig’s Canopy Crane. Among the participants were Professor Beate Jessel from the German Federal Agency for Nature Conservation (BfN), Wolfram Günther from the Environmental Ministry of Saxony, Rüdiger Dittmar from the City of Leipzig and Professor Christian Wirth from the German Centre for Integrative Biodiversity Research (iDiv) and Leipzig University (UL).
Intact floodplains and floodplain forests are hotspots of biodiversity and the basis of important ecosystem services: they provide habitat for a large number of plants and animals, offer recreational spaces and regulate our climate. This is why they are extremely valuable for us humans – and why they need to be protected. But there can be no floodplain without water – regular flooding is a distinct feature of this ecosystem and connects its various habitats. Leipzig’s floodplain forest, one of the largest of its kind in Central Europe, is suffering from drought, climate change and, in particular, human intervention affecting the water balance.
“Leipzig’s floodplain is suffering from a chronic disease – and that disease is called ‘the Neue Luppe river’,” said Professor Christian Wirth during the joint press conference of Saxony’s Environmental Ministry and the City of Leipzig. The artificial waterway protects the surrounding area from flooding but also drains the floodplain, prevents flooding and separates the habitats. “Today, many floodplains are no longer flooded, meadows turned into farmland and former wetlands are completely dry.”
Leipzig’s floodplain forest suffering from drought stress
The hardwood forest that defines Leipzig’s floodplain forest has been degenerating visibly for a long time. This includes the dominant role of maple trees populating the understory. Normally, this would be prevented by regular flooding as maple trees do not like standing on moist ground. However, there has been no flooding in a long time. As less light reaches the lower layers of the forest, oak seedlings can no longer grow. “If we look at the forest with its oak trees today, we actually only see the past,” said Christian Wirth. “If we were able to look into the future, we would see a maple forest.”
The effects of this development in combination with the acute drought stress of recent years are studied with the help of iDiv’s Canopy Crane and the project “Lebendige Luppe” (Living Luppe). Observations and measurements of recent years showed a significant drop in the growth rates of the three main tree species oak, ash and maple. In 2018, the leaves started to fall in July and autumn came early. An alarming sign: “In a floodplain forest, this should not happen at all, because the trees should be in contact with ground water all the time. Obviously, this is no longer the case here,” explained Christian Wirth. The researchers also found signs of significantly reduced transpiration from the canopy. For the people of Leipzig, this has some very practical consequences: the floodplain forest can no longer regulate the climate.
Under these circumstances, the trees are also no longer able to fight back diseases or natural enemies – ash and maple trees are struggling in particular.
Ecological instead of technical flooding control
To counteract this development, a revitalization of the floodplain is required. “The floodplain needs water – dynamic water in particular and along the entire floodplain area,” said Christian Wirth. To achieve this, floodplain areas need to be connected to old waterways and a dynamic flow of the water must be enabled. The Neue Luppe river could become a flooding area; farmland should be turned into meadows.
Saxony’s Environmental Minister Wolfram Günther understands the gravity of the situation: “To revitalize the floodplain forest, different demands and requirements need to be integrated in an overall concept with a greater environmental focus. This also requires cooperation between the municipalities involved. This is what we are working on now.” The ministry and the city plan to reconnect old waterways with the north-western part of the floodplain along with further restoration efforts at the lower part of the Weiße Elster to allow for a typical flooding and ground water situation.
In the medium term, Saxony’s Environmental Ministry aims to integrate existing projects, such as “Lebendige Luppe”, into an overall concept for the development of Leipzig’s floodplain landscape including the entire floodplain area of the Elster and Luppe rivers in Saxony. One thing is for sure: while immediate action is needed right now, it will take years until nature has recovered. “If we do not solve this issue, we will suffer from it in many ways,” said Christian Wirth.
Prof Christian Wirth
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig / Max Planck Fellow at the Max Planck Institute for Biogeochemistry, Jena
Head of the Department for Systematic Botany and Functional Biodiversity at Leipzig University
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German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Phone: +49 341 9733106