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Environmental Ministry of Saxony and City of Leipzig agree an measures to improve state of Leipzig’s floodplain forest
Leipzig. Die floodplain forest of Leipzig is one of the largest of its kind in Central Europe. But the floodplain is put under huge pressure - not only by draught and climate change but also by 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 Prof 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 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 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 ist kind in Central Europe, suffers from draught, climate change and, in particular, from human intervention into the water balance.
“Leipzig’s floodplain suffers from a chronic disease - and this disease is called ‘the New Luppe river’”, said 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 suffers from draught stress
The hardwood forest, that defines Leipzig’s floodplain forest, has been degenerating visibly for a long time. This also includes the dominating role of maple trees populating the understory. Normally, this would be prevented by regular flooding as maple trees do not like to stand on moist ground. However, there has been no flooding in a long time. As less light gets to 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 draught stress of recent years are studied with the help of iDiv’s Canopy Crane and the project “Lebendige Luppe“ (Lively 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 began 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 indications for significantly reduced transpiration from the canopy. For the people of Leipzig, this has some very practical consequences: The floodplain forest no longer regulates the climate.
Under these circumstances, the trees are also no longer able to fight back diseases or natural enemies - ash and maple trees are particularly struggling.
Ecological instead of technical flooding control
To counteract this development, a revitalisation 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 allowed. The New Luppe river could become a flooding area; farmland should be turned into meadows.
The gravity of the situation is also understood by Saxony’s Environmental Minister Wolfram Günther: “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 of the involved municipalities. This is what we are working on now.” The ministry and the city plan to reconnect old water ways with the north-western part of the floodplain as well as of restoration efforts at the lower part of the Weiße Elster to allow for a typical flooding and ground water situation.
On the medium term, Saxony’s Environmental Ministry aims to integrate running projects, such as the “Lebendige Luppe” project, 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 actions are 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.