About

Rivers and their floodplains are among the most species-rich habitats in Germany. At the same time, they are also among the landscape structures most used by humans. Whether through flood protection, hydropower, agriculture, fishing or tourism - floodplains have been significantly changed in their morphology and hydrology for around 200 years. The impairment of the natural water and bedload balance had a particularly serious impact on the “wild” dynamic rivers of the Alps. Due to “taming”, they lost a large part of their unique habitat diversity. Habitats with extreme location conditions, such as gravel and sand banks near the banks, can now only be found to a large extent on a few river sections in Bavaria. As a result, the numerous highly specialized species also declined sharply. Many of the early successional species are now threatened with extinction. Whether the national and international goals for preserving biological diversity can be met depends to a large extent on the future treatment of the river floodplains.

The aim of the study is to show how the effectiveness of river restoration as well as the protection and reintroduction of target species can be increased. By linking the analysis of historical and current landscape structures and the population decline of the target species, threshold values for habitat structures that are essential for the establishment of populations should be derived. This should result in quantitative target values for future renaturation projects, which will improve the success of revitalization projects and at the same time also reintroductions. The German Alpine rivers are used as a model ecosystem. They are highly relevant for the preservation of biological diversity in Germany. The following questions are to be answered within the scope of the study:

• How are the changes in floodplains related to the decline of endangered target species?

• What connections are there today between the abundance of target species and the habitat structure? Are there differences between the historical and current realized niche of the target species?

• To what extent have habitats with the required structure and size been restored through renaturation measures?

• What successes have been achieved with regard to the establishment of target species?

Potential study for the reintroduction of wild river species in the Bavarian Alpine region (2016–2017)

As part of the BfN's Alpine River Landscapes hotspot project, a one-year study is being carried out on behalf of the WWF to assess the potential for protective measures and for the reintroduction of selected wild river species. The aim is to give recommendations for possible measures to revitalize the sites as well as to strengthen the population and develop wild river species.

The study refers to hotspot regions 2 and 4, i.e. “Ammergebirge, Nieder Werdenfelser Land and Upper Isar” as well as “Ammer-Loisach-Hügelland and Lech-Vorberge”. The project period extends from October 2016 to September 2017.

Of the wild river species, some of which are highly endangered in Bavaria, the study examines German tamarisk (Myricaria germanica), dwarf cattail (Typha minima), riparian grass (Calamagrostis pseudophragmites) and the slave ant (Formica selysi).

The project includes a detailed literature search and expert surveys on the past and current distribution of the species. In combination with field surveys, an overview of the population situation of the individual populations in the hotspot regions mentioned is created. The results are intended to show where support measures for isolated populations or reintroductions are necessary in the project area and make sense from a technical perspective. Revitalization measures that have already been carried out or planned on the Alpine rivers are also included in the designation of potential areas for resettlement. Furthermore, technical recommendations are given for the individual reintroductions, in particular on the location of the donor populations as well as on cultivation and application methods.

Final report (20218)

Partner

Federal Agency for Nature Conservation (project page)

University of Applied Sciences Erfurt

University of Hanover

WWF Germany

International Publications

Wagner TC, Woellner R, Kloska V, Kollmann J (2024) Biogeomorphological floodplain dynamics along a degradation gradient of an Alpine river. – River Research and Applications 40, 1125–1141. https://doi.org/10.1002/rra.4267

Wagner TC, Woellner R (2023) A new set of metrics and framework to assess the colonization potential of riverscapes by wind-dispersed plant species. – Scientific Reports 13, 20097. https://doi.org/10.1038/s41598-023-47477-y

Woellner R, Wagner TC, Crabot J, Kollmann J (2022) Spatio-temporal patterns in degradation and restoration of gravel bars along Alpine rivers. – River Research and Applications 38, 738–756. https://doi.org/10.1002/rra.3933

Woellner R, Wagner TC (2019) Saving species, time and money: Application of unmanned aerial vehicles (UAV) for monitoring of an endangered alpine river specialist in a small nature reserve. – Biological Conservation 233, 162–175. https://doi.org/10.1016/j.biocon.2019.02.037

Woellner R, Bräuchler C, Kollmann J, Wagner TC (2022) Biological Flora of Central Europe: Chondrilla chondrilloides (Ard.) H. Karst. – Perspectives in Plant Ecology, Evolution and Systematics 54, 1–20. https://doi.org/10.1016/j.ppees.2021.125657

Woellner R, Scheidegger C, Fink S (2021) Gene flow in a highly dynamic habitat and a single founder event: Proof from a plant population on a relocated river site. – Global Ecology and Conservation 28, 1–12. doi: 10.1016/j.gecco.2021.e01686

German Publications

Woellner R, Kollmann J, Zehm A, Wagner TC (2020) Gute Aussichten für den Alpen-Knorpellattich in Deutschland? Erste Ergebnisse von Monitoring und Wiederansiedlung lassen hoffen. – ANLiegen Natur 42, 139–142. https://www.anl.bayern.de/publikationen/anliegen/doc/an42111woellner_et_al_2020_alpen_knorpellattich.pdf

Woellner R, Müller N, Reich M, Wagner TC, Kollmann J (2019) Artenhilfsmaßnahmen für gefährdete Wildflussarten - eine Potenzialstudie an den bayerischen Alpenflüssen anhand von vier Beispielarten. – Natur und Landschaft 94, 509–516. https://doi.org/10.17433/12.2019.50153753.509-516

Woellner (née Harzer) R, Kollmann J (2018) Die letzte Population des Alpen-Knorpellattichs in Deutschland: Gefährdungsanalyse und Förderung der Art. – ANLiegen Natur 40, 13–16. https://www.anl.bayern.de/publikationen/anliegen/doc/an40101harzer_et_al_2018_alpen_knorpellattich.pdf