Did you know that the Riemeisterfenn is one of Berlin’s last remaining original moorlands? It is a protected area. It offers a glimpse into the city’s natural past.
The Riemeisterfenn sits on the edge of the Grunewald forest in Steglitz-Zehlendorf. Once, it was a marshy depression and part of the Riemeistersee. The lake has largely silted up since the beginning of the 20th century. Now, it forms a unique habitat.
For over 100 years, the Riemeisterfenn saw cycles of drying and re-wetting. It was once a nutrient-poor moor. Surface water transformed it into a nutrient-rich shallow body of water. An alder swamp developed in its eastern part.
Despite these changes, rare moor species still survive here. Look closely. You might spot marsh willowherb, fen bedstraw, swamp calla, or marsh fern.
The Riemeisterfenn is part of the Grunewald lake chain. Today, a canal connects it to the Krumme Lanke to the southwest. It also connects to the Langes Luch nature reserve to the north.
Back in the day, a “Riedmeister” managed the area’s lakes and moors. “Ried” is German for moor. Over time, Riedmeister evolved into Riemeister. The Riemeistersee, and later the Riemeisterfenn, took its name from this official.
Groundwater extraction significantly impacted the Riemeisterfenn. Berlin’s population boomed between 1861 and 1910. Securing drinking water led to the construction of wells. These wells lowered the groundwater level. The Grunewald lakes and moors lost their groundwater connection. The Riemeistersee dried up in 1911. Since 1913, the Berlin waterworks pumped Havel water into the lake chain. This measure maintains the wetlands and shore areas.
In 1957, the waterworks built the Riemeisterfenn water plant. They constructed its technical facilities underground to protect the landscape. Its thatched roof building hid the technical structure. The plant can extract 20,400 cubic meters of water daily. This supplies only a small percentage of Berlin’s water. It primarily serves the villa districts nearby. The waterworks closed in the 1990s but remained ready for use. A fire damaged the building in 2018.
The Riemeisterfenn covers 7.2 hectares. A 1987 decree protects its flora and fauna. The goal is to preserve mesotrophic moor ponds and alder swamp forests. It also aims to create new settlement opportunities. Rare plants thrive here. These include the endangered swamp orchid and the flowering rush. Alder swamp forests benefit from alternating wet zones. Non-native plants are removed.
In 1998, a connection to the lakes was established. This followed a dam breach in the 1960s. This measure was controversial. It threatened the moor’s nutrient-poor environment. The Berlin Senate prioritized rare plants and moor formation. Fish died after the dam was closed. However, the lake has since expanded again.
The Onkel-Tom-Strasse borders the Riemeisterfenn to the northeast. The street is named after the former Onkel Toms Hütte inn. This inn was popular with Berliners. It had a rural charm. The city approved building a restaurant with a stable in 1884. In 1978, the dilapidated building was demolished.
The Riemeisterfenn. It is a reminder of Berlin’s natural history. It also shows us the challenges of balancing urban development. It is essential to preserve these unique habitats. They provide refuge for rare species. They also offer a peaceful escape for us.