The agriculturally used farmland with its meadows and spruce forests separate only a few meters southeast of Münsing from the more unspoilt terrain. With every step the floor begins to vibrate more and more clearly. Pines and birches characterize the sparse forest, in which rainwater accumulates between heaped peat dams – until a central, open raised bog with cotton grass opens up.
That’s just what is superficially noticeable. Elisabeth Pleyl speaks of an enormous biodiversity when she stands on the edge of the Münsinger Filz. “We found 14 species of dragonflies here alone,” reports the specialist in peatland restoration at the Bad Tölz-Wolfratshausen district office. In addition, the felt offers a refuge for larger, rare animal species such as the wood sandpiper, a species of the snipe family that uses this moist terrain to forage during migration.
So that the Münsinger Filz can keep its climate protection and habitat function for rare animal and plant species, the Tölzer Moorachse working group has rewetted the area over a large area and thus renatured it. The work, including planning, took five years and was completed by the end of the previous year. Pleyl’s team drew in 180 peat dams, behind which the rainwater accumulates an average of up to half a meter.
In the course of time, the water surfaces will become overgrown with peat moss. Thanks to their enormous sponge effect, the plants can store a particularly large amount of moisture. In this respect, they mitigate the consequences of climate change because they absorb rainwater immediately after heavy rainfall and only release it again with a delay of many days and weeks. This reduces the risk of flooding. Because the rainwater is held back in place instead of pouring into the area like a flash flood.
The original character of the 60 hectare Münsingen felt threatened to be lost. From the end of the 19th century to the first half of the 20th century, the peat from the moors was partly mined in hand peat digs, partly over a large area, and the areas were drained for this purpose. In times of need, the moors were used as fuel or bedding in the cattle sheds, as Pleyl explains. The ground began to dry out and became more and more forested.
The Münsinger felt therefore had to be thinned out before the rewetting process could begin. The Schwabbruck master forestry manager Eduard Huber and his team felled around a thousand solid cubic meters of wood, mostly spruce. They had to be removed from the planned water damming areas, otherwise massive bark beetle infestation would have threatened, as he says.
According to project manager Pleyl, the owners have made 46 hectares of the Münsinger felt area available for renaturation, i.e. around three quarters. About half of this could be rewetted. This means that less climate-relevant carbon dioxide (CO₂) escapes into the atmosphere, which contributes to global warming. Because in the damp subsoil, the carbon remains bound in the peat. On the other hand, microorganisms in dried out peat layers break down the peat into CO₂, which gets into the air. According to Pleyl, this corresponds to an amount of around 15 tons of CO₂ per year and hectare of renatured moorland. Extrapolated to the entire 20 renatured hectares of the Münsingen felt, around 300 tons less carbon dioxide escape into the atmosphere each year. “And there are so many positive side effects associated with water retention in the moor, especially for plants, animals and the water balance,” explains Pleyl.
In the direction of Degerndorf, the layers of peat in the Münsinger Filz are up to six meters thick. It took at least 6,000 years to grow that far. “Peat grows a millimeter a year,” says Pleyl. In order to be able to move on the unstable ground, the renaturation team worked with light chain-guided excavators to build the dams. With less than 320 grams of load per square centimeter of earth, according to Pleyl, the pressure on the ground is no greater than when a person walks on the ground.
The human factor also plays an important role in the preservation of the moors’ landscape. So far, only one owner has mowed his litter meadow regularly on the northeastern edge of the fen. In this way he prevented the area from slowly growing. But now Pleyl was able to persuade three other directly adjacent owners to do the same: a valuable contribution to species protection as well. The litter meadows are essential for survival for the rare wart-biter – a species of grasshopper. The transition zones between raised bogs and fens are an important habitat for special butterfly species. “The caterpillar feeds on raised bog plants, for example,” says Pleyl. “The adult butterfly flies to the litter meadows to look for food.”
Overall, the Münsinger Filz is part of around 12,000 hectares of moor in the district, which corresponds to a share of around eleven percent. So far, 560 hectares have been rewetted, making an important contribution to protecting the climate and species.