Interesting facts 

Mires – endangered Jewels of Nature

Mires are one of the most valuable habitats in Switzerland. They are home to a variety of endangered animal and plant species. Because they are extremely sensitive to human interventions, they are now under strict protection.


Mires are formed where water cannot drain off into deeper soil layers, but is dammed on the surface in depressions and remains there. The soil is thus permanently saturated with water. In this, mires differ from marshes in which the ground also dries out from time to time. This has consequences for the vegetation. When plants die, they are normally degraded to humus. This forms the basis for the thriving of new plants. In mires, this cycle works quite differently. Due to the constant moisture, dead plants are only partially or not at all degraded. Dead leaves and stems are rather decomposed to peat. In this way, over the course of time a layer of peat is formed at the bottom of the humid depression, which becomes thicker over the years. However, this growth process is extremely slow: the peat layer in bogs increases only one millimetre per year. So it takes 1000 years for a peat layer of one meter height.

At some point the entire water -saturated depression is filled up with peat. The growth of the peat layer continues however. But, the mire changes its character - and it is also called differently: so far it was a fen, now a raised bog develops. The two concepts have nothing to do with the altitude (there are also fens in the mountains and raised bogs in the valley area) and also nothing with the thickness of the peat layer. The difference is rather the supply of the plants with water. In the fens they get the necessary moisture directly from the nutrient-rich ground water, with which the depression is saturated. In the raised bog, on the other hand, only rainwater is at their disposal. Since this contains virtually no nutrients, only highly specialized and frugal plants can live in raised bogs.

Mire areas are considered as unproductive soils for agriculture. That’s why they have been drained in a large scale in Switzerland since the middle of the 19th century and have consequently been destroyed permanently. The peat was partially exploited in industrial scale and used as fuel as well as soil improvement and fertilization in horticulture.

Today the remaining mire landscapes are strictly protected. The corresponding legal foundations are based on a referendum in 1987. At that time, the Swiss army intended to set up a weapon field in the midst of the raised bog landscape on the high plateau in Rothenthurm (Canton Schwyz). The project was combatted with a national initiative aimed at protecting the mires and bog landscapes of particular beauty. The Swiss electorate clearly approved the request.

Despite the rigorous protection regulations, numerous mire landscapes are still endangered. This applies in particular to the fens. Although these are no longer destroyed by large-scale meliorations, they are often negatively affected by inappropriate use, local drainage or nutrient input from adjacent areas.