The Dürren maar area was made a nature conservancy in 1979 along with the Holzmaar. It represents the second-oldest volcanic eruption site in the Holzmaar group (Hetsche – Dürres maar – Holzmaar) and is now filled with a transitional moor. The bog is subdivided into 3 zones: Various sedges grow from the bank in the bordering fen (riparian zones with water). After this are peat bogs, again blended with sedges. In the centre, cotton-grasses and the peat bogs dominate. The current water table is at approx. 6 m below the bog surface, which is again fed by rainfall near the surface.