Der Wert von Befestigungsanlagen für den Erhalt der Biodiversität am Beispiel der Schnecken (Mollusca: Gastropoda)

Significance of fortifications for biodiversity conservation: The example of terrestrial gastropods (Mollusca: Gastropoda) Significance of fortifications for biodiversity conservation: The example of terrestrial gastropods (Mollusca: Gastropoda) The different microhabitats of the walls of historical fortifications harbor a gastropod fauna that is significantly distinct from that of the surroundings (such as meadows and forests). The communities on the vertical planes of the walls display the highest heterogeneity, and thus a high susceptibility to anthropogenic disturbances. Parts of the heterogeneity can be seen to result from different renovation intensities and stages of (re-) colonization. Many red-listed species were found in the microhabitats of the walls. The importance of fortifications for biodiversity conservation and the role of stone wall restoration is illustrated for Balea perversa, which is a critically endangered species in the German federal state Northrhine- Westphalia. The analysis of the regional databank revealed that about one third of all records are from stone walls, one third is from (semi-) natural habitats and for one third (literature records) the habitat is unknown. The largest population (both in terms of population size and density, and in terms of the area inhabited) once occurred at the fortification "Burg Sparrenberg" in Bielefeld but it was reduced to a very small, habitat-limited population in the course of an intensive wholefortification renovation work. In contrast to the walls of (late) medieval fortification, recent fortifications such as the "Westwall" do not harbor a distinct fauna. Yet, these new structures may be valuable for research on the influence of the surrounding landscape on succession and community assemblage.