Impacts of Woodland Fragmentation on Species’ Occurrences – The Combination of a Habitat Model with Landscape Metrics

Habitat fragmentation can be defined as the modification of once natural habitats into smaller, isolated subareas surrounded by other types of habitat (more or less hostile; the matrix; e. g. Valladares et al., 2006). Fragmentation includes both, the separation of habitats and habitat loss, but the most dramatic and consistently negative effects on biodiversity can be attributed to habitat loss (Fahrig, 2003). In our central European man-made landscape more and more habitats become destroyed or fragmented because of the increasing anthropogenic need of available land and despite the growing knowledge about the problem. Roads, residential, and industrial areas separate formerly connected habitats into small remnants and thus create small subpopulations. Accordingly, habitat fragmentation and the associated effects like (1) the biodiversity decline of stenotopic species in smaller habitats (Desender et al., 1999; Magura et al., 2001), (2) the loss of genetic diversity and variability (Debinski & Holt, 2000; Keller & Largiader, 2003), and (3) a higher probability of inbreeding in smaller populations, belong to the main reasons for extinction of species (Groom et al., 2006). Especially stenotopic species with low dispersal power are endangered because the exchange of specimen between different habitat patches is reduced or entirely inhibited (Hanski et al., 1995). Thus, standardised, comprehensible quantification methods of fragmentation are greatly important for the development of management and conservation plans for habitat networks.