Landscape response functions for biodiversity - assessing the impact of land-use changes at the county level

摘要

Assessing the impact of land-use change on biodiversity is an important task in the context of global-change scenarios. Here, conceptual considerations, descriptions of a model solution and results of a case study for the regional scale are presented. Land-use was seen as an integrative variable, which depends on natural, as well as on socioeconomic parameters. Economic processes have been externalized by using results of economy driven base-scenarios about land-use change at the county level. Tendencies from these scenarios were extracted, expanded to a set of sub-scenarios, and transformed into land-use maps by a land-use model. These land-use maps were evaluated with respect to biodiversity at the ecosystem level. The results of the evaluation of the single sub-scenarios were summarized to response functions, which describe the sensitivity of landscape attributes toward land-use changes. It is stated that biodiversity is not a generic indicator and can only be assessed after defining the context. Here, only ecosystems with low hemeroby (`semi-natural' ecosystems) were considered. The concept of hemeroby, which describes the degree of human disturbance on ecosystems, was used as a qualitative complement to the quantitative concept of biodiversity. Biodiversity was assessed by means of six indicators for three aspects of biodiversity: composition, structure and function. The model was applied in a case study dealing with the impact of extensification of grassland on biodiversity in the county Havelland, west of Berlin. In general, the compositional aspect of biodiversity demonstrated the clearest response. Structural diversity reacted only moderately, but a strong impact of land-use change on connectivity was indicated by an increasing proximity of semi-natural biotopes. The latter was proven by evaluating the connectivity of semi-natural grasslands from the perspective of the white stork (Ciconia ciconia). All response functions showed a high heterogeneity in spatial and functional aspect. At the landscape level, the heterogeneity was hidden behind a supposed moderate reaction of landscape. This underlines the demand for a spatially explicit realization of land-use scenarios and for the consideration of a wide range of scenarios by means of response functions