The Swiss agrienvironmental programme and its effects on selected biodiversity indicators

Summary

In Switzerland, parallel to agri-environmental measures which apply directly to the field management, farmers had to convert at least 7% of their land to ecological compensation areas – ECA. Major ECA are extensified grassland, traditional orchards, hedges, and wild flower strips. In 2000, the situation shows that farmers practise the agri-environmental scheme all over Switzerland with a total of 120,000 hectares of different types of ECA. The introduction of ECA throughout the country's agricultural area can be seen as a large scale landscape restoration experiment. Its biological effects are evaluated in a monitoring programme. In a case study area of about 6 km2, in 1997, biodiversity indicators (spiders, carabid beetle and butterflies) were recorded following a stratified sampling design. Every field in the area was categorised and digitised. Habitat and landscape features that influence the indicators are analysed as well as the role of the ECA in this context. Hypothetical influencing factors are tested with the Canonical Correspondence Analysis (CCA) and partial CCA, and are categorised as follows: (1) habitat (habitat type, plant species richness); (2) landscape (habitat heterogeneity, variability, diversity, proportion of land use types in classes); and (3) space (geographical coordinates). The correlative models developed for spider and carabid beetle assemblages revealed that the most important factor is the habitat type (directly influenced by management practices). However, for spiders, land use types like ECA and natural areas in the surrounding landscape are significant factors too. The model developed for butterflies shows that species assemblages are sensitive to the habitat type and plant species richness but not to landscape features.