The figure below illustrates the diversity of species communities of vascular plants, breeding birds and butterflies in the 2005-2009 surveying period. The greater the similarity between species communities in 1-km2 sampling areas, the lower the indicator value, and vice versa. As a rule, species communities in landscapes of the Southern and Central Alps are the most diverse, while species communities in landscapes of the Central Plateau are the most uniform
Mean Simpson’s Index of all pairwise comparisons of 1-km2 sampling areas. The more darkly colored a biogeographical region, the more diverse its species communities.
Comments
• In part, species communities in the Jura are almost as uniform as those found on the Central Plateau. Interestingly enough, the two regions partially differ to a very considerable degree as regards mean butterfly diversities (cf. Z7 indicator “Species Diversity in Landscapes”).
• The difference between the Central Plateau and the Jura on the one hand and the Alps on the other hand is due to both natural causes and human land use. Because of their wider ranges of altitudes and their more marked reliefs, it is only natural that alpine regions be home to more diverse species communities than low-land regions. However, the uniformity of species communities on the Central Plateau and in the Jura has most likely also been brought about by the intensive land use these two regions are subjected to, which made local particularities disappear.
• The absolute indicator value computed for Switzerland overall (see Appendix 1) cannot be directly compared to the indicator values computed for its individual biogeographical regions. Since biogeographical regions are defined by standardized floral and faunal distribution patterns (Gonseth et al., 2001), the diversity of species communities is bound to increase when looking at the country as a whole.
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