Diversity of species communities in meadows and pastures
The uniqueness of a habitat is demonstrated by its special location-specific species composition that appeared over time. Rare species lend a particularly special character to a location. The uniform input of atmospheric nitrogen, the intensified use of natural resource, the loss of local farming methods and the spread of already common species by humans (seeding, seed dispersal by vehicles etc.) are among the causes of the local extinction of rare species and of the propagation of widespread species. This loss of habitat uniqueness makes them increasingly uniform and banal.
The overall diversity of the species communities in meadows and pastures has declined since the early 2000s. While the diversity of species communities in the plant and moss categories remained constant, a reduction in the diversity of mollusc species can be observed. Among mollusc species, the number of frequently-occurring species lacking special habitat requirements has increased while the number of rarer species has declined. This decline is clearly indicative of a standardisation of the «Meadows/pastures» habitat throughout Switzerland, which is tantamount to biodiversity loss.For this reason, status and development are assessed as negative.
As part of Biodiversity Monitoring Switzerland, the species composition of vascular plants, mosses and molluscs (snails) in approximately 1600 sampling areas measuring ten square metres is recorded every five years. Taking the species composition into account, the similarity between all sampling areas (Simpson’s index) is calculated and recorded separately for each overall habitat type (forest, meadows and pastures, farmland, built-up areas, Alpine pastures, mountains) and each of the three species groups. The higher this value, the greater the diversity between the sampling areas. Greater diversity in terms of the presence of different species communities is positive, and uniformity is not desirable as it is indicative of a loss of biological diversity.
|Targeted trend||Initial value||Final value||Variation in %||Observed trend||Assessment|
|Growth||Average 2001-2007||(1) Average 2012-2018, (2) Average 2012-2018, (3) Average 2011-2017||(1) -2.12%, (2) -1.15%, (3) -19.96%||(1) Stabilisation, (2) Stabilisation, (3) Decrease||negative|
|(1) Plants, (2) Mosses, (3) Molluscs|