Biotopes of national importance
Many previously widespread habitats are now severely reduced in area. To conserve the diversity of habitats and the rare and threatened species found in them, alluvial zones, mires, amphibian spawning sites and dry meadows and pastures are protected by national biotope inventories.
Habitats are populated by special species, which are adapted to the conditions that prevail there. If the quality of such sites changes, the risk arises that these specialised species will be lost. The widespread “generalist” species remain and new species migrate to the site. The original habitat and the associated specific species disappear and the ecosystem’s functions are lost.
Even in the period between 2001 (1997-2001 survey) and 2006 (2002-2006 survey), almost a third of the mires were found to have become drier, richer in nutrients and more deficient in light. These negative changes generally appear to have continued up to 2017 (2011-2017 survey).
It is mainly in the raised bogs that the mean nutrient index has continued to rise. The causes for this are the continuing active drainage of many raised bogs. Peat is broken down in dry peaty soils and nutrients are released. Plants with a higher nutrient requirement become established. In addition, the nitrogen inputs from the atmosphere cause undesirable overfertilization of the mires. No significant general increase was detected in the blanket bogs. The dry meadows and pasture areas were also becoming richer in nutrients.
We observed significant falls in the moisture index in nearly all types of bog. They continue to dry out. In contrast, dry meadow and pasture areas have become wetter since 2006 (1998-2006 survey), which represents a negative development for these environments. A similar situation affects the light index, which decreased nearly everywhere, indicating a general trend towards shadier and denser conditions.
- Related indicators
- Areas designated for biodiversity
For purposes of identifying changes in the vegetation in the nationally important raised and blanket bogs, dry meadows and pastures and water meadows, weighted random samples were drawn from the relevant inventories so as to represent the (biogeographic) regions of Switzerland, the vegetation types, the different subject sizes and the different elevations.
Vegetation data previously surveyed in the WBS from many of the selected subjects were repeated so that conclusions could be drawn on completion of the first WBS survey of changes in mires and in dry meadows and pastures. This was the case in 130 of the 255 bog subjects (767 plots in previously surveyed so-called unit areas in Monitoring the Effectiveness of Habitat Conservation, including 539 unit areas in blanket bogs and 192 in raised bogs). In the case of dry meadows and pastures, 591 so-called “test areas” (TFA) already surveyed for the first time when they were inventoried were repeated.
The presence of plant species in the mapped areas and their degree of cover were determined in the field. Ecological indicator values exist which specify the extent to which the presence of the species is restricted to certain environmental conditions (humidity, nutrients etc.). The nutrient levels are extrapolated from the mean values of the ecological indicator values in the relevant mires.