One of the core BDM indicators, Z9 monitors the number of species and changes in the number of species occurring in Switzerland’s various habitats such as forests, settlements, arable land and waterbodies.
Data currently available reveal that in the past five years, mean species numbers of vascular plants, mosses and mollusks (snails) have been increasing on alpine pastures and in the mountains. Unlike grassland and forests, where numbers of both mosses and mollusks have been found to be rising, arable land and settlements only display increases in mollusk species numbers. Species groups surveyed for the Z9 indicator newly include aquatic insects as well.

The Z9 indicator is designed to document changes in the species diversity of habitats. Now that second surveys have been finalized, initial trends are emerging. What strikes the eye is the increase in species numbers—particularly at the montane, subalpine and alpine levels—that may be observed for all the species groups and habitat types BDM covers. While there were no decreases affecting whole species groups or habitats observed, certain individual species are on the decline (cf. Z8 indicator “Population Size of Common Species”).

Insights gained into these developments so far will become even more telling in years to come. As surveys of aquatic insects have only started in 2010, there are obviously no change data available yet.

Development of species numbers (95% confidence interval for mean changes, 2001/05 – 2006/10)