How BDM data is used

BDM contributes to improving knowledge about biodiversity. Its data is requested by numerous stakeholders. Here are some examples of how BDM findings are used.

Impact of climate change on biodiversity

Thanks to the two-decade time series, BDM data can also be used to make statements about how the spatial distribution of species is changing. It has been found that some species now occur at higher altitudes than was the case 20 years ago. Among other things, this migration to higher altitudes is associated with the rise in temperatures due to climate change.

  • The bar plot shows how many metres per 10 years the individual groups of organisms migrate upwards on average. The values for vascular plants are the lowest, followed by mosses and breeding birds. The increase in aquatic insects even exceeds that of the air isotherm.
    The average altitudinal migration of the organism groups is derived from the increase in the mean temperature indicator value for the observed species over 10 years. The average air temperature has increased to such an extent that locations with the same temperature are now 92 metres higher than 10 years ago (dashed line).

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Butterflies in biodiversity promotion areas

BDM is able to record butterflies with pinpoint accuracy using GPS. If a transect runs through biodiversity promotion areas (BPAs), more butterfly individuals are counted than in sections along intensively used meadows and pastures. However, we are a long way away from achieving the densities of individuals that we are accustomed to from dry meadows and pastures of national importance, even in BPAs. Similar patterns can also be found in the diversity of vascular plants, as an analysis of data from ALL-EMA shows.

  • The bar plot shows the individual densities of butterflies on various meadows and pastures: The values for BPA meadows and pastures are significantly higher than for the associated intensively utilised grassland, but they are also 2-3 times lower than those for dry meadows and pastures.
    Average number of butterfly individuals in the analysed meadows and pastures. Only the target and indicator species according to the Agriculture-Related Environmental Objectives (AEO species) were taken into account. The error bar indicates the 95% confidence interval.

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Increasing monotony in snails

The photo shows a mollusk (scientifically Vertigo pigmaea) on a leaf. The snail is just under 2 millimetres in size.

The diversity of species communities in meadows and pastures is calculated from the BDM data. This is one of 52 legislative indicators used to monitor the legislative objectives. The time series shows that the species communities of snails are becoming increasingly similar. Closer analysis reveals that there are only a handful of species that play a decisive role. Among them is the crested vertigo, an already common snail species whose distribution is increasing. Among the other species, by contrast, are rare species whose frequency is declining.

  • he graph shows the proportion of sampling areas colonised by Vertigo pigmaea over time. This proportion increases from 10 to 20 per cent to 20 to 30 per cent in the period from 2010 to 2020.
    The abundance of the crested vertigo (Vertigo pygmaea) has increased significantly in recent years. The straight line shows the trend with the 95% confidence interval.

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Basis for the Swiss butterfly index

Impression of BDM field work: A field worker catches a butterfly with a net on an alpine pasture.

The BDM's butterfly data is highly suitable for supplementing the records compiled by info fauna. This is because particularly spectacular or very rare species are often reported, while the data on medium-frequency species is rather sparse. BDM makes an important contribution to this with its regular sampling grid and standardised recording methodology. The butterfly index can be calculated from the combined dataset. As the graphs below show, the population of thermophilic species has increased in recent years, while psychrophilous species have tended to decline.

  • The graph shows how the butterfly index for 46 thermophilic species has increased. In 1990, the value was around 75 index points; by 2020, it had risen to 120 points.
    Population trend of the 46 butterfly species that are considered heat indicators. Heat indicators include the mallow skipper (Carcharodus alceae) and the short-tailed blue (Cupido argiades).
  • The graph shows how the butterfly index for 23 cold-indicating species has decreased. In 1990, the value was between 100 and 120 index points, in 2020 only between 95 and 75 points.
    Population trend of the 22 butterfly species that are considered cold indicators. Cold indicators include the dewy ringlet (Erebia pandrose) and the Alpine grayling (Oeneis glacialis).


  Butterfly Index

Hotspot Special Edition

Cover of the Hotspot special issue on 20 years of biodiversity monitoring in Switzerland.

The Hotspot special edition on 20 years of BDM shows who works behind the data and highlights current developments in biodiversity.

Current findings

BDM's current findings are available on the FOEN website, in the section on environmental indicators.