Effects of Selected Factors on Biodiversity in Swiss Agricultural Landscapes

Switzerland’s agricultural landscape harbours a great variety of species and habitats, some of which are endangered. This study sheds light on various direct and indirect, positive and negative factors influencing biodiversity.

As part of Agroscope’s ALL-EMA Monitoring Programme, data on the state of habitat, plant, butterfly and breeding-bird diversity from three national monitoring programmes were analysed together with various factors directly or indirectly associated with biodiversity at landscape scale.

Too little biodiversity in lower-lying areas of the Swiss agricultural landscape

In Switzerland, contributions for ecological focus areas (EFAs) have been part of the direct payment system since 1993 and are intended for the promotion and conservation of species and habitats in agricultural landscapes.

Although the promotion measures are making an impact in a number of  cases, a first ALL-EMA status report highlighted a biodiversity deficit, particularly in agricultural areas of the Swiss lowlands and hilly regions, where species diversity is markedly lower than in higher-lying zones, despite favourable abiotic conditions. To promote species and habitat diversity in Swiss agricultural landscapes that are impacted by various biotic and abiotic conditions through targeted measures, the various determining factors must also be understood at larger spatial scales.

Biodiversity assessment study using data from three monitoring programmes

The state of biodiversity in Switzerland’s agricultural area was assessed based on the species diversity of four biodiversity indicators: (1) Habitat types; (2) Plants; (3) Butterflies; and (4) Breeding birds. The surveys were conducted in a total of 170 survey squares of 1 km² each, i.e. at landscape level, spread across the agricultural zones (lowland zone up to summer grazing areas) and the main regions of the Agriculture-Related Environmental Objectives over the time period 2015 to 2019 (sampling of one-fifth of all survey squares per year).

The survey was based on data from the following programmes:

Programme 1: The data on plants and habitats stemmed from Agroscope’s ‘ALL-EMA’ programme (www.allema.ch).

Programme 2: The butterfly data were from ‘Biodiversity Monitoring Switzerland’ (www.biodiversitymonitoring.ch).

Programme 3: The ‘Common Breeding Birds Monitoring Programme’ of the Swiss Ornithological Institute Sempach supplied the data on breeding birds (Monitoring of common breeding birds – Swiss Ornithological Institute (vogelwarte.ch) ).

Land-use intensity directly reduces biodiversity

Intensive use of fertilisers and plant-protection products is commonly considered to be one of the main reasons for decreased biodiversity in the landscape. The model used in the study confirmed this assumption in that it identified a markedly negative direct impact of management intensity on the diversity of habitats and various species groups at the spatial level of entire landscapes.

EFAs and organic management promote biodiversity

Larger shares of EFAs in the surveyed landscape squares were associated with higher biodiversity. These areas thus make an important contribution as feeding, shelter, nesting and overwintering spaces, which are normally no longer sufficiently available in an intensively managed landscape.

The analysis also pointed to a direct positive correlation between organic management and biodiversity at landscape level.

Abiotic factors impact biodiversity indirectly as well as directly

In previous research projects, biodiversity-relevant factors such as temperature were usually viewed as factors with a direct impact and were investigated locally. Little attention was paid to indirect correlations between different factors at landscape level. However, the study highlights strong correlations between abiotic conditions and biodiversity. Temperature, for example, not only influenced the state of biodiversity of an agricultural landscape directly, but also indirectly, by having a considerable impact on the way a landscape is utilised as well as on management intensity. When designing agricultural policy measures such as collaborative approaches at the landscape level for the large-scale promotion of biodiversity, it is therefore also necessary to take into account indirect factors at landscape level as comprehensively as possible.