Is the Abandonment of Organic Grassland a Threat to Alpine Insect Diversity?

Abstract

Land abandonment is a multifaceted, nonlinear, worldwide phenomenon that is influenced by a variety of factors and opinions. The goal of this study was to understand the significance of land abandonment for true bugs and syrphids in three grassland management regimes that includes abandoned, intensive, and extensive alpine organic grasslands. In 2021 and 2022, we sampled true bugs and syrphids by applying observation plot and sweep netting sampling methods. Extensive grasslands had significantly higher true bug and syrphid abundance compared to abandoned grasslands. However, no difference of species richness was found in studied grassland regimes. Large numbers of unique species (25.5% true bugs and 21.5% syrphids) only occurred in the abandoned grasslands but not in intensive and extensive grasslands. Similarly, true bug assemblages in abandoned grasslands differed significantly from assemblages in intensive and extensive grasslands. We found that extensive grassland can manage to increase true bugs and syrphid abundance. Likewise, undisturbed abandoned grassland is not a threat to insect diversity, and supports the survival of more unique true bug and syrphid species. A mosaic landscape consisting of abandoned grassland along with grassland having different, mainly extensive, management intensity could be an ideal arrangement for alpine biodiversity conservation.