Conservation value of traditional meadow irrigation for carabid beetles

Abstract

Locally adapted and evidence-based management strategies are needed to counteract the current insect declines. In Central Europe, semi-natural grasslands are biodiversity hotspots having a high conservation value, but are threatened by both abandonment and agricultural intensification. We investigated the potential of traditional lowland meadow irrigation as a biodiversity-friendly grassland management strategy using carabid beetles as indicator organisms. We analysed carabid beetle species richness, the occurrence of species of conservation concern, and trait composition in relation to meadow irrigation and fertilization. Moreover, we conducted bipartite network analysis in order to reveal species-habitat networks. The key finding is that the species richness of carabid beetles in irrigated and non-irrigated meadows was similar, but irrigation positively influenced species and individual numbers of carabids of conservation concern. Meadow irrigation, but also fertilization, further shaped carabid beetle species-habitat-networks indicating species-specific preferences for differently managed meadows. Finally, the trait composition was affected: carabid beetles in irrigated meadows were on average larger, more predacious and less mobile than in non-irrigated meadows. We therefore recommend the preservation and restoration of this traditional grassland management practice for biodiversity conservation in suitable regions, but also call for future studies to further increase conservation evidence.