Keeping Raised Bog Remnants Wet Stabilizes Characteristic Pollinator Communities

Recent studies report declines in abundance and species richness of pollinator communities. In response, nature managers aim to promote pollinators primarily through vegetation manipulation. However, long-term studies that evaluate pollinator community development in restored areas under active management are scarce. To assess whether landscape-level conservation efforts are able to sustain a characteristic pollinator community, we study abundance and richness trends of hoverflies (Diptera: Syrphidae), bees (Hymenoptera: Apidae s.l.), and butterflies/diurnal moths (Lepidoptera), as well as their characteristic species over 30 years within the restored and intensively managed Dutch raised bog system Bargerveen. We describe positive and stable trends in the overall abundance and species richness of pollinators, primarily Apidae and Syrphidae. These trends contrast with nation-wide declines. The effects of recent dry years were evident in declining butterfly abundance trends, although not as pronounced as in national trends. In addition, abundance of species characteristic of raised bog systems remained stable, suggesting that benefits also applied to these generally more sensitive species. Implications for insect conservation : Results from this case study show that conservation efforts in raised bog systems can support and improve pollinator abundance and richness, as well as populations of characteristic and vulnerable species. We argue that the positive and stable population trends of pollinators in Bargerveen are primarily a result of large-scale water management, and that landscape-level hydrological management has the potential to act as a buffer against drivers of insect decline even within predominantly agricultural landscapes.