Pollinator conservation and restoration in semi-natural ecosystems

Abstract

Semi-natural ecosystems are areas with biological and physical characteristics that resemble natural ecosystems but are also affected by anthropogenic disturbances. Semi-natural ecosystems are also areas with high insect pollinator diversity. Land management actions within semi-natural ecosystems may therefore be important to counteract future declines of insect pollinators. However, current restoration strategies for insect pollinator communities are based on evidence from agricultural ecosystems, which have frequent human interventions to ensure plant success, neglect the importance of nesting materials, and primarily benefit generalist species. To inform management actions for the conservation and restoration of insect pollinators in semi- natural ecosystems, I (1) synthesized the current understanding of the effects of common land management actions on insect pollinators on public lands in the US, (2) identified habitat characteristics which structure the taxonomic and functional diversity of bee communities, (3) evaluated the strength of influence of mechanisms associated with diet breadth across groups of bee species and (4) designed a conceptual model which can be used to select flowering plant species to provide food resources for bee communities in semi-natural ecosystems. Management actions that increase the abundance of floral and nesting resources to support bee species from different functional groups are required to conserve and restore insect pollinator communities in semi-natural ecosystems. I found that (1) management actions have positive, neutral, and negative effects on insect pollinators, but research trends vary depending on the taxon and habitat type, (2) the taxonomic and functional diversity of bee communities are structured by the abundance of both floral and nesting resources, (3) patterns of abundance across space and time have a more positive effect on the diet breadth of bumble bee species compared to non- bumble bee species, and (4) wildflower species that receive a high visitation rate and richness, occupy functionally important positions within bee-flower interaction networks, and are spatially and temporally widespread are important to provide bee communities with food resources in semi-natural ecosystems. These wildflower species may be particularly important to include within seed mixes to revegetate semi-natural ecosystems and provide food resources for insect pollinators.