Landscape context influences the bee conservation value of wildflower plantings

Authors: MCCULLOUGH, CHRISTOPHER - Virginia Tech; Angelella, Gina; O'ROURKE, MEGAN - National Institute Of Food And Agriculture (NIFA)

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2021
Publication Date: 4/26/2021
Citation: McCullough, C.T., Angelella, G.M., O'Rourke, M.E. 2021. Landscape context influences the bee conservation value of wildflower plantings. Environmental Entomology. 50(4):821-831. https://doi.org/10.1093/ee/nvab036.
DOI: https://doi.org/10.1093/ee/nvab036

Interpretive Summary: Planting wildflowers on farms is a common strategy design to counteract the negative effects of habitat loss and provide nesting and floral resources to support bee populations. Semi-natural landscapes such as forests and wetlands surrounding farms can also provide important nesting and floral resources for bees and can change how effective wildflower plantings are at conserving bee species. Collaborating scientists from Virginia Tech, USDA-ARS, and USDA-NIFA have surveyed bees on farms in the Mid-Atlantic with and without wildflower plantings. They determined that wildflower plantings were most likely to increase the number of bees on farms that had an intermediate amount of semi-natural habitat in the surrounding landscape, but the amount of semi-natural habitat was more effective at increasing both the number of bees and the number of bee species found on farms. This research shows when wildflower plantings would be most effective, and suggests conserving the semi-natural habitat surrounding farms may be especially important for the conservation of native bees

Technical Abstract: Pollination provided by bees is a critical ecosystem service for maintaining and enhancing agricultural production. However, bee populations are at risk from multiple stressors such as habitat loss, pesticides exposure, and disease. Wildflower plantings on farms to provide habitat and resources for bees is a common mitigation strategy. In many instances, government programs are available for private-landowners to subsidize the installation of these plots. Semi-natural habitat (SNH) in the landscape is also important for conserving bee populations and may alter the effectiveness of wildflower plantings in conserving bee communities. In this study, we tested the effectiveness of wildflower plantings and interactions with SNH in the landscape for promoting bee abundance and richness. Bee surveys were conducted over two years at 22 sites in eastern Virginia and Maryland. Wildflower plantings, averaging 0.22 ha in size, were installed and maintained by cooperators at 10 of the sites. In total, 5,384 bees were identified from 85 species. Wildflower plantings did not alter or enhance bee communities independently, but bee abundance was greater on farms with plantings and 20-30% SNH in the surrounding landscape. Bee abundance and richness had nonlinear responses to increasing SNH in the landscape surrounding the sites. The positive effects for richness and abundance peaked when SNH was approximately 40% of the landscape. Similar to predictions of the intermediate-landscape complexity hypothesis, fewer bees were sampled from wildflower habitats where the surrounding landscape had more SNH. Results indicate that small wildflower plantings in the Mid-Atlantic U.S. had a minimal effect on bee conservation on the scale studied and that conserving SNH across the landscape may be a more important conservation strategy