Wild bees as winners and losers: relative impacts of landscape composition, quality, and climate

Authors: KAMMERER, MELANIE - Pennsylvania State University; Goslee, Sarah; DOUGLAS, MARGARET - Dickinson College; TOOKER, JOHN - Pennsylvania State University; GROZINGER, CHRISTINA - Pennsylvania State University

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2020
Publication Date: 1/21/2021
Citation: Kammerer, M., Goslee, S.C., Douglas, M.R., Tooker, J.F., Grozinger, C.M. 2021. Wild bees as winners and losers: relative impacts of landscape composition, quality, and climate. Global Change Biology. 27:1250-1265. https://doi.org/10.1111/gcb.15485.
DOI: https://doi.org/10.1111/gcb.15485

Interpretive Summary: Wild bees are crucial for pollinating both crops and wild plants, but they are threatened by both habitat loss and climate change. Few studies have examined both of these threats simultaneously. Wild bee species have different needs for nesting sites, and for the seasonal timing and quality of flowering plant availability, so we expected the importance of habitat loss and climate to differ by species or functional group. We analyzed a long-term UGSG dataset of wild bee abundance from Maryland, Delaware, and Washington DC, USA with over 100,000 records. Despite our expectations, temperature and precipitation were far more important than surrounding landscapes for nearly all groups of wild bees. In the eastern US, changing climate poses a major threat to wild bee communities.

Technical Abstract: Wild bees, like many other taxa, are threatened by land use and climate change, which in turn jeopardizes pollination of crops and wild plants. Understanding how land-use and climate factors interact is critical to predicting and managing pollinator populations and ensuring adequate pollination services, but most studies have evaluated either land-use or climate effects, not both. Further, bee species are incredibly variable, spanning an array of behavioral, physiological and life history traits that can increase or decrease resilience to land use or climate change. Thus, there are likely bee species that benefit, while others suffer, from changing climate and land use, but few studies have documented taxon-specific trends. To address these critical knowledge gaps, we analyzed a long-term dataset of wild bee occurrences from Maryland, Delaware, and Washington DC, USA, examining how different bee genera and functional groups respond to both land-use and climate factors. Despite a large body of literature documenting land-use effects on wild bees, in this study, climate factors emerged as the main drivers of wild-bee abundance and richness. Almost all our models in both seasons (spring or summer/fall) indicated that temperature and precipitation were more important predictors of wild-bee communities than landscape composition, landscape quality, or topography; however, relationships varied substantially between wild-bee genera and functional groups. In the Northeast USA, past trends and future predictions show a changing climate with warmer winters, more intense precipitation in winter and spring, and longer growing seasons with higher maximum temperatures. In almost all of our analyses, these conditions were associated with lower abundance of wild bees. Wild-bee richness results were more mixed, including neutral and positive relationships with predicted temperature and precipitation patterns. In the Northeast USA, changing climate poses a significant threat to wild-bee communities.