Assessing Pollinator Friendliness of Plants and Designing Mixes to Restore Habitat for Bees

Abstract

The worldwide decline in bee populations is threatening the delivery of pollination services, thus leading to the development of pollinator restoration strategies. In the United States, one way to protect and restore bee populations is to use seed mixes composed of pollinator-friendly native plants to revegetate federal lands following disturbance. However, we lack information about which native plant species and mixes are best for bees. We assessed the attractiveness and use by bees of 24 native plant species that are standard for revegetation projects (focal plants) on national forest lands in western Montana. Focal plants that had the highest visitation rate, attracted the most bee species, supported specialist bee species, and bloomed for extended periods across the landscape were considered "pollinator-friendly." Our results suggest that Salix bebbiana, Arctostaphylos uva-ursi, Lupinus sericeus, Rosa woodsii, Symphoricarpos albus, Erigeron speciosus, Symphyotrichum foliaceum, and Gaillardia aristata could create a seed mix that is effective for pollinator restoration on public lands. Pollinator-friendliness score cards are provided to allow land managers to select plant species to include in restoration mixes that benefit pollinators. Identifying mixes of pollinator-friendly native plant species that are available for restoration will allow land managers to both revegetate disturbed habitats and restore bee communities on federal lands. The methods developed in this project can be used to design seed mixes for pollinator restoration on other public lands.

Bee and butterfly records indicate diversity losses in western and southern North America, but extensive knowledge gaps remain

“…In response to these changes, policymakers and managers can prioritize pollinator habitat restoration. An active current area of research is techniques for and efficacy of such restoration efforts, which range from concentrated gardens of pollinator-friendly plants to broad, landscape-scale seeding with native flowering species [137][138][139][140][141][142][143][144]. Objectives of such restorations are to ensure consistent diversity and abundance of pollinator forage plants over the full growing season as well as availability of cover, protection, and pollinator nesting materials.…”

Plant selection for pollinator restoration in seminatural ecosystems

“…Furthermore, studies from the Intermountain West in the US (Glenny et al . 2022b) and the Pampas of Argentina (Malena et al . 2021) ranked plants using criteria related to the attractiveness of each plant species for pollinators, the ability of a plant species to proliferate in the environment, and the cultural importance of a plant species, ultimately creating a composite score for managers to select the most important plants and design a single seed mix for restoring pollinator communities and ecosystem health (Figure 3).…”

“…Revegetating landscapes with the fewest number of plant species that support the maximum number of pollinator species and pollination services may be important to implement costeffective restoration projects (Williams and Lonsdorf 2018). Furthermore, studies from the Intermountain West in the US (Glenny et al 2022b) and the Pampas of Argentina (Malena et al 2021) ranked plants using criteria related to the attractiveness of each plant species for pollinators, the ability of a plant species to proliferate in the environment, and the cultural importance of a plant species, ultimately creating a composite score for managers to select the most important plants and design a single seed mix for restoring pollinator communities and ecosystem health (Figure 3). However, if each criterion is weighted equally and information that is gathered across multiple habitat types are integrated, then the resulting planting mix may not establish within a specific habitat type or meet a defined restoration goal.…”

“…Within each bloom period (pink rectangles), a scorecard that integrates information across desirable plant traits can help in identifying the most effective plants for pollinator restoration. In this example, adapted from a study assessing the pollinator value of plants available to the US Forest Service for restoration in Montana(Glenny et al 2022b), plant species were ranked depending on the observed pollinator visitation rate, visitation richness, value to species of conservation concern (SCC), bloom duration, and frequency of occurrence across the landscape; rankings were then totaled into a composite to select the best overall plants for pollinators (green composite score).…”