Submitted to: Insect Conservation and Diversity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2016
Publication Date: 6/18/2016
Citation: Elwell, S.L., Griswold, T.L., Elle, E. 2016. Habitat type plays a greater role than livestock grazing in structuring shrubsteppe plant-pollinator communities. Insect Conservation and Diversity. doi: 10.1007/s10841-016-9884-8.

Interpretive Summary: Livestock grazing is a common practice in grassland environments. Pollinators are a vital part of these environments, but little is known about the impact of grazing on pollinators. A study of paired grazed and ungrazed grassland sites was conducted in south central British Columbia, Canada, to assess the degree of change in pollinators and plants. Sampling resulted in 5907 bees, flies, beetles, wasps and butterflies that represented 253 species. Grazing increased the amount of shrubs and bare soil at the expense of grasses and herbaceous plants. Despite these changes in vegetation there was no evidence of changes to pollinator abundance, number of species, and kinds of pollinators present. Results suggest that under responsible management regimes diverse pollinators and plants can be maintained. It highlights the importance of balanced land management.

Technical Abstract: Livestock grazing is a prevalent grassland disturbance and can negatively impact biodiversity. Pollinators constitute a vital component of grassland ecosystems, but the impact of grazing on pollinator diversity has seldom been assessed in North America. We assessed vegetation structure, and pollinator and flowering plant abundance, richness, diversity, and community composition in four pairs of spring grazed/ungrazed sites in south-central British Columbia, Canada. Sampling was completed in two threatened shrubsteppe habitat types – antelope-brush and big sagebrush shrubsteppe – therefore we also investigated whether pollinator or floral communities differed between habitats. Pan-trapping surveys captured 5907 bees, flies, beetles, wasps and butterflies constituting 253 species. We found that the percent cover of shrubs and bare soil increased with grazing, while the height of grasses and forbs decreased. In contrast, pollinator and flowering plant abundance, richness, diversity, and community composition were not significantly affected by grazing. Flowering plant and pollinator community composition did differ significantly between shrubsteppe habitats. Our results indicate that grasslands in North America, when managed responsibly, can maintain pollinator and flowering plant diversity under grazing pressure. The continued effort of land managers to balance ecological integrity and economic viability will be important for the conservation of grassland pollination systems.