Semi-natural habitat enhancements provide valuable habitat for wild pollinator communities

Wild insect communities are key contributors to agriculture through crop pollination. However, many conventional practices in crop production harm beneficial insect populations. There is growing evidence suggesting that the establishment of functional plant species within semi-natural agricultural areas supports pollinators, either by providing foraging or nesting resources. Planted hedgerows of native woody species within crop margins, as well as set-aside fields sowed with grasses and/or flowering herbaceous plants, are examples of such habitat enhancements. However, hedgerows have shown varying support of pollinators, and set-asides have not been assessed for their pollinator conservation potential across management types.

We investigated the pollinator conservation potential of enhanced semi-natural areas in the Lower Fraser Valley of British Columbia. First, we assessed community diversity of wild bee and syrphid fly communities across crop margin types (planted hedgerows, remnant hedgerows, and unplanted weedy edges). While we found that pollinators visited flowers in hedgerows more often than in weedy margins, we did not observe overall community differences among margin types, suggesting that weedy margins are also valuable for pollinators. Second, we evaluated pollinator diversity in three agricultural field types (traditional grassland set-asides, grassland set-asides with added flowers, and active crop fields) and concluded that both set-aside practices supported pollinators better than crop fields did. While traditional set-asides without flowers provided few floral resources, the enhanced abundance and diversity at these sites suggests they may supply nesting sites for ground-nesting bees. Our findings provide evidence that semi-natural habitat enhancements supply key resources for insect pollinators in agricultural landscapes.