Field edge flower plantings have variable effects on wild bee abundance, richness, nesting success, and crop pollination, independent of the surrounding landscape

Abstract

To mitigate the effects of habitat loss on bee conservation and crop pollination, farmers are encouraged to plant flowers along the edges of crop fields. However, it is unclear where and to what degree these flower plantings are effective. Recent studies suggest that flower plantings may be less effective if they are established in landscapes with either very low or very high amounts of non-crop habitat. Moreover, while field edge flower plantings often increase the abundance and richness of bees in field edges, it is unclear whether this improves crop pollination or bee nesting success, which could increase bee populations over time. In this study we examined how field edge flower plantings and the landscape context in which they are established affect wild bee conservation and crop pollination. Across two years we established flower plantings of 0.1–0.5 ha along the edges of 17 of 34 commercial cucumber fields arranged across a gradient of landscape complexity. We then measured wild bee abundance, richness, and crop pollination in and around cucumber fields with and without plantings and assessed the nesting success of stem-nesting bees. We found that both field edge flowers and landscape-scale non-crop habitat had independent, positive effects on bee abundance, richness, nesting, or crop pollination in one of the two years of the study, and that the effects of field edge flowers on bees and crop pollination were not influenced by the surrounding landscape. We also found that managing field edges in a way that maintains naturally-occurring flowers may matter as much or more than flower plantings for short-term increases in bee abundance and richness. However, certain species of planted flowers might be associated with improved bee nesting success, an outcome important for both bee conservation and sustained crop pollination.