(Beyond Pesticides, September 18, 2008) New research in the forthcoming issue of Biological Conservation reveals that roadsides maintained “conventionally” with the use of herbicides, non-native fast-growing grasses and frequent mowing support less native bee diversity and abundance than roadsides restored with native plants. Focus on the importance of native bees has increased in light of the recent honeybee crisis. Roadsides restored to native plants could serve as valuable protective corridors of native pollinators, which are threatened by pesticide use and habitat fragmentation.
Jennifer Hopwood, PhD, the author of “The contribution of roadside grassland restorations to native bee conservation,” performed the research in Kansas, where a very small amount of unplowed prairie remains. The intensification and spread of agriculture has reduced the availability of suitable nesting sites, particularly for ground-nesting bees, and has limited food sources as a result of reduced floral diversity. Dr. Hopwood found more than twice the bee abundance in roadsides with native plants and increased bee diversity. The restored roadsides have 79 species of bees, whereas the conventionally managed roadsides only have 53. Roadsides in Kansas account for more than 650,000 acres of continuous corridors, which, if restored to native plants, could add significantly to viable bee habitat.
In addition to struggling as a result of reduced floral resources/food sources due to herbicide use, the introduction of non-native grasses and agricultural intensification, bees are extremely sensitive to insecticides in numerous chemical classes. The use of insecticides and herbicides has been implicated in global pollinator decline.
Bees are the most significant taxon of pollinators, and there are over 4,000 species of native bees in North America. Although honeybees are often given the bulk of the credit for pollination of agricultural crops, recent research has shown the significance of wild bees’ contribution to pollinating the food we eat. A study in New Jersey and Pennsylvania reports that the majority of flower visitation in watermelon and tomato is from wild bees, despite the fact that 64% of farmers in the study rented honeybees.
The management of rights-of-way such as roadsides, railroad lines and power lines often involves herbicide use, even though alternatives exist. The restoration of roadsides with plants native to the region is one way to reduce herbicide use, save fossil fuels (less mowing required) and help support a diverse and abundant pollinator community.
In addition to encouraging departments of transportation to adopt roadside restoration of native plants, individuals can encourage native bee populations at home. For more information on creating suitable nesting grounds and planting appropriate plants, visit the Xerces Society’s website.