(Photo by Marjorie Strauss)
(Photo by Marjorie Strauss)
Mention the Department of Transportation and images of traffic-stalled road construction or closed one-lane bridge repairs instantly come to mind; the DOT as a conservation agency? Not so much. But the Maine Department of Transportation is currently in the middle of a two-year study of roadside habitats along state highways in cooperation with the Maine Natural Areas Program of the Department of Agriculture, Conservation, and Forestry that will define various habitats occurring in roadside areas and how they are used by pollinators. This information will provide a baseline of typical roadside habitats and plant species that can be used to improve vegetation management decisions that will benefit these insects, especially the rusty patched bumble bee, which was listed as an endangered species in March. It’s now a federal crime to harm or kill the bees, which were once abundant along the East Coast and through South Dakota and parts of Canada, but whose population has seen its numbers fall by 87 percent in recent decades, according to experts. Efforts are under way across the country to better understand how to manage and improve habitats for the rusty patched and other pollinators and restore their population numbers.

In Maine, federally funded studies began in 2016 when locations were surveyed across the state to first inventory plants, and then bees and butterflies, said Judith Gates, director of Maine’s DOT environmental office. Once results were reviewed, in 2017 smaller plots were selected for further study based on their potential for use by pollinator species. Studies are being conducted by crews of entomologists hired by the Natural Areas Program, the administrator of the federal grant. Their surveys, which are currently ongoing and will continue next year, will include identifying the insects and the host plants that are attracting the pollinators.

If you’ve traveled along Maine’s I-95, you may have noted signs indicating the start and end of roadside pollinator study areas. According to Gates, sites were narrowed down to along the interstate system, where the DOT has the most flexibility for mowing. The results of the study will show what the baseline is and where populations are and will help outline vegetation management strategies for preserving and improving existing habitat.

Roadsides cover more than 10 million acres of land in the United States and, in some states, they are the largest holdings of public land. Transportation rights-of-way are a significant, yet often overlooked, resource for pollinator conservation. In landscapes denuded of natural areas by large-scale agriculture or urbanization, roadsides are an increasingly important component of regional habitat networks. The wildlife living on roadsides touches communities in every state, province, and county of North America. Further, roadsides offer valuable habitat because they are typically set aside from further development and because they stretch across the landscape, connect remnant habitat patches and create a linear refuge for wildlife.

Western and Midwestern states have already begun their preservation efforts. Colorado, for example, became friendlier to pollinators this May by passing the “Colorado Pollinator Highway” Resolution, referring to an area along Interstate 76 from the Nebraska state line to Arvada, Colorado, whose designation will allow better vegetation management, education and outreach to support pollinator habitat along the roadway.

Mowing of roadside vegetation generally has three aims: to improve driver visibility, to provide room for a vehicle to pull off the road if needed, and to prevent encroachment of brush or trees. Gates says Maine roadsides are largely maintained to keep dangerous fixed objects out of the roadsides and to ensure safety of drivers and of road crews working on the verges and medians. Nationally, she elaborates, states may have more rights-of-way that are not forested, as Maine’s are. The seed Maine uses to plant the edges of its highways is purchased from these states, as we don’t have any native seed mix available. The mix has clovers and broadleaf plants but no invasives. With the current study, Maine’s own mowing practices are being evaluated with regard to both safety concerns and pollinator preservation.

Gates says that while efforts are being made to create pollinator corridors across the country, “We’re not really sure how pollinators act.” Some may populate the ridges and hillsides, while others may prefer the valleys. Another issue is timing of roadside mowing. In some parts of the Midwest, mowing roadsides twice a year, early and late in the growing season, resulted in the highest plant diversity and was most beneficial for flower-visiting insects. Other areas found that mowing once a year in July knocked back dominant grasses and promoted wildflower growth. In Maine the approach may be to keep shrubs down and mow after the wildflowers have bloomed, but not in the fall when there are fewer flowers available for foraging pollinators. “There’s no one way to preserve,” Gates notes.