Paul Bunyan, the SPAM museum and a giant twine ball are just a few of Minnesota’s beloved roadside attractions. These don’t interest insects, but plants along the strips of pavement often do. For pollinators experiencing declines and habitat loss — including monarch butterflies and native bees — these corridors are particularly important.
Since roadsides also serve as corridors for automobiles, mounds of road salt linger for months. This struck Emilie Snell-Rood, an associate professor in the College of Biological Sciences, during her first winter in Minnesota. Knowing that sodium is a component of road salt and a micronutrient required by animals, Snell-Rood launched a study assessing how elevated levels affect butterflies, and found elevated sodium levels in roadside milkweed and impacts on developing monarchs.
Questions abounded and drafts for new research proposals began. Since monarchs and bees often use roadside plants, understanding how runoff impacts their development is important for conservation efforts. Roadsides accumulate heavy metals from car wear and tear, nitrogen from exhaust, and the effects on the health of pollinators remain largely unknown.
“The questions are interesting at a basic level,” Snell-Rood says, “but they also have these really important and direct translations.” The Environmental and Natural Resources Trust Fund awarded Snell-Rood and her collaborators on the project a multi-year grant to tackle some of these questions. Collaborators include CBS faculty members Elizabeth Borer and Clay Carter, and College of Food, Agricultural and Natural Resource Sciences faculty members Dan Cariveau, Karen Oberhauser and Marla Spivak, along with colleagues from the Minnesota Department of Natural Resources (DNR).
Surveys in the field kicked off this summer with technicians crisscrossing the state to collect data, covering 3,000 miles, or the distance from Brooklyn to the Golden Gate Bridge. For three years, Snell-Rood will split her time between the roadside, field plots and lab. As site selection began earlier this year, surveys completed by the Monarch Joint Venture — a project that aims to conserve monarchs — helped narrow down the possibilities to 50 roadside sites throughout Minnesota ranging from country roads to heavily-traveled thoroughfares. Snell-Rood is thrilled that work is underway. “This project will help us answer some really interesting questions about how nutrients and heavy metals interact to affect plant and pollinator health,” she says.
DNR staff and others will use results to develop best management practices along roadsides. Many eyes are on the “Monarch Highway” initiative, which aims to improve habitat along Interstate 35 — a critical migration corridor for monarchs. Subtle changes in management could improve pollinator health in roadsides, whether it’s planting species that don’t accumulate certain nutrients in nectar or mowing areas with higher heavy metals. Roadside pull-offs to view thriving monarchs and native bees will hopefully join Minnesota’s list of roadside attractions in the coming years. —Claire Wilson