Skip to Content

Roadside Habitat for Monarchs

Sep 01, 2021


  • Conservation Stories
  • Recent Research

“There are idle spots on every farm, and every highway is bordered by an idle strip as long as it is; keep cow, plow, and mower out of these idle spots, and the full native flora, plus dozens of interesting stowaways from foreign parts, could be part of the normal environment of every citizen.” 

--Aldo Leopold, A Sand County Almanac

If you pay attention when you drive cross country in North America, you’ll notice what ecologist Aldo Leopold noticed back in 1949—although the landscape has been dramatically changed from its pre-developed state, there are spaces on the margins of daily life where native plants and the wildlife that depend on them thrive. 

Many researchers believe that roadsides are one of the essential habitat sectors for monarch recovery. Monarch caterpillars depend on milkweed, a hardy native plant that flourishes in disturbed habitat such as roadsides. With its thousands of miles of rights-of-way, transportation departments across North America have everything they need to create monarch havens just a few steps beyond the shoulder line. 

Creating and appropriately managing roadside habitat is part of the “All Hands on Deck” approach to restoring monarch habitat. The monarch population has declined by more than 80 percent in the last two decades—a reduction that many scientists attribute to the loss of sufficient milkweed, which monarchs need to survive. The All Hands on Deck approach calls for the combined efforts of land managers from multiple sectors (agriculture, municipal areas, transportation corridors, and agricultural conservation lands) to establish enough milkweed to restore the monarch population. 

The Rapid Assessment survey, created by the Monarch Joint Venture in collaboration with a number of partners, is one of the tools available for managers to collect information about the quality of monarch habitat on roadsides. This survey evaluates the availability of monarch resources such as milkweed and nectar-producing plants present at a given roadside location. The survey also notes the presence of monarch eggs, caterpillars, and adult butterflies, and can be customized to collect information that is specific to the needs of each management organization. The pollinator scorecard is a similar assessment tool created by the Rights-of-Way as Habitat Working Group at the University of Illinois-Chicago. 

Habitat evaluators like these can show managers where to focus their efforts and indicate what practices will work best to create optimum roadside habitat for monarchs and other pollinators. Often, this means changes in mowing practices. Some departments have made the switch from mowing the entire right-of-way to mowing only the safety zone, as well as decreasing the frequency of mowing. This allows milkweed patches to stay standing long enough to nurture caterpillars into adult butterflies, and also supports a large diversity of other pollinators and wildlife that use the habitat strips in the rights-of-way. 

One thing that roadside managers have in common is a keen interest in controlling invasive species along roadways. While invasive species may provide some value to pollinators, and they might yield a misleading habitat quality score using habitat evaluation tools, they can be incredibly detrimental to the health of native plant ecosystems if not controlled. Using data from rapid assessment surveys can help roadside managers decide when and where treatments might be necessary to make room for habitat that is more beneficial to pollinators. 

The idea of roadways flanked by fields of blooming flowers is an enticing one, but the switch to roadside pollinator habitat isn’t necessarily sunshine and daisies right away. It might take a few seasons for beneficial native plants to establish. But with patience, appropriate management can lead to roadsides studded with appealing Midwest favorites such as bergamot, black-eyed Susans, wild roses, and hundreds of others. 

For roadside managers interested in taking the extra step toward monarch conservation, habitat assessment tools can play a key role in Candidate Conservation Agreements with Assurances, or CCAAs. The monarch is a candidate species under the Endangered Species Act, which means it is at risk and likely to become a threatened or endangered species if no action is taken to prevent it. A CCAA agreement between land managers and the U.S. Fish and Wildlife Service strives to create and manage habitat to support the current monarch population, and also ensure that land managers will not have to take additional conservation measures if the butterfly becomes listed in the future. 

There are still a lot of questions to be answered about roadside habitat, but Aldo Leopold might have appreciated the approach for its ability to bridge the worlds of ecology and daily human priorities, inviting the average commuter to give a little more thought to the parallel worlds passing by on the side of the highway. 

Article written by Jackie Bussjaeger, MJV Assistant Program Manager. Header photo by Wendy Caldwell. For more info about MJV's roadside habitat assessment tools, contact Laura Lukens at

The Monarch Joint Venture is a 501c3 nonprofit organization and a national partnership of federal and state agencies, non-governmental organizations, businesses and academic programs working together to conserve the monarch butterfly migration. The content in this article does not necessarily reflect the positions of all Monarch Joint Venture partners.