The National Academies

NCHRP 20-119 [Completed]

Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies

  Project Data
Funds: $350,000
Research Agency: University of Minnesota
Principal Investigator: Karen Oberhauser
Effective Date: 3/13/2017
Completion Date: 9/13/2019
Comments: A pre-publication of the final report is available at http://www.trb.org/main/blurbs/180186.aspx.

In response to the decline of critical pollinators, including butterflies, a presidential memorandum entitled, “Creating a Federal Strategy to Promote the Health of Honey Bees and Other Pollinators,” established the Pollinator Health Task Force, of which the U.S. Department of Transportation is a member. The monarch butterfly is found throughout the lower 48 states, Hawaii, southern Canada, and northern South America. Because of its large bright orange and black-patterned wings and its migration path spanning much of the northwestern hemisphere, its decline has been more noticeable than most other pollinators. This butterfly has experienced a precipitous population decline.  Thus, it is under review by the U.S. Fish and Wildlife Service for listing as a threatened species (a decision is anticipated by June 30, 2019). The reasons for its decline listed in scientific and popular science literature include: habitat and food source loss, invasive plant species that outcompete milkweed, pesticide use, and illegal logging in its very limited overwintering grounds. There is a need to study the relationship between roadside habitat and the various life stages of monarch butterflies as one of the proactive conservation strategies for the species.
The objective of this research is to develop and validate a methodology for transportation practitioners to determine if roadway corridors are sources or sinks (beneficial or detrimental) to the monarch butterfly and how to maximize the beneficial aspects and minimize the detrimental impacts. The methodology should address a broad range of variables related to the project objective such as, but not limited to, the following:
  • Accounting for the differences and similarities between the eastern and western monarch butterfly populations, and migratory and non-migratory populations;
  • Analyzing mortality rates related to roadsides;
  • Considering traffic volume, speed, right-of- way width, and roadway width;
  • Assigning functional values for different roadside vegetation types;
  • Evaluating the effects of adjacent land use and habitat;
  • Considering roadway right-of-way maintenance practices (e.g., mowing, salt, burning, timing, pesticides); and 
  • Considering environmental variables (e.g., climate, precipitation, elevation and aspect).
While the methodology should be directly applicable to most situations, it should also outline decision-making processes and criteria that would assist transportation practitioners in identifying flexible solutions. Ultimately, the methodology should allow users to select and prioritize the most advantageous locations for butterfly habitat enhancement on a landscape scale (i.e., how large do habitat patches need to be and are there considerations of the amount of habitat adjacent to the roadways that would make selections of particular roadside locations more beneficial than others?).
The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can be realistically accomplished within the constraints of available funds and contract time. Proposals must present the proposers’ current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective. A kick-off teleconference of the research team and NCHRP shall be scheduled within 1 month of the contract’s execution. The work plan must be divided into two phases with tasks, with each task described in detail. Phase 1 will consist of information gathering, culminating in the submission of an interim report. The interim report will describe the work completed in the Phase 1 tasks and provide an updated work plan for the Phase 2 tasks, an outline of the methodology, and the proposed sites to validate the methodology. There must be a face-to-face meeting with NCHRP to discuss the interim report. No work shall be performed on Phase 2 without NCHRP approval. Phase 2 shall include the development and validation of the methodology. The final deliverables will include (1) the validated methodology that transportation practitioners can use to determine if roadway corridors are sources or sinks (beneficial or detrimental) to the monarch butterfly; (2) a final report documenting the entire project, incorporating all other specified deliverables of the research; (3) an electronic presentation on the methodology that can be tailored for specific audiences; (4) recommendations on needs and priorities for additional research; and (5) a stand-alone technical memorandum titled “Implementation of Research Findings and Products” (see Special Note B for additional information). Proposers may recommend additional deliverables to support the project objective.
STATUS:  A pre-publication of the final report is available at https://www.trb.org/main/blurbs/180186.aspx. 

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