Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies (2020)

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2020 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 942 Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies Alison B. Cariveau Wendy Caldwell Eric Lonsdorf Chris Nootenboom Karen Tuerk Emilie Snell-Rood University of Minnesota St. Paul, MN Eric Anderson environMental incentives Denver, CO Kristen A. Baum oklahoMa state University Stillwater, OK Jennifer Hopwood Xerces society for invertebrate conservation Portland, OR Karen Oberhauser University of Wisconsin Madison, WI Subscriber Categories Highways • Environment Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transporta- tion results in increasingly complex problems of wide interest to high- way authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRB’s relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s recommendations are proposed to the AASHTO Board of Direc- tors and the National Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Academies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement, rather than to substitute for or duplicate, other highway research programs. Published research reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 942 Project 20-119 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-48132-8 Library of Congress Control Number 2020935714 © 2020 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. 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The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; the FHWA; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of the report.

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. John L. Anderson is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Board’s varied activities annually engage about 8,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.

C O O P E R A T I V E R E S E A R C H P R O G R A M S CRP STAFF FOR NCHRP RESEARCH REPORT 942 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs William C. Rogers, Senior Program Officer Jarrel McAfee, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications NCHRP PROJECT 20-119 PANEL Field of Special Projects Mark D. Masteller, Ames, IA (Chair) Stacy A. Armstrong, Missouri DOT, Jefferson City, MO Larry E. Bonner, California DOT, San Luis Obispo, CA Susan D. Hargrove, Illinois DOT, Springfield, IL Meghan W. Hedeen, Georgia DOT, Atlanta, GA Christopher E. Smith, Minnesota DOT, St. Paul, MN David Cohen, FHWA Liaison Michael Gale, U.S. Fish & Wildlife Service Liaison AUTHOR ACKNOWLEDGMENTS We thank Iris Caldwell and Klaudia Kuklinski at the Energy Resources Center (University of Illinois— Chicago) for their help with the Metrics and Targets Taskforce in the review of other pollinator habitat rating systems. We thank Emily Geest, Jeremy Kaplan, Ashley Knoch, Nick Haas, Grace Haynes, and Patrick Parish for the tireless effort collecting field data for the project. Many thanks to members of the Snell- Rood Lab who worked on aspects of a related project (funded by the Minnesota Environment and Natural Resources Trust Fund) on the nutrition of roadside plants for pollinators, in particular, Megan Kobiela, Tim Mitchell, Alex Shepard, and Lauren Agnew, with help in the field from Rebecca Meyer and Annika Herdtle. We thank Laura Lukens, Kyle Kasten, and Cora Lund Preston at Monarch Joint Venture (MJV) for their help in designing and implementing the project. We thank all of the members of our Research Advisory Group and departments of transportation managers who assisted throughout the project, in particular Rich Baker (Minnesota Department of Natural Resources), Chris Smith and Tina Markeson (Minnesota Department of Transportation), Alyssa Barrette and Christa Schaefer (Wisconsin Depart- ment of Transportation), Stephanie Dobbs and Susan Hargrove (Illinois Department of Transportation), Iris Caldwell (Energy Resources Institute, University of Illinois—Chicago), Dennis Markwardt (Texas Department of Transportation), Dennis Martin (Oklahoma State University), and Wayne Thogmartin (U.S. Geological Survey). (continued on page vii)

NCHRP Research Report 942 provides guidance for roadside managers to determine the potential of their roadway corridors to provide habitat for monarch butterflies and tools and decision support mechanisms to optimize that potential in a manner that is compatible with the continued operation and maintenance of the roadside. In response to the decline of critical pollinators, including butterflies, a presidential memo- randum 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. Depart- ment 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 north- western hemisphere, its decline has been more noticeable than most other pollinators. This butter fly 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. The reasons for the decline listed in scientific and popular science literature include: habitat and food source loss, invasive plant species that outcompete milkweed (the monarch’s required reproductive food source), pesticide use, and illegal logging in the butterfly’s very limited over wintering grounds. Under NCHRP Project 20-119, the University of Minnesota was asked to develop and validate a methodology for transportation practitioners to determine if roadway corri- dors are sources or sinks (beneficial or detrimental) to the monarch butterfly and how to maximize the beneficial aspect and minimize the detrimental impacts in a manner that is compatible with the continued operation and maintenance of the roadside. To accomplish the research objective, the research team (1) accounted for the differences and similarities between the eastern and western monarch butterfly populations, and migratory and non- migratory populations; (2) analyzed mortality rates related to roadsides; (3) considered traffic volume, speed, right-of-way width, and roadway width impacts; (4) assigned func- tional values for different roadside vegetation types; (5) evaluated the effects of adjacent land use and habitat; (6) considered roadway right-of-way maintenance practices; and (7) considered the impact of environmental variables such as climate, precipitation, eleva- tion, and aspect. The report provides an overview of the values and threats associated with roadside habitats and how roadside corridors can support high densities of milkweed and varieties of nectar-producing plants beneficial to monarchs and other pollinators. F O R E W O R D By William C. Rogers Staff Officer Transportation Research Board

Four tools were developed for roadside managers to enhance their ability to identify and develop habitat for monarch butterflies along the roadways they manage: (1) a landscape prioritization model that identifies roadsides with the greatest potential for monarch con- servation; (2) a rapid assessment protocol for evaluating monarch habitat quality along roadsides; (3) a habitat calculator that computes monarch habitat quality scores from the rapid assessment data for adaptive management; and (4) best management recommenda- tions to provide decision support, including guidance on mowing practices, a herbicide resource sheet, and regional milkweed guides to help road management crews recognize milkweed growing along their roadways. AUTHOR ACKNOWLEDGMENTS (Continued) The roles of the authors were as follows. Alison Cariveau at MJV led the project overall and was lead author for the report. Karen Oberhauser was the original Principal Investigator at the University of Minnesota; when Ms. Oberhauser moved to the University of Wisconsin, Emilie Snell-Rood became Principal Investigator at the University of Minnesota. Wendy Caldwell oversaw the project for MJV and provided feedback and guidance throughout the project. Kristen Baum (Oklahoma State University) was involved in the design of the Rapid Assessment protocol and led the field testing in Oklahoma. Eric Anderson (Environmental Incentives) was involved in the design of the Habitat Calculator, conducted user interviews, and created the manager workflow diagram. Eric Lonsdorf and Chris Nootenboom (Insti- tute on the Environment, University of Minnesota) developed the Landscape Prioritization Model and authored the chapter and user guide. Karen Tuerk (MJV) designed and completed all of the program- ming for the Monarch Habitat Evaluator in Survey123, wrote the user guide, and was the geographic information system (GIS) specialist for the project. Jennifer Hopwood (Xerces Society for Invertebrate Conservation) co-led the best management practices and decision support team with Alison Cariveau, authored Frequently Asked Questions and Monarchs, Herbicides, and Weeds, in addition to a set of regionally specific milkweed identification handouts.

1 Summary 7 Chapter 1 Background 7 Monarch Butterflies and Pollinators 8 Suitability of Roadside Rights-of-Way as Habitat for Monarchs 9 Opportunities for Monarch Habitat in Roadside Rights-of-Way 11 Tools for Roadside Managers 11 Product A: Landscape Prioritization Model for Roadside Habitat for Monarchs 12 Product B: Rapid Assessment of Roadside Habitat for Monarchs 12 Product C: Roadside Monarch Habitat Calculator 12 Product D: Best Management Practices and Decision Support 13 Tool Use Scenarios, Interactions Between the Products 15 Chapter 2 General Research Approach 15 Meetings 16 Webinars 16 Survey of Transportation Managers 16 User Profile Interviews 17 Reviewing Existing Tools and Protocols 18 Expert User Testing 19 Field Testing with Biotechnician Crews 20 Chapter 3 Product A: Landscape Prioritization Model for Roadside Habitat for Monarchs 20 Introduction 20 Habitat Modelling 21 Milkweed Suitability 22 Nectar Availability 23 Pesticide Exposure (Ei) 23 Overall Habitat Quality (Hi) 23 Core Habitat 24 Roadside Potential 24 Benefits 25 Risks 27 Roadside Suitability Overall 27 Data Sources 27 Discussion C O N T E N T S

29 Chapter 4 Product B: Rapid Assessment of Roadside Habitat for Monarchs 29 Background 31 Rapid Assessment Protocol 32 Integrated Monarch Monitoring Program Methods 33 Field Trials 33 Minnesota—Protocol Comparison 34 Minnesota—Broadscale Surveys 35 Field Trials—Oklahoma 38 Field Surveys with Multiple Protocols 42 Discussion 47 Chapter 5 Product C: Roadside Monarch Habitat Calculator 47 Background 47 Methods 48 Monarch Breeding Habitat 49 Adult Monarch Foraging Habitat 52 Context/Threats 55 Management 56 Running the Habitat Calculator 56 Field Testing the Habitat Calculator 56 Results 56 Minnesota 59 Oklahoma 59 Discussion 62 Chapter 6 Product D: Best Management Strategies and Decision Support 62 Survey of Transportation Managers 62 Methods 62 Survey Questions 64 Survey Results 66 Survey Conclusions 68 User Profile Interviews 68 Methods 69 Findings 69 Habitat Calculator—Use Scenarios 70 Most Common Users 70 Decision-Support Tree 70 Decision-Support Materials 71 Existing Resources 73 New Materials Developed 95 Discussion 96 Chapter 7 Conclusions and Suggested Research 99 Bibliography 104 Acronyms

A-1 Appendix A Manager Workflow Diagram: Use of Roadside Habitat for Monarchs Decision Support Tools B-1 Appendix B User Guide for the Landscape Prioritization Model for Roadside Habitat for Monarchs C-1 Appendix C Rapid Assessment of Roadside Habitat for Monarchs: Field Protocol and Datasheet D-1 Appendix D User Guide for Rapid Assessment of Roadside Habitat for Monarchs and Habitat Calculator: Monarch Habitat Evaluator Tool E-1 Appendix E Best Management Practices Resource Sheet: Monarch Butterflies, Weeds, and Herbicides F-1 Appendix F Regionally Specific Roadside Milkweed Recognition Fact Sheets