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

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1 Overview This project examined the potential for roadway corridors to provide habitat for monarch butterflies and developed tools for roadside managers to optimize potential habitat for monarch butterflies in their road rights-of-way (ROWs). The following products were developed through the project, all of which are available to interested departments of transportation: Product A: A Landscape Prioritization Model for Roadside Habitat for Monarchs to assist roadside managers with identifying locations that are both compatible with their road and right-of-way (ROW) maintenance objectives and ranked in suitability for monarch habitat conservation. The national geographic information system (GIS) model can be enhanced with state or more local information to further refine priori- tization of sites. Product B: A Rapid Assessment of Roadside Habitat for Monarchs protocol enables roadside managers to quickly survey a roadside area to evaluate the current status of the habitat quality for monarchs. The assessment focuses on functional components of monarch habitat: breeding habitat, foraging habitat, threats and landscape context, and roadside vegetation management practices. Data are entered into Esri Survey123, software used by most state transportation authorities; the survey may be customized by each state, and results are easily tracked and summarized within each state depart- ment of transportation. Product C: The Roadside Monarch Habitat Calculator transforms Rapid Assessment data into monarch habitat quality scores, metrics that can be used to compare sites within a road system or state and inform land managers of needed conservation actions. Data gathered in this assessment create an adaptive management feedback loop in order to track success of efforts through time and improve future conservation practices. The functional components of the rapid assessment are combined into one Monarch Habitat Quality Score but also reported independently to inform adaptive management. Product D: Decision-support tools for roadside managers were developed to help align road authority objectives and regulations with conservation goals in a way that is eco- nomically and environmentally additive. A survey of roadside management entities across the U.S. helped identify areas where roadside management objectives and bar- riers intersect with conservation objectives, and findings were used to inform the tools developed through this project to ensure the tools were adopted by and useful to road authorities. Online and print materials were also developed to support land managers in their conservation-oriented decisions, including a decision tree, milkweed guides, a weed and herbicide resource sheet, and a set of frequently asked questions. S U M M A R Y Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies

2 Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies Products A through D are available online (https://monarchjointventure.org/ roadsidehabitat) for departments of transportation who want to learn more about the habitat in the road corridors they manage. The Rapid Assessment developed in this project was published in a peer-reviewed paper (Cariveau et al. 2019a). The tools published in Esri products are readily used by most transportation departments. Products B and C are combined into a Roadside Monarch Habitat Evaluator module that may be customized by each state for its use. Managers may then view their site data and habitat scores in a spatial map layout or in a spreadsheet depending on their information needs. Findings A survey of roadside managers as well as by interactions with transportation professionals throughout the project found a high degree of interest and dedication to providing polli- nator and monarch habitat along roadways. Further investigations indicated that variable amounts of knowledge and time could be allocated to pollinator work. Funds for pollinator work are generally extremely limited, so cost savings from altered management is an impor- tant topic. Tremendous variation was found in the reported use of key management tech- niques, including mowing and herbicide application, indicating opportunities for alteration in the area of vegetation management. In field trials, high-quality monarch breeding habitat was found in roadside ROWs areas. Field studies in Minnesota and Oklahoma showed high levels of milkweed and monarch use of milkweed in roadside ROWs as well as nectar plants. Concurrence was found between the Rapid Assessment of Roadside Habitat for Monarchs to another more intensive monarch habitat monitoring protocol. This study addressed the question of whether habitat along roads is suitable for monarch butterflies. The research, including data collected in this project, suggested that roadsides are promising habitat for monarchs. With respect to host plants, over half of randomly selected roadsides contain milkweed, and surveys detailed in this report highlight densities over 2,000 stems of milkweed per mile. Roadside sites also included a variety of nectar plants beneficial not only to monarchs but also to a diversity of pollinators. Risks to monarchs and their habitat in roadside corridors were reviewed, including impacts of vegetation management, particularly mowing that is required for maintenance of safety standards. While mowing for traffic visibility kills some monarch larvae, it also maintains open roadside habitat favorable for monarchs. Mowing can be used to control invasive and undesirable plant species, and milkweed regrowth is heavily used by egg-laying monarchs. Roads also present danger of traffic collisions for monarchs, although these effects appear to be more concentrated in particular funnel areas during migration. Monarchs in roadside ROWs may also experience increased exposure to road salts, heavy metals, and insecticides applied to nearby agricultural or developed areas, any of which could present risks to monarch survival and development. However, current research, although still unpublished, suggests that the majority of roadside milkweed is of suitable nutritional quality for monarchs (i.e., not toxic). Roadside sodium and heavy metals (espe- cially zinc) vary with traffic volume and distance from road. Most metal levels are below what is toxic for monarchs. While sodium levels do reach toxic levels, this seems to be limited to milkweeds along the highest traffic roads and in the buffer zones that are often mowed just adjacent to the road. Screens for pesticides do find residues on at least a quar- ter of roadside milk weeds; however, the majority of the chemicals that show up in these screens are fungi cides and herbicides. Current work is clarifying the presence of sub-lethal levels of neonicotinoids. Taken together, this work in progress suggests that most roadside

Summary 3 milkweed, especially along the majority of roads (which are moderate to low traffic volume), harbor milkweed of suitable nutritional quality for monarchs. In summary, threats along roadway corridors exist for monarchs and other pollinators, but in the context of the amount of habitat needed for recovery of sustainable populations, roadsides are of vital importance. As detailed in this report, tools, including a Landscape Prioritization Model and a Habitat Calculator, were developed to assist managers in under- standing the habitat they manage and improving their ability to enhance these habitats through adaptive management. The Landscape Prioritization Model developed in this project is the first of its kind at this scale. It provides a transportation manager the ability to evaluate the landscape in their state with regard to areas where diverse roadside habitat could complement already existing natural habitats or where high-quality roadside plantings might create a corridor of suitable habitat where there is otherwise very little. In addition, this model depicts roads and their associated hazards in a way that helps managers to think about the importance of traffic volume, traffic speed, and (ROW) width, all factors that can potentially affect the roadside environment for monarchs. Together, this landscape information and road metrics inform managers’ understanding of their road systems in a novel way. The Rapid Assessment of Roadside Habitat for Monarchs is a way for transportation managers to readily assess the habitat currently in their ROWs and to track it through time. While many land management entities often lack time and capacity to conduct habitat assessment work, this tool was designed to be quick and easy to implement with different skill levels and also feeds into broader scale monarch and habitat monitoring initiatives and tracking efforts. Tracking and evaluating monarch habitat projects using the Rapid Assessment creates a feedback loop of information that will tell ROWs managers the base- line quality of their site, as well as continued tracking of how the project is doing. In turn, this will provide a valuable data set that will improve the seed mix design and habitat management practices implemented by the land management authority as they learn what is performing well, and what may not be. Not only will this reduce costs over time, but if applied in an adaptive management framework, the quality of the habitats for monarchs and pollinators should also improve (or minimally be sustained) over time. The Roadside Monarch Habitat Calculator provides managers an easy way to interpret breakdown of the functional components of the habitat. Using data collected through the Rapid Assessment, it provides users with scores about how a particular project or site area is performing in the areas of monarch breeding habitat, foraging, landscape context and threats, and management. The scores for each of these components are combined into an overall score but are also presented independently such that a land manager can pinpoint specific problem areas that could be improved on that site. For example, if the breeding habitat score for a site is low, this means that it is lacking sufficient milkweed host plants for monarchs. Actions to increase the milkweed density at that site could improve the habitat score over time. The Habitat Calculator also provides a reportable metric that can be used in internal or external reporting. These scores can be viewed in an online map or spreadsheet format. Several types of decision-support tools were provided in response to the needs of the roadside management community. There were several information needs, including guid- ance on mowing, herbicide applications, milkweed identification, and native seed guides (including milkweed). This led to identifying some resources that were currently available and linking to them in the online manager toolbox. Several other new materials were devel- oped. Regionally appropriate Milkweed Guides are available. These single-sheet handouts

4 Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies may be given to road management crews to help them to identify milkweed growing in their roadside corridors and choose appropriate management actions, such as avoiding the application of herbicide to milkweed and planning mowing activity to avoid when monarchs are breeding in their locality. “Monarch Butterflies, Weeds, and Herbicides” is a resource sheet that is also available. Recognizing that road managers operate within single states, information sharing was facilitated across states, including case studies. A set of frequently asked questions and their answers optimizes information sharing about best practices. Future Research Needs There were several gaps in knowledge where expert opinion was used to develop the project tools. To improve the tools over time, the following research priorities were identified: • Exploration of how field-level habitat quality values (such as derived from the Habitat Calculator) and use of roadside areas by monarchs relate to the landscape factors depicted in the Landscape Prioritization Model. • Milkweed and nectar plant abundance in various land-use types and regions of the U.S. and how these values relate to the habitat quality within road ROWs in various regions. • Response of milkweeds, nectar plants, and monarch eggs and larvae to management practices, including mowing and haying at various times of year. • Differences in utilization of various species of milkweed by monarchs in roadside areas. • Quantification of traffic collisions (adult mortality) in relation to production of mon- archs in roadside habitat (and in relation to traffic volume, speed, and surrounding habitat type). • Chemical exposure risks to monarchs in highly agricultural or heavy traffic areas, e.g., >30,000 cars a day, typical of highly urbanized areas (pesticides and vehicle/road chemical runoff/drift). • Effective treatments of invasive species to enhance future restoration activities. • Economic studies on the short-, mid-, and long-range costs of implementing monarch/ pollinator programs within a roadside management entity, which may be influenced by the upcoming proposed decision by U.S. Fish and Wildlife Service (USFWS) for species listing under the Endangered Species Act. • Assessing the value of roadsides as important habitat corridors in “habitat deserts,” such as areas in the Midwest that are dominated by agriculture. Research Recommendations • Roadside management authorities may use the Landscape Prioritization Model to iden- tify areas for monarch breeding habitat restoration or improved management where fewer threats to monarchs are posed. • Roadside managers may assess their roadside ROWs with the Rapid Assessment proto- col to gain valuable information about the roadside areas they manage. This could take the form of an inventory of the habitat they manage to find out the proportion of areas that provide high-quality habitat, or to estimate the milkweed density their road system provides, or other similar objectives. Managers also may wish to compare the habitat characteristics for areas under different management regimes, such as modified mowing practices or areas that have been restored with a particular seed mix. For all pre-, post-, and long-term restoration or improved management projects, assessment of the habitat builds a base of information that can be used in an adaptive management framework to improve benefits to monarchs and pollinators and cost-effectiveness of conservation practices.

Summary 5 • The habitat quality scores generated automatically by the Habitat Calculator may be used to identify high-quality sites and sites where habitat could be improved. • Departments of transportation are encouraged to use the decision-support tools and best management practices information made available through the website https:// monarchjointventure.org/roadsidehabitat to support their monarch conservation efforts. Educational objectives can be built into roadside management programs to engage diverse stakeholders, train management staff about how to properly maintain diverse native plant communities, and to increase awareness about monarch and pollinator conservation needs. Conclusions Land use changes have caused dramatic losses of habitat for monarchs across much of their breeding and migratory range. Roadside habitats provide a unique opportunity to influence habitat availability on a large scale (number of acres) and in distribution across the landscape. In some urbanized and agricultural parts of the monarch range, roadside habitats are a primary source of breeding habitat. Therefore, increasing the abundance and quality of those critical areas is an important contribution to a larger strategy to con- serve monarchs, other pollinators, other wildlife species, and to provide other impor- tant ecological services. It is possible that in these “habitat deserts,” roadsides may act as important corridors or refuge areas during migration. An initial set of tools and decision-support mechanisms are provided to support road- side managers in these efforts. This project reflects partnerships between conservation organizations, universities, and roadside authorities to enhance the objectives of all parties by developing and improving strategies for monarch conservation. An “all hands on deck” approach to conservation is needed to protect monarch butterflies, and this work assists transportation authorities in pursuing opportunities to implement proactive and volun- tary approaches to provide pollinator habitat in roadway corridors. In doing so, transpor- tation agencies can also appeal to the growing public attention and calls for monarch and pollinator conservation. Opportunities Moving forward, opportunities remain to pursue implementation to more widely pro- mote the findings of this project through a) a well-designed, interactive website tailored to the needs of roadside managers, b) trainings in how to use the tools created, c) scientific writing regarding the outcomes of the field research, and d) more outreach and public relations around best management practices, case studies, and sharing of successes across states. This work has also highlighted opportunities for future research and assessment. For instance, future research needs have highlighted knowledge gaps with respect to mowing, adult mortality from collisions, and the value of roadside corridors isolated from core habitat—all research topics that would benefit from agency-university interaction and collaboration. This work has also identified a need for integrating the recommenda- tion tools with the budget and labor needs of individual transportation agencies—for instance, determining the optimal course of action based on Habitat Calculator scores will depend on the agency. An agency with a low budget may invest in preserving the highest value roadsides, while an agency with a modest budget for restoration may invest in roadsides with high potential value, but current low to moderate habitat. As agencies begin to use these tools, there are many opportunities for assessment and refinement of the tools and recommendations.

6 Evaluating the Suitability of Roadway Corridors for Use by Monarch Butterflies This project has also created several opportunities with respect to broader conservation goals. First, while this project focused on monarchs, this species serves as a flagship species for many other species, both plant and animal, that support natural ecological functions. Preserving monarch habitat and associated nectar plants and host plants (which are a great nectar plant for many insect pollinators) no doubt has beneficial impacts on hundreds of other species. This is particularly important given recent outcries of a pending “insect apocalypse” as negative effects of pesticide use, habitat destruction, and climate change are leading to precipitous declines across more than 40% of insect species (Sanchez-Bayo and Wyckhuys 2019). Second, while this work has focused on roadside ROWs, many of the tools and recommendations are relevant to other types of ROWs. ROWs alongside railroads, power lines, and gas lines also present valuable opportunities for habitat as they can act as habitat corridors and cover millions of acres across the country. There is overlap between outcomes of this project and management decisions related to mowing, landscape context, invasive species control, collisions, chemical exposure, and prioritization of sites for res- toration. It is hoped that some of the general lessons learned in roadside management for monarchs can also be applied to conservation opportunities in other ROWs.