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1-1 Chapter 1 Introduction Animal pollinators are central to human wellbeing, agricultural production, global economic health, and the viability of native plant communities and wildlife. Thirty-five percent of global crop production is dependent on pollinators, including 87 of the worldâs 124 most commonly cultivated crops (Klein et al. 2007). Also, many minerals, vitamins, and nutrients needed to maintain human health come from insect-pollinated crops (Eilers et al. 2011). Pollinators are essential for the reproduction of about 85 percent of all flowering plants (Ollerton et al. 2011) and are critical for wildlife food webs (Kearns et al. 1998; Summerville and Crist 2002). Insects, including bees, wasps, flies, beetles, butterflies, and moths, are the primary pollinators in much of North America (Allen-Wardell et al. 1998; Kearns 2001), yet a number of insect pollinators are in decline. Pollinators that have undergone troubling and dramatic declines over the past few decades include rare species with narrow habitat needs, as well as formerly common and widespread species like the rusty patched bumble bee (Bombus affinis) and the monarch butterfly (Danaus plexippus) (Hatfield et al. 2016; Semmens et al. 2016; Schultz et al. 2017). Factors leading to pollinator decline include habitat loss, pesticide use, diseases, parasites, climate change, and the spread of invasive species. 1.1 Why Roadsides Are Important to Pollinators Threats to pollinators may have profound consequences for ecosystem health as well as our food systems (Kearns et al. 1998; Spira 2001; Steffan-Dewenter and Westphal 2008). Roadsides can help mitigate habitat loss for pollinators. State departments of transportation (DOTs) manage substantial amounts of land and associated natural resources across North America, including upward of 10 million acres of roadside land in the United States (Forman et al. 2003). These acres hold the potential to create a network of habitats to support pollinators in urban and rural areas. Roadsides can provide habitat for all life stages of a diverse community of pollinators (Hopwood et al. 2015), including imperiled pollinators. Roadsides may also act as corridors for pollinators (see review in Hopwood et al. 2015), connecting remnant habitat patches and aiding pollinators to move through landscapes or expand their ranges. Mining beesâsuch as this bee visiting an apple blossomâand other wild pollinators are critical for food production. Photo Credit: Nancy Lee Adamson/Xerces Society
Chapter 1. Introduction 1-2 In some places, roadsides are home to intact native plant communities that are no longer found in surrounding lands (New et al. 2021). Searching for prairie remnants in some parts of the Corn Belt in the Midwest, for example, often requires scouring roadsides and railroad rights-of-way. In heavily altered landscapes, even those roadsides without intact native plant communities can be the only semi-natural habitat present (e.g., Brown and Sawyer 2012). For some listed or imperiled species of pollinators, roadsides include some of the last remaining patches of their habitat. Widespread species that are struggling, such as the monarch butterfly or the rusty patched bumble bee, are not completely reliant on roadsides habitat, but roadsides are still an important component of their survival (e.g., Thogmartin et al. 2017; Evans et al. 2019). A number of state DOTs have an interest in managing roadsides to support pollinators (e.g., Hopwood et al. 2016b; National Cooperative Highway Research Program Project 25-59 Conduct of Research Report), but as more species of pollinators become listed or are being considered for listing under the Endangered Species Act (ESA), DOTs also want regulatory certainty. Currently (March 2022), there are 48 pollinating insects listed under the federal ESA (nine bees, 35 butterflies, two moths, one fly, and one beetle). This includes two species that are either a candidate species or proposed for listing, and many more species with declining populations and the potential to be listed. Figure 1- 1 shows the number of species that are currently listed or a candidate for listing by region. Figure 1-1. Map of the United States, with the number of pollinator species that are currently listed or candidates for listing under the Endangered Species Act (as of March 2022) within each of the 16 regions covered in these guides. ï· Alaska: 0 ï· Maritime Northwest: 5 ï· Inland Northwest: 1 ï· Hawaii: 8 ï· California: 2 ï· Great Basin: 2Â ï· Southwest: 2 ï· Rocky Mountains: 3 ï· Northern Plains: 4 ï· Southern Plains: 1 ï· Midwest: 4 ï· Great Lakes: 5Â ï· Southeast: 3Â ï· Florida: 8 ï· MidâAtlantic: 4 ï· Northeast: 3 Roadsides provide monarch butterflies with food for adults as well as caterpillars. Photo Credit: John Anderson 0 5 1 2 2 2 1 43 4 5 3 8 4 3 8 GUIDE REGIONS
Chapter 1. Introduction 1-3 In addition to supporting pollinators, other benefits of healthy roadside vegetation include a safe driving environment, reduced soil erosion, enhanced rainwater infiltration, improved water quality, reduced wind velocity, carbon sequestration, and habitat for a variety of wildlife, including predator and parasitoid insects that reduce crop pests. 1.2 About This Guide This guide is intended to provide relevant guidance to rights-of- way owners and operators for roadside vegetation management practices that support pollinators, as well as strategies that are compliant with the ESA. This guide will help DOTs and other entities that manage roadsides understand pollinators generally and imperiled pollinators specifically, and it provides information on how to manage roadsides with the goal of avoiding further declines of these important species, averting the need for them to be listed under the ESA in the future. This guide will also help DOTs make informed management decisions to coordinate ESA compliance with their operations, reduce future regulatory uncertainty, contribute to pollinator conservation and recovery, and increase awareness and the associated societal values for the ecosystem services pollinators provide for agriculture and native ecosystems alike. This guide is one of 16 guides, one for each region identified based on ecoregions and distributions of pollinators (Figure 1-1). Each guide includes general information applicable across all 50 states as well as region-specific information developed for the habitats and pollinator species expected to occur in and adjacent to roadways of this region. The intended users of this guide are staff from transportation planning, design, construction, maintenance, and environmental disciplines, as well as communication staff. This guide was informed by review of scientific literature, research reports, and other relevant information, including input from transportation agency practitioners and researchers with expertise on imperiled pollinator species or roadside restoration. This input was obtained through detailed online surveys sent to leading pollinator and roadside revegetation researchers from across the United States and to DOT staff from around the country. Experts were asked to identify the relative benefit of specific conservation actions for imperiled pollinators and provide input on the opportunities for DOTs to implement practices that support pollinators. Participants included researchers from universities, state agencies, consultants, and non-governmental organizations. DOT staff were asked about current practices and potential barriers to implementing additional conservation measures. In total, 70 transportation professionals from DOTs representing agencies from 33 states responded, with 47 percent of respondents self-identifying their expertise within their agency as âEnvironmental,â 27 percent as âMaintenance,â 13 percent as âLandscape Architecture,â 3 percent as âConstruction,â 1 percent as âPlanning,â and 9 percent as âOther.â Listed species: A species listed as endangered or threatened under the federal ESA; the species has been determined to be in danger of extinction in the near or foreseeable future by the U.S. Fish and Wildlife Service.  Candidate species: A species that has been found warranted for listing under the ESA, but whose listing is precluded by higherâpriority species. Proposed species: A species that has been proposed for listing as threatened or endangered under the ESA. Petitioned species: A species for which a petition to list the species under the ESA has been received and is being evaluated. Imperiled species: A species that is in decline and may be in danger of extinction. This term includes species that are not legally protected under the ESA.Â
Chapter 1. Introduction 1-4 This guide includes eleven chapters, some of which have specific audiences and others that may be more broadly of use to transportation officials. Table 1-1 provides an overview of this guide and how it can be used. Table 1-1. Using this guide. Chapter Contents Chapter 2, Pollinator Biology and Roadsides This chapter includes background information on pollinator biology, including:Â Â ï· a primer on pollinators and their habitat needs, ï· pollinator conservation status, and ï· how pollinators use roadsides. Chapter 3, Imperiled Pollinator Profiles This chapter includes profiles of listed, candidate, and imperiled pollinators in this region. The profiles contain:Â Â ï· life history information, ï· the current range of distribution within the region, ï· flight times for adults, ï· larval activity for management timing for butterflies and moths, ï· important plants, and ï· guidance to help integrate a speciesâ biology into management plans. Chapter 4, Native Pollinators and the Federal Endangered Species Act: Compliance Strategies for State Departments of Transportation This chapter provides:Â Â ï· background on the ESA and ï· information about strategies for compliance as it relates to imperiled pollinators. Chapter 5, Considering Imperiled Pollinators in Transportation Planning, Design, and Construction This chapter discusses when and how pollinators need to be considered in the transportation planning, design, and construction phases of project delivery. It identifies:Â Â ï· opportunities to include pollinatorâfriendly design elements and ï· how project design and construction can incorporate measures to avoid and minimize potential impacts on pollinators.
Chapter 1. Introduction 1-5 Chapter Contents Chapter 6, Roadside Maintenance and Vegetation Management for Pollinators This chapterâs audience is maintenance staff, planners, or those designing revegetation plans. This chapter provides:Â Â ï· an overview of how vegetation management practices affect pollinators and ï· regionâspecific adjustments of practices to better support imperiled pollinators. Chapter 7, Revegetation and Pollinators: Design and Implementation This chapter includes:Â Â ï· a guide on how to support imperiled pollinators through revegetation and ï· detailed regional plant species lists. Chapter 8, Creating Climateâ Smart Pollinator Habitat along Roadsides This chapter explores ways to increase climate resiliency for pollinators. Chapter 9, Surveys, Monitoring Strategies, and Habitat Assessments Surveys can determine the presence of imperiled species, and monitoring can be used to better understand the impacts of practices on pollinators. This chapter includes:Â Â ï· survey and monitoring protocols and ï· habitat assessment tools to evaluate and prioritize habitat enhancement opportunities. Chapter 10, CostâBenefit Considerations for Pollinator Management on Roadsides This chapter provides:Â Â ï· stepâbyâstep processes to help DOTs make choices about actions that can support imperiled pollinators and ï· context for balancing the costs of conservation actions with the benefits. Chapter 11, Communication Support This chapter includes:Â Â ï· plans for communicating within DOTs as well as with the general public about how individual DOTs are supporting pollinators proactively and ï· links to videos, recorded presentations, a regional slide set that can be adapted for agencies, and other tools. Chapter 12, References This chapter includes bibliographic references for materials cited throughout the document.Â