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Valuing Wildlife Crossings and Enhancements for Mitigation Credits 2 2.0 SUMMARY OF LITERATURE REVIEW, SURVEY, AND PRACTITIONER INTERVIEW FINDINGS 2.1.1 Legal, Planning, and Policy Considerations To comply with federal National Environmental Policy Act (NEPA), Endangered Species Act (ESA), and Clean Water Act approvals and permits, as well as state regulatory approvals and permits, transportation projects that affect wildlife connectivity may be required to provide mitigation for maintaining safe passage of wildlife. A consideration of applicable federal laws for protecting wildlife is necessary to understand wildlife connectivity mitigation for transportation projects. The Federal Highway Administration (FHWA) website (https://www.fhwa.dot.gov/environment/env_sum.cfm) gives a thorough review of federal wildlife legislation affecting transportation infrastructure in the United States. Additional detail about wildlife-related legislation applicable to transportation projects can be found in Table 1 of the California Department of Transportation (Caltrans) Wildlife Crossings Guidance Manual (Caltrans 2009). National Environmental Policy Act Planning NEPA applies to all federally funded actions, including federally funded and approved state DOT actions. Under NEPA, state DOTs must analyze environmental impacts of transportation projects, including reduced wildlife connectivity, with a systematic, interdisciplinary approach. Projects that would decrease wildlife connectivity or increase WVCs could be considered an adverse environmental effect, which under NEPA, could require state DOTs to provide mitigation in the form of wildlife crossings or other connectivity enhancements to reduce the adverse effect of the project. The NEPA planning process can serve to bring stakeholders and scientific expertise together to identify effective wildlife connectivity mitigation options for a highway project (see section 5.3 and 5.4), providing state DOTs an opportunity to consider wildlife connectivity mitigation early in the planning and funding process. Endangered Species Act Compliance The requirement for wildlife connectivity mitigation is sometimes a result of the potential âincidental takingâ of species listed under the ESA. If a transportation project would impede the movement of a threatened or endangered species and adversely affect individuals, then the U.S. Fish and Wildlife Service (USFWS) could require state DOTs to implement wildlife connectivity mitigation measures (Caltrans 2009). State DOTs may choose to implement either permittee-responsible mitigation, an in-lieu fee program (where available), or purchase credits via a USFWS-approved conservation bank (USDOI 2013). As of 2008, Huijser et al. (2008a, 2008b) listed 21 federally listed threatened or endangered species in the United States for which road mortality is among the major threats to their survival, including: â¢ Mammals: Lower Keys marsh rabbit (Sylvilagus palustris hefner) in Florida; Key deer (Odocoileus virginianus clavium) in Florida; desert bighorn sheep (Ovis canadensis nelsoni) in peninsular California; San Joaquin kit fox (Vulpes macrotis) in California; Canada lynx (Lynx canadensis) in Colorado, Oregon, Montana, Minnesota, and Idaho; ocelot (Leopardus pardalis) in Texas; Florida panther (Puma concolor coryi) in Florida; and red wolf (Canus lupus rufus) in North Carolina â¢ Reptiles: American crocodile (Crocodylus acutus) in Florida; desert tortoise (Gopherus agassizii and Gopherus morafkai) in Arizona, California, and Nevada; gopher tortoise (Gopherus polyphemus) in Alabama; Alabama red-bellied turtle (Pseudemys alabamensis) in Alabama and
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 3 Mississippi; bog turtle (Glyptemys muhlenbergii) in New Jersey, New York, North Carolina, and Pennsylvania; copperbelly water snake (Nerodia erythrogaster neglecta) in Indiana, Michigan, and Ohio; and eastern indigo snake (Drymarchon couperi) in Alabama, Florida, and Georgia â¢ Amphibians: California tiger salamander (Ambystoma californiense) in California; reticulated flatwoods salamander (Ambystoma bishopi) in Alabama and Georgia; and Houston toad (Bufo houstonensis) in Texas â¢ Birds: Audubonâs crested caracara (Polyborus plancus audubonii) in Florida; Hawaiian goose (Branta sandvicensis) in Hawaii; and Florida scrub-jay (Aphelocoma coerulescens) in Florida Bissonette et al. (2008a) identified additional threatened and endangered species that are targets for wildlife crossings, including the grizzly bear (Ursus arctos) in Montana; Prebleâs jumping mouse (Zapus hudsonius preblei) in Colorado; arroyo toad (Anaxyrus californicus) in California; pygmy owl (Glaucidium brasilianum cactorum) in Arizona; Blandingâs turtle (Emydoidea blandingii) in Minnesota; and diamondback terrapin (Malaclemys terrapin) in Delaware and Georgia. Buying conservation bank credits is an option to mitigate unavoidable impacts of transportation projects on federally listed species when on-site avoidance, minimization, or compensation measures are not available. Conservation banking has grown exponentially in recent years. As 2013, conservation banks were available for 35 different species (USDOI 2013). Poudel (2017) reported that there were 137 conservation banks in the United States, generating mitigation credits through the conservation of approximately 160,000 acres of land for species listed under the ESA. Nearly 95% of the habitat protected by conservation banks is in the State of California, although considerable growth has recently occurred in Oregon, Texas, Florida, and North Carolina (Pindilli and Casey 2015). Information on these banks can be found at the Regulatory In-lieu Fee and Bank Tracking System (RIBITS), maintained by the U.S. Army Corps of Engineers (USACE), online at https://ribits.usace.army.mil. Despite the need for wildlife crossings or other connectivity enhancements to mitigate impacts of transportation projects on federally listed species, no conservation banks have established or currently hold credits generated from wildlife connectivity mitigation. To date, it appears that the only federally listed species for which USFWS has calculated mitigation credit requirements based on impacts to wildlife connectivity from a transportation project is the Florida panther (see section 5.2). Habitat Conservation Plans Under the authority of the ESA, state DOTs mitigate for impacts to federally listed species by developing HCPs (see USFWS 2011). HCPs are science-based, multispecies plans developed to offset incidental take. HCPs must accompany an application for an incidental take permit. In a sense, HCPs are a type of advance mitigation, whereby a future projectâs âcovered activitiesâ are permitted for âtake.â Mitigation measures vary among HCPs, but most incorporate offsite mitigation whereby the agency administering the HCP acquires protected land to mitigate the effects of development activities. HCPs are said to promote more effective preservation of high-value habitat sites, including those that provide habitat connectivity (Wilkinson et al. 2009). State DOTs increasingly use HCPs to protect federally listed species in regional transportation planning, especially for the species noted above where roadways are a demonstrated extinction risk. There is a trend toward regional-scale HCPs, or specifically toward multispecies HCPs (Lederman 2017, Lederman and Wachs 2016). Examples of regional HCPs for transportation projects that could affect federally listed species include the Balcones Canyonlands Conservation Plan, which covers Texas DOTâs impacts on eight federally listed species, including the endangered golden-cheeked warbler (Setophaga chrysoparia) and the delisted black-capped vireo (Vireo atricapilla) (City of Austin and Travis County 1996); the
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 4 Western Riverside County Multiple Species Habitat Conservation Plan, which covers Caltransâ impacts on 146 covered state-listed, federally listed, and other special-status species (Riverside County Transportation and Land Management Agency 2003); and the San Joaquin County MultiâSpecies Habitat Conservation and Open Space Plan, which covers Caltransâ impacts on 97 covered state-listed, federally listed, and other special-status species (San Joaquin Council of Governments 2000). Thus, an increasing number of transportation projects will likely need to consider development of an HCP to meet mitigation requirements under the ESA. It is reasonably foreseeable that acceptable mitigation measures for many federally listed species could include wildlife connectivity mitigation. Compensatory Mitigation Under the Clean Water Act Under the authority of the Clean Water Act, USACE may require compensatory mitigation for actions affecting streams, wetlands, and other waters of the United States. Section 404 prescribes allowances for compensatory mitigation for unavoidable losses of aquatic resources, which may include the purchase of mitigation credits. Although the purpose of the Clean Water Act is to maintain clean water, many transportation projects involve modifications to existing drainage structures (i.e., bridges and culverts) that require Clean Water Act approval; thus, opportunities exist to incorporate safe passage for wildlife. In addition, a disproportionate number of federally listed species use wetland and stream habitats, providing state DOTs with an additional impetus to explore options for wildlife connectivity mitigation at existing drainage structures to generate wetland mitigation credits based on metrics that quantify the ecological linkages provided by wetlands and floodplains (see section 5.3). As of 1991, wetland habitats fully supported 60% of all threatened species and 40% of all endangered species (Flynn 1996). Wildlife connectivity mitigation is thus often required where highways cross streams and wetlands, and opportunities often exist to enhance wildlife connectivity at highway bridges and culverts. For example, bridges can be extended beyond their stream widths to provide for terrestrial wildlife movement along riparian corridors (Clevenger and Waltho 2000), and wildlife shelving along culverts can facilitate passage by terrestrial small-medium vertebrates (Foresman 2001). The Ecological Approach to Transportation Planning and the Integrated Ecological Framework In 2006, FHWA, the U.S. Bureau of Land Management, the U.S. Environmental Protection Agency, National Marine Fisheries Service, the National Park Service, USACE, the U.S. Department of Agriculture, Forest Service, and USFWS, along with several state DOTs, and others published Eco- Logical: An Ecosystem Approach to Developing Infrastructure Projects (Brown 2006), in which FHWA and its federal partners presented their commitment to using an ecosystem approach to infrastructure project mitigation via advance mitigation. Generating advance credits for wildlife connectivity mitigation would provide policy options and tools to conserve wildlife corridors and sensitive species, which would align with federal and state directives for maintaining or enhancing wildlife movement at a regional scale (e.g., Western Governorsâ Association 2008, Governorâs Office of Planning and Research 2018). Developing a crediting system for transportation project impacts is identified as a key step in the ecological approach to integrate transportation and conservation planning (see Brown 2006). This advance mitigation approach was further developed and presented as the Integrated Ecological Framework (IEF) that the Transportation Research Board prepared as part of the second Strategic Highway Research Program (SHRP 2) (NAS 2012, 2013). The IEF would provide a useful approach for implementing wildlife connectivity projects via mitigation credits under an Advance Mitigation Program, which would address many of the predictable adverse impacts on wildlife that result from future transportation projects. The focus of this study aligns with step 6 of the IEF, which relates to developing âa consistent strategy and metrics to measure ecological impacts, restoration benefits, and long-term performanceâ (NAS 2012). After project-specific avoidance and minimization measures are taken,
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 5 unavoidable impacts could be mitigated by applying credits from in-kind or other out-of-kind wildlife connectivity mitigation. An advance mitigation crediting strategy to value wildlife connectivity would require a move away from a piecemeal, project-by-project wildlife connectivity mitigation approach toward a coordinated, statewide or regional approach. Regional conservation plans (e.g., Regional Conservation Investment Strategies [RCIS] in California) or regional permits (e.g., regional HCPs) incorporate a high level of specificity about the predicted impacts of planned transportation projects to identify an appropriate level of wildlife mitigation. The use of such plans could facilitate more effective mitigation by providing an early assessment of regional mitigation needs of future landscape-level impacts from multiple infrastructure projects, which would be more efficient than traditional project-by-project mitigation (Beatley 1992, Lederman and Wachs 2014, 2016). Furthermore, providing wildlife mitigation that could be applied to multiple transportation projects on a larger geographic scale could contribute to landscape connectivity at identified habitat corridors and facilitate speciesâ movement via wildlife crossings or other connectivity enhancements. Programmatic Mitigation Plans State DOTs have long planning horizons, and FHWA allows state DOTs to develop a mitigation framework as part of their planning process to address future impacts of transportation projects (see 23 Code of Federal Regulations [CFR] 450.214 â Development and content of the long-range statewide transportation plan, and 23 CFR 450.320 â Development of programmatic mitigation plan). These âprogrammatic mitigation plansâ can be developed at local, regional, or statewide scales for an ecosystem, watershed, or species. The plans can encompass multiple environmental resources, including wildlife habitat and can be integrated with other plans that prioritize wildlife crossings, such as statewide connectivity assessments/strategies, state wildlife action plans, species recovery plans, growth management plans, or land use plans. Although federal laws and regulations pertaining to federal highways, including national highway safety, do not specify the adherence to a specific planning framework, the FHWAâS Planning and Environmental Linkages (PEL) program encourages âa more seamless decision-making process that minimizes duplication of effort, promotes environmental stewardship, and streamlines project deliveryâ (Breck et al. 2015). To that aim, Brown (2006) and IEF provide guidance to incorporate advance mitigation into the transportation planning process. The planning and environmental linkage planning process was recently amended to reflect FHWAâs January 2018 Working Agreement with the U.S. Coast Guard, USACE, the U.S. Environmental Protection Agency, USFWS, and the National Marine Fisheries Services to implement Executive Order 13807: Establishing Discipline and Accountability in the Environmental Review and Permitting Process for Infrastructure issued on August 15, 2017, (see https://www.environment.fhwa.dot.gov/nepa/oneFederal_decision.aspx), also known as One Federal Decision. The purpose of the agreement is to accelerate and coordinate the planning, environmental review, permitting, and decision-making for FHWA major infrastructure projects and support the intent of the executive order. Generating credits for wildlife connectivity mitigation measures would be most effective under an advance mitigation framework for many reasons. First, wildlife connectivity mitigation seeks to restore habitat connectivity and benefit populations across a regional landscape, so its implementation requires an extensive analysis of the various environmental and human factors contributing to wildlife movement. This analysis requires an understanding of future traffic patterns and land development with respect to focal speciesâ movement patterns, population stability, and genetic diversity (e.g., Ament et al. 2014).
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 6 Such analyses of wildlife connectivity, as well as future human transportation requirements, are a requisite step of advance mitigation programs. Advance mitigation programs have been more effective at creating better environmental protection and alleviating transportation problems than performing mitigation for transportation projects on a project-by- project basis (Greer and Som 2010). Sciara et al. (2017) assessed the evidence for cost savings realized through advance mitigation from avoided upfront costs and reduced transportation project delay and found that most practitioners of advance mitigation reported cost savings. They estimate that advance mitigation could reduce project delays related to environmental review by 1.3 to 5 months per project. Costs savings described by Sciara et al. (2017) that would apply to wildlife connectivity mitigation include reduced costs as a result of greater flexibility in project scheduling; expedited project approvals and lack of procedural delays; and cheaper land acquisition or construction materials before price escalation. Furthermore, Sciara et al. (2017) argue that advance mitigation could minimize legal costs by reducing the likelihood of legal challenges for environmental reasons. Lastly, advance mitigation is a proper framework for crediting wildlife connectivity mitigation because agency priorities and transportation project schedules are often misaligned, such that mitigation opportunities are missed (ARC Solutions 2017). For example, most wildlife connectivity mitigation is implemented after being identified during transportation project planning, and funding is then pursued from various sources, which may or may not be available on the same schedule as the transportation project. Advance mitigation could serve to address this planning and funding disconnect. Furthermore, many wildlife connectivity mitigation projects could yield outstanding ecological benefits, but a delay in their implementation could potentially lead to a permanent loss of the opportunity. Because of increasing development in many places with high- value wildlife resources, these circumstances are becoming more common (Brown 2006), and advance mitigation could serve to better address such opportunities. State DOTs, working with federal and state partners, could use the IEF as a blueprint to guide their development of consistent valuation and crediting methods (see table ES.1 of NAS 2012). Once a consistent strategy and metrics are identified to quantify the adverse effects of a transportation project on wildlife connectivity, or the restoration benefits of a wildlife connectivity mitigation measure, the subsequent steps are to âcarry out innovative, ecosystem-based crediting strategies, interagency agreements, mitigation plans, programmatic consultations, and permittingâ (NAS 2013). Highway Funding and Authorization Acts The Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA- LU; Public Law [P.L.] 109-59) of 2005 contains several sections that address improving wildlife connectivity and reducing WVCs. Under SAFEATEA-LU, the Transportation Enhancements Program helps fund environmental mitigation and includes a provision for reducing vehicle-caused wildlife mortality while maintaining habitat connectivity (Section 101(a)(35) of Title 23 United States Code). Section 6001 also requires early consultation among state DOTs and natural resources agencies and tribes and consideration of applicable plans (e.g., federally listed species recovery plans, state wildlife action plans). Early consultation provides more opportunities for state DOTs to consider wildlife mitigation strategies, including discussions about wildlife connectivity mitigation, early in the transportation planning process. Consultation is required to involve a âdiscussion of potential environmental mitigation activities and potential areas to carry out these activities, including activities that may have the greatest potential to restore and maintain the environmental functions affected by the plan.â This and other provisions of the SAFETEA-LU that allow for funding of wildlife connectivity mitigation, such as the Transportation Alternatives Program (National Transportation Alternatives Clearinghouse 2012, FHWA 2014), have since been canceled or superseded by subsequent FHWA funding authorizations. These include the Moving Ahead for Progress in the 21st Century Act of 2012 (MAP-21; P.L. 112-141) and the
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 7 Fixing Americaâs Surface Transportation Act of 2015 (FAST Act; P.L. 114-94). Ament and Callahan (2019) provide a summary of six key federal transportation programs that allow their funds to be expended on wildlife mitigation from MAP-21 and the FAST Act. Wildlife Connectivity Mitigation Costs Effective wildlife connectivity mitigation along highways can be expensive. Recently constructed structures in Colorado cost about $300,000 to $1,475,000, with associated fencing costing approximately $98,900 per lane mile (Kintsch et al. 2019). State DOTs do not generally have dedicated funding for wildlife connectivity mitigation, so mitigation often competes with other highway assets for program funding. Wildlife connectivity mitigation measures are usually constructed based on opportunity, either to mitigate for a proposed transportation project or where strong public interest exists for conserving economically valuable species like big game (Smith 2019). To implement wildlife connectivity mitigation, multi-stakeholder partnerships are often necessary to leverage funding. The Nevada Department of Transportation (NDOT) provides an overview of funding resources for wildlife connectivity mitigation in chapter 7 of its Prioritization of Wildlife-Vehicle Conflict in Nevada, including the available federal programs and other potential funding from local governments, non-profit organizations, and citizen initiatives (Cramer and McGinty 2018). 2.1.2 Potential Valuation Metrics for Wildlife Connectivity Mitigation Credits Mitigation credits are typically based on units of measure that can be quantified (e.g., an acre of land) and monetized (e.g., the dollar value of that land) (Kagan et al. 2014). According to Pindilli and Casey (2015), âcredits [at conservation banks] represent the biodiversity benefits that conservation banks yield.â Determining the number of credits for a wildlife mitigation measure is typically a function of habitat area, habitat condition, location, and/or focal species and includes species counts, population abundance, and/or breeding pair observations (Pindilli and Casey 2015). USFWS (2012a) states that âa credit may be equivalent to: (1) an acre of habitat for a particular species; (2) the amount of habitat required to support a breeding pair; (3) a wetland unit along with its supporting uplands; or (4) some other measure of habitat or its value to the listed species.â No common metrics are used in the United States to measure the mitigation value of wildlife crossings and other connectivity enhancements; nor are there standard methods to calculate the number of credits that could be generated from these types of mitigation. Only a handful of wildlife connectivity mitigation projects to date have generated mitigation credits, and only one project in California has generated credits for a stand-alone wildlife crossing. An extensive body of research provides potential metrics that could be used to either quantify the conservation value of wildlife connectivity mitigation to focal species and the resulting number of mitigation credits or quantify the impacts of future transportation projects to wildlife connectivity and the resulting number of mitigation credits that a state DOT could purchase to mitigate an unavoidable impact. These topics are explored further below and in section 5.0. The published literature reveals that wildlife connectivity mitigation aims to conserve wildlife and reduce WVCs, so mitigation credits could quantify the benefits to humans and wildlife. The metrics potentially useful for calculating credits for wildlife connectivity mitigation measures fall into four categories: (1) condition-based connectivity metrics, (2) function-based connectivity metrics, (3) model-based connectivity metrics, and (4) avoided cost metrics. Condition-Based Connectivity Metrics Condition-based metrics are based on the physical, chemical, and biological attributes of a system (NAS 2012). For wildlife connectivity mitigation, condition-based metrics would likely quantify the physical attributes of a highway. Caltrans and the California Department of Fish and Wildlife (CDFW) calculated
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 8 the number of credits based on an existing highway footprint for the Laurel Curve Wildlife Habitat Connectivity Project (Laurel Curve Project) on Highway 17 in Santa Cruz County (see section 5.1) (Caltrans and CDFW 2017). This is the only wildlife crossing structure that has generated wildlife connectivity mitigation credits in the United States. Although this quantification method is straightforward and equates to a common conservation bank accounting metric based on an area of habitat, it does not actually account for the ecological gain from the mitigation; however, the crossingâs placement itself was based on years of research. The metric assumes that, within the zone where wildlife connectivity would be improved, increasing permeability of a larger footprint would equate to greater benefits to focal species, which may not necessarily be true. Other possible condition-based attributes that could be factored into the value of a wildlife crossing or other connectivity mitigation measure include the number of existing drainage structures not designed for wildlife (e.g., bridges and culverts) but that potentially provide safe wildlife passage, the presence of potential barriers (e.g., fences and jersey barriers), and the extent of adjacent natural plant communities. Incorporating these attributes into the valuation would be plausible in cases where extensive information about a focal speciesâ highway crossing behavior and its use or lack of use of existing structures exists (Servheen and Shoemaker 2003) or in cases where these behaviors can be systematically assessed (Kintsch and Cramer 2011). Although condition-based metrics like these do not explicitly quantify ecological gain, they would be calculated based on a putative increase in connectivity due to changes in various highway attributes. Several road characteristics could be considered when evaluating the adverse impacts on wildlife connectivity from future transportation projects. The proportion of successful highway crossings by wildlife likely declines with increasing road size (number of lanes), traffic volume, and vehicle speeds. The number of WVCs likely increases with road size, traffic volume, and average speed (Clevenger and Waltho 2000). Therefore, direct impacts could be measured based on the increased area of impervious surface or the area of degraded wildlife habitat at locations where a highway creates a barrier to wildlife movement or prevents natural migrations (Booz-Allen & Hamilton, Inc. 1999). Metrics to quantify indirect impacts could include the area of natural habitat lost to future development as a result of a transportation project, based on land use transport modeling (NAS 2016). The condition-based metrics affecting large species could include traffic volume, speed limit, and type of median. For small focal species, other highway characteristics could include traffic volume, lane width, and median characteristics (Ernest and Sutherland 2017). Traffic volume, typically measured by average annual daily traffic (AADT) and road width, are commonly cited as the major factors inhibiting road crossings (Beringer et al. 1990, Lovallo and Anderson 1996, Riley et al. 2006, Jacobson et al. 2016). Because traffic volume has a substantial influence on wildlife crossing behavior and is typically correlated with highway attributes such as lane width and number of lanes, some researchers have used AADT as a surrogate for other condition-based measurements of highway permeability (Jaeger et al. 2005, Charry and Jones 2009). Thus, traffic volume and projected increases in AADT could be used to quantify the number of credits needed to mitigate unavoidable transportation project impacts. However, the range of AADT values estimated for the point at which the highway becomes a barrier to various species is wide (Jacobson et al. 2016). Species-specific data would be necessary if traffic volume were used as a metric to quantify mitigation requirements for a transportation project. A study of collared grizzly bears around U.S. Highway 2 along the southern border of Glacier National Park indicated that traffic volume could be measured to evaluate wildlife connectivity for bears; when the highway exceeded 100 vehicles per hour, the road became a barrier to bear crossings (Waller and Servheen 2005). Measurements of traffic volumes 10 years later indicated fewer hours per day were available for grizzly bears to safely cross the road (Waller and Miller 2015). In the same region
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 9 of Montana, Ament et al. (2014) combined traffic demand forecasting models with wildlife connectivity models to predict the crossing locations where mitigation would be necessary for grizzly bears in the future. By forecasting the impacts of increased human development on traffic, state DOTs could plan to mitigate predictable impacts on wildlife long before they occur, which would be cost-effective because it would focus limited resources where they would most benefit wildlife connectivity. Furthermore, such efforts to predict future wildlife connectivity mitigation needs would align with the framework of an Advance Mitigation Program, whereby wildlife crossings and other connectivity enhancements could be prioritized based on predicted impacts of a regional or statewide transportation plans. Function-Based Connectivity Metrics Function-based metrics would focus on habitats, structures, and processes as the basis for measuring wildlife connectivity (NAS 2012). Such metrics could value the ecological gain to focal species from wildlife connectivity mitigation by quantifying rates of movement of these species to accurately describe observed population dynamics (Kadoya 2009). The most robust and scientifically defensible valuation would require empirical biological data for all identified focal species on a road-by-road basis to identify the most cost-effective wildlife connectivity mitigation because species have specific preferences of crossing structures (Clevenger and Waltho 2000). For focal species that are easily monitored and highly valued by society, such as big game or large carnivores, it may be reasonable to calculate a single metric in a particular landscape. For example, using camera traps, Andis et al. (2017) measured wildlife movement of four large mammal species near a highway and compared it with wildlife movement through 15 adjacent underpasses to determine the effectiveness of the crossings. For a greater diversity of focal species or because of a lack of information, several function-based metrics could be combined that relate to the speciesâ population abundance, demography, movement, habitat quantity and quality, or/and genetic diversity. To calculate the ecological improvement attributable to wildlife connectivity mitigation, data are needed to quantify the degree to which the mitigation measure(s) enhance the population viability of focal species. Methods have been developed to accurately monitor the number of individuals, sex, and genetics of many taxa using wildlife crossings via remote cameras, track pads, radio telemetry, and noninvasive genetic sampling (e.g., hair snares). For rare species such as large carnivores, noninvasive genetic sampling has been effective at quantifying the increase in habitat connectivity provided by wildlife crossing structures used by black bears (Ursus americanus; Dixon et al. 2006), grizzly bears (Clevenger and Sawaya 2009), and wolverines (Gulo gulo; Sawaya et al. 2019). Such monitoring (e.g., via hair sampling) could quantify both the number of animals using a wildlife connectivity mitigation measure and the demography and population viability of focal speciesâ populations before and after implementing a wildlife crossing or other connectivity enhancement. Potential function-based metrics for calculating mitigation credits for wildlife connectivity projects could include the area of reconnected or fragmented habitat of focal species. This metric could be quantified as the habitat area that a focal species gains access to from the construction of a wildlife connectivity mitigation measure. In Oregon, the Willamette Partnershipâs Ecosystem Credit Accounting System includes several credit calculators that consider the context and connectivity of a mitigation site (Willamette Partnership 2013). For example, the credit calculator for upland prairie sites gives more weight to sites that are closer to other large prairie patches and have natural vegetation along the path between the site and the closest other prairie patch. Also, as part of the Willamette Partnership, Oregon DOT, in partnership with the Oregon Department of Fish and Wildlife and The Nature Conservancy, is piloting a fish passage banking system. A fish passage credit calculator quantifies the beneficial impacts on native migratory fish habitat from a restoration project that provides fish passage at existing barriers. The calculator takes information about the miles of potential fish use above the barrier, the quality of
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 10 instream conditions, the riparian cover along the stream banks, and its interaction with the floodplain to calculate an overall score of habitat quality. That score is then multiplied by the habitat quantity (stream or watershed acres) to calculate credits or debits (Willamette Partnership 2017). The pilot project will test and evaluate the approach, conduct some credit bank projects, and determine if a fish passage credit bank could be applicable statewide (Oregon Department of Fish and Wildlife 2015). A similar although less straightforward approach could be used to quantify credits for well-studied terrestrial species, such as big game populations with known seasonal ranges connected by migration routes that intersect highways. For example, it would have been possible to quantify the acres of winter- and summer-range habitat for pronghorn (Antilocapa americana) that was maintained as accessible by constructing an overpass in Wyoming (see Sawyer et al. 2016). For credit generation, empirical evidence would be required to demonstrate the effectiveness of the proposed mitigation for the focal species because there are species-specific preferences of crossing structures (Clevenger and Waltho 2000). Gender would also be important to monitor because crossing preferences can vary by sex (e.g., family groups of bears [females with cubs]) choosing overpasses over underpasses (Ford et al. 2017) or wolverine passage across a high-volume highway (Sawaya et al. 2019). Thus, the objectives of the crossing are important to consider for function-based metrics because male movement across a wildlife crossing structure would suggest that genetic connectivity is maintained or restored, but demographic effects could still occur if female movement is limited. Other possible metrics analogous to the habitat quality assessment of the fish passage credit calculator could include wildlife crossing prioritization metrics used by Huijser et al. (2009), such as land use security, because locating wildlife crossings between tracts of intact, protected lands with connectivity to other protected lands is more likely to recover species (USDOI 2013). For example, the USFWS (2001) method for determining mitigation credits for the California red-legged frog (Rana draytonii) calculates more credits for parcels of land that facilitate habitat connectivity by assigning points for the âconnectivityâ subcategory of the âImportance to Recoveryâ criteria category. A 0.5-point credit is generated for the subcategory âconnectivityâ for any project that provides, or contribute significantly to, connectivity between: (1) separate populations of frogs; (2) separate core areas; and/or (3) separate critical habitat. Thus, in theory, wildlife crossings that connect large blocks of intact habitat, especially those protected from development, would generate more mitigation credits because greater numbers of species and individual animals would potentially benefit. Credits based on function-based metrics should reflect the desired ecological outcome of a wildlife connectivity mitigation measure. An ecosystem approach defined by Brown (2006) involves the development of performance goals and outcomes for wildlife mitigation projects. Table 1 presents several performance goals and outcomes suggested by Brown (2006) that relate to wildlife connectivity mitigation that could serve as potential function-based metrics to value wildlife connectivity mitigation. Table 1. Possible performance goals and outcomes that could be used to value wildlife connectivity mitigationa Possible Performance Goal Possible Outcomes Sustain Population Ecology Maintained or increased population size and density Balanced population sex and age structure Reduced mortality and sustained viability Maintained or increased population growth Maintain Species Distribution and Abundance Sustained direct and indirect presence Preserve Prevalence of Indicator Species Increased population size
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 11 Possible Performance Goal Possible Outcomes Long-term wildlife crossing use Maintain Number of Species with Improved Population Status Species counts Maintain Fish and Wildlife Connectivity Removal of X linear feet of barriers Improved habitat suitability index scores Maintained or increased of X acres or miles of adjacent habitat areas Improved access to X acres or miles of critical foraging areas Reduce WVCs Reduced number of WVCs Minimized maintenance costs (i.e., carcass collection) Improved Recreation Increased wildlife populations for viewing, hunting, and other activities (calculated based on state's market value of individual big game) a The listed performance goals and outcomes are adapted from Brown (2006) to include only those related to wildlife habitat connectivity. The metrics used to identify potential wildlife crossings or âlandscape linkagesâ could also be suitable to identify function-based metrics for valuing wildlife connectivity mitigation credits. Beier et al. (2005) developed a wildlife connectivity prioritization method that has been adopted by many practitioners to identify a set of 16 landscape linkages in southern California. The Arizona Wildlife Linkage Assessment (Nordhaugen et al. 2006) followed this multi-stakeholder, collaborative approach and evaluated statewide landscape connectivity in two dimensions: biological value, and threat and opportunity. Linkages with high rankings in both dimensions are the highest priority areas for accommodating continued movement of selected focal species and where wildlife crossings or other connectivity enhancements are most needed. To quantify biological value, the following criteria are typically the most important for identifying landscape linkages: (1) the size of wildlands connected, (2) the habitat quality of the smaller connected wildland, (3) the restoration potential of the linkage area, and (4) the occurrence of threatened and endangered or other special-status species (Beier et al. 2007). Although standard methods to enumerate credits based on these criteria do not exist, they could be effective metrics for valuing wildlife connectivity mitigation credits. Similarly, Smith (1999) identified and prioritized âecological interface zonesâ along highways in Florida by asking practitioners to rank various criteria used to prioritize locations of wildlife underpasses. He identified 11 criteria, ranked as follows: 1. Chronic roadkill sites 2. Known migration/movement routes 3. Identified hot spots of focal species 4. Landscape linkages (designated greenways) 5. Presence of listed species 6. Identified strategic habitat conservation areas
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 12 7. Riparian corridors (with potential for retrofitting existing structures) 8. Core conservation areas 9. Presence of separated required ecological resources (e.g., a forest patch and ephemeral wetland breeding area for amphibians that is separated by a highway) for a species or set of species 10. Public ownership (or in public land acquisition program) versus private lands 11. Potential to be included in proposed road improvement project One or more of the above metrics described by Smith (1999) could be used to define a metric for valuing wildlife connectivity mitigation credits, which would, in effect, combine several factors to measure the ecological gain from a highway crossing or other connectivity enhancement. Similarly, four of five metrics developed by Huijser et al. (2009) to identify potential sites for wildlife crossings and other connectivity enhancements could be incorporated into the value of mitigation credits. These include: 1. Local Conservation Valueâthe value of the highway mitigation to local wildlife conservation regardless of regional significance 2. Highway Mortalityârelative rate of WVCs as a proxy for motorist safety risk 3. Land Use Securityâthe degree to which lands adjacent to the site are secured de facto for conservation 4. Regional Conservation Significanceâthe potential significance of highway mitigation to address wildlife conservation concerns of regional significance The average score of the criteria was used to determine the relative importance for mitigation efforts among sites. Huijser et al. (2011) added a sixth category, species observations alongside the highway, to prioritize locations where wildlife crossings would be most effective in Jackson Hole, Wyoming. Criteria such as these could be incorporated into the calculation of mitigation credits as modifiers to the overall credit generation. Clevenger (2005) and Clevenger and Huijser (2011) discuss the guiding principles for planning and measuring performance of wildlife connectivity mitigation that should be considered when developing function-based metrics for wildlife connectivity mitigation. These principles include (1) reducing mortality and facilitating movement within populations and genetic interchange; (2) ensuring that the biological requirements of finding food, cover, and mates are met (including migration); (3) facilitating dispersal from maternal ranges and recolonization after long absences; (4) facilitating populations to move in response to environmental changes and natural disasters; and (5) providing long-term maintenance of metapopulations, community stability, and ecosystem processes. Because of the wide variation in speciesâ life histories and movement, any function-based metric aimed at enumerating these objectives would be species-specific and would depend on both the behavior of the focal species and the landscape structure (Wade et al. 2015). Therefore, Clevenger (2005) recommends using a hierarchical approach to identify function-based metrics for valuing wildlife connectivity mitigation, whereby the conservation value of wildlife crossings are evaluated at three âlevels of connectivity:â (1) genetic connectivityâwildlife movement within populations via genetic interchange, which could be documented by predominantly adult male movement across road barriers; (2) demographic connectivityâgenetic connectivity among populations, which could be documented by confirmed adult female movement across road barriers; and (3) functional connectivityâgenetic and demographic connectivity among
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 13 populations, including dispersal from maternal ranges, movement in response to environmental change and disturbance, and the long-term maintenance of metapopulations and ecosystem processes, which could be documented by confirmed dispersal of young females that survive and reproduce. Model-Based Connectivity Metrics Researchers and wildlife managers in many states have employed computer models to identify wildlife concerns along highways, including big game migration routes (Sawyer et al. 2009, Coe et al. 2015), wildlife movement corridors (Benz et al. 2016), WVC hotspots (Ramp et al. 2005, Shilling and Waetjen 2015, Gunson et al. 2011), crucial habitat linkages for focal species (Beier et al. 2008), and ecological connectivity (Theobald et al. 2012). For example, extensive research has found that ungulates use riparian corridors as movement pathways, and models have been developed for many species to statistically determine the explanatory factors that influence WVCs (Gunson et al. 2011). For some focal species and landscapes, researchers have developed robust predictive models that could inform credit valuation, including species distribution models, animal movement models, and habitat-based population viability models. Models linking geographical information systems (GIS) data with population viability models using species demographic data could be applied to evaluate the effectiveness of wildlife connectivity mitigation at stabilizing or maintaining populations (Clevenger 2005). Statistical models such as these and other geospatial landscape connectivity tools have the advantage of being transparent and repeatable and are less subject to differences in opinion or interpretation (Beier et al. 2009). Habitat connectivity has been modeled from a variety of perspectives (see Kindlmann and Burel 2008 or Rudnick et al. 2012), with some of the most common approaches using graph theory (Pascual-Hortal and Saura 2006), least-cost paths (Adriaensen et al. 2003), circuit theory (McRae et al. 2008), Brownian bridge models (Sawyer et al. 2009), landscape permeability (Anderson and Clark 2012, Gray et al. 2016, Theobald et al. 2012), and linkage designs (Beier et al. 2008). Such models could be used to identify and prioritize the best locations for wildlife connectivity mitigation. Wildlife connectivity models are often derived from empirical field data on species movement and often incorporate both condition- and function-based metrics to estimate species movement, habitat connectivity, or various other landscape connectivity factors. The models can assess the baseline habitat connectivity of a given location along the highway. Multispecies models also incorporate important criteria such as migration corridors, breeding sites, and seasonal ranges of many focal species. In locations where these analyses have been performed at an appropriate scale and are statistically validated to assess their predictive power on other road sections in similar landscapes, it would be reasonable to value wildlife connectivity mitigation credits based on predicted increases in modeled connectivity for focal species. Mimet et al. (2016) provide a hypothetical model to evaluate the potential increased wildlife connectivity that could result from installing wildlife crossing structures for multiple species. To quantify the value of potential wildlife crossings, a global index of the initial connectivity was computed, then the increase in network connectivity provided by the crossing was estimated. To evaluate multispecies connectivity values, connectivity gains were run through a principal components analysis. Regional habitat connectivity analyses are important to the development of a crediting strategy for wildlife connectivity mitigation because they provide a starting point for state DOTs to identify potential metrics and available datasets. For example, the California Essential Habitat Connectivity Project (Spencer et al. 2010) used the best available science, data sets, and spatial analysis techniques to identify 192 large remaining blocks of intact habitat or natural landscape linkages to be maintained, such as movement corridors and migration routes required by wildlife. The metrics used to identify these âessential connectivity areasâ could be useful for valuing wildlife crossings or other connectivity enhancements; these metrics include the areaâs index of ecological condition (see Davis et al. 2003),
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 14 acreage of protected lands, species diversity, acreage of habitat for listed species, acreage of wetlands, and density of surrounding development. The Vermont Wildlife Linkage Habitat Analysis (Austin et al. 2006) incorporated multiple data layers into a GIS map that includes the ecological value of habitat near highways, roadkill data, development density, land use data, the amount of core habitat surrounding a potential linkage, and other information to predict the location of wildlife linkage habitats in proximity to highways. The results of this analysis produced a wildlife crossing value GIS layer with values from 1 to 10 to rank the relative priority of areas for wildlife crossings within different regions of Vermont (Austin et al. 2006). As state natural resources agencies revise their state wildlife action plans, they are encouraged to analyze wildlife connectivity (Association of Fish and Wildlife Agencies 2012). Wade et al (2015) present various frameworks that state DOTs and natural resources agencies could follow for connectivity planning and detail eight steps for resistance-surface-based modeling (e.g., least-cost paths). Avoided Cost Metrics Cost-benefit analyses of wildlife connectivity mitigation aimed at reducing WVCs with large ungulates in the United States and Canada have demonstrated that, when installed at suitable sites, crossing structures can simultaneously enhance human safety, preserve wildlife, and save money over the long term (Huijser et al. 2009). In areas where WVCs are numerous, such as regions of the eastern United States with abundant white-tailed deer (Odocoileus virginianus), measuring reductions in WVCs could provide a metric for valuing wildlife connectivity mitigation. On average, U.S. motorists had a 1 in 167 chance of colliding with a deer (Odocoileus spp.), elk (Cervus elaphus), moose (Alces alces), or caribou (Rangifer tarandus) in 2018, and these WVCs were estimated at 1.33 million annually between July 1, 2017, and June 30, 2018 (State Farm Mutual Automobile Insurance Company 2018). The increasing development of regional and statewide plans to prioritize WVC hotspots and wildlife linkage areas, such as those in California (Huijser and Begley 2019), Idaho (Cramer et al. 2014), Montana (Huijser et al. 2007), Nevada (Cramer and McGinty 2018), and Oregon (Trask 2009), encourage state DOTs to include wildlife connectivity mitigation into transportation projects because the benefits are often shown to exceed the costs over the life of the project based on the metric of reduced WVCs. Constructing wildlife crossings or other connectivity enhancements at high-priority locations can be effective in terms of the avoided costs (i.e., reduced WVCs), so it would be practical to use avoided cost metrics (i.e., lower costs due to reduced WVCs) to quantify wildlife connectivity mitigation credits. The most common method for evaluating the effectiveness of wildlife connectivity mitigation at reducing WVCs is to compare the number of WVCs that occurred before and after implementation of the mitigation. Typically, crash data from three to five years before and after implementation are compared (Huijser et al. 2008b). Crash and carcass data regarding collisions with large mammals are available in most states, largely due to property damage and safety concerns (e.g., Garrett and Conway 1999, Hubbard et al. 2000, Waller and Servheen 2005, Farrell and Tappe 2007, Huijser et al. 2008a, Wakeling et al. 2015). WVCs are also well documented at some locations for a variety of smaller species, including mammals (Clevenger et al. 2003, Orlowski and Nowak 2004, Ford and Fahrig 2007); birds (Orlowski and Siembieda 2005); reptiles and amphibians (Rudolph et al. 1998, Carr and Fahrig 2001, Eigenbrod et al. 2008, Roe et al. 2006, Sillero 2008, Elzanowski et al. 2009); and even insects (Rao and Girish 2007). The annual cost of avoided WVCs can be calculated and compared to the cost of the mitigation measure(s) amortized over the projected life time of the project (e.g., Huijser et al. 2009), which could identify locations where wildlife connectivity mitigation credit generation is economically justifiable for improving human safety and benefitting wildlife. Many state DOTs have existing monitoring programs or have partnered with state natural resources agencies and/or universities to study roadkill and/or WVCs. In some states, where WVCs are a safety
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 15 concern, data collection for WVC carcasses and crashes is standardized to prioritize highway segments with high WVC rates. Carcass reporting by state agencies is becoming more efficient and accurate as a result of mobile devices (i.e., Utah, Idaho, Arizona) and volunteer reporting (Waetjen and Shilling 2017). In other states, WVC mortalities are often greatly underreported in crash databases (e.g., Donaldson 2017), carcass data collection is inconsistent, and reporting is not centralized. In rural areas of the western United States, accurately quantifying roadkill is costly because of increased technician travel times and intensive data collection (CDFW pers. comm. 2019a). Furthermore, for certain species that are rare or difficult to detect, WVC data may not be numerous enough to use this approach as a basis for mitigation credits without a pre- and post-construction monitoring plan. However, under certain situations and for certain focal species, state DOTs and/or natural resources agencies could use the reduction in WVCs as an accurate metric to develop credits for wildlife connectivity mitigation. 2.1.3 Monetary Valuation of Wildlife Connectivity Mitigation Credits To monetize the value of wildlife crossings or other connectivity mitigation, it is necessary to calculate the value (price) of credits. The economic impacts of WVCs could be an important metric for calculating credit values. Various non-market valuation techniques, including revealed preference techniques, stated preference techniques, or techniques based on poaching fines and restitution could be used to calculate the value of animals that would be restored or maintained by a wildlife crossings or other connectivity enhancement (Land & Water Australia 2005, Duffield and Neher 2019). In the absence of data to value the species that could benefit from a wildlife crossing or other connectivity enhancement, the value of the mitigation credits would need to be calculated based on an accepted unit of measure for other mitigation credits that benefit the same species. For example, where conservation banks exist for listed species, wildlife connectivity mitigation credits could be converted to acres in a conservation bank and calculated as equivalent to the number of acres that could be purchased with the same amount of money as the wildlife connectivity mitigation. Revealed Preferences Techniques The value of a wildlife mitigation project also could be estimated based on the amount of money that people are willing to spend to use, conserve, or restore the wildlife populations that would benefit from the mitigation. Values are available for consumptive uses of wildlife, and for big game in particular, where hunting license costs and associated hunter expenditures (e.g., Huijser et al 2009) could be used to estimate the dollar value of an animal. Additional expenditures for non-consumptive uses of wildlife (e.g., wildlife watching) could also be considered. Non-consumptive expenditures are significant and have increased from $59.1 billion in 2011 to $75.9 billion in 2016 (USDOI 2017). The 2016 Recreation Use Values Database (Rosenberger 2016) provides a list of 44 economic valuation studies that estimate the value of wildlife watching in the United States and Canada from 1958 to 2015. Stated Preference Techniques A common method used to estimate the value of environmental resources involves asking people directlyâfor example, through a surveyâhow much they value a good or service. This method discloses peopleâs âwillingness to payâ for a good or service, via contingent valuation (see Bateman and Willis 2001). This dollar amount could provide useful information about the economic utility of wildlife connectivity mitigation measures that maintain or enhance wildlife populations. Richardson et al. (2014) used contingent valuation to quantify the economic values associated with roadside bear viewing in Yellowstone National Park, finding that on average, visitors are willing to pay around $41 more in entrance fees to ensure that bears are allowed to remain along roads in the park. This translates to a total willingness to pay of more than $12 million annually across all visitors.
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 16 Willingness to pay valuation methods for natural resources have been used mostly for ecosystem services and land protection value estimates, but society may also be willing to pay more to conserve lands that provide vital linkages to wildlife across highways within a larger landscape context of protecting connections between areas of large, high-quality wildlife habitat. Thus, it stands to reason that wildlife connectivity mitigation credits could be greater for wildlife crossings or other connectivity enhancements located adjacent to, or between, protected lands because future development is limited in protected areas. Generally, the more land protected as natural habitat surrounding a wildlife crossing or other connectivity enhancement, the less risk or degree of uncertainty about whether wildlife would use it. Various researchers have estimated both the market and non-market components of ecosystem service values associated with land protection (see Costanza et al. 1997). A survey in Ohio estimated that respondent households were willing to pay $16.80 to $29.16 per year for a conservation easement program to prevent development of a riparian corridor along the Grand River (Blaine and Smith 2006). In the Netherlands, respondents to a survey regarding efforts to reconnect (defragment) two different landscapes provided an average willingness to pay of approximately at $180.00 per respondent (van der Heide et al. 2008). Similar economic valuation efforts could be used by state DOTs to estimate societal preferences for wildlife habitat connectivity. The National Research Council (2004) reported that, given the effort and expense, it was rare to see mitigation valuation or trading based on these econometric techniques. However, these techniques are increasingly in use, especially for cost-benefit analyses to support federal grants to fund projects. Willingness to pay valuation methods are also widely used to estimate the economic value of natural resources and ecosystem services that are not traded in markets and for which no economic behavior is observable, or the passive use values of natural resources or services (Vincent et al. 1995). Individuals may be willing to pay for the continued existence of wildlife through the preservation of habitat connectivity because wildlife and their habitat have intrinsic values to society even if a person does not use or visit the resource. Duffield and Neher (2019) summarize the current literature of passive use value estimates for selected species and populations that could be of interest to state DOTs. They reported several dozen species-specific passive use value estimates from the literature, but reported many gaps associated with species most at risk in road collisions. They estimate per-animal passive use values for elk ($37,000); grizzly bear ($4,133,000); wolf, inside/outside protected areas ($2.0 million/$56,500); and desert tortoise ($8,200). Duffield and Neher (2019) note that there are no cases where state DOTs have used passive use values for valuing wildlife affected by transportation infrastructure, there are other types of infrastructure projects that have relied on passive use value estimates. Monetizing Wildlife Connectivity Mitigation Credits Assigning a monetary value to environmental attributes that are lost and gained provides a common scale for the valuation of transportation project impacts (Kagan et al. 2014). Given that the monetary value of certain focal species could be calculated, wildlife connectivity mitigation credits could conceivably be quantified to provide a common scale for the valuation of transportation project effects on those species. For example, the number of individual wildlife, by species, that would potentially benefit from wildlife connectivity mitigation could be approximated from studies on animal movement using telemetry, track beds, remote cameras, or other appropriate monitoring methods (e.g., Clevenger et al. 2008). Mitigation credits could then be generated based on the value of those individual animals. State DOTs commonly monetize impacts such as accidents or vehicles emissions and evaluate highway projects with cost-benefit analyses, such the Cal-B/C model used by Caltrans (Booz-Allen & Hamilton, Inc. 1999). Similarly, state DOTs could quantify the monetary impacts of wildlife connectivity mitigation in terms of property damage, human injury, and/or death by measuring wildlife mortality and/or WVCs before and after construction of a wildlife crossing or other connectivity enhancement. Bissonette et al.
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 17 (2008b) estimated that the average cost of WVCs involving deer in Utah was $3,470 per incident, which included the costs of human fatalities, human injuries, vehicle damage, and the loss of the deer killed. In British Columbia, insurance claims related to WVCs averaged approximately $1,600 per claim in 2000, with estimated clean-up costs of an additional $25 to $350 per accident, depending on the size of the mammal (Sielecki 2010). Donaldson (2017) calculated that deer-vehicle collisions are the fourth costliest of the 14 major collision types in Virginia, averaging more than $533 million per year. In California, the total annual cost (2017) of WVCs was estimated to be at least $307 million, up 11% from 2016, based on observations of reported traffic incidents and carcasses. If accidents that are claimed to insurance companies, but un-reported to police, were included, Shilling et al. (2018) estimated those costs could be as high as $600 million per year. These cost estimates from California are much higher than those provided by other researchers, with property damage estimated at $17,343 per WVC and human injury costs of $105,228 and $506,217 for minor and major injuries per WVC, respectively. Researchers have analyzed studies of wildlife crossings to identify the threshold value of ungulate-vehicle collisions (per year) at which various wildlife connectivity mitigation measures would start to generate economic benefits in excess of their costs (i.e., the break-even point). Huijser et al. (2009) evaluated the costs and estimated effectiveness of various mitigation measures for reducing WVCs and developed a cost-benefit model as a decision-support tool for determining the most cost-effective mitigation measures to reduce WVCs and improve wildlife habitat connectivity. They estimated that the costs (in 2007) for a seasonal wildlife warning sign was $3,728; an underpass with fencing and jump outs was $538,273; an animal detection system with fencing and gaps was $836,113; and an overpass with fencing and jump outs was $719,667. Huijser et al. (2009) then estimated the average overall cost of WVCs for ungulates in 2007 as $6,617 for deer, $17,483 for elk, and $30,760 for moose. These costs included vehicle repair, human injuries, fatalities, accident attendance, value of the animal to hunters, and carcass removal. The average annual cost per kilometer of building and maintaining fencing with wildlife underpasses and jump outs was $18,123. Given these costs, the break-even point for one of the most effective mitigation measures, fencing with underpasses on a divided four-lane road, was estimated for deer, elk, and moose as 3.2, 1.2, and 0.7 WVCs per kilometer per year, respectively. Thus, if a road section has costs (i.e., WVCs) that exceed these threshold values, then the benefits of fencing with wildlife underpasses on a divided four-lane road would exceed the costs over a 75-year time period. Similarly, previous cost-benefit analyses by Reed et al. (1982) estimated that wildlife fencing in combination with underpasses required 11.3 deer-vehicle collisions per kilometer per year before the benefits of the mitigation exceed the costs. This threshold is higher primarily because it does not include the costs associated with human injuries and fatalities, or the values of wildlife that are not easily monetized like hunting. More recently, Gagnon et al. (2015) used the costs from Huijser et al. (2009) to demonstrate that savings accrued by constructing wildlife crossings, fencing, and other connectivity enhancements for reducing collisions with elk would exceed the costs to implement such measures within five years. Likewise, Ford et al. (2011) used the value for deer presented by Huijser et al. (2009) for bighorn sheep (Ovis canadensis) to show the cost- effectiveness of various lengths of highway fencing at reducing WVCs. These analyses demonstrate that wildlife connectivity mitigation can be cost-effective when valued in terms of human safety and property damage, even on highway sections with relatively low incidences of WVCs. For condition-based metrics, calculating the price per credit and quantifying the number of wildlife connectivity mitigation credits would be more speculative because of the lack of a biological metric on which to base the predicted ecological gain from a wildlife crossing or other connectivity mitigation measure. As a result, credit quantification could be arbitrary and potentially inconsistent, so it would be useful to base the valuation of credits on the cost of a wildlife crossing or other connectivity enhancement. For example, the USFWS (2012b) Panther Habitat Assessment Methodology uses the average cost of FDOT bridge/box culvert crossings as the basis for calculating the number of
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 18 conservation bank acres required for purchase to mitigate the impacts of increased traffic from development projects on the Florida panther (see section 5.2). For model-based connectivity metrics, the monetary valuation or quantification of credits would require several assumptions about the effectiveness of a wildlife connectivity mitigation measure at either maintaining or enhancing wildlife passage across a highway or conserving or recovering focal species. Model-based metrics to value wildlife connectivity are not explicitly linked to the ecological gain that would result from a wildlife crossing structure or other connectivity enhancement. These metrics could thus be categorized as practice-based metrics, whereby âa conservation outcome is expected to be achieved by implementing a specific practiceâ (i.e., mitigation measure) and its implementation is a âproxy for performanceâ (Pindilli and Casey 2015). Poaching Fines and Restitution Lastly, the value of wildlife could be approximated by the restitution paid for animals that are unlawfully taken, whether enforced by USFWS for violations of the ESA (81 Federal Register 41862) or by states for poaching (Cramer et al. 2014, 2016). Edwards (2017) provides restitution values for illegally taken game species in the United States, with the most common species being wild turkey (Meleagris gallopavo), white-tailed deer, black bear, and elk. The authors conducted an online survey to elicit information from experienced practitioners on how they were developing approaches, protocols, and requirements for wildlife connectivity mitigation (Appendix A). The information gathered from the survey also provides insight into the current use of mitigation credits for wildlife crossings and other connectivity enhancements, and if applicable, the valuation metrics and methods used. Because the literature review revealed limited information about valuation metrics and methods for wildlife connectivity mitigation crediting, the survey was also developed to identify the most-experienced individuals willing to discuss their specific programs and projects in follow-up phone interviews. 2.2.1 State DOT Experience with Wildlife Connectivity Mitigation The online survey revealed a consensus among state DOT and natural resources agency practitioners that dedicated wildlife crossings provide a direct benefit to wildlife and a highway safety improvement to the public by reducing collisions with large animals. The survey results also showed that the development of crediting and valuation systems for wildlife crossings is in the early stages in less than a handful of states. However, there is keen interest in the development of mitigation programs for wildlife connectivity. More than half of the respondents to the survey indicated that, if their state provided the option to have a credit system for wildlife connectivity mitigation, they would take advantage of such a system. Survey respondents stated that a wildlife connectivity mitigation crediting program would offer increased flexibility for state DOTs to satisfy compensatory mitigation needs for wildlife connectivity impacts. State DOTs are developing individual approaches to address wildlife connectivity through mitigation measures, which tend to be specific to a focal species within a transportation project corridor and/or geographic region. Respondents to the survey largely confirmed (84%) that their state incorporates wildlife connectivity assessment and mitigation considerations early in the transportation project planning process and the transportation project programming and design processes. At the project level, wildlife connectivity mitigation is typically considered collaboratively during the environmental review process and usually involves state DOTs engaging with federal and state natural resources agencies with jurisdiction over wildlife resources. When federally listed threatened or endangered species could be
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 19 affected, USFWS is consulted. In several states, respondents said that wildlife advocacy groups were also included in planning efforts involving wildlife connectivity assessments or evaluations of mitigation needs related to specific transportation projects. Survey respondents indicated that several states are exploring the valuation or crediting of wildlife connectivity mitigation. Most are in the early development or exploratory stages such as the Transportation Sub-team of the Panther Recovery Implementation Team in Florida. California's wildlife and transportation agencies are piloting a wildlife connectivity mitigation credit approach and have signed a credit agreement for one project, the Laurel Curve Project (see section 5.1) (Caltrans and CDFW 2017). The online survey also revealed that several state DOTs have experience with advance mitigation and/or in-lieu fee mitigation programs, which demonstrate their familiarity with non-traditional mitigation instruments to address impacts on wildlife. These programs often require collaboration with multiple stakeholders. An example of an in-lieu fee program is one that was set up through a memorandum of agreement between FHWA, Colorado DOT (CDOT), and USFWS for the threatened Canada lynx in Colorado (FHWA et al. 2015). The program allows highway projects to contribute to a fund rather than providing mitigation for adverse effects on lynx habitat under the ESA. The required financial contribution is calculated as a specified percentage of total project construction costs using a sliding scale and is tied to the type and severity of the adverse effect that the transportation project is expected to have on lynx. The total financial contribution to the fund is capped at 5% of the total construction costs. Funds would accumulate until they could be spent on mitigation that would provide a significant conservation benefit to Canada lynx habitat and movement throughout the state. Funds cannot be indefinitely sequestered; they must be spent wholly, or in part, at least once every three years. CDOT has an Advance Mitigation Program, the Shortgrass Prairie Initiative, that provides programmatic clearance for CDOT activities in the eastern third of Colorado for 20 years through the acquisition of lands and conservation easements that support several rare, threatened, and endangered species. As part of this initiative, CDOT, USFWS, and FHWA have invested resources in more comprehensive and proactive wildlife habitat conservation that would otherwise be spent as project-by-project mitigation. California respondents indicated that Caltrans has a new framework to implement wildlife connectivity mitigation through its Advance Mitigation Program. This program dedicates at least $30 million annually for four years to the planning and implementation of advance mitigation projects. Since January 2017, CDFWâs new RCIS program provides a collaborative planning process through which wildlife connectivity mitigation projects can be identified and qualify as eligible for advance mitigation credits. Obstacles to a broader nation-wide adoption of advance mitigation programs or mitigation crediting systems for wildlife connectivity were apparent from the survey and interviews. Obstacles mostly related to the frequency of need for advance mitigation credits in a region and the lack of funding for both the development of a wildlife connectivity mitigation crediting program and advance mitigation approaches to evaluate impacts and prioritize wildlife connectivity mitigation. The lack of a standard set of metrics and methods to calculate wildlife connectivity mitigation credits for wildlife, the topic of this study, was also an apparent hurdle to overcome. 2.2.2 Examples of Crediting Approaches to Wildlife Connectivity Mitigation Ninety-one percent of respondents to the survey strongly confirmed that mitigation credits for impacts on wildlife connectivity impacts are not available to state DOTs. Only one state DOT, Caltrans, has participated in a proof-of-concept effort to coordinate the development of advance wildlife connectivity mitigation, whereby credits can be applied as compensatory mitigation for the ecological impacts of other Caltrans transportation projects. Since that undertaking, new state legislation became effective whereby,
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 20 under specific conditions, including the availability of a CDFW-approved RCIS, wildlife crossing structures may qualify as enhancement actions for advance mitigation crediting. Few other examples were identified where mitigation credits have been generated from wildlife crossings and other connectivity enhancements, or where credits have been available to mitigate other kinds of transportation project impacts. FDOT provided an example of calculating mitigation credits by evaluating habitat connectivity under the Florida Department of Environmental Protectionâs (FDEP) Uniform Mitigation Assessment Method (UMAM) (see section 5.3). For further insight into state DOT efforts to identify the mitigation values of wildlife crossings and other connectivity enhancements, follow-up phone interviews were conducted with survey respondents in Arizona, California, Colorado, and Florida with extensive experience with wildlife connectivity mitigation in their state (Appendix A). Interviewees included: â¢ Eight state DOT planners or environmental managers â¢ Seven wildlife biologists at state natural resources agencies â¢ One federal transportation agency staff 2.3.1 Legal, Planning, and Policy Framework Considerations Interviews with experienced practitioners revealed that state DOTs and natural resources agencies are increasingly collaborative in their efforts to reduce WVCs and provide safe passage for wildlife across highways. This cooperation is driven by the need to simultaneously improve public safety, reduce the substantial costs of WVCs, conserve big game, and provide passage for smaller sized wildlife. The major barriers to further collaboration are staff and funding shortages and the different timescales for transportation and wildlife planning processes. Support for Advance Mitigation Advance mitigation was generally viewed by those surveyed as a useful tool for state DOTs to satisfy compensatory mitigation needs for potential transportation project impacts on wildlife connectivity. Practitioners are interested in opportunities to establish advance mitigation programs or to receive credit for needed wildlife connectivity mitigation during transportation planning and prior to transportation project impacts occurring. Californiaâs Advance Mitigation Program (Caltrans 2018) is the only example of a program that has performed wildlife connectivity mitigation to establish credits, to be applied as mitigation for other infrastructure projects (see section 5.1), and interviews with Caltrans practitioners focused largely on this program. Californiaâs Advance Mitigation Program planning process includes three steps. First, a statewide assessment is performed to estimate the potential compensatory mitigation needs. Next, regions are identified that could potentially provide advance mitigation opportunities that meet the Advance Mitigation Program objectives, and a regional advance mitigation needs assessment is performed. Lastly, candidate advance mitigation projects are scoped and proposed at the District level for possible funding through the Advance Mitigation Program (Caltrans 2018). Caltrans compensatory mitigation needs are predicted for endangered species and other permitting requirements. However, it is possible that continued research in California, such as recent WVC analysis focused on mule deer (Odocoileus hemionus) (Huijser and Begley 2019), will help Caltrans make informed decisions on the potential implementation of advance mitigation measures at the most problematic highway locations based on human safety, biological conservation, and economics.
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 21 Under specific conditions, fish passage and wildlife crossing structures may be eligible for advance mitigation crediting under new state regulations codified about the same time as Caltrans Advance Mitigation Program. The California legislature passed a law, effective in 2017, officially creating the CDFW RCIS program (Fish and Game Code Â§Â§ 1850â1861). CDFW (2018) recently released its RCIS Program Guidelines. The RCIS program provides a new framework to guide proactive, landscape-level conservation planning that differs from the existing regulatory authority of the California Natural Community Conservation Planning program and provides for additional mitigation actions beyond those allowed under Californiaâs existing conservation and mitigation banking programs. An RCIS is voluntary and is intended to be a multi-stakeholder plan that identifies and prioritizes actions, including mitigation measures, that would promote conservation of species, habitats, and other natural resources to facilitate advance mitigation, such as for transportation projects. An RCIS includes an evaluation of habitat connectivity for focal species and identifies wildlife linkages where wildlife connectivity could be maintained or enhanced (CDFW 2019). For the implementation of advance mitigation projects consistent with an RCIS, Fish and Game Code authorizes the creation of MCAs between CDFW and another party. MCAs could be used to define a crediting mechanism whereby wildlife crossing structure construction could be used for offsetting effects of future transportation projects. The RCIS enabling legislation allows mitigation credits created under an MCA agreement with CDFW to be used, sold, or in special circumstances, transferred. Because CDFWâs RCIS program is the only one of its kind in the United States, it has a flexible framework that allows for project proponents/sponsors to propose the metrics used to calculate mitigation credits as long as they provide a sound rationale (CDFW pers. comm. 2019a). Under the CDFW (2019b) Draft MCA Guidelinesâto be incorporated as section 5 of the RCIS Program Guidelines (CDFW 2018)âan MCA must: (1) describe the unit of measurement (e.g., acres, linear feet) for credits; (2) provide a credit evaluation that explains the approach used to formulate the quantity (number) and value (price) of credits; and (3) provide a credit table that shows the number and type of credits to be released according to specific regulatory uses (CDFW 2019b). CDFWâs Draft MCA Guidelines also detail the development of credit release schedules, the transfer and use of credits, and the reporting requirements to account for the proposed credits. A wildlife biologist with CDFW (pers. comm. 2019a) highlighted three advantages of advance mitigation under its newly created RCIS program: (1) it would provide a cheaper and faster mitigation crediting process than traditional mitigation because approval is only required by one agency (CDFW); (2) it would allow for greater flexibility in the types of credits generated and methods used to quantify them; and (3) it would allow for temporary wildlife mitigation, such as non-permanent habitat enhancements, to qualify as eligible for mitigation credits. This information aligns with the findings of Sciara et al. (2017) that advance mitigation programs could produce overall cost savings to state DOTs, largely from reduced permitting delays and improved coordination and consultation with regulatory agencies. To assess impacts of future transportation projects under an Advance Mitigation Program, GIS methods have been developed to aggregate predicted terrestrial impacts of road projects in California (Thorne et al. 2009). Such methods do not address the impacts of transportation projects on highway connectivity, but Thorne et al. (2009) suggest that habitat connectivity information could be included from regional conservation plans and/or wildlife connectivity models to identify target areas for preservation. Concerns About Mitigation Measures Within the Right-of-Way Some state DOTs have concerns about encumbrances that could arise after construction of mitigation measures within the highway right-of-way that they are responsible for maintaining. If the credit area conflicted with a future maintenance need or highway expansion, then any loss of credit-generating action
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 22 would need to be replaced as part of the overall compensation. Likewise, issues with wildlife connectivity mitigation within the right-of-way could arise if a wildlife crossing structure needed to be replaced or repaired as a result of reduced function. Although federal funds often largely pay for the construction of wildlife crossing structures, state DOTs bear the cost burden of maintenance (ARC Solutions 2017). Mitigation structures must be maintained and repaired to ensure their continued use and effectiveness (Cramer and Bissonette 2005). Imposing such requirements for the maintenance of wildlife connectivity mitigation projects was noted as a legal concern by a practitioner at FDOT (FDOT pers. comm. 2019). However, a California practitioner suggested that, because the mitigation would be within the right-of- way, it would be easier for Caltrans to uphold maintenance requirements when compared to other offsite mitigation projects (Caltrans pers. comm. 2019). Interagency Coordination Although institutional challenges remain for creating a regional ecosystem framework that aligns state DOT goals and objectives with those of natural resources agencies, numerous state DOTs have effectively coordinated with their respective state natural resources agencies to identify and prioritize landscape linkages or wildlife corridors. For example, CDOT and other agencies developed a multi-agency Memorandum of Understanding (CDOT et al. 2008) for the I-70 Mountain Corridor programmatic environmental impact statement, which outlines a shared vision for enhanced wildlife connectivity and reduced WVCs. An interagency technical advisory committee of biologists from multiple state and federal agencies (A Landscape-Level Inventory of Valued Ecosystem Components or ALIVE) was formed to develop a landscape-based approach to consider wildlife needs (CDOT et al. 2008). The ALIVE committee analyzed ecosystem connectivity and identified 13 high-priority locations where evidence suggested that the highway impedes the migration, movement corridors, or zones of dispersal for elk, mule deer, bighorn sheep, and Canada lynx. The committee recommended mitigation measures that included enhancing existing or creating new wildlife crossing structures. Collaborative approaches such as this were widely supported by the practitioners interviewed, although it was apparent that some state DOTs have better working relationships with USFWS and their state natural resources agencies than others. Funding Obstacles Practitioners consistently pointed to the lack of funding as one of greatest obstacles to constructing wildlife crossings and other connectivity enhancements; the lack of funding is supported by other research (Kociolek 2014, Ament et al. 2015) and is largely because funding for transportation projects gives priority to motorist safety over wildlife conservation. In general, WVCs are less severe than other types of crashes, resulting in fewer deaths and serious human injuries (Huijser et al. 2007). Thus, the relative costs of WVCs are usually less than the costs of other types of vehicle collisions. Under most state DOT funding programs with accounting methods that do not value wildlife, wildlife connectivity mitigation projects often do not receive funding because they would provide less economic benefit than other motorist safety projects (CDOT pers. comm. 2019). According to practitioner survey responses, the ecological benefits of wildlife connectivity mitigation are currently not given high priority in most highway projects, which supports the need for an alternative mitigation approach that could integrate conservation priorities. 2.3.2 Potential Valuation Metrics for Wildlife Connectivity Mitigation Credits Methods to calculate mitigation credits for a given wildlife connectivity mitigation project are not well developed and the survey conducted as part of this research found that only Caltrans and FDOT have generated mitigation credits for wildlife crossing projects.
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 23 Support for Function-Based Metrics Generally, planners and environmental managers at state DOTs support using function-based metrics to value mitigation credits for wildlife crossings and other connectivity enhancements and applying the generated credits (via debits) to the impacts of other transportation projects. This support aligns with research by Bennett et al. (2017) that recommends credits for mitigation markets incorporate measures of ecological function and biodiversity. However, practitioners provided limited examples. The best example is FDOTâs incorporation of habitat connectivity benefits into the wetland mitigation assessment for focal species that use wetlands and watercourses as movement corridors between large blocks of intact habitat (see section 5.3). When asked about the function-based metrics potentially used to value mitigation credits, in general, most practitioners interviewed responded that âit would depend on the species.â Because different species have widely variable life histories, habitat requirements, and dispersal abilities, accommodating the needs of multiple species is inherently difficult (Mimet et al. 2016), and practitioners noted that quantifying mitigation credits for multiple focal species would be challenging. If function-based metrics were used to value wildlife connectivity mitigation credits, practitioners generally agreed that most feasible metrics would be based on attributes related to the ecological improvement for a single focal species, rather than multiple species. When asked if wildlife mitigation credit valuation should be calculated based on a standard set of metrics for landscape-level wildlife connectivity or as a tailored set of metrics for single species or multispecies, Caltrans staff responded, âBecause the needs of small, protected species such as tortoises, turtles, kangaroo rats, salamanders and frogs are much different than the regional context for landscape-level connectivity, it would be more appropriate in California to have either just a tailored set of metrics or a combination of these and landscape-level metrics. It is highly unlikely that any one set of metrics would meet our needs in Californiaâ (Caltrans pers. comm. 2019) For most function-based metrics that could be used to quantify credits for a wildlife connectivity mitigation project, monitoring animal through-passage of a wildlife crossing or other connectivity enhancement would be required. If the release of mitigation credits depended on such a performance standard, a Colorado practitioner suggested that a standard monitoring approach would be necessary to evaluate whether it was effective at providing the promised levels of through-passage to focal species (CDOT pers. comm. 2019). Although most wildlife crossings built in the United States have been monitored via remote cameras to verify their usage by focal species (e.g., Cramer and Hamlin 2016), standard protocols are not typically used (Caltrans pers. comm. 2019, FDOT pers. comm. 2019). In a review of the state of the practice over a decade ago, Cramer and Bissonette (2005) found that a limited number of the 460 terrestrial wildlife crossing structures in the United States were monitored for effectiveness. Support for Avoided Cost Metrics Mitigation credits could be quantified for wildlife connectivity mitigation by calculating an increase in motorist safety via a measured reduction in WVCs. This metric is commonly used in the literature to evaluate the effectiveness of wildlife crossings (see section 2.1.3), and practitioners suggested it as a proxy for quantifying improved motorist safety. A California practitioner highlighted the value of roadkill data collection for identifying areas where mitigation credit values should be highest for wildlife crossings and other connectivity enhancements in locations that maintain or restore genetic connectivity for desert bighorn sheep (CDFW pers. comm. 2019a). Because many state DOTs have existing programs for collecting data about WVCs, in certain situations, this metric could be among the most straightforward metrics available to calculate mitigation credits for wildlife connectivity projects. In California, Shilling et al. (2018) evaluated WVCs and identified stretches of highway where WVC are most likely. They
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 24 reported five valuable recommendations that would apply to state DOTs seeking to apply mitigation credits for wildlife crossings that use a motorist safety metric as part of the credit calculation: (1) systematically collect and share WVC data; (2) require collection and analysis of WVC data for transportation projects before they are approved and funded; (3) protect driver safety and wildlife by building WVC-reduction projects; (4) form new partnerships among university and non-governmental organization (NGO) scientists, citizen groups, and local agencies interested in reducing WVC impacts; and (5) systematically evaluate effectiveness of WVC reduction to keep improving. Need for Consistent Credit Quantification Whatever metrics and methods are used to calculate mitigation credits for wildlife connectivity mitigation, the practitioners interviewed generally agreed that there should be consistent quantification of the benefits to focal species from wildlife connectivity mitigation (credits) and the impacts of mitigated transportation projects (debits). Ideally, the metrics used to calculate wildlife connectivity mitigation credits would be easy to measure, based on the focal speciesâ biology, and result from collaboration and agreement among stakeholders. Need for Empirical Data The valuation of wildlife connectivity mitigation explored by this study is improved when empirical biological data exist for focal species on a road-by-road basis to identify the most cost-effective decisions. Decision makers need information on the ecological importance of each linkage area and ways to identify the most important linkages. Typically, a suite of focal species and associated habitats are identified that have the greatest need for enhanced connectivity. Developing a crediting system for wildlife connectivity mitigation would require a robust analysis of focal speciesâ habitat and movement patterns, including migration corridors, breeding sites, and seasonal ranges, and how highways affect these topics. Highly mobile species that require large habitat areas are the most sensitive to highways (Mimet et al. 2016). These species also include many large mammals that are economically valuable for recreation and/or more costly in terms of vehicle damage and human injuries due to their large body size. Thus, where highways negatively affect big game and/or large mammalian carnivore populations, metrics to quantify the value of wildlife connectivity mitigation could likely incorporate their value to society and/or the cost of WVCs. If credit release were to be based on wildlife crossing performance, monitoring would need to follow a rigorous study design that includes pre-construction versus post-construction comparisons of animal movements across highways (see section 4.6). One of the most straightforward metrics used to evaluate the effectiveness of a wildlife connectivity mitigation project would be to measure increased driver safety using the number of reduced WVCs after implementation as a proxy. To quantify WVCs, most state DOTs have data-collection protocols in place. NDOT provided a summary of state DOT efforts in the western United States to collect and map WVCs and roadkill, map wildlife linkages, and create prioritization processes (see table 55 of Cramer and McGinty 2018). In Colorado, CDOT has standard operating procedures for collecting data about all accidents involving wildlife from the Colorado State Patrol (CDOT pers. comm. 2019). In Arizona, WVC data are collected via a smartphone application, Survey123 for ArcGIS, which is shared among state agency staff (Arizona Game and Fish Department pers. comm. 2019). South Dakota DOT uses a similar smartphone application to collect and store WVC data (Cramer 2017). Also, perhaps more than any other impact of highways on wildlife, roadkill is clearly quantifiable, and roadkill surveys could be used to monitor the effectiveness of a wildlife connectivity mitigation project. Colorado has operating protocols for collecting carcass information any time CDOT staff handles roadkill
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 25 or wildlife injured by a vehicle (CDOT pers. comm. 2019). Utah Division of Wildlife and Utah DOT (2019) collect similar data and publish them online. However, standardized road survey protocols are not available, and only a handful of studies have sought to identify the optimal sampling approach needed for roadkill surveys of different taxa (Bager and Rosa 2011, Costa et al. 2015, Ford et al. 2011). Several biological considerations must be considered to use roadkill as a metric for evaluating the effectiveness of wildlife connectivity mitigation, including the relationship between roadkill and surrounding wildlife population abundance, and the road avoidance behavior of some species in response to traffic volume (i.e., roadkill rates decrease as traffic volume increases because animals are less likely to cross the road) (Eberhardt et al. 2013, Teixeira et al. 2017). Data Limitations The lack of data about rare or elusive focal species could be an obstacle to developing mitigation credits for a wildlife connectivity mitigation project. For example, in Colorado, a CDOT practitioner suggested that, for low-density, wide-ranging focal species such as Canada lynx, it would be difficult to quantify mitigation credits for a wildlife connectivity project because the degree of benefit to Canada lynx would be difficult to measure. While the highway crossing behavior of Canada lynx has been studied in Colorado (Crooks et al. 2008, Baigas et al. 2017), the biological benefits of various highway crossing structures to Canada lynx remains unpredictable. Canada lynx have been documented crossing at-grade over Colorado highways on numerous occasions, but CDOT has not documented the speciesâ use of existing wildlife connectivity mitigation projects in the state (CDOT pers. comm. 2019). This uncertainty, combined with the technical difficulties of effective on-site mitigation, led CDOT to develop an option to use a percentage of total construction costs to calculate funds required for contribution into a Canada lynx in-lieu fee fund (see section 2.2.1). Video surveillance (Dodd et al. 2007) or noninvasive genetic sampling (Clevenger and Sawaya 2009, Dixon et al. 2006), potentially combined with spatial capture-recapture models (Royle et al. 2017), could quantify increased habitat connectivity provided by wildlife connectivity mitigation; however, these methods are not certain to be effective for species like Canada lynx. Furthermore, Clevenger (2005) suggests that if population-level impacts are used as the metric for valuing wildlife connectivity mitigation, elusive carnivores and other large mammals would not be suitable focal species because of their demographic characteristics and sample size limitations. Many other factors also affect a population, so it would be difficult to isolate the effect of wildlife connectivity mitigation measures. A practitioner in Colorado also suggested that data limitations for common, relatively easy-to-monitor species could present an obstacle to valuing wildlife connectivity mitigation. Colorado Parks and Wildlife has collected global positioning system (GPS) collar locations from numerous big game studies, but the lack of data from certain herds, including migration routes and seasonal habitat use, would be an obstacle to developing metrics to value wildlife crossing structures (CDOT pers. comm. 2019). This is despite the fact that big game are among the most easily monitored wildlife because of their large size and visibility. Practitioners with CDOT also mentioned the need for current data about focal species and how they interact with highways because observations and expert opinions gathered over decades may not necessarily reflect current conditions. New development or other human impacts occur rapidly and could have altered the movement of focal species, increasing uncertainty about the future effectiveness of proposed wildlife connectivity mitigation measures (CDOT pers. comm. 2019). Adopting Existing Wetland Mitigation Assessment Protocols for Credit Quantification To demonstrate the improved wildlife connectivity provided by wildlife crossing structures, FDOT has incorporated the habitat connectivity metrics provided by FDEPâs UMAM (Bardi et al. 2004). Although this legally mandated tool is focused on mitigation requirements for impacts to wetlands and surface
Valuing Wildlife Crossings and Enhancements for Mitigation Credits 26 waters, it includes metrics that value the ecological connectivity provided by drainage culverts and bridges associated with streams and wetlands. Further detail on this approach is provided in section 5.3.