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Suggested Citation:"1.0 Introduction." National Academies of Sciences, Engineering, and Medicine. 2020. Valuing Wildlife Crossings and Enhancements for Mitigation Credits. Washington, DC: The National Academies Press. doi: 10.17226/25731.
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Valuing Wildlife Crossings and Enhancements for Mitigation Credits 1 1.0 INTRODUCTION State DOTs and their regional and local partners are increasingly focused on wildlife connectivity because mounting evidence demonstrates the effectiveness of wildlife crossing structures (i.e., overpasses and underpasses) and other connectivity enhancements at improving motorist safety and conserving wildlife. Wildlife crossings and other connectivity enhancements can be cost-effective measures to facilitate animal movement across highways for numerous species and are necessary for the recovery of many threatened and endangered species. Many state DOTs are beginning to incorporate wildlife connectivity planning into their long-term transportation plans. Mitigation crediting may provide a valuation approach that state DOTs could employ to promote the construction of wildlife connectivity projects and mitigate certain transportation project impacts. Evaluating current practices and emerging, innovative valuation approaches will provide state DOTs with information to more efficiently meet environmental permit requirements and develop successful mitigation measures, as well as help meet environmental stewardship goals and responsibilities. This study synthesizes current information about mitigation crediting practices used by state DOTs and their partners for calculating and applying mitigation credits for wildlife crossings and other connectivity enhancements that provide safe passage for wildlife across highways. It examines various facets of mitigation crediting for wildlife connectivity, focusing specifically on the valuation metrics and methods used for credit development and related findings for state DOTs to consider when developing a program for advance mitigation and crediting for wildlife connectivity. The terms “credit,” “wildlife connectivity mitigation,” and “advance mitigation” are used throughout this report and are defined as follows: • Credit—unit of exchange that serves as the currency for valuing biodiversity, ecosystem services, or an expected ecological outcome. In the context of this report, credit specifically references a measure of gain in wildlife connectivity functions through the restoration, enhancement, or protection of habitat connectivity by wildlife crossings and highway enhancements that increase permeability for focal species. • Wildlife connectivity mitigation—any functional wildlife crossing structure (underpass or overpass), or other highway enhancements (e.g., retrofits of existing culverts, fencing, jump outs, or driver warning devices) used to mitigate the fragmentation effects of transportation projects to wildlife and habitat connectivity. In this report, this term is used synonymously with “wildlife crossing(s) and/or other connectivity enhancement(s).” • Advance mitigation—a process in which credits generated from mitigation measures can be applied at a later date to mitigate unavoidable impacts of future transportation projects and to satisfy permit conditions. Funding for advance mitigation is provided early in the planning process to implement mitigation measures that generate credits that can be purchased by state DOTs to mitigate future transportation projects (Sciara et al. 2015a). By considering mitigation development early in the planning process, there is an opportunity to better align mitigation with regional conservation priorities, including wildlife connectivity. The impetus for a state to establish an advance mitigation/crediting program that includes wildlife connectivity credit establishment is based on the opportunity to provide additional, effective wildlife connectivity than is required to mitigate for adverse impacts as part of a transportation project as well as help address the need for added flexibility in addressing the legacy wildlife connectivity impacts and motorist safety impacts of the roadway itself.

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There is mounting evidence demonstrating the effectiveness of wildlife overpasses and underpasses in improving motorist safety and conserving wildlife.

The TRB National Cooperative Highway Research Program's NCHRP Web-Only Document 280: Valuing Wildlife Crossings and Enhancements for Mitigation Credits synthesizes current practices used by state DOTs and their partners for calculating and applying mitigation credits for wildlife crossings and other connectivity enhancements that provide safe passage for wildlife across highways.

Accompanying the report is a Power Point presentation entitled, "Valuing Wildlife Crossings and Enhancements for Mitigation Credits."

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