August 19, 2020

Environmental, Natural Resources, & Energy Law Blog

Legal Analysis of Wildlife Corridor Acts’ Potential to Reverse Biodiversity Decline - Stephanie Oxley

Legal Analysis of Wildlife Corridor Acts’ Potential to Reverse Biodiversity Decline

Stephanie Oxley - LLM Student

  1. Significance of Habitat Connectivity and Safe Passage for Wildlife Conservation

Over a hundred years of road, rail, agricultural, and human sprawl have crisscrossed the United States, creating barriers and hazards to wildlife movement. These developments have downsized natural habitat and split it into fragments and isolated islands. Habitat fragmentation impairs species from interacting, leading to inbreeding and loss of genetic diversity. Impacts from climate change, droughts, fires, and weather changes will increasingly make safe crossings and connectivity between habitats an imperative for wildlife survival as the need arises to find new water resources, nutrients and cooler temperatures.


Roadway barriers impairing wildlife movement and the animal fatalities resulting from wildlife-vehicular collisions (“WVCs”) significantly contribute to biodiversity decline. There is a lack of scientific data collection on the number of animals killed per year trying to cross roads; however, estimates of those fatalities range as high as 400 million animals killed per year trying to cross U.S. roads.1 Road mortality is identified as the biggest threat to 21 federally listed species, with fifty percent of all endangered Florida panther deaths attributed to WVCs. 2 WVCs take a toll on humans as well with approximately 200 annual fatalities and costs averaging $8 billion a year.3


Recently, executive orders and state bipartisan legislation aimed at connecting wildlife habitat and creating safe crossings along wildlife corridors have emerged. Since March of 2019, New Mexico, Colorado, Oregon, Wyoming, New Hampshire, and Virginia have all passed wildlife corridor acts (“corridor acts”). Other states are considering similar legislation, including California, Utah, and Pennsylvania. The acts are a significant development in efforts to conserve wildlife and reverse the trend in biodiversity decline.


Corridors and safe crossings potentially result in significant advances in wildlife conservation. The Pronghorn Path in Wyoming became the first federally designated wildlife corridor in 2008. This corridor bisects US Hwy 191, where 140 mule deer and pronghorn were hit and killed annually.4 Subsequently, two overpasses and six underpasses with wildlife fencing were erected to provide safe passage, and the total number of WVCs dropped by 81% in those locations.5 In addition, a telemetry study confirmed improved habitat connectivity by following the movements of animals fitted with radio collars. The study found a 60% increase in back-and-forth movements by mule deer and 300% by pronghorn.6 The efficacy of this effort contributed to Wyoming’s designation of another three wildlife corridors by executive order.

As exemplified above, wildlife corridor and safe-crossing projects can potentially make a significant contribution to reducing biodiversity decline by connecting habitats and reducing roadway deaths. A recent flurry of state measures to codify a process for identifying corridors and improving connectivity is a hopeful sign for biological conservation that ensuring habitat connectivity and safe passage will become the standard.

  1. Important Corridor Act Elements for Effective Wildlife Conservation


New Mexico (“NM”) was the first state to pass a wildlife corridor act in March of 2019. Oregon (“OR”) and New Hampshire (“NH”) soon followed. Colorado (“CO”) and Wyoming (“WY”) governors signed executive orders, which may not have the longevity of legislative enactments. Depending on the state’s law, generally, an executive order (“EO”) can be replaced by a subsequent governor. Nonetheless, both executive orders call for immediate corridor actions that are likely to have a meaningful effect on wildlife conservation in those states. In February 2020, Virginia (“VA”) became the most recent state to pass a corridor measure.


The most important components to include in a corridor act are: a) the creation of an action plan, b) regular action plan updates, c) a mandate and authority to implement actions, and d) public participation. Many of the current corridor acts include these elements with varying degrees of potency. The following discussion will review the substance of these elements and survey effective and less effective approaches by the states in applying these elements. I also propose additional provisions to tackle unresolved issues of wildlife conservation on corridors and connectivity barriers in addition to roadways identified by the legislation.


  1. An Action Plan


A dynamic action plan should include: a) scientifically collected data, b) data analysis identifying naturally occurring wildlife corridors and barriers to connectivity, and c) a prioritized list of proposed actions/projects to improve safe passage along corridors. An action plan should be regularly updated to respond to new data and reflections on completed corridor actions.


  1. Scientific Data Collection To Identify Corridors & Prioritize Actions


Technological capabilities in tracking wildlife movements have improved, enabling wildlife managers to better understand migration patterns and to locate important wildlife corridors and barriers to migration.7 In discussing the 90% reduction in WVCs after building a wildlife underpass and overpass on a busy CO highway, a state biologist explained that the key to their success was placing the safe crossings where animals naturally travel. 8 In a14-year study reviewing the efficacy of 29 of 81 wildlife crossings constructed along 76 miles of MT’s I-93, video footage revealed that mule deer preferred overpasses and large culverts, elk and moose exclusively used overpasses, black bear used every structure, and grizzly bears exclusively used large culverts.9 The study found that some of the crossing structures were not effective.


Collecting scientifically sound data on wildlife movements and barriers to that movement before implementing an action is critical in placing an effective corridor crossing. The cost of a wildlife crossing can be in the millions, and those funds are more available if projects successfully reduce WVCs and show conservation connectivity improvements. Knowledge of the various species using a corridor will help agencies make better choices to provide effective safe passage for a location’s biodiversity. Collected information will help agencies make efficient decisions in prioritizing crossing projects.


Corridor acts including direction and prioritization of actions are more likely to manifest. Prioritizing corridor projects establishes a goal on which to aim efforts. It puts a state agency and the legislature on notice to budget and allocate resources for the material realization of a corridor project. Relevant agencies will make plans on how to implement actions to begin realizing the plan.


  Most current corridor legislation has directed its state department of transportation (“DOT”) to work cooperatively with the state’s wildlife agency in the creation of an action plan. NH and WY are the only states without an action plan. Although WY’s EO does not contain an action plan per se, it provides a similar framework for agencies to gather data, identify corridors using sound science, and make recommendations for additional wildlife corridors.10 NH’s corridor act contains strong declarations affirming wildlife conservation, provides useful definitions, and directs its DOT to act with wildlife corridors in mind.11 However, NH’s act is without a prescribed process for information gathering and corridor identification, which can result in inefficient and costly efforts made in locations of little consequence to wildlife movements. Also, without a prioritized list of projects, agency and legislators will not have corridor projects in mind when budgeting and allocating resources. A corridor act has little consequence on wildlife conservation if it does not culminate in an action that improves connectivity and creates safe passage.


  1. Action Plans Need Frequent Updates To Reflect Changes

On average, passed corridor acts have required action plan updating every 5 years, which is an important component to a corridor act. The corridor act will be more accurate if it is updated regularly to respond to new data. Climate change will invariably influence wildlife movements as drought, fire, and weather changes impact ecosystems. These changes may affect previous habitat identification and may factor into a reprioritization of the action list. In addition, agency reflections on completed projects may inform the agency requiring changes to and reprioritization of identified corridor projects. Most importantly for conservation purposes, reviewing and updating action plans will renew efforts to achieve corridor projects among agencies, legislatures, stakeholders, and the public.


  1. Clarity and Accountability Are Enhanced By Inclusion of Definitions


Definitions provide clarity and accountability about what is to be accomplished in an act. They explain the parameters of agency responsibility. Undefined key terms can cause confusion, which may result in less effective outcomes. The term “wildlife corridor” has been defined in some acts. In explaining that the term links two or more habitats, NH is the only act to make sure that “fish passage” is included in the definition. This addition is important because many corridor acts tend to contemplate large mammal movement, and without further explanation an agency may only think to consider large mammal corridors. In addition to understanding how to implement an act, definitions help create accountability by enabling a legislative body, a court, and/or the public to check on the proper administration of the corridor act.


  1. Effective Corridor Acts Include Authority to Implement Projects


To achieve biodiversity conservation, it is necessary for an act to mandate agency action and to provide authority to act on identified corridor projects. These provisions will prompt agencies to direct resources toward realizing a prioritized corridor project as opposed to legislation that only acts as a data clearinghouse.


Thus far, only DOTs have been authorized to implement corridor projects. Although this focuses a majority of corridor projects on roadway infrastructure and crossings, these efforts can make a substantial contribution to wildlife conservation. Roadways present a pressing hazard for wildlife with potentially 400 million animals killed a year on U.S. roadways.12 The broader the authority given to DOT to construct prioritized corridor projects, the more successful the act will be. NM’s corridor act was passed for the primary purpose of granting authority to DOT to create safe wildlife crossings that might be needed for conservation purposes outside of planned roadway infrastructure projects.13 OR grants its DOT a similarly broad authority to construct corridor projects, but limits those priority actions to those that relate to WVCs.14 CO and WY require DOT to consider big game migration in all levels of planning, and CO mandates construction of prioritized corridor projects as funds become available.15 NH’s corridor act has a similar directive, but limits its DOT to making minor adjustments to roads for conservation purposes, and requires additional approval for any wildlife construction projects.16 VA’s act does not instruct its DOT to include wildlife corridors in the planning process, but it is required to consider mitigation measures on any infrastructure projects threatening connectivity of habitat in an identified corridor.17 On its face, the corridor act of VA is the least likely to result in DOT taking an initiative to act on a priority wildlife corridor project, unless it happens to be located in a planned infrastructure project.


Only the WY EO formally designates wildlife corridors. The other acts outline a process for identifying corridors. Most of the acts instruct the wildlife agency to report and recommend priority corridor projects to the legislature. This may eventually result in the recommended action, but a provision providing tools to a wildlife agency to improve corridor connectivity will facilitate conservation efforts. Below, I will discuss this topic and make a proposal.


  1. Public Notice and Comment Facilitate Materialization of Project


Public notice and comment on action plans can both galvanize public support and/or opposition. Public comment gives agencies the opportunity to consider additional information and to respond to concerns, which may result in a better corridor project. Public participation can also energize a project and generate funding. Residents of Tucson, Arizona passed a sales tax increase in part to fund a $9.5 million wildlife overpass and underpass project to connect habitat bisected by a 6-lane highway.18 Also, in Southern California, concerned local citizens contributed 80% of the projected cost to construct an $87 million wildlife bridge connecting isolated habitat.19 Construction of an important but expensive corridor may hinge on public knowledge and support of the project.


With the potential resources available, one would expect all of the corridor acts to contain provisions for public notice and comment. However, with the exception of those in NM, OR, and WY, most acts do not contain a public comment period.20 NH does not contain an action plan or a framework for identifying and proposing corridor projects on which the public can comment. CO does not have public notice or comment, but it tasks agencies with looking for funding for corridor projects, including from the public.21 The extent of public participation in VA’s act is limited to posting a map on a public portal showing the location of high priority wildlife corridors.22 In enacting its EO, WY noted that making wildlife movements and habitats known to the public would give hunters an advantage.23 Even if the corridor location is not disclosed, the information will likely become known. Resolving this issue in future corridor legislation will be important in the acts ability to conserve biodiversity.


  1. Proposal to Lessen Barriers Along Length of Identified Corridor and to Conserve Wildlife on Identified Corridor and Habitat


Identification of wildlife corridors is important for conservation and reducing WVCs. However, that identification can create further threats to a species. In addition to corridor identification providing an easy target for hunters, a landowner might capitalize on the knowledge that their property is within a corridor and sell rights to hunters. Species survival often depends on its ability to be elusive. It would benefit wildlife conservation to include provisions in corridor acts that grapple with connectivity barriers beyond roadways and provide protection for identified wildlife corridors.


Roadways may be the most significant barrier and hazard to wildlife movement along a corridor. However, a non-exhaustive list of additional barriers includes fencing, agricultural developments, pipelines, power lines, dams, water diversions, and recreational activities in sensitive areas during nesting times. Managing these additional barriers is important in facilitating habitat connectivity.


Imposing restrictions related to corridor protections on private property owners is a politically sensitive issue. Even though there was strong bipartisan support for NM’s wildlife corridor bill, legislators were concerned that the measure would cause conflicts with landowners.24 To pass the bill, it was amended to ensure that landowner participation would be voluntary.25 Thus, including a provision in corridor legislation to engage in early discussions with landowners within the boundaries of a wildlife corridor or habitat will be important.


Agencies have had success using a variety of legal and market-based tools to achieve cooperation from landowners. Idaho’s wildlife agency and DOT involved stakeholders and found two landowners willing to allow easements on their land. This protected 1800 acres from development, connected two state land habitats, and allowed for construction of two crossings over a highway where 6000 mule deer and pronghorn crossed regularly.26 Agency efforts securing easements or acquiring land can have lasting benefits for wildlife; but where it is not possible, voluntary landowner cooperation may be secured by offering payment for a conservation service through fees or tax benefits. To meet Clean Water Act requirements, a utility offered to pay riparian landowners to plant trees along an Oregon river, providing shade to help naturally cool the water temperature.27 The effort succeeded in cooling river temperatures with the added conservation benefit of reviving a river ecosystem. Both the CO and WY corridor orders suggest incentivizing voluntary landowner cooperation. 28 There are numerous possibilities. Using a market-based strategy to encourage landowners to voluntarily facilitate movement and to refrain from causing harm to wildlife on the corridor will create an act that significantly conserves wildlife.


  1. Corridor Acts Potentially Curb and Reverse Declines in Biodiversity


Corridor acts with a framework for collecting data, identifying wildlife movements, and prioritizing actions to improve connectivity and safe passage are a boon for wildlife conservation. An act mandating and authorizing state DOTs to implement prioritized corridor projects and to make considerations for a diversity of species in future projects will result in a victory for biodiversity restoration. If the legislative momentum continues, corridor acts will have even greater impacts on biodiversity conservation that tackle connectivity barriers along the entire length of an identified corridor and make efforts to conserve wildlife on that corridor.

The horizon for more corridor legislation looks promising. Federal activities are underway to provide corridor funding and to create a federal corridor system. In July of 2019, the America’s Transportation Infrastructure Act proposed granting states $250 million toward the development of wildlife corridors and crossings.29 To expand big-game hunting opportunities, the Secretary of the Interior provided grants to states researching big game migration.30 A Wildlife Corridors Conservation Act, creating a federal corridor system was introduced in Congress in 2019 and is expected to be reintroduced to Congress with further bipartisan support in 2020.31 Bipartisan efforts to pass federal corridor legislation and allocate funding show broad support for corridor projects. This points to a brighter future for wildlife conservation.


1 Wildlife-Vehicle Collision Reduction Study: Report to Congress, August 2008.; and Braunstein, Mark Matthew, U.S. Roads Kill a Million a Day, Culture Change, (

2 Wildlife-Vehicle Collision Reduction Study: Report to Congress, August 2008.; and Defenders of Wildlife, Watch Out for Wildlife Facts,; and see (Gaskill, Melissa, The Plight of Florida Panthers, Nature, Feb. 12, 2019, The panther population is ~120-230 individuals; they need a range of 75-200 miles to hunt and breed and are now limited to 5% of their historic range. Sixty wildlife-crossing structures with fences were built along FL I-75, and a sharp reduction in panther fatalities were reported in these locations.

3 (Bies, Laura, Senate committee advances bill funding wildlife crossings,, August 13, 2019,; and ( .)

4 (Andrews, Candace Gaukel, Video: the Pronghorn Path, the First Federally Protected Wildlife Corridor, Good Nature Travel, Oct. 16, 2014,; and (New Crossing Structures benefit Wyoming wildlife, Associated Press, Nov. 2, 2012

6 (Id.)

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12 Braunstein, Mark Matthew, U.S. Roads Kill a Million a Day, Culture Change, (

13 (Dax, Michael, New Mexico’s Wildlife Corridors Act: A Path Toward Success, Rewilding Earth, June 16, 2019,

14 (

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18 (Loomis, Brandon, $9.5 million bridge just for wildlife opens near Tucson, AZ Central, May 11, 2016.)

19 (Weber, Christopher, California to Build Largest Wildlife Crossing in World, Associated Press, Aug. 20, 2019,

21 CO EO (

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24 (Dax, Michael, New Mexico’s Wildlife Corridors Act: A Path Toward Success, Rewilding Earth, June 16, 2019,

25 (Id.)

26 (Skroch, Matt and Callero, Nic; Idaho Workers to Make Travel Safer –for Drivers and Big Game,, January 27, 2020.)

27 (Porter, Laura et al., Water Quality and Temperature Trading in the Tualatin Basin, The Water Report, Issue #123, 2014.)

28 (; and, (

29 Senate and Environmental Works Committee, America’s Transportation Infrastructure Act, (

31 Wildlife Corridors Conservation Act, Wildlands Network, (