Mitigation Measures and Recommendations in the USA to Reduce Environmental Impacts of Transportation Infrastructure on Wildlife

Fengxiang Qiao, Boya You, Qing Li^* and Lei Yu

Innovative Transportation Research Institute, Texas Southern University, 3100 Cleburne Street, Houston, Texas, 77004, USA

Corresponding Author:

Qing Li
Post-doctoral Fellow
Innovative Transportation Research Institute
Texas Southern University, 3100 Cleburne Street
Houston, Texas, 77004, USA
Tel: 713-313-7532
E-mail: liq@tsu.edu

Received date: July 14, 2017; Accepted date: July 25, 2017; Published date: July 29, 2017

Citation: Qiao F, You B, Li Q, Yu L (2017) Mitigation Measures and Recommendations in the USA to Reduce Environmental Impacts of Transportation Infrastructure on Wildlife. Environ Pollut Climate Change 1:135. 10.4172/2573-458X.1000135

Copyright: © 2017 Qiao F, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Abstract

Serious and adverse conservation consequences of transportation infrastructure have not only altered the landscape but have also become a source of pollution to impact the entire environment and the living styles of wildlife in the planet. The design, construction, operation and management of transportation infrastructure should therefore consider their environmental and ecological impacts from the point of views of conservation biology and environmental science. This paper summarizes the mitigation measures in the USA to avoid, minimize and mitigate negative environmental and ecological impacts of transportation infrastructure on wildlife movements, including wildlife crossing structures and fencing. The review of existing efforts to enhance wildlife crossings in the USA and federal/state level guidelines and recommendations are presented, together with the cost-benefit analyses. It is recommended that each local transportation agency proposes implementation steps to examine the current practices to reduce the negative impacts of transportation infrastructure on wildlife and make recommendations on how to systematically incorporate the successful design practices into their local transportation projects.

 

Keywords

Environmental impacts; Ecological impacts; Wildlife; Transportation infrastructure; Mitigation measures; Cost-benefit analyses

Impact of Transportation Infrastructure on Wildlife

On July 7, 2017, some passengers at the New York John F Kennedy (JFK) International Airport encountered a flight delay due to the slow marching of about 40 diamondback terrapins (a kind of turtles) crossing the tarmac of the airport [1], which is the busiest international air passenger gateway into North America [2]. This situation is similar to what Schweber [3] described in Figure 1 and is definitely one of the typical examples illustrating the impacts of transportation infrastructure on wildlife.

There is an increasing need of transportation infrastructure in peoples’ daily lives with the development of transportation related technologies and the evolution of civilization of human beings in the recent centuries. About 20% of land area in the United States is directly and ecologically impacted by roads [4,5], including habitat fragmentation/isolation, connectivity loss, quality changes, barrier effects, mortality/road kill, direct and indirect effects to threatened and endangered species, etc. [5,6]. Serious and adverse conservation consequences have not only altered the landscape but also become a source of pollution to impact the entire environment and the living styles of wildlife in the planet [4]. For example, habitat fragmentation by highways led to inbreeding among the mountain lions in the Santa Monica Mountains in Greater Los Angeles [7]. So the design, construction, operation, and management of transportation infrastructure should consider their environmental and ecological impacts from the perspective of conservation biology and environmental science.

Part of the transportation infrastructure such as roadsides, railway margins, and waterways sometimes serve as linear habitats for wildlife, particularly small mammals and insects [8,9]. For example, birds may feed on the grit on roads and mountain goats are attracted by roadside vegetation. In this way, road construction creates high quality edge habitat [10]. However, in most cases, roads create barriers and serve as an inhospitable environment for most. For example, road construction and expansion reduce the area of natural habitat and landscape connectivity by transforming natural habitat into pavement, which will significantly affect the movement of animals that regularly move to different habitats [11]. Animals were prevented from crossing the road to meet their daily, seasonal and basic biological needs because of the high traffic volume and high-speed vehicles. Besides, noise and artificial lighting effects, such as traffic noise and the light from vehicles, can reduce bird population densities [12] and noise levels have been shown to affect animal use of wildlife crossing structures [13].

Additionally, road kill (wildlife-vehicle mortality) is responsible for the reduction in wildlife population. State Farm’s insurance claims State of Texas in the USA has the highest number of wildlife-vehicle collision (WVCs) involving deer, elk and moose from 2012 to 2013 [14]. A report presents that the annual cost of reported WVCs in South Dakota is $107.9 million and the wildlife values are over $29.6 million each year [15]. In 2010, the costs of 4,668 WVCs to Pennsylvania were $14,484,804 [16].

Mitigation Measures

Mitigation measures have been developed and applied to avoid, minimize and mitigate negative impacts of transportation on wildlife movements. The most commonly applied mitigation measures to reduce WVCs are wildlife crossing structures and fencing.

Wildlife crossing structures

Wildlife crossing structures are designed to increase permeability and habitat connectivity across roads and reduce motor vehicle collisions with wildlife, consequently reducing the likelihood of damage to motor vehicles [17]. Wildlife crossing structures include underpass tunnels, viaducts, overpasses, amphibian tunnels and culverts [16].

Wildlife crossing structures are designed to increase permeability and habitat connectivity across roads and reduce motor vehicle collisions with wildlife, consequently reducing the likelihood of damage to motor vehicles [17]. Wildlife crossing structures include underpass tunnels, viaducts, overpasses, amphibian tunnels and culverts [16].

The design of the wildlife crossing structure is associated with landscape and wildlife species groups. The wildlife species groups are defined and documented in the Wildlife Crossing Structure Handbook are shown in Table 1, while the general design specifications of wildlife crossing structures are in Table 2.

Table 1: Wildlife species groups [5].

Table 2: Minimum and recommended dimensions of wildlife overpass/underpass designs [5].

It is noticeable that bird species as an important member wildlife family have been neglected from the crossing structure. The inclusion of birds in the list ensures transportation project design and construction to respect and leave intact the natural environment, particularly vegetation, water systems and wetland, along the roads to be built. Most of the structures are for wildlife only; however there are indeed some can also serve for seasonal drainage and human activities. Each of them has different dimensional specifications.

Fencing

Fencing is a common and robust mitigation measure to reduce WVCs with large mammals [18,19], to keep selected species away from roadways and sometimes guide wildlife to safe crossing structures [5]. The fences are typically implemented at the ‘hotspots’ of WVCs and need to extend further than the hotspot to prevent ‘fence end run’ [20]. Both the home range for the target species and the length of the ‘hotspot’ are considered in fence’s design [21,22]. Fences are typically installed on both sides of a roadway with both ends ending opposite of each other to prevent animals to be kept on roads by a one-side fence. Fencing is typically implemented in conjunction with wildlife crossing structures because fencing alone may increase barrier effects and incidentally impedes wildlife access to critical resources such as water, forage and cover [23-25].

Construction Guidelines for Wildlife Fencing and Associated Escape and Lateral Access Control Measures (AASHTO) reviewed current state of knowledge and practice regarding the design, implementation and maintenance of wildlife fencing. Fence material and dimensions are discussed in the guidelines, regarding three species groups: large mammals, medium mammals and reptiles and amphibians. Arizona Game and Fish Department published guidelines for wildlife compatible fencing to assist landowner, project manager and land management agencies in designing fences with least impact to wildlife [25]. Specific recommendations of fencing are documented in this report for different species including pronghorn, bighorn sheep, deer, elk, etc. Guidelines of effectiveness measurements and maintenance of fences can be found in roadway design manual published by Pennsylvania Department of Transportation (PennDOT) in the USA.

Structure Selection and Placement

Four basic principles regarding wildlife crossing structure placement are: topographic features, multiple species, adjacent land management and larger corridor network [5]. Wildlife crossings should be placed where movement corridors are associated with dominant topographic features. Sections of roadways can be ignored where terrain and land cover are unsuitable for wildlife and their movement. Besides, crossings should be designed to accommodate multiple species. Most importantly, wildlife crossings must connect to larger corridor networks, but not ‘ecological dead ends’ [5]. Different approaches used by transportation agencies to locate wildlife crossing structures are summarized in Table 3. Each of them has different needs of data and models.

Table 3: Summary of wildlife crossing structures placement approaches.

It should be noted that there is no simple formula to determine the spacing of wildlife crossings because each site is different and design should be landscape- and species-specific. For example, water frogs prefer the tunnels to the grass while agile frogs prefer grass [26]. Thus, crossing success highly depends on the material and design of tunnel. Moreover, improper design may lead to negative effects.

Planning resources for wildlife crossing structures site selection include but not limited to:

• Maps (aerial photos, land cover-vegetation maps, topographic maps, land ownership maps and wildlife habitat maps)

• Data (wildlife movement model data, wildlife ecology field data, wildlife road-kill data, and road network data)

Detailed descriptions of each resource and how it can be used for project-level and systems-level planning can be found in Chapter 3 of the Wildlife Crossing Structure Handbook.

The USA Federal and State Level Guidelines and Recommendations

Overall views of existing efforts to enhance wildlife crossings in the USA

In the USA, the Wildlife Crossing Structure Handbook provides key design and ecological criteria, construction and maintenance guidelines, effective monitoring techniques and solutions to wildlife-vehicle interactions by offering effective and safe wildlife crossing examples. This handbook defines a series of criteria, which can be used for future project prioritization. Three key questions during the planning process are identified in the handbook: 1) where should wildlife crossing structures go; 2) what should they look like; and 3) how will they perform [5]. Correspondingly, project and program level considerations are identified for planning, placement and design of wildlife crossing structures.

Many states in the USA do not have a standardized process of data collection, analyses, and project prioritizations. Several regional and statewide projects have developed their own framework and procedures, which can be used as references. Table 4 shows the summary of data collection, analyses and prioritization methods by state [15].

Table 4: Summary of data collection, analyses and prioritization methods by state.

Commonly, these states examine WVC data, collect WVC carcass data, map carcass data and crash data to identify problem areas, perform analysis using AADT data for all roads; and perform analysis using wildlife habitat maps and wildlife linkage maps in their project prioritization process. Some states have developed guidelines for wildlife crossings to standardize the processes of data collection, data analysis, planning, project prioritization, design, effectiveness measurement and maintenance. As examples, the guidelines and reports in Florida, California, South Dakota, and Texas are summarized in following subsections.

Florida

Wildlife crossing guidelines have been developed for use by the Florida Department of Transportation (FDOT) to evaluate proposed projects or retrofit projects on the State Highway System. Key recommendations and guidelines include:

• Any state or federal highway safety criteria or FDOT design requirements cannot be compromised. If not approved, consider redesigning and coordination with agencies to select the feasible feature

• No restriction of legal access to or negatively impact on neighboring property owners without written approval

• Having no damaging impact on existing drainage system

• Cost efficient and biologically effective feature that meets the requirements of USFWS and FWC and regulatory agencies as well

• Avoiding and minimizing upland and wetland habitat as well as lighting at the sites accessible for maintenance

• Considering cost-benefit analysis while implementing different types of features

• Active review and monitoring of post-construction upon request

California

The Califorrnia Department of Transportation (Caltrans) published a Wildlife Crossings Guidance Manual, which is a literature-based guide on how to identify and assess wildlife crossings and includes a review of best practices and effective strategies [27]. A Wildlife Crossing Process Decision Tree to identify wildlife crossings is proposed in this manual. This manual provides a series of methodologies (e.g. survey methods, data collection approaches) for baseline assessment and project impact assessment. Moreover, methodologies to identify wildlife crossings are documented in this report: 1) repeated observations of wildlife crossings, 2) a section of roadway with a high rate of vehicle-animal collisions, 3) professional judgments of biologists, 4) field surveys of obvious wildlife corridors, 5) suspected movement corridors with track plates, raked soil, remotely-triggered cameras to identify species present, 6) modeling of wildlife corridor based on occurrences, wildlife habitat, and habitat connectivity, 7) GIS models analyses, and 8) combined detection approaches.

South Dakota

South Dakota Department of Transportation (SDDOT) reported that the most common WVC data source is law enforcement and safety departments. However, carcass data collection is loosely enforced and there are very limited resources for data management. South Dakota adopted three steps to identify high priority areas for WVC problems: 1) crash and carcass data collection through South Dakota Accident Reporting System database, 2) mapping of crash data using ArcGIS, and 3) agency collaboration and cooperation. SDDOT also proposes the process and framework for agencies to identify mitigation measures with decision support tools.

Texas

Table 5 summarized the impacts of transportation on endangered and threatened animals in Texas. There is no statewide process to report WVC carcass data at TxDOT and TxDOT environmental staffs in headquarters are unaware of the magnitude of WVC in state [15]. There are 25 semi-autonomous districts in TxDOT, which makes difficult to track actions, raise awareness and support for wildlife mitigation actions. Besides, planning for wildlife in transportation is locally driven and also driven by the U.S. Fish and Wildlife Service.

Table 5: Endangered and threatened animals in Texas [33].

The Programmatic Agreement of the 2013 Memorandum of understanding between TxDOT and Texas Parks and Wildlife Department (TPWD) defined Best Management Practices (BMPs). In that agreement, a list of Rare, Threatened, and Endangered species of Texas and some standard recommendations were provided to avoid killing or harming any wildlife species during the implementation of TxDOT projects. These recommendations include a) Vegetation BMPs; b) Water quality BMPs; c) Aquatic mitigation; d) Invasive species BMPs; e) Reptile BMPs; f) Rookeries; g) Stream Crossings and h) Wildlife crossings.

Examples of efforts by TxDOT are presented in the cases of bobcats and bat colonies. In Texas, use of culverts by bobcats was positively related to the openness ratio of the culvert and the amount of vegetation adjacent to the culvert. Fences erected to funnel wildlife toward culverts did not increase overall use of culverts, but may have increased use of the high-quality culverts [28]. Modified culverts were tried on US-98 in Texas for ocelots and bobcats [29]. Existing culverts were modified with a 0.46 m wide × 0.30 m high (18 inch × 12 inch) elevated concrete walkway to allow animals to move through even when water was present. However, ocelots were not shown to use the culverts. This was largely attributed to the low population in the area. More recently, Tewes et al. [30] studied the ocelots along transportation corridors in southern Texas by looking at road kill and habitat features to help determine locations for future crossings and develop management strategies.

Another example is the bat colonies. Bats frequent some bridges and even box culverts on TxDOT right-of-way. Some TxDOT districts have built box culverts that contain recessed roofs with textured surfaces to provide roosts for bats. If bat colonies are found on existing structures, contact the Texas Parks and Wildlife Department to determine what steps should be taken that may affect the bats. Incorporate these wherever possible. TxDOT has posted information regarding bats and structures on its DOT website. Bat Conservation International is a non-profit organization that has published a primer on bats and highway structures and alternative design details for accommodating bat roosts. Texas is one of states that are managing bridges for bats with greater success [31].

Costs-Benefits of Mitigating Measures

The costs associated with mitigating wildlife/vehicle conflicts can be substantial and these costs increase through time. It was estimated the average costs for each deer, elk, and moose collision are US$8,015, US$17,475 and US$28,600 respectively [32], which include costs associated with vehicle repair, human injuries, human fatalities, towing, accident attendance and investigation, hunting and recreational value of the animal concerned and carcass removal and disposal. Other costs fobr maintenance, financing and impact of construction on traffic are excluded. Furthermore, costs and benefits can vary widely for different sites and situations (e.g. geographic locations, effectiveness, frequency of WVCs, surrounding terrain). Table 6 summarizes the costs of various mitigation measures and their effectiveness in reducing WVCs, specifically deer-vehicle collisions (DVCs).

Table 6: Summary cost/benefit of mitigation measures* [22].

The materials costs of several types of structures for enhancing wildlife passage for a variety of mammals are estimated in Table 7 and were derived from the 2003 Caltrans Contract Cost Data book. These costs are variable depending upon site and application-specific characteristics and include material costs alone; installation and maintenance costs are additional. It is suggested that collaboration with a design engineer and project manager are essential in understanding the design and costs associated with proposed structural improvements or installation.

Table 7: Crossing structure materials costs of caltrans [27].

Conclusion and Recommendations

In this paper, the mitigation measures and cost-benefit analyses to reduce the environmental and ecological impacts of transportation infrastructure in the USA are reviewed and summarized. It is recommended that each local transportation agency proposes implementation steps to examine the current practices to reduce the negative impacts of transportation infrastructure on wildlife and make recommendations on how to systematically incorporate the successful design practices into their local transportation projects.

Acknowledgement

The authors acknowledge that this paper is supported in part by the National Science Foundation (NSF) under the grant #1137732. The opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funding agencies.

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