Study of European Design Approaches to Enhance Wildlife Habitat

A recent U.S. study entitled Wildlife Habitat Connectivity Across European Highways highlighted Europe’s success in using innovative transportation designs to protect, preserve, and enhance the natural environment. This study was coordinated by the Federal Highway Administration (FHWA), U.S. Department of Transportation, American Association of State highway and Transportation Officials (AASHTO) and the Transportation Research Board; and was conducted by a select research team. Some of the research team research team’s findings and recommendations are presented below.

Summary of Recommendations. Habitat enhancement and re-establishment of habitat connectivity, which focus on reversing the damage transportation corridors have done to wildlife habitat, movement and survival, are gaining increasing attention in the U.S. with state and federal agencies. Although there are two Executive Orders that address compensation for habitat loss, EO 11990 (Protection of Wetlands) and EO 13112 (Invasive Species), the research team noted that European nations have stronger policy for avoiding impacts to wildlife and habitat and recommended that two ideologies from European policies be implemented in the U.S:

• An ecological (holistic) rather than individual species perspective for compensation/mitigation
• The principle of compatible land-use management in areas of highway structures built for wildlife passage.

The research team is also contemplating recommending policy to consider a broader context in which adjacent private lands could be included potential sources of contiguous wildlife habitat.

Habitat preservation and enhancement provided in conjunction with highway improvement projects contribute to the triple bottom line associated with sustainable development (economic, environmental and societal benefits) in many ways:

• Safety. Motorist safety can be greatly improved by structures that provide safe passage for wildlife and prevent animals from being on highways, and the significant costs related to motorist injuries and fatalities can be reduced.
• Value added. Habitat enhancements can improve the value of properties adjacent to highways and potentially add parkland opportunities that will benefit generations to come.
• Stability and survival. Critical flora and fauna connectivity can stabilize local ecosystems and ensure species survival.
• Environmental quality. - Wetland restoration and creation, which have been the most common forms of habitat restoration in the U.S., provide hydrological benefits such as stormwater retention (flood control), control of soil erosion, and filtration of water pollutants.

Implementing Sustainable Development. A process for implementing sustainable development into the protection and enhancement of the natural environment should follow the same logic as for other important environmental resources:

• Impact avoidance during construction, operation, and maintenance
• Impact minimization
• Impact mitigation
• Potential enhancement where feasible at relatively little or no additional cost.

After efforts at avoidance and minimization have been exhausted and the unavoidable adverse impacts to the natural environment have been identified, mitigation plans must be developed. The research team noted a myriad of mitigation measures in addition to the typical wetland restoration.

Structural Measures. The research team suggested numerous structural methods that are experiencing significant success in Europe and could be implemented more consistently in highway designs throughout the U.S. These include:

• Figure 1: Linville Viaduct, North Carolina

  Figure 2: Green Bridge Over A20 Near Grevesmulen, Germany

  Figure 3: Culvert Underpass for Reptiles and Amphibians

  Roadways constructed on viaducts, which pose the least impact to the natural environment (Figure 1), allow for excellent habitat/wildlife connectivity underneath, and minimize impact to for aquatic species.
• Fencing, which guides wildlife to crossing areas. Earthen ramps and one-way gates allow wildlife passage out of the right-of-way.
• Overpasses, or Green Bridges/Ecoducts, which have been the most successful structure as they allow passage for the largest spectrum of animals (Figure 2).
• Underpasses, which can be serve dual functions of facilitating drainage patterns and wildlife movements (Figures 3).
• Multi-use Structures, which are usually in the form of pedestrian and bicycle bridges that have a lane closed and covered with vegetation and natural features for wildlife crossing.
• Noise Barriers, which provide nesting for birds, but need to be used sparingly to prevent further habitat segmentation.
• Specialized Structures, which are tailored to one species, especially endangered species.

The team also noted some measures that have been tried, but not proven to be successful, including reflectors that beam light from headlights of approaching vehicles into adjacent habitats. Wildlife warning signage for motorists is not effective when used as a stand alone measure, but is effective when combined with speed limit signs, and even more so when flashing lights are added. Another variation that proved to be effective is one implemented by the Swiss, who use solar-powered heat sensors to detect animal presence and then trigger an electronic wildlife warning/speed reduction sign (Figure 6).

Nonstructural Measures. Nonstructural measures to modify animal and motorist behavior have also been tried, such as foams containing human, predator, or unpleasant smells applied to trees or structures; ultrasound; road lighting; and population control. While these are the most cost-effective, they have not always been successful. Those that were successful were only slightly so when used alone.

A Broad New Approach to Habitat Enhancement in U.S.

Within the U.S, a new regional perspective to sustainable highway design has been evolving recently through state and federal environmental protection agencies. The focus is on primarily:

• Wetlands/Habitat Banking
• Ecosystem Planning
• Right-of-Way Habitat Restoration.

Wetlands and Habitat Banking. Instead of the traditional on-site wetland/habitat mitigation approach, off-site (regional) wetland/habitat mitigation “banks” are being introduced in situations where on-site conditions are extremely limited. In general, a larger more contiguous habitat is preferable if ecological or habitat mitigation banking enhances the management and functions of an ecosystem by establishing larger, more sustainable mitigation sites that can:

• Provide an array of habitat types, especially within the wetland banks that require "buffer zones"
• Provide critical links to upland habitats and wildlife corridors
• Be of far greater benefit to fish and wildlife populations
• Ease management activities.

Economically, wetlands and habitat banks can be a means to recover some mitigation costs. In addition to the regulatory-required mitigation area, banks provide additional habitat acreage that can be sold to third parties to serve as mitigation for future construction projects in the same watershed or ecosystem.

A growing number of state departments of transportation are encouraging this mitigation option. Some excellent examples of upland and wetland banks across the U.S include Tennessee's Wolf River wetland bank, Michigan Mitchell's Satyr butterfly habitat bank, and Florida DOT's wetland banks.

Advanced Ecosystem Planning. The U.S. Fish and Wildlife Service and state environmental protection agencies have recently begun establishing protected ecosystems and "comprehensive mitigation plans." Highway construction projects within the boundaries of these protected ecosystems now have to provide mitigation that is consistent with overall ecosystem objectives, not just local habitat requirements. Examples include:

• Restoration of the south Florida ecosystem (Everglades)
• West Virginia's Appalachian Corridor H project, which addresses impacts to the Allegheny highlands ecosystem
• Washington's Mountain Loop Road project, which protects the Sauk River watershed
• Montana's Northern Rocky Mountains and Flathead River Ecosystem project to enhance grizzly bear habitat connectivity.

Right-of-Way Vegetation Restoration. AASHTO and FHWA are supporting on-going research into and the practice of right-of-way vegetation restoration with an ecosystem-level approach. This practice promotes economical landscaping that fosters habitation by native and regionally appropriate species within the highway corridor. Further information on this technique is highlighted in FHWA's newsletter, Greener Roadsides (Web site included in list below).

Keys to Success

Planning and Research. Proper wildlife research must be done prior to any alteration/restoration to wildlife habitat and/or related construction of crossing structures. Excellent sources of information include wildlife biologists, local hunters, and wildlife mortality ("road kill") data. Regional habitat computer models can be used to assess wildlife behaviors and patterns. Geographic information system (GIS) technology complements this tool by mapping ecotypes and possible linkage zones.

Wherever appropriate, human access and use should be coordinated with wildlife crossing structures, such as the addition of bicycle paths, pedestrian paths, picnic areas, observation areas, and park benches.

Monitoring and Maintenance. Crossing structures are typically monitored for one year and then revisited three to five years later. Monitoring methods include tracking, photography, infrared video, radio tracking and electronic counters. In Europe, computerized dispersion models (POLYWALK, SmallStep) are used to identify and evaluate a highway barrier's impact on species and landscape suitability.

Maintenance of the structures and adjacent habitat is critical to a sustainable habitat connection. Some sites will also require active seeding and maintenance of native plants on and adjacent to the structure. Local and national environmental groups can take part in long-term monitoring of the site, and eventually assume maintenance responsibilities, and even ownership.

Funding and Economics. Habitat enhancement projects should be coordinated with highway construction activities to take advantage of heavy machinery being available. Creative funding should always be explored through state and federal environmental protection grants, state and federal highway funding, and non-profit environmental groups, such as The Nature Conservancy. The establishment of parkland, preserves, eco-tourism sites, wetland banks, and habitat banks are perhaps the best means for providing sustainable funding for mitigation sites.