Case Study: Wildlife Crossings and Connectivity

Wildlife Connectivity

Ecosystems, native plants and, wildlife populations depend on habitat connectivity in order to survive. Connectivity is more than just wildlife corridors or linkages; it is the quality of a landscape which allows living things to live and move naturally. Wildlife movement is needed for many purposes, including foraging, reproduction, and migration. Wildlife populations decline when they are no longer able to move naturally, and natural movement is declining due to growth and transportation infrastructure.

Growth in Rural Areas

Nearly 90% of the land in the SACOG region is considered rural—mainly consisting of agriculture, protected/semi-protected open space, and rural residential development. Rural populations are projected to increase by 184% from 2005 to 2035. As rural populations increase, so will the demand for more roads and highways to serve transportation needs (also leading to an increase in total vehicle miles traveled). Transportation infrastructure growth has an unintended consequence—heightened risk to animals living in and moving through the region.

Wildlife Conflicts with Rural Transportation

[Roads and highways create a barrier effect for wildlife movement, resulting in habitat fragmentation and habitat loss, the two leading causes of species decline.

• Habitat fragmentation occurs when infrastructure is built in wildlife habitat, effectively barring natural ecological processes and movement. In the SACOG region, the urbanized core is fragmented, as there are only remnant native wildlife and plant communities. The rural areas are much less fragmented, but they face significant pressures to grow and develop. While 89% of the region is considered undeveloped land, less than 3 percent is protected wildlife habitat.
• Habitat loss occurs when people build infrastructure on land previously used by wildlife. As roads and highways are built, land around the transportation corridors is developed for residential, commercial, agricultural and industrial uses. These practices diminish natural resources and ecosystems. The International Union for Conservation of Nature (IUCN) estimates 40% of the world’s mammals are affected by habitat loss.
• Species decline occurs when individual animals and populations become isolated from each other and from essential natural habitat. Isolation leads to smaller, less stable populations due to inbreeding and low reproduction rates. According to the IUCN, half of all mammals in the world are declining, and one-third of all mammals are threatened. Exacerbating the species decline is roadway kills, which affect diminished populations significantly more than healthy populations.

Animal-Vehicle Collisions

Every year up to 1.5 million animal-vehicle collisions (AVCs) are reported in the United States, killing more than 200 people and injuring nearly 30,000. These accidents result in vehicle repairs and personal injuries costing over $1 billion annually. The majority of AVC deaths occur in rural areas. In turn, motorists kill nearly one million birds, reptiles, amphibians and mammals every day.

Wildlife Crossings

In order to link natural habitats, facilitate movement, and help protect animals from being killed by motorists, wildlife crossings over roads and highways are necessary. Currently, transportation projects are planned, funded, and designed before considering the potential impacts to wildlife and sensitive biological resources. The California Department of Transportation (Caltrans) is just beginning to incorporate wildlife crossings to transportation infrastructure. Extremely few structures are crossing-specific, but hundreds of transportation structures have had features added in order to make them accessible by wildlife. However, many more wildlife crossings are needed in order to save human lives and wildlife species. Crossings and linkages are categorized by environmental scientists in this way:

This case study will focus on wildlife crossing structures. The most common crossing structures are underpasses, pipes, and culverts. These structures can help facilitate safe passage for wildlife across an unsafe and unnatural barrier.

Case Study State Highway 16

State Highway 16, a two-lane rural highway

According to Dr. Fraser Shilling, Co-Director of the UC Davis Road Ecology Center, there are two main types of crossing that will be affected by increased volume on Highway 16: 1) landscape connectivity in the Eastern Coast Range, home to large mammals like elk and deer and 

Additionally, aquatic connectivity is in critical condition in much of California due to land-use, road development, and storm-water runoff. Disconnected stream systems are poor habitat to many native aquatic species, including fish. Highway 16 crosses seven creeks and sloughs between the town of Madison and the Rumsey casino. A culvert or bridge is located at each juncture, but most of them are too small for the volume of water in the creek, as evidenced by the frequent flooding along the highway. These inadequate structures contribute to the existing severe channel down-cutting and bank erosion along the creek, which further reduces aquatic connectivity and severs potential wildlife movement opportunities along the riparian. Wildlife are able to use these areas during summer months, but when the creeks become full, wildlife are forced to cross the highway surface.¹

Existing and Needed Policies & Practices

Europe is more concerned and well-informed about the effects transportation has on wildlife than the United States. Wildlife crossings, first created in France around 1950, have become standard practice in the development of roads and highways throughout European countries. In 2001, the U.S. Federal Highway Administration (FHWA) co-sponsored a wildlife crossings study tour of five European countries in order to obtain information the U.S. could use and implement. The U.S. does not have standard wildlife policies, practices, or requirements. However, there are at least 253 sizeable crossings for larger animals, 149 smaller crossings, and 397 aquatic crossings in the U.S. While State Departments of Transportation have recently started incorporating wildlife crossings into planning, the frequency of these efforts varies greatly. As there is no statute requiring attention to habitat connectivity, regulating habitat fragmentation (due to inadequate wildlife crossings, land sub-division, and traffic) has depended on standard environmental regulation (such as CEQA) that is not designed for this important task. Perhaps because of this, funding to help restore and protect connectivity has been hard to come by for governments and conservation organizations. California and the U.S. need new statutory requirements for habitat protection, restoration, and connectivity.

Existing Funding for Crossings

An effective wildlife crossing can be very expensive and funding is limited. Research, design, construction, maintenance, and habitat connectivity are all vital aspects of a successful crossing. The national Transportation Equity Act for the 21^st Century (TEA-21) provided dedicated funds for wildlife crossing structures and non-structural projects (such as fencing, signage, data collection and monitoring). Under the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU), TEA-21’s replacement, such dedicated funding is not available, though an expanded Transportation Enhancement (TE) category has recently incorporated funding assistance for wildlife crossings on both new and existing roads and habitat connectivity measures. Another funding source is the Environmental Enhancement and Mitigation Program (EEMP), which offers grants up to $350,000 every year for local, state, and federal governmental agencies and to nonprofit organizations, for projects to mitigate the environmental impacts caused by new or modified public transportation facilities. These projects include acquiring, restoring, or enhancing watersheds, wildlife habitat, wetlands, forests, or other natural areas. Once land and transportation agencies and officials understand the serious impacts of roads and highways, hopefully environmental impacts can be significantly reduced.

Change in Transportation Policy

The International FHWA study makes several recommendations for including wildlife habitat and safety in transportation planning practices. Recommendations include: incorporating wildlife issues into strategic plans, implementing stronger analysis of plans and alternatives, implementing a habitat-mitigation policy, and creating a “habitat banking” system similar to the current wetland banking programs.

Opportunities and Innovations

Caltrans is embarking on a statewide assessment of habitat and wildlife connectivity called the California Essential Habitat Connectivity Project. The project is intended to identify critical wildlife corridors and connectivity areas so wildlife needs can be evaluated earlier in state and regional planning processes. Wildlife habitat information will be incorporated into land use and transportation models, which will allow land use and transportation planners to consider avoiding, minimizing, or mitigating impacts to habitat and wildlife connectivity in scenario and long-range planning.

Questions for future study

• What is the best way to protect current wildlife corridors from land development that would prevent movement?
• How should wildlife corridor protection be prioritized?
• What are additional wildlife crossing ideas?

Footnote

i Dr. Fraser Shilling, Co-Director of the UC Davis Road Ecology Center, contributed to this article.