Wild Collaboration + Road Ecology 101 = Safe Passage for Wildlife

From Spring 2021 NCWF Journal article, “Wild Collaboration: Safe Passage project applies road ecology principles in Western North Carolina,” by Frances Figart

A coalition of local, state, tribal and federal agencies, land managers, community members and conservation organizations is balancing the needs between native wildlife and the ever-growing human populations in east Tennessee and western North Carolina. The Safe Passage collaboration is working to make a perilous 28-mile stretch of I-40 in the Pigeon River Gorge safer for drivers and wildlife.

Research for the project is an example of road ecology, the study of how life is altered for both plants and animals when roads are nearby. Besides the risk of dying in attempts to cross, individual animals are disturbed by noise, light, and air pollution from roads near their homes. But highways create more insidious issues detrimental to entire species. 

“Collisions may be road ecology’s most obvious concern, but fragmentation is roadkill’s pernicious twin,” wrote Ben Goldfarb in The Atlantic. He demonstrated how roads are one of the largest causes of habitat fragmentation around the world due to the fact they carve up large landscapes where wildlife corridors had previously been unimpeded for millions of years. 

It wasn’t until the late 1990s that Harvard professor Richard Forman coined the term “road ecology,” and researchers began to study effects like the increased heart and respiratory rates of American black bears sizing up their crossing options along the I-40 right-of-way in the Pigeon River Gorge.

“Besides the immediate needs to improve animal and human safety, road mitigation is important for the survival of entire species,” said Steve Goodman, a wildlife biologist with National Park Conservation Association conducting research in the gorge. “The highways crisscrossing America are separating into jigsaw pieces what used to be one large piece of contiguous landscape where animals were free to roam and travel large distances in search of food, shelter, and mates. 

Wildlife is so stressed by crossing some busy highways that they will soon stop trying to cross altogether. When this happens, the result is the barrier effect, which means animals are subdivided into increasingly smaller isolated populations that can no longer interact. When species can no longer migrate across roads to reach the resources they need, their reproductive and survival rates plummet. Thus, the fragmentation of wildlife habitat eventually leads to extinction of species—a global problem.”

Habitat must be protected

The big picture is that wildlife crossings alone cannot solve the wildlife mortality problem. As our world warms, habitat must also be protected from development and fragmentation. As the population grows, so does the need to expand infrastructure. New roads are needed; old roads need to be widened. At the same time, private land is developed, and habitat is lost or degraded. Without incorporating road ecology into a planning framework, wildlife corridors can be severed, leaving remnant fragments of habitat resulting in increasing wildlife mortality.

“Interstate 40 cuts Great Smoky Mountains National Park off from large public lands such as the Cherokee and Pisgah National Forests to the northeast,” said Christine Laporte, eastern program director of Wildlands Network. Laporte helps steer the Safe Passage Fund Coalition. 

“Projected movements of climate-driven species suggest there will eventually be a high concentration of animals migrating northward into the Appalachians from further south. Securing habitat and safe passage across roadways is imperative here in the Southern Appalachian Mountains and throughout the Eastern Wildway —an extensive wildlife corridor linking eastern Canada to the Gulf of Mexico.”

WN’s chief scientist, Dr. Ron Sutherland, began to strategize for ways to address the problem in the Pigeon River Gorge back in 2015, and now partners with NPCA to direct the gorge research. He defines habitat connectivity as the degree to which organisms are able to move freely across the landscape. 

“A wildlife corridor is the term we use for a defined movement pathway that—if protected or restored—would provide essential habitat connectivity for one or more species,” he said. “Naturally one of the best places to put wildlife crossings is where you have a wildlife corridor that gets cut off by a highway.” 

High cost of wildlife collisions

Forest birds, reptiles, amphibians and small mammals are all at risk from vehicle collisions and the habitat fragmentation caused by roads. But colliding with a white-tailed deer, black bear, or elk causes the most property damage and safety risk for motorists. The cost of a deer-vehicle collision averages around $6,000; running into an elk can cost upwards of $17,000. 

Collision-related costs include not only those associated with vehicle damage and insurance but also dollars spent on human injury, illness, and mortality resulting from collisions, as well as costs related to highway delays and the lost value of wildlife associated with hunting. All these add up to roughly $12 billion in the U.S. annually. 

And those costs “are mostly based on human safety parameters and do not begin to touch on the high values associated with biological conservation or the economic value of wildlife to a local or regional economy,” said Dr. Liz Rutledge, North Carolina Wildlife Federation’s director of wildlife resources.

Road ecologists, conservation biologists and wildlife managers prescribe a buffet of wildlife crossing structures coupled with roadside fencing as the best method of increasing road permeability and habitat connectivity as well as decreasing collisions. But in the steep vertical terrain of the Pigeon River Gorge, the best solution is not always as obvious or as easy to implement as in more open landscapes. 

“Compared to out West, there is a relatively small amount of federally protected land in the East, and the Smokies and surrounding National Forest lands make up a substantial portion of it,” Goodman said. “Because of high-quality habitats and protections in the park, core populations of black bear and elk—and many other species—serve as source populations for dispersal into surrounding lands. Regionally and nationally, this area is widely considered to be of high conservation value and comprises key habitat corridors and associated hubs that are critical for the long-term flow of both plants and animals.”

He added, “In addition to reducing wildlife road mortality and improving public safety, our work will help ensure ecosystem resiliency across the broader landscape, particularly in the face of environmental changes and increased fluctuations due to climate change. Thus, another justification, and perhaps the most important for our work, is its eventual value of improving wildlife connectivity across the larger fragmented landscape.” 

Bill Holman, North Carolina’s state director of The Conservation Fund, said the Safe Passage project dovetails with his organization’s long-term work on fragmentation issues in western North Carolina. “The Fund has worked closely with the North Carolina Wildlife Resources Commission to create a new wildlife management area for elk and other wildlife in Haywood County that adjoins the park,” he said. 

“Our watershed protection work in Maggie Valley also provides a corridor for elk to move from the Smokies into the Plott Balsams and Great Balsams to the south. We’re also able to acquire key properties in North Carolina and Tennessee that wildlife can use to migrate from the Smokies across the Pigeon River Gorge; we handed off one conservation acquisition at Wilkins Creek to Southern Appalachian Highlands Conservancy a couple of years ago. Having healthy populations of elk, bear, and other wildlife draws visitors to western North Carolina and east Tennessee and sustains local economies.” 

Safe Passage: The I-40 Pigeon River Gorge Wildlife Crossing Project

“As habitat fragmentation continues and vehicle traffic increases, it becomes increasingly important to prioritize connectivity for wildlife to safely traverse roadways to fulfill their biological needs and reduce risk to drivers associated with wildlife-vehicle collisions,” Rutledge said. “The Safe Passage project’s focus on larger species creates educational opportunities to discuss the effects that both fragmentation and roadways have on smaller species, including aquatics, so we know that numerous other species will benefit from this collaborative work as well.” 

Potential solutions to the problem of wildlife mortality in western North Carolina might include new box culverts designed for wildlife, open-span bridges, bridge extensions, or underpasses to help large ungulates such as elk cross more easily. Vegetated wildlife overpasses that, when used in combination with nine-foot-tall fencing, have proven to help the greatest variety of species cross safely and to drastically reduce wildlife-vehicle collisions.

“Safe Passage is a bold initiative to provide just that—safe passage—for people and wildlife across an iconic Appalachian landscape,” said Ben Prater, southeast program director for Defenders of Wildlife. “It addresses a critical need for safe transportation and animal welfare. It’s our challenge to find the financial resources, meet the logistical challenges of construction, secure community buy-in, and attract the political goodwill to make it a success.”

Increasing highway permeability in the Pigeon River Gorge will be a giant step toward improving animal population health. But this effort will represent only the first project in a series of much-needed regional mitigation efforts. The I-40 corridor could serve as a model for other interstate highways that also disrupt the Southern and Central Appalachian corridor as well as the Eastern Wildway. 

“It is only in the last few years that changing attitudes have allowed room for acceptance of designs and expense to facilitate wildlife movement,” says The Wilderness Society’s Hugh Irwin. “This highlights the importance of the long view—it takes time for the right climate to exist for grand and ambitious plans like Safe Passage to find the right environment to thrive.”