Bridging highways could save the lives of bears and other large mammals.
Highways have given humans an unprecedented level of mobility, allowing drivers to access almost anywhere in North America by car. These roads are also very dangerous, the high speeds at which cars travel can make a small mistake a deadly crash. People are not the only ones who are at risk, as millions of animals include bears are killed by collisions with cars each year, hurting populations and causing around 8$ billion dollars in damages.
But the carnage of roadkill is avoidable. Wildlife crossings, structures that connect areas of forest or wilderness that have been bisected by highways, have been popping up in North America. Bypassing the highways allows the safe passage of bears, wolves, moose, and other large mammals, most of whom are running out of habitat. These bridges have drastically improved the numbers and health of these species, and could potentially expand the amount of wilderness space available for them to live.
The most obvious danger to wildlife that highways pose are collisions with vehicles. On the open road, cars travel fast, at speeds of 80 km/hr or greater, giving little to reaction time for drivers to stop for animals. Even if a driver did react quickly enough to avoid hitting an animal on the road, doing so would still be very dangerous. A driver could swerve into another lane or overcorrect and there’s no guarantee that other drivers will be able to make the same adjustments. Clayton Lamb is an ecologist with the University of Alberta studying the effects of humans presence on grizzly bear populations. His work has shown that human access into the wilderness via roads, both highways and resource roads, makes it more likely that animals will be in conflict with people or be and creates new opportunities for bear mortality.
But that’s only part of the problem. Highways in Western North America are often built through large expanses of wilderness. Large mammals such as bears or wolves need lots of space and roads cut down the available habitat. “Animals simply avoid roadways,” says Lamb. “The outcome of this habitat avoidance is a subtle form of habitat loss.” The situation isn’t getting any better. About 10,000 km of new resource roads added in British Columbia every single year. For comparison, the width of the contiguous United States only about 4,509 km. “As roads are pushed into previously inaccessible areas we are seeing an incremental erosion of wilderness in the west,” Lamb says.
Splitting up land also means splitting up populations, which can reduce gene flow and lead to genetic isolation. Without new individuals adding new genetic, a population can become susceptible to diseases. While highways may be a way for humans to connect, they serve as barriers for wildlife, keeping populations from mixing and having greater genetic diversity.
Bridge Over Troubled Traffic
There may, however, be a way to protect wilderness areas and wildlife from the dangers of highways without disrupting travel. Wildlife crossings have started up pop up in areas of Western Canada and the United States. These are structures that allow animals to cross roads safely, including bridges over highways or tunnels underneath the roads. One study showed an 80% reduction in the wildlife collisions on the Trans-Canada Highway thanks to wildlife crossings.
Wildlife crossings not only provide safe passages for bears and other species of animals, but they greatly increase the amount of habitat without drastically changing land use. This improves not only the amount of habitat but without the dangerous barrier of the highway, the quality of the habitat. Linking areas of wilderness also allow for different populations to interact, keeping gene pools diverse and populations stronger. Populations that can interact and interbreed have more genetic diversity. Lamb says “Wildlife crossings have been effective in restoring genetic connectivity for wildlife”
This is particularly important for species such as bears. Bears are apex predators, animals at the top of the food chain who have no other species hunting them. Apex predators are important for ecosystems, they keep the populations of their prey and smaller predators down and create a more robust ecosystem. Scientists call this trophic cascade, where the presence of top predators provides benefits throughout a food web. This means wildlife crossings could not only mean stronger bear populations but a stronger ecosystem overall.
There are many ecological benefits to building more wildlife crossings over highways. However, these structures are expensive to construct and questions still remain on whether new roads should be outfitted with overpasses or if old roads need to be retrofitted. Wildlife overpasses also don’t address the added air and noise pollution caused by cars and trucks on the road. Additionally, many public lands are used for their natural resources, these industries are responsible for much of the gravel road networks in North America and wildlife crossing are not feasible over this type of road network. More work needs to be done with land management and industries to make resource extraction more sustainable and in line with wildlife conservation.
There is, however, hope. Aside from making highways safer for wildlife, the crossings make travel safer for humans using the roads. More and more wildlife crossings are built each year, helping reduce collisions with bears, moose, wolves, and other large animals. An exciting initiative called Yellowstone to Yukon is working on several projects that would create a connected wilderness stretching from Northern Canada to Yellowstone National Park. The vision is to connect over 2000 miles of wilderness in one of the last intact mountain ecosystems on Earth.
Work still remains to give bears a protected habitat and humans do not have a great history of sharing the land with other large mammals.
- Vox has a great video one wildlife crossing and explores why there aren’t more of them.