Wildlife corridors, also referred to as wildlife crossings or animal bridges, were pioneered in the 1950s in France for reasons that were not friendly to animals: They were a way for hunters to coral deer. Since then, however, the concept has been expanded as a way to actually help wild animals, while simultaneously helping to curtail auto accidents that occur when large animals are hit by cars.
The Impact of Shrinking Natural Habitats
Humans have been altering the natural landscape since we evolved from hunter gatherers to farmers – a period referred to as the Neolithic Revolution, which began around 10,000 B.C. Yet, it was the Industrial Revolution, which started in Britain in the 18th century when humans started to have a dramatic impact on the natural world, and notably wild animals.
Not only did the expansion of where people live and work impact other species, but rural areas have also been impacted, as railways and eventually highways cut through wilderness areas. These ribbons of steel and asphalt present insurmountable, and even deadly, barriers for migrating wildlife, essentially chopping up their natural habitats.
When wild animals’ natural habitats are restricted, so does their access to food and potential mates. The result can be starvation as well as a restricted, gene pool, resulting in less healthy animals, and increasing the risk of extinction.
How Wildlife Corridors Save Animals and People
Wildlife crossings are also called animal bridges because they serve as a bridge, or a lifeline, that helps to keep natural habitats somewhat intact. Simply put, a wildlife corridor gives animals a safe route over or under a rail line, highway, or road. This improves access to food and increases the pool of available mates, resulting in a healthier wild animal population.
Wildlife corridors can also be tunnels that go under the roadway. While tunnels are a helpful alternative if crossings can’t be created. However, a wildlife overpass can be planted with native vegetation that creates a continuation of the ecosystem. This benefits not just animals, but native insects and plants.
In addition to the benefits to wildlife, giving animals an alternate route to crossing roadways and highways helps to prevent traffic accidents when motorists either hit an animal or swerve to avoid hitting one.
People around the world are building animal bridges to help local wildlife and keep people safe. Here are some notable examples of wildlife corridors around the world:
1. Natuurbrug Zanderij Crailoo “Ecoduct,” Hilversum, The Netherlands
Natuurbrug Zanderij Crailoo, which translates to “sand quarry natural bridge,” is located in the Netherlands, southeast of Amsterdam. It’s the world’s longest wildlife bridge. At 800 meters, or about a half of a mile long, it spans a highway, railway, river, sports complex, and business park. Completed in 2006, the corridor has created a safe route for deer, wild boar, and badgers to move freely between two wooded areas.
Natuurbrug Zanderij Crailoo isn’t the only wildlife crossing in the Netherlands. The country boasts more than 600 “ecoducts,” another term for wildlife crossings. Some of these ecoducts include small tunnels under roadways for fox and mice to travel freely.
2. Compton Road Wildlife Corridor, Brisbane, Australia
In Brisbane, Australia, 60 animals were being killed every year on the busy Compton Road when trying to cross it. So, a professor at Griffith University, Dr. Darryl Jones, set out to find a solution. The Compton Road wildlife crossings include not just a bridge over the busy roadway, but tunnels and canopy bridges as well.
Here’s a video with Dr. Jones talking about the Compton Road crossings:
Heavy rope has been used to weave canopies that enable possums to swing across the roadway, as if they were in the bush, and there are poles that gliders can leap to. There are tunnels under the road for small animals, links skinks and lizards.
Kangaroos and wallabies started using the vegetated overpass almost immediately. In the first 10 years since opening in 2003, only three wallabies have been killed on the highway, down from an average of 14 every year before construction.
3. Trans-Canada Highway Wildlife Corridors, Banff, Canada
Banff National Park in Alberta is one of the busiest tourist locations in Canada. It’s also bisected by the Trans-Canada Highway and the main southern rail line, the most important cross-country transportation corridor in the nation, with a steady stream of traffic year-round.
Not only are wild animals at risk when crossing this busy thoroughfare, but people have also been injured or killed when their vehicles collided with animals trying to cross it. Because of the danger to people and wildlife, in the late ‘80s, when construction upgrades began on the busy highway, 25 percent of budget was earmarked to reducing wildlife collisions.
In 1996, Parks Canada began constructing fencing along the entire length of the highway where it ran through Banff National Park, comprising 55 miles on each side. In addition to the fencing, park managers had a series of 38 wildlife underpasses and six overpasses built – a project that was not without ridicule by some Canadians. Yet, the past two decades have proven the project to be an outstanding success, drawing wildlife conservationists and other stakeholders from all over the world to model it back home.
200,000 Wildlife Corridors and an 80% Reduction in Animal-Vehicle Collisions
Elk began using the overpasses even before they were completed. In addition to elk, grizzly bears, moose, garter snakes, toads, and other wild animals have used the corridors. In all, over 200,000 wildlife crossings have been recorded. Grizzly bear biologists have found that the wildlife crossings have stopped the genetic isolation of the bears, which has improved the health of the population as a whole. Furthermore, animal-vehicle collisions are down by over 80 percent.
Due to the success of the project, more ecoducts are planned along the Trans-Canada Highway beyond the park to further protect wildlife and motorists.
Here’s a video from Parks Canada that documents the success of the project:
4. Henry Street Corridor, North Amherst, Massachusetts
Not all wildlife corridors are designed for bears and moose. On Henry Street in North Amherst, Massachusetts, spotted salamanders have been able to cross the road since 1987 using specially-constructed tunnels.
Spotted salamanders make the move every spring between their forest home and the vernal pools where they lay their eggs before returning again to the woodlands. The larvae then hatch and grow into young adults over the summer, who make their own trip to the woods before winter.
Unfortunately for the salamanders of North Amherst, a busy street lay between these two locations. Originally, concerned residents would scoop the little amphibians into buckets and carry them across, but in 1987 several groups worked together to construct a pair of tunnels to make the salamanders’ journey safer.
While some salamanders still cross aboveground, about 100-200 use the tunnels every year. Currently, the population of spotted salamanders in North Amherst is around 350, considered a healthy number to maintain their population.
5. Crab Routes on Christmas Island, Australia
The migration of the red crabs on Christmas Island off the coast of Australia is a big deal every holiday season. Over a two-week period in late December and early January, 50 million red crabs travel from their forest burrows to the sea, where they spawn and release their larvae into the saltwater. Afterwards, they return to their forest homes.
This heroic journey takes the crabs across many busy roads. Some roads are closed when the numbers of crabs become too great. However, wildlife underpasses and a bridge have also been built to helps the critters on their epic journey. To date, 31 underpasses have been created and a bridge build in a spot where a tunnel couldn’t be dug. The unique wildlife bridge lets the crabs climb the almost perpendicular sides via metal webbing.
Here’s a video of the crabs crossing the special bridge:
6. Turtle Tunnels Along the Railways, Kobe, Japan
Turtles are another species that have been impacted by the roads and railways crossing the path of their migration routes. In Japan, turtles were getting stuck between railway switches and then crushed by trains. So, The West Japan Railway Company and Suma Aqualife Park partnered to build tunnels under the rail lines to give the turtles a safe route under the rails.
The tunnels are not enclosed, but open from above so that workers can see if a turtle has not been able to get out.
Here’s a video of the turtles using the tunnels:
7. Nutty Narrows Bridge, Longview, Washington
Squirrels in Longview, Washington have had their own wildlife corridor since 1963. Over half a century ago, a bridge was constructed high above the roadway running between an office building and a city park, giving squirrels a safety route.
The bridge has become such a popular attraction that several more squirrel bridges have been erected in Longview.
8. Sonoran Desert Wildlife Passages, Tucson, Arizona
Aerial view of the Oracle Road wildlife underpass. Photo: Elizabeth Deupree, with support from Lighthawk, Inc. courtesy of Coalition for Sonoran Desert Protection.
A $9.5 million overpass and underpass system constructed in the Sonoran Desert outside Tucson, Arizona has helped to protect desert wildlife and motorists. Deer, bighorn sheep, javelinas, tortoises, and other wildlife use the system of overpasses and underpasses, and since they were constructed starting in 2000, elk and vehicle collisions alone are down by 90 percent.
9. Elephant Underpass, Kenya
An elephant underpass at the foot of Mount Kenya is reuniting two separated populations with great success. Built in 2013 for $250,000, the passageway has united the 2,000 elephants who live on Mount Kenya with a population of 5,000 elephants who live on the plains on the other side of a busy road.
The Mount Kenya passageway isn’t only elephant underpass on the continent. Others have been built in South Africa. In addition, India and China have also created safe passageways for elephants.
Here’s a video from the Lewa Wildlife Conservancy of the Mt. Kenya elephant passageway:
As with other species, the elephant populations have become increasingly isolated because of human development, and with access to a greater number of potential mates, there’s hope that the genetic health of the few remaining wild elephant populations will improve.
10. Collegiate Peaks Scenic Byway Wildlife Corridor, Colorado
Elk and mule deer on Colorado’s Western Slope are safer today because of a wildlife corridor under Highway 285, which allows them to move freely from their summer range in the mountains to their winter home along the nearby Arkansas River.
At a price tag of $3.5 million, the Collegiate Peaks wildlife corridor is part of the state’s efforts to end the widespread deaths of wild animals on Colorado’s roadways. In 2018 alone, over 4,000 bighorn sheep, bears, coyotes, and other species were killed in collisions with vehicles, at a cost of $80 million.
Colorado is part of a project by the Department of the Interior to identify and preserve wildlife corridors in the western states. Unfortunately, the main aim of the project seems to be to preserve “big game” for hunters, but at least there’s a recognition that wild animal populations should be able to move freely in areas that are their native habitats.
According to study published in PNAS, as reported by the Guardian, human beings have destroyed 83 percent of the wild animals on Planet Earth. Providing safe passage for them to reach critical parts of the natural habitat that we’ve intersected is the least of which we can do to help them survive.