Wildlife Bridges

By Kenedy Witherow
Sustainable Investment Group (SIG)

Have you ever been driving and wondered if there is a solution to reducing roadkill? Or wished someone could provide a solution to this problem to save the animals (and yourself) from some pain? I certainly have.

Roadkill is a major issue today that is not only dangerous for wildlife, but also can be life threatening for humans too. In the United States alone, there are more than 1 million automobile accidents per year involving wildlife, costing more than $8 billion in medical costs and vehicle repairs annually.

Some estimate that automobile collisions kill more than a million animals every day, which makes collisions the leading cause of death for many vertebrate species. Along with that, infrastructure often splits animal populations and habitats, which reduces the space animals have while also making it more difficult for them to find food, water, shelter, and mates.

With all of that in mind, it’s clear to see that we need a solution to this problem. That is why, in recent years, it has become more and more popular to design and build highway crossings for animals.

What are Wildlife Bridges?

The concept of a wildlife bridge first began in France in the 1950s, and it took off in the Netherlands, which now has more than 600 crossings to protect badgers, elk, and other mammals. Their largest wildlife crossing, Natuurbrug Zanderij Crailoo, is more than 0.5 miles long! It leads animals to safety across a roadway and nearby railways.

A wildlife bridge is what it sounds like – it’s a specially designed passage that goes above or below roadways that helps animals cross safely, while also protecting motorists.

Aerial image of the Natuurbrug Zanderij Crailoo crossing in Hilversum, Netherlands

Aerial image of the Natuurbrug Zanderij Crailoo crossing in Hilversum, Netherlands, which spans more than half a mile! Image sourced from https://www.atlasobscura.com/places/natuurbrug-zanderij-crailoo.

In Alberta, Canada, the Trans-Canada Highway divides Banff National Park into two. Between 1996 and 2016, 6 wildlife bridges and 38 wildlife underpasses were built for wildlife to cross safely. Studies have shown that these passes have been very successful! Between 1996 and 2016, studies demonstrated that the crossings have helped the grizzly bears maintain a wide selection of mates to stabilize their genetic flow, and the crossings resulted in an 80% reduction in motor accidents involving wildlife.

aerial photo of wildlife bridge in Banff National Park

Wildlife bridge in Banff National Park, offering a safe way for animals to cross. Image sourced from How creating wildlife crossings can help reindeer, bears – and even crabs | Wildlife | The Guardian

Wildlife bridges have been slower to take off in the US than in other countries, but there have been several crossings constructed in the Western US in recent years. Arizona has constructed 20 crossings since 2000 and has experienced a 90% drop in wildlife-related highway accidents in an area known for migrating elk populations. In 2018 in the state of Washington, authorities constructed an underpass and 2 bridges, and before they had even been finished, deer were actively utilizing the bridges to cross safely!


The less common approach is to construct ecoducts for smaller creatures. In 1995, the city of Davis, California built a 6-inch-wide tunnel for frogs to pass under the road towards a wetland. This is another clever method of saving some animals from becoming roadkill.

Newest US Wildlife Bridge

In Los Angeles, the Wallis Annenberg Wildlife Crossing, the largest wildlife crossing in the world, recently broke ground on Earth Day 2022 and is expected to be completed in 2025. This wildlife bridge will cross 10 lanes of traffic and scientists expect it to majorly improve the genetic material of populations in the Santa Monica Mountains and surrounding areas, while also providing local wildlife with a better quality of life.

Planning for this wildlife bridge took over a decade and was aided by the famous mountain lion “P-22” who played a large role in gathering support for the project and making it possible.

P22 became famous after becoming the only mountain lion to have successfully crossed the 10-lane interstate from the Santa Monica Mountains into Hollywood Hills and Griffith Park, where he “visited” neighborhoods in the area and became a celebrity. People would find him on their porches, in their backyards, or walking through town. People posted him all over social media and he became an ambassador for wildlife protection. P22 was tracked and studied by the National Park Service since March 2012 until his death in December of 2022. Unfortunately, P22 was hit by a car in December and was euthanized at the San Diego Zoo after they also discovered underlying medical issues. He lives on as a symbol for urban wildlife protection and inspired a new era of urban conservation.

To follow the progress of the Wallis Annenberg Wildlife Crossing, you can visit https://savelacougars.org  and watch a timelapse of the construction. I’m eager to learn about the effects on wildlife once the bridge is constructed.

rendering of the Los Angeles wildlife bridge

Rendering of the Los Angeles wildlife bridge, courtesy of the National Wildlife Federation. Image sourced from https://dailybruin.com/2022/07/17/worlds-largest-wildlife-crossing-begins-construction-in-los-angeles.

Wildlife bridges can help save billions of animals from being hit by automobiles each year, while also keeping people safe. They also can help reduce the impact of infrastructure on fragmenting ecosystems and animal populations. I hope to see more wildlife crossing projects in the future, and I hope that it can become the norm for roadways all over the world.







© 2023 Sustainable Investment Group (SIG). All rights reserved.