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Wildlife Crossings in Southern California

Updated: May 9, 2023

By Gabriela Lopez

If you have ever traveled alongside mountains and grasslands on the California highways, there is a good chance you have noticed wildlife crossing signs. People in urbanized areas in Los Angeles and Orange Counties may encounter the occasional black bear, deer, or mountain lion in their neighborhoods- especially if they reside closer to our local mountain ranges. Therefore, many people in our local counties are very close to these animals’ native habitats and our adjacent national and state parks put us in their natural habitat where we have to be more mindful when driving.

Wildlife and motor vehicle accidents can be unfortunately common on the roads and highways nearby to natural habitats, such as roads winding through forests or highways crossing through mountain ranges. According to National Geographic, there are more than one million automobile accidents per year involving wildlife in the United States alone. This shows that major infrastructure development, such as roads and highways, directly harms wildlife and divides animal populations, natural corridors, and habitats. It becomes more difficult for these animals to migrate, find food and shelter, and mate, which results in negatively impacting their genetic diversity and overall population.

Photo Credit: Gemma Ferrando

As major infrastructure development has grown, the native species in California has decreased, affecting the way wildlife migrates through their habitats. One way that government agencies have begun mitigating this impact on native habitats is the introduction of wildlife crossings to major urban areas. Wildlife crossings are bridges or tunnels that are built over or under major roads and highways to help local animals cross through to the rest of their habitat without risking their lives. Some wildlife crossings are concrete channels built beneath freeways, while others are green bridges that are built to look like natural pathways. These types of wildlife crossings are also known as an underpass, a viaduct, or an overpass. An underpass is a crossing in the form of a tunnel usually beneath a freeway, highway, or toll road, whereas an overpass is a bridge connecting one habitat to another by crossing over a freeway. A viaduct is similar to an underpass in that the wildlife will usually cross under a roadway, but it is much more open and allows the land to be left untouched while a road is constructed above. When deciding to construct a wildlife crossing, various agencies made up of scientists, policy makers, and city planners, must consider which habitats should be connected and which type of crossing should be used.

The first wildlife crossing was developed in France in the 1950s, later becoming very popular in the Netherlands, where over 600 crossings were constructed to help different native animal populations, such as wild boar, roe deer, and the endangered European badger. Over time, construction of wildlife crossings began in other countries, such as Canada, Australia, and most recently, in the United States. Here in the U.S., there are a few projects underway to help our wildlife migrate safely through their native habitat. In this century alone, the United States has constructed these wildlife crossings in multiple states, with each area experiencing the positive effects of introducing the local wildlife to safer and natural pathways. Some examples referenced by National Geographic are states Arizona and Washington, which both saw a decrease in the number of highway incidents involving wildlife and an increase in the usage of these crossings by the local wildlife.

Successful corridors have seen an increased number of crossings by large mammals, including bears, mountain lions, coyotes, and elk. Researchers have been able to see an improvement to species’ growth in population and genetic diversity thanks to the migration

Photo Credit: Trisha White

that these crossings have allowed, one example being the black bear. It has also made the roads and highways near natural habitats safer to drive as these crossings have decreased the number of motor vehicle incidents involving wildlife. Further detail describing how these crossings have helped our wildlife can be found here. Our urban development and infrastructure has clearly impacted our environment and the plants and animals living in surrounding habitats, but the introduction of wildlife crossings/corridors has greatly improved the conditions of these habitats and has allowed animals to safely roam through their natural habitats. Currently, there are many wildlife crossing construction projects ongoing, with a few notably happening right here in Southern California.

A new construction project in Los Angeles has been approved to add a wildlife crossing over Highway 101 and kicked off construction on Earth Day, April 22, of 2022. It is currently projected for completion sometime during 2025. This new wildlife crossing will not only allow the large mammals of the area to pass over 10 wide lanes, but it will also be the largest constructed wildlife crossing in the world to date! The placement of this crossing is crucial for the survival of the native wildlife, in particular, the mountain lion. The Santa Monica and Santa Susana mountain ranges are divided by this busy highway, causing unsafe and near impossible crossing for animals living in the habitats. With this disconnect, the wildlife, such as our mountain lions, are unable to roam across the mountains and find other food sources or mates outside their immediate family. This problem has become one of the main reasons that the National Wildlife Federation and the Santa Monica Mountains Conservancy partnered together to construct the largest wildlife crossing in the world. Furthermore, Governor Gavin Newsom has also promised $50 million for similar projects throughout California. Overall, this plan is just the beginning of evolving our urban infrastructure to blend in the surrounding environment so native species can coexist and thrive alongside us.

Photo Credit: Wallis Anneberg Foundation - model image illustrating how the bridge will help animals cross traffic.

As we continue to develop and expand our infrastructure, we will continue to have run-ins with our native wildlife and risk negatively impacting their habitats. With the establishment of wildlife crossings, these impacts can be mitigated and the number of accidents involving wildlife can continue to decrease. Various sources have pointed to the positive outcomes of implementing these crossings in the natural environments surrounding urban areas, therefore, staying informed of the potential spaces available for preserving wildlife and their habitats is incredibly important to secure thriving ecosystems. Doing our part in staying informed, contacting your local government, and continuing to drive safely on our highways are just some of the ways we can continue protecting our wildlife and ensure that they have the necessary connections to roam freely in their natural habitats.

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