July 16th, 2012 by

When driving down the highway, I usually find myself wincing as I pass under a bridge. The idea of 1,000-pound cars and trucks driving over me in my little car is never something that has made me comfortable. But I am not sure how I would feel looking up to find a bear or a moose casually walking across the bridge above me.

A green bridge over a highway in Boeblingen, Germany.

A green bridge over a highway in Boeblingen, Germany. Credit: Klausfoehl/Wikimedia Commons

In Canada and other countries, wildlife overpasses have been built or are being built to cater to passing wildlife such as bear, elk and lynx. These bridges provide safe and secure pathways for animals to cross over busy highways and freeways. The overpasses, also known as green bridges or ecoducts, are generally covered with soil and vegetation constructed to resemble the forests that lie on either side of the bridge. What do the animals think about these overpasses and do they use them? In Canada’s Banff National Park, there are currently 41 structures for wildlife crossing. Since they started monitoring usage in 1996, 11 species of large mammals like bears, elk and cougars have gone across these green bridges more than 200,000 times. These structures are definitely a step in the right direction when it comes to creating opportunity and safety for wildlife and also serve as a reminder that the construction of roads creates a huge impact on many wildlife species and the environment they live in.

A black bear in Waterton Lakes National Park in Alberta, Canada.

A black bear in Waterton Lakes National Park in Alberta, Canada. Credit: Katrina Bowman/Flickr

Every day, animals lose their homes to highway construction, timber harvesting, agriculture conversion and urban and residential developments. And those animals whose habitat is left behind often find themselves dealing with habitat fragmentation, as new roads and highways are being paved right in the middle of many species homes. For most animals, the ability to periodically change location is an important part of life. When forests are cut down to make way for roads, the areas where wildlife were once free to roam are divided into smaller subdivisions of land. When species are confined to these isolated areas, the stability of their population suffers with increased difficulty in finding food and breeding ground, and while many species can create homes and nests in small sections of forests, many need much more area to survive.

American Forests has recognized the threat forest fragmentation poses to ecosystems and wildlife and is working to build back habitat for a variety species. In Louisiana, we are working with the National Wild Turkey Federation to replant 20,000 bottomland hardwoods to reconnect the area’s forest for migrant birds, mammals, reptiles and amphibians. We are also working in the Lower Rio Grande Valley to connect fragmented ecosystems along the Rio Grande River that were separated by urbanization and farmland. This project will help rebuild habitat for species like the endangered ocelot and jaguarundi, as well as migratory birds.

As the world population continues to grow, it’s likely that forests and other ecosystems will often come face to face with issues around new roads and developments. It is important to be aware that human impact is the cause for much of the habitat loss and habitat fragmentation. Planting trees to reconnect forests and building overpasses as a way for animals to travel across busy highways are both good steps in the right direction.