Big Axes: Deconstructing the Walls for Colorado Wildlife

A wildlife overpass over Colorado Highway 9 between Cremmeling and Silverthorne helps mitigate animal vehicle collisions in the area.
Hugh Carey / Summit Daily

Although I’ve never been a big game hunter, I’ve killed three deer in Colorado and will probably give a bull a headache. Not to mention my slaughter among rabbits and other small creatures.
Cars were my weapon, not guns.

Driving at dusk or in the dark of night will inevitably result in close brushes of wildlife, large and small, on many roads and highways. Even daylight has its risks.

Colorado is now redefining that dangerous and frightening feature between wildlife habitats and high-speed travel that we take for granted. State lawmakers delivered the message last year when allocating $5 million to wildlife connectivity that includes highways in high-priority areas.

In late December, government agencies identified seven locations where that money would be spent. It ranges from Interstate 25 south of Colorado Springs to Interstate 13 north of Craig near where it enters Wyoming. New fence and radar will be installed. Interstate 550 North Ridgway will get a tunnel.

The bowl was not deep enough to produce overpasses like the bridges that cross Interstate 9 between Silverthorne and Crempling or one between Pagosa Springs and Durango. But $750,000 was allocated for design work for the I-25 crossing near Raton Pass with a similar amount for the design of the I-70 crossing near Vail Pass.

In this way and others, Colorado could better compete for a tranche of the $350 million Congress appropriated in the 2021 Act to invest in infrastructure and jobs to improve wildlife connectivity.

This is on top of the I-25 bridge planned for the segment between Castle Rock and Monument to complement the four tunnels installed in the expansion project in recent years.

We focus on how we treat roads and wildlife habitats. We have always worked to protect human lives and property by reducing collisions. Our views have expanded. Human safety is still important, but so is the lives of creatures.

When we built the Interstate Highway System between 1956, and with the completion of I-70 through Glenwood Canyon, 1992, we paid little attention to wildlife. There were exceptions, like the deer narrow tunnel in Westville that was installed in 1969.

Biologists in the 1990s began to emphasize highways as home destroyers. They said the expansion of road networks leads to the creation of islands of wildlife habitat. Fragmented habitats lead to reduced gene pools and, in extremes, the risk of species extinction in some areas, which is called extinction.

I-70 has become a marquee for this. Wildlife biologists are starting to call it the “Berlin Wall of Wildlife.” The relevance of this phrase was clearly demonstrated in 1999 when a grown lynx was released just months before it attempted to cross I-70 near Vail Pass. He was struck dead.

With this graphic image in mind, wildlife biologists held an international competition in 2011 that featured I-70. The goal was, at least in part, to discover less expensive materials and designs.
Colorado’s pace has accelerated since a 2014 study documented declining West Slope mule deer numbers. In 2019, the incoming governor of Polis State issued an executive order to state agencies directing them to work together to solve road environment problems.

Two wildlife flyways along with tunnels and fencing north of the Silverthorn completed in 2017 are valuable examples. Studies have shown a 90% reduction in crashes.

“A reduction of 80 to 90% right off the bat is very typical for these structures,” says Tony Cady, director of planning and environment for the Colorado Department of Transportation.
State agencies, working with nonprofit groups and others, pored over the data to determine the state’s top 5% priority road segments. This data may give Colorado an additional advantage in accessing federal funds.

The two studies found 48 high-priority segments on the western slope and 90 east of the continental divide, including the Great Plains, according to Michelle Cowardan, a wildlife biologist with Colorado Parks and Wildlife. The Craig and Meeker areas have lots of high-priority routes, and much of I-76 between Fort Morgan to Julesburg has many high-priority segments.

Some jurisdictions go deeper. Eagle County has completed a wildlife contact study, and in the Aspen area, a nonprofit called Safe Passages has secured funding to begin identifying high-priority sites in the Roaring Fork and Crystal River valleys.

These new studies attest to a shift in public attitudes. The wildlife connection has become institutionalized in the way we think about transportation corridors, says Rob Ament of Montana State University’s Western Transportation Institute. Instead of waste, he says, transit has become a cost of doing business.

This is happening internationally as well. “My world is just exploding,” he said while reciting crossing elephants in Bangladesh and tigers in Thailand and working with other species in Argentina, Nepal and Mongolia.

If in some ways it’s taking too long, we’re redefining the relationship between highways and wildlife.

Allen Best
Great hubs/image courtesy

Allen Best publishes Big Pivots, which focus on climate change and Colorado’s energy and water transitions. See more at

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