Big Pivots: Dismantling Wildlife Walls in Colorado

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

Although I was never a big game hunter, I killed three deer in Colorado and probably gave an elk a terrible headache. Not to mention my carnage among rabbits and other little critters.
Cars were my weapon, not guns.

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

Colorado is redefining that risky, jagged boundary between wildlife habitat and high-speed travel that we take for granted. State lawmakers delivered a message last year by allocating $5 million for wildlife connectivity involving highways in high-priority areas.

In late December, state agencies identified seven places where that money will be spent. They run from Interstate 25 south of Colorado Springs to Highway 13 north of Craig near its entrance into Wyoming. New fence and radar technology will be installed. Highway 550 north of Ridgway will have an underpass.

The pot was not deep enough to produce overpasses such as two that cross Highway 9 between Silverthorne and Kremmling or one between Pagosa Springs and Durango. But $750,000 was allocated for the design work of the I-25 crossings near Raton Pass with a similar amount for the design of an I-70 crossing near Vail Pass.

In this and other ways, Colorado can better compete for a slice of the $350 million allocated by Congress in the 2021 Infrastructure Investment and Jobs Act to improve wildlife connectivity.

This is in addition to the I-25 overpass planned for the segment between Castle Rock and Monument to complete the four underpasses installed in the expansion project in recent years.

We are changing the way we look at roads and wildlife habitat. We have long strived to protect lives and property by reducing collisions. Our perspectives have broadened. Human safety still matters, but so does creature life.

When we built our highway system between 1956 and, with the completion of I-70 through Glenwood Canyon, 1992, we paid little attention to wildlife. There were exceptions, such as the narrow underpass for deer in West Vail installed in 1969.

Biologists in the 1990s began to emphasize highways as house wreckers. The expansion of road networks, they said, created islands of wildlife habitat. Fragmented habitat leads to shrinking gene pools and, at the extreme, the threat of species extinction in some areas, called extinction.

I-70 has become the marquee for this. Wildlife biologists have started calling it the “Berlin Wall for Wildlife”. The relevance of this phrase was clearly illustrated in 1999 when a transplanted lynx released a few months before 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 involving I-70. The goal, at least partially realized, was to discover less expensive materials and designs.
Colorado’s pace has picked up since a 2014 study documenting declines in West Slope mule deer populations. In 2019, a new Polis governor issued an executive order to state agencies directing them to work together to address road ecology issues.

Two wildlife overpasses and underpasses and fences north of Silverthorne completed in 2017 are valuable examples. Studies have shown a 90% reduction in collisions.

“An 80 to 90 percent reduction right off the bat is pretty typical for these structures,” says Tony Cady, planning and environmental officer for the Colorado Department of Transportation.
State agencies, working with nonprofit groups and others, analyzed the data to delineate the 5% highest priority road segments in the state. This data may give Colorado a head start in accessing federal funds.

Both studies found 48 high-priority segments on the western slope and 90 east of the Continental Divide, including the Great Plains, reports Michelle Cowardin, wildlife biologist for Colorado Parks and Wildlife. The Craig and Meeker areas have many high priority routes, and much of I-76 between Fort Morgan and Julesburg has many high priority segments.

Some jurisdictions dive deeper. Eagle County has completed a wildlife connectivity study, and in the Aspen area, a nonprofit called Safe Passages has secured funding to begin identifying the highest priority locations in the Valleys of Roaring Fork and Crystal River.

These new studies show a change in public attitudes. Rob Ament of the Western Transportation Institute at Montana State University says wildlife connectivity is becoming institutionalized in the way we think about transportation corridors. Instead of being an extravagance, he says, the crossings are becoming a cost of doing business.

This is also happening internationally. “My world is exploding,” he said, reciting crosses for elephants in Bangladesh, tigers in Thailand and work for other species in Argentina, Nepal and Mongolia.

While in some ways it will take time, we are redefining the relationship between highways and wildlife.

allen best
Courtesy picture

Allen Best publishes Big Pivots, which focuses on climate change and energy and water transitions in Colorado. See more at

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