From a bird’s eye view, it’s easy to see how the landscape is divided between built and natural environments.  

It was from this vantage point on an early morning flight over the Roaring Fork Valley that Julia Kintsch showed a group of elected officials and journalists the places where Roaring Fork Safe Passages hopes to bridge connections for the valley’s wildlife to move safely through the area.  

“This whole valley was once winter range for animals,” Kintsch said. “Now, people also live here in towns and fields, and all the things we do here … you have all these things that are drawing animals into this area, and you have the highway here. So that’s why we see the conflict.”

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Bruce Gordon, who piloted the ECO Flight trip over the valley on Wednesday, Sept. 4, has been flying in the region for over 40 years, the last 30 or so of which have included flights for the environmental education and advocacy flight organization.

“More and more people are starting to live there, and it’s becoming less safe for the animals to cross,” Gordon said. “We’re seeing more and more wildlife killed as we build out.”

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Measuring human-wildlife conflict on roadways

In 2023, the Colorado Department of Transportation collected 7,163 carcasses off roads. The department warns that this data only includes roadkill reported by its maintenance crews, Parks and Wildlife’s roadkill app, U.S. Forest Service employees and members of the public — none of whom are obligated to report the incidents.

Other, “conservative estimates” from Roaring Fork Safe Passages put the actual number of animals struck each year closer to 20,000.

Colorado’s northwest region had the second-highest reported volume in 2023, with just around 100 fewer reports than the southwest corner. In total, CDOT reported 2,389 animals were killed on roadways in the northwest, up from 2,141 the previous year.  

Mule deer account for the largest percentage of animals hit and killed. In 2023, 1,530 deer were killed in the northwest corner, followed by elk with 211 reported.  Colorado Parks and Wildlife estimates that 2% of the state’s mule deer are killed annually in vehicle collisions, making the road-kill rate greater than the annual hunter harvest. 

The cost of development

Human development can impact species as fast-paced roadways and buildings disrupt migratory routes and habitats.

As development pressure intensifies, there are “fewer and fewer places for animals to go and their movements are being constrained,” Kintsch said.

This is particularly true for elk and deer, which are a primary target of the Roaring Fork Safe Passages project and others in the state.

“What we’re seeing in some of these areas is that some of these herds that used to be more migratory, historically, are really reducing the range where they’re going, and they’re moving less and less or shorter and shorter distances because of all these constraints on the landscape,” Kintsch added.

In the short-term, this can reduce the herds’ overall health, potentially reducing genetic connectivity and reproduction success of the species, Kintsch said.

“The elk population, particularly in Eagle County and here in Pitkin County, we’ve documented a pretty severe decline in just the population size,” she said, adding that declines in herd health and size have been seen in Summit County as well.

Creating passages in the Roaring Fork Valley

Roaring Fork Safe Passages is part of a growing wave of advocates working to create new ways for animals to traverse and navigate Colorado’s landscape as development booms. Kintsch, a senior ecologist for ECO-Resolutions, has worked on many wildlife crossing projects across the state and is helping the Roaring Fork group prioritize and plot safe passages in the valley.

Greg Poschman, chair of the Pitkin County Board of Commissioners, remarked before Wednesday’s flight that he has never seen a nonprofit grow as quickly as Roaring Fork Safe Passages has, with it drawing significant local and nonpartisan support.

The county board of commissioners recently approved a $26,000 contribution to the effort. The city of Aspen also contributed $26,000.

In the Roaring Fork watershed, wildlife-vehicle collisions are the leading cause of crashes reported to law enforcement. They make up 30% of crashes in the region, according to data from the Colorado Department of Transportation.

To date, the group, led by Executive Director Cecily DeAngelo, has completed a prioritization study along the valley’s two main roadways, Colorado highways 82 and 133. The study identified six priority areas where wildlife crossing infrastructure would have the most meaningful impact, the top of which is a stretch along Highway 82 between the Aspen/Pitkin County Airport and Woody Creek neighborhood.  

While each area has individual challenges and opportunities, all six areas were selected because they have high rates of vehicles and wildlife, high traffic speed and volume, and there’s a disruption of habitat.

“We definitely try to put the crossing structures in places where we know the animals want to be in places in the landscape where they want to move,” Kintsch said. “That’s a really important piece to making sure that they’re well-used and they’re effective.”

Now, the group is working to identify what type of mitigation or infrastructure will work best at each spot before it begins seeking funding for the designs.

While overpasses and underpasses created for wildlife crossings are the most visible, impactful and expensive of these structures, there are many other types of mitigation structures including culverts and fencing.

Take, for example, a box culvert visible just as you take off going east from the airport. This was designed as a wildlife passage that deer, bobcats, fox and mountain lions all use, Kintsch said. Elk, however, are more wary of predators and won’t use something dark and small like that, she added.

“With all the ongoing development, especially right along the highway corridor, if we don’t act now to do some of these things to protect not just buildings but also to protect the areas leading to them, then you’re going to have completely segregated wildlife populations north and south of the highway,” Kintsch said. “We have an opportunity to look at what’s left and look at where we might be able to maintain some of that connectivity.”

A burgeoning movement of safe passages

The opportunity in the Roaring Fork Valley is just one of many wildlife crossing projects gaining traction in Colorado and across the country.

“Especially in the last five years, but even looking back 10 years, we’ve seen a lot of momentum nationally, but also specifically in Colorado,” Kintsch said. “Colorado has really emerged as a national leader in terms of pursuing these projects.”

In total, the Colorado Department of Transportation and its partners have built over 40 wildlife underpasses and three overpasses.

In Colorado, a lot of the momentum started on Colorado Highway 9 south of Kremmling. In 2016, two wildlife overpasses (the first in the state), five wildlife underpasses, 29 wildlife guards, 61 escape ramps and 10.3 miles of wildlife fencing were constructed along 10.5 miles of roadway.

In the first five years of the project, there was a 90% reduction in wildlife-vehicle collisions along this stretch, a Colorado Parks and Wildlife study shows. Mule deer, elk, black bear, moose, pronghorn and bobcats were all documented using the crossings.

Since then, crossings and fencing have been or are being constructed on Colorado Highway 13 north of Craig, on Interstate 25 south of Denver between Castle Rock and Monument, on West Vail Pass, on U.S. Highway 160 west of Pagosa Springs, and Interstate 70 in Genesee.

Additionally, projects to build a bighorn sheep overpass on U.S. Highway 40 near Empire and for several structures on East Vail Pass are seeking funding to be built.

Similar to the effort in Roaring Fork, Eagle and Summit counties have both conducted reports to identify and prioritize places for wildlife crossings. 

The high concentration of these efforts in Northwest Colorado is not a coincidence. This corner of the state is home to “the largest herds of deer and elk in the nation just by number,” Kintsch said.

“So, there are several projects in that area where they’re looking at different ways to accommodate those movements,” she said. “Some of the concern is just, ‘Can we build enough crossing structures to accommodate just the magnitude of that movement and the sheer numbers?'”

While these projects compete for growing, but limited, funding opportunities — including the first-ever pot of federal funding for wildlife crossings in the 2021 Infrastructure Investment and Jobs Act and a $5 million fund created in Colorado — there is some strength in numbers. The volume of projects can demonstrate the need for funding and the success of such efforts — both of which will keep the momentum building.

“Success breeds success,” she added.