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Illustration by Jason Holley

Are Trails in Colorado Harming Wildlife?

Colorado is in the midst of a trail-building bonanza. But research has revealed an inconvenient truth: The humans recreating on these trails are negatively impacting wildlife populations throughout the state. Is there a way to spend time in the backcountry responsibly without endangering the state’s fauna?

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One morning this past August, I pedaled my mountain bike through high-alpine meadows that made everything seem limitless, even me. Specks of crimson, cobalt, purple, and ivory dotted the grasses like marks from a pointillist’s brush, and the small lakes I passed blazed blue along the trail linking the Rabbit Ears rock formation to the Steamboat Springs ski area some 20 miles away. At the last lake on the route, I saw a moose. And it saw me.

I braked to a stop, and my riding buddies halted behind me. Seeing moose around Steamboat isn’t unusual; the animals have taken to lounging on the ski runs and in the aspens separating those trails. But moose are crotchety creatures, as likely to charge humans as to flee from them, so as soon as we noticed this one wading among the reeds at the edge of the pond, we dashed off-trail into the pines to give it space. The 50 feet between us grew to 75, then 100 as we hiked through dense shrubbery that scratched my legs and pulled at my bike.

Once we’d skirted the pond and rejoined the trail to continue our ride, we congratulated ourselves for our wildlife-savvy evasion. Yes, traipsing around off-trail was onerous, but we’d respected the moose’s need for space. Or so we thought.

Colorado appears to be different than the rest of the United States, where people reportedly spend about 90 percent of their lives indoors. Here, residents make a point of getting outside to hike, picnic, ski, run, climb, fish, hunt, mountain bike, or pilot an off-highway vehicle: 69 percent of Coloradans log some form of outdoor recreation one or more times per week. Many of the state’s 84.7 million annual visitors come to do the same. All that recreating contributed $62.5 billion to Colorado’s economy in 2017 (up from $34.5 billion in 2013). Colorado’s population has also grown; we now number 5.7 million humans, compared to 2.9 million in 1980. To keep pace, we’re adding new trails to our 39,000-mile network. Colorado Parks and Wildlife (CPW) estimates that by 2026, municipalities and state parks will need to build 3,464 more miles of trail to accommodate the state’s hunger for adventure.

That’s a lot of biggering, to quote my daughter’s favorite Dr. Seuss story, The Lorax. And, like that book’s mustachioed title character, scientists are documenting how humans can have unfortunate consequences for nature.

Courtney Larson, a Ph.D. student in ecology at Colorado State University, reviewed 274 studies performed on recreation and wildlife in a literature review that PLOS ONE published in 2016. In 93 percent of those papers, recreation had at least one effect on wildlife, and many of those effects (59 percent) were negative.

Some of the studies documented how increasing trail traffic may mean that animals spend most of their time avoiding humans rather than finding food, mating, or caring for young. Other papers monitored elevated heart rates in animals that didn’t (or couldn’t) flee—suggesting wildlife may be more freaked out by our presence than they seem. “One person walking quietly for a couple of miles on a trail doesn’t seem like it would be very impactful, so people have a hard time believing that they’re actually affecting wildlife,” Larson says. “But it’s cumulative. It’s the effect of hundreds or thousands of people.”

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Research hasn’t yet identified just how many people are too many and which activities are the most damaging. Two patterns that have emerged in the research show that off-trail travel—like my detour to avoid the moose—is one of the most alarming issues for wildlife, because animals habituate to humans behaving in predictable ways on roads and trails. Another finding concludes that loud noises have an adverse effect on wildlife.

There may be no single “worst” user group, but taken all together, outdoor recreationists rank among the top threats to species that are listed as federally threatened or endangered. One review of federally subsidized resource extraction activities placed outdoor recreation at number two, while another study put it at number four (behind non-native species, but higher than energy extraction and pollution).

Another factor researchers must account for is that species vary in their tolerances for human beings (magpies thrive near us; golden eagles don’t). Some adaptations in animals may have far-reaching consequences on the ecosystems critters are a part of. One 2018 analysis published in Science found that at least 62 species are avoiding human contact by becoming more nocturnal—so when mountain bikers and runners don powerful headlamps and take to the dirt during summer’s coolest hours, we’re pursuing wildlife into their very last refuge: darkness.

Retired researcher Rick Knight walks near his home north of Fort Collins. Knight was a professor of wildlife conservation at CSU for 30 years. Photo credit: Nick Cote

Gray mist and a raw, bone-chilling wind make the flat grassland of Roberts Ranch seem more like the Scottish Highlands than the Front Range of Colorado, but inclement weather doesn’t deter Rick Knight. Ever since his Boy Scout days, he’s made outdoor recreation a rain-or-shine habit, and on this 35-degree day in May, he and his wife, Heather, have saddled up their riding mules to monitor raptor nests near Steamboat Rock north of Fort Collins.

Knight retired from CSU in 2017 after 30 years of teaching and conducting research on wildlife conservation. But as an emeritus professor today, he continues to advise and educate students and collect wildlife data—even on weekends. Today’s mission to Steamboat Rock isn’t dictated by any formal study but fulfills Knight’s personal curiosity about the habits of local eagles, prairie falcons, ravens, kestrels, and hawks. He knows that golden eagles have struggled to successfully raise their eaglets here, and he’s invited me to join him on this foray to observe their recent activity.

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“I used to be a mountaineer,” says Knight, who led rock climbs as a graduate and postdoctoral student at the University of Washington. Even now, Knight’s confident strides across the trail-less hillside hint at his past. “But I was appalled by other climbers and their complete lack of interest in the nature around them,” he recalls. “They were so focused on getting to the top that they were oblivious to their impact on flowers, or birds.” Wary raptors, for example, will flee their nests at a climber’s approach, leaving incubating eggs unattended. Such consequences seemed obvious to him, but they weren’t apparent to his fellow outdoorsmen.

So Knight dedicated much of his career to investigating recreation’s ramifications on wildlife—a field he helped pioneer. His 1995 book, Wildlife and Recreationists: Coexistence Through Management and Research, was the first to address the subject, and his studies from more than 20 years ago remain relevant today. His 1998 examination of songbirds in City of Boulder Open Space properties observed that nesting success was lower within a 100-meter radius of mixed-use trails. That same year, he published a paper describing how rock climbing correlated with a diminished number and variety of cliff plants at California’s Joshua Tree National Park.

Yet Knight refuses to conclude that recreationists are the problem. Rather, he posits, it’s a simple lack of understanding that their favorite activities might actually have unfortunate repercussions for wild plants and animals that is the real issue. “When people look behind them after they’ve hiked or biked a trail, the landscape seems unchanged, so it’s natural to think, I didn’t hurt anything!” Knight says, noting that the effects of over-logging or over-grazing are much more visible, so people point the finger there, or at other user groups—which is ultimately futile. It would be more beneficial to conduct an honest self-appraisal. “We humans have the potential to over-everything,” Knight says, “and that includes recreation.”

However, we also have the capacity to do just about everything better: We’ve developed less impactful logging strategies, and we’re making strides with energy extraction. We can do the same with trails, Knight argues. “There are so many ways we can manage for coexistence,” he says. “But the first step—and this is the hardest step—is to believe that we can over-recreate, just like we can over-log and over-dam our rivers.” Once they acknowledge their potential for harm, trail users can accept—and perhaps even demand—trail designs and policies that minimize recreation’s negative effects.

Scientists are just beginning to figure out what “better” trails might look like. So far, research suggests that it’s best to concentrate trails in heavily trafficked areas and leave other areas untouched. (As someone who prefers far-flung backcountry rambles to more manufactured settings, I wince at these findings.) Instead of building trails along streams and rivers as humans have long done, we should route new trails away from the water sources that wildlife rely on; existing trails might be rerouted to permit wildlife greater access.

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Trail closures can also lessen recreation’s impact when wild creatures are most vulnerable. Knight advocates closing climbing routes near nesting areas during nesting seasons, in addition to prohibiting access to trails through critical winter habitat. Boulder, Larimer, and Jefferson counties have adopted seasonal closures to protect nesting raptors and provide winter refuge to elk and mule deer through the snowiest months of the year.

Studies on dogs’ impacts have mixed conclusions. One suggests that dogs amplify human disturbance but also found little impact to wildlife when dogs are leashed. Despite that uncertainty, some land managers have prohibited all dogs on high-use trails—which Knight thinks is smart, given the current evidence.

But we all still have a lot to learn, Knight says. “We’ve got to empower the human imagination to think creatively about our use of space and our use of time so wildlife has a chance,” he says, before adding: “People aren’t the problem. People represent our only solution.”

Knight trains his binoculars at the ash-gray sky. We’ve spotted no golden eagles. It’s quiet: Only a pair of ravens emerges for an extravagant flight full of dramatic dives and spirals beside Steamboat Rock. “Just for the joy of it!” exclaims Knight. Then he lowers his lenses for a panoramic view of the scrubby hills rising to sandstone turrets, and he sighs. “I love this land.”

Throughout my research for this article, I asked sources to identify places within Colorado that exemplified the worst effects of rampant trail use. I also asked for examples of the kinds of progressive trail management Knight envisions. Both roads led me to the Eagle Valley.

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Over the past 20 years, biologists with CPW have noticed significantly fewer calves among Eagle’s elk population, which is unpoetically named E16 and extends from Vail to Glenwood Canyon. The agency expected dropping numbers because it had issued more hunting licenses in an attempt to shrink the herd from 10,000 animals (in the early 2000s) to within 5,500 to 8,500, the target set for E16 by CPW’s management plan. It’s currently at 6,055, but district wildlife manager Craig Wescoatt started noticing that in July, when he’d expect to see calves trailing seven out of every 10 cow elk, he counted just three calves for every 10 mothers.

“Either they’re not hitting the ground, or they’re not living very long once they do,” says Wescoatt, who’s lived and worked in the Eagle Valley for 35 years but has never seen a decline in reproduction rates like the one he’s witnessing now. He believes trail use is partly to blame.

Of course, Eagle’s elk also experience habitat loss courtesy of expanding housing development and increased pressure from predator species (bear and mountain lion populations appear to be growing in numbers). “I do think that it’s death by a thousand cuts,” Wescoatt says. “But outdoor recreation is definitely a factor. We’re seeing a lot more people out in the habitat that wildlife used to have to themselves.”

He’s also seen firsthand how elk vanish when people arrive: In 2013, when trails were built on Eagle’s Haymeadow parcel of open space, elk stopped wintering on the land, where they’d typically congregate. So in December 2017, when Eagle County Open Space acquired neighboring 1,540-acre Hardscrabble Ranch, Wescoatt urged locals to consider the property’s value to wintering elk. Parts of the citizenry, however, were eager to build trails there that would connect to ones within the adjacent Hardscrabble Special Recreation Management Area administered by the Bureau of Land Management (BLM). Plus, agricultural operations would continue on Brush Creek Valley Ranch and Open Space (as it’s now called).

Management proposals for that parcel could’ve become a downward spiral of warring priorities—like many of the adversarial land-use negotiations in which Wescoatt has participated over the years. Instead, Phil Kirkman and Diane Mauriello, of Eagle County Open Space, launched a comprehensive outreach campaign and recruited Wescoatt to the cause. They hosted stakeholder meetings to discuss how the land should be used. The Vail Valley Mountain Trails Alliance also founded the Trail Ambassador program in April 2018 to discourage trail users from poaching closed trails. Volunteers positioned themselves at trailheads to educate people about why they couldn’t use the trails (cameras documented 190 infractions over nine days in spring 2017 but just 44 over two months in 2018). “I don’t think there’s any better way of getting compliance than peer pressure,” Wescoatt says.

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A trail in Brush Creek Valley Ranch and Open Space in Eagle County, which has some of the most progressive trail management policies in the state. Photo courtesy of Eagle County Open Space

Eagle’s county commissioners integrated CPW’s recommendations into the management plan for Brush Creek Valley Ranch and Open Space, and the plan authorizes Eagle County Open Space to alter recreational policies should the trails’ impacts turn out to be greater than anticipated. The parcel’s trails will remain closed from one hour after sunset till one hour before sunrise in order to return the land to wildlife at night. Sensitive areas for wildlife are also closed from December 15 through June 30, although that summer date can be extended or abbreviated based on wildlife managers’ field observations of elk calving.

The recreating public embraced the proposal as presented, and in April 2018, part of the parcel opened to anglers, cyclists, and hikers. Workers will begin constructing trails in 2020.

“I’ve been around a long time, and this is the most progressive attempt I’ve seen to balance recreation and wildlife needs ahead of time, instead of coming back after the fact and trying to make it work,” says Wescoatt, who adds that achieving that balance required compromise—and an informed citizenry. “People want to do what’s right for animals; there’s no doubt about that. I just don’t think the information was out there for people to know what was happening with wildlife.”

Wescoatt hopes that Brush Creek Valley Ranch and Open Space can serve as a prototype for future trail development. “Ultimately, it’ll be what the public wants to see,” Kirkman says. “How do they want these lands managed? How do they want wildlife managed?” Education isn’t all that’s required for collaboration: It takes a shared consensus that nature is more than pretty scenery. People have to decide that wildlife matters.

Not every community gets a blank slate of undeveloped land to shape as Eagle did. Most land managers have to work with trail systems that already stress area wildlife, but even in those places, I found evidence that we’re getting better at managing trails—especially when we’ve got good data on local fauna.

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CPW just embarked on a two-pronged, six-year study to examine trail-use impacts on elk populations in the Roaring Fork Valley and the mountains above Steamboat Springs. One part of the study fits elk with tracking collars and vaginal implants to monitor birth rates; the other installs trail cameras to capture elk behavior relative to human recreation activity. “Our goal is to learn about trail activity as it relates to wildlife, to see if we can be smarter about those trails,” says Eric Bergman, a CPW wildlife research scientist.

Managers at Boulder County Parks and Open Space and Larimer County Department of Natural Resources monitor population numbers and locations, which are keys to identifying species’ declines—or overabundance. (“Seeing a large number of one particular species doesn’t necessarily mean that all is well and balanced,” says Jeff Moline, resource planning manager for Boulder County Parks and Open Space.) Examining that data alongside trail-use trends, managers can observe correlations and tweak policies accordingly. When burrowing owls built a nest near a popular regional trail, for example, managers rerouted traffic around it—though users complained about the subpar temporary trail surface.

Some Coloradans, especially those of us who have lived here for a while, have come to expect that we can recreate wherever we like, whenever we like. But issues such as the state’s skyrocketing human population, development, and global climate change simply won’t let us sustain that sense of entitlement any longer—not if we truly want to keep our staggeringly rich and abundant wildlife.

Land managers need to change the way they build and oversee trails, but trail users also need to adapt—which means we’ll have to resign ourselves to new norms. I’d rather not give up nighttime rides on singletrack, but I probably should. I’m even more reluctant to accept that we probably can’t build many more of the long-mileage, back-of-beyond trails I adore: We’ve already sliced up most of the land, and wildlife desperately needs the few remaining pockets of privacy to survive. We all must prepare ourselves for more traffic on existing trails. We may be growing in numbers, but that doesn’t mean trails can—or should—expand at the same rate.

And I now expect the recreation contingent to lead the way in wildlife conservation, even if that means accepting compromises to our favorite outdoor activities. If I expect it from loggers, grazing operations, and energy developers—and I do—I should be willing to join the vanguard, too.

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