If You Build It

The Kawuneeche Valley is a picturesque swath of meadow and forest, some 15 miles long, that runs along the western edge of Rocky Mountain National Park. Through its heart flow the headwaters of the Colorado River, lifeblood of the American West, so diminutive this early in its 1,450-mile journey that, in many spots, you could wade it with ease. Stands of lodgepole pine rise above sweeping prairie; moose and elk elegantly browse the Colorado’s banks. The valley’s beauty, however, conceals a dark truth. The Kawuneeche is in an advanced state of ecological collapse — a reality that only reveals itself when you dig into its past.

A century ago, the Kawuneeche — whose name is derived from a word meaning “coyote creek” in the language of the Arapaho, who, along with the Ute and other Tribes, have long called the valley home — was a lush expanse of wetlands maintained by the diligent toothwork of North American beavers. Their massive dams ran to and fro, shunting the Colorado and its tributaries onto their floodplains and swelling them into ponds larger than football fields. Beaver-built wetlands irrigated towering willows, which in exchange furnished Castor canadensis with food and damming material, plant and rodent locked in symbiosis. Cutthroat trout teemed in pools, and boreal toads bred in wetlands. Little wonder that, in his 1913 book “In Beaver World,” Enos Mills, the naturalist who helped to found Rocky Mountain, deemed beavers the “original conservationist.” Protecting them, Mills declared, “would help keep America beautiful.”

Over time, however, the Kawuneeche’s beaver-built utopia crumbled. Settlers sowed non-native grasses to feed livestock and dug ditches to drain wetlands. Hunters wiped out wolves and other predators, permitting voracious herbivores to later proliferate and mow down willows. And the National Park Service, having deemed beavers tree-felling, land-flooding nuisances, allowed trappers to kill more than 200 in the 1940s. Those and other stressors conspired to parch the once-wet Kawuneeche. “We’ve lost 90% of the water in this valley,” David J. Cooper, a senior research scientist emeritus at Colorado State University, told me.

Similar stories have transpired across the West, where few ecosystems, once afflicted, fully rebound. In Rocky Mountain, though, the Kawuneeche Valley Restoration Collaborative, or KVRC, a coalition that includes the Park Service and a host of partners, has made a multimillion-dollar bet that recovery is still possible. The members of the collaborative, which formed in 2020, have high and diverse hopes for the initiative. Saving the Kawuneeche will, they believe, enhance wildlife habitat, protect drinking water, filter out the sediment clouding downstream lakes and reservoirs, and defend the area against wildfire, among other benefits. “Restoring and protecting the headwaters of the Colorado River should be important to everyone,” said Kaci Yoh, philanthropy director at the Rocky Mountain Conservancy.

To that end, KVRC is deploying a range of approaches, among them controlling invasive vegetation, planting willows and fencing riparian areas to keep out hungry herbivores. Most of all, the group is banking on one of the West’s most innovative restoration techniques: imitating — and then enlisting — beavers themselves. But reversing decades of ecological degradation is no easy task, even with the assistance of rodent engineers. Can the collaborative restore the Kawuneeche to its erstwhile glory — before it unravels entirely?

WINTER 2025] If You Build It - Portrait

Scientist David J. Cooper has studied the park’s wetlands for nearly 40 years.

©DAVE SHOWALTER

One fall morning — the golden brushstrokes of aspen brightening the hillsides, frost glazing the grass — I paid a visit to the Kawuneeche Valley. I’d come to rendezvous with KVRC’s leaders at the Holzwarth Historic Site, where several cabins attest to the resolve of John and Sophia Holzwarth, German immigrants and saloonkeepers who’d fled Denver when prohibition came to Colorado. Beginning in 1917, the Holzwarths homesteaded the valley and established a dude ranch, feeding tourists trout and deer. The pelts of beavers — as well as mink, marten and other mammals — helped fund the operation. “The most beaver I ever caught, I caught 28 beaver in 31 days,” the Holzwarths’ son Johnnie once boasted.

KVRC’s members began to arrive, among them Isabel de Silva Shewell, the Park Service ecologist who manages the project. It was an eclectic group, reflecting the collaborative’s goals and values: There were representatives from Grand County government, a water utility and nonprofits, including Trout Unlimited and The Nature Conservancy. Also present was Cooper, sporting a cowboy hat and snowy beard, whom the group had tasked with leading and monitoring the restoration project. Few people better understood the Kawuneeche’s shocking transformation than Cooper, who’d begun studying Rocky Mountain’s wetlands in 1987. “This is a horror film for an ecologist,” he said, shaking his head.

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We headed into the Holzwarths’ former pastures to see the carnage. To an untrained gaze, the bronzed meadow looked lovely, but to Cooper’s eye it was disfigured. The wizened skeletons of chest-high, half-dead willow shrubs — “zombie willows,” de Silva Shewell called them — lifted their brittle arms as if in supplication. Without willow shading them out, exotic plants such as timothy and clover sprawled everywhere. The only beaver dams in evidence were long-dry berms topped with invasive reed canary grass and Canada thistle. I asked Cooper what this spot was like when he began working here. He smiled ruefully. “Our feet would have been wet,” he said.

If the Kawuneeche Valley is a horror movie, its opening scene occurs more than a century ago, with the arrival of colonists. Yet the Kawuneeche mostly survived those early assailants; as recently as the 1990s, 10-foot-tall willows and multiacre beaver ponds endured. In recent decades, however, the valley’s deterioration has accelerated, fueled by the appetite of a gigantic interloper: moose.

Historically, Colorado was not totally unfamiliar territory to Alces alces, the largest member of the deer family. Nineteenth-century settlers noted its presence, and killed one near the future Rocky Mountain National Park. But those animals were likely transients from Wyoming, rather than members of an established population. Then, in 1978 and 1979, Colorado’s wildlife department captured two dozen of the half-ton ungulates in Wyoming and Utah and released them near Rocky Mountain — a cavalier decision made with flimsy environmental review, and at least partly to satisfy hunters.

Moose quickly multiplied in Colorado, and by the 1990s they’d reached the Kawuneeche in force. The ecosystem was ill prepared. De Silva Shewell estimates that a typical adult male consumes an average of about 45 pounds of willow daily, while a large elk eats some 3 pounds of willow a day. And, with likely more than 150 moose in the park, there are many mouths to feed. “I’ve got my head on a swivel when I fish around here, because you’ll see several moose an hour,” Celia Sheneman, Trout Unlimited’s representative on KVRC, told me.

As moose populations exploded, beavers crashed, deprived of the plant they relied upon as both foodstuff and dam-building wood. Without beaver ponds soaking the valley floor, the Kawuneeche began to dry out, becoming ever less suitable for thirsty willows. A soggy expanse of wetlands devolved into dry meadows, a new, nearly beaverless ecosystem that Cooper and others have dubbed the “moose-elk-grassland state.”

If browsing is the problem, one simple solution is to keep moose out. Cooper and de Silva Shewell led us to an exclosure, surrounded by nearly 8-foot-high wire mesh, that the Park Service erected in 2011 to protect 16 acres from willow-hungry ungulates. De Silva Shewell opened a rusted gate and walked into what she called the “secret garden.” We were immediately engulfed by a jungle of willows, many taller than me, so dense that we had to walk single-file. It was a tantalizing glimpse into the shrubby paradise that once blanketed the Kawuneeche. “Fences are not an ideal tool, but they’re effective for our purposes right now,” de Silva Shewell said — at least until the willows have grown high and thick enough that moose won’t immediately mow them down.

A certain semiaquatic rodent, too, seemed enthused. The exclosure straddled the Colorado, which a beaver colony had interrupted with a 40-foot dam woven from gnawed willow and alder — presently under construction, judging from its patina of fresh mud. Pooled water trickled around the dam’s flank, dampening sedges and soaking the earth to hydrate willows and expedite their growth.

Granted, this humble pond was a far cry from the glorious castorid empire that once reigned here. In a 1920 aerial photo that de Silva Shewell showed me, the valley was so chockablock with beaver wetlands that the Colorado River didn’t have a discernible channel. That the occasional dam now merited celebration hinted at just how far baselines had shifted. Moreover, the beavers had been forced to incorporate dead pine in their dam, since most willows, despite the exclosure, remained too slender and scarce to furnish adequate construction material. “They need some real lumber,” Cooper said.

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The lesson: fencing out moose helped, but it wasn’t enough to swiftly restore the Kawuneeche. Instead, KVRC would have to take dramatic action — and give the valley’s beleaguered beavers a more substantial boost.

The Kawuneeche Valley isn’t the only basin to suffer a beaver apocalypse. As many as several hundred million beavers once frolicked in North American waterways before the fur trade virtually wiped them out. Aided by trapping restrictions and reintroductions, they’ve since made a heartening comeback; today 10 million to 15 million inhabit the continent. Yet countless streams remain beaverless — in part because, without beaver dams slowing and spreading flows, creeks tend to erode rapidly into gullies and become entrenched within their own banks. Streams that can’t overflow onto their floodplains, in turn, can’t soak water-loving willows, which wither and die. A stream that lacks beavers, in other words, becomes ever less suitable for their return.

To see how KVRC plans to break that vicious cycle, we drove upriver from the Holzwarth site to a tributary aptly called Beaver Creek and wandered onto the floodplain. Beaver-dug canals and burrows, decades or centuries old, threatened to trip us. The stream itself was a pitiful, incised furrow, its collapsing banks sloughing off in refrigerator-sized clods. The long-dilapidated beaver infrastructure brought to mind a ruined kingdom, like Angkor or Petra.

Yet this lost city was returning to life. A half-dozen workers in hard hats and vests attacked stacks of cedar lumber with chainsaws, and others slotted the wood, fastened together with steel rods, into notches carved in the banks — a crew of human beavers. We met up with Jeremy Shaw, a research scientist at Colorado State, who explained the method behind the chaos. The Park Service and the KVRC team were constructing 29 separate damlike structures in Beaver Creek that would form ponds and capture sediment, thus rebuilding the eroded streambed and pushing the creek back onto its floodplain. A 31-acre exclosure would prevent moose from devouring the willows that would someday flourish in the dampened soils. It was an intensive fix for a severe problem.

“It’s really too far gone for beaver to come back and do it on their own,” Shaw said. “We’re trying to jump-start it.”

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We wandered downriver to see a completed structure known as a beaver dam analog, or BDA. Pine logs, thinned from a nearby wildfire mitigation project, poked from the stream, their butts jammed into the bed. Needle-covered boughs woven through the posts finished the dam. Behind it, the stream had deepened into a broad, sluggish pool in reasonable imitation of a beaver pond — “instant gratification,” as Shaw put it. Still, he hoped that BDAs — along with two other categories of damlike features known as simulated beaver structures and post-assisted log structures — would ultimately attract the genuine rodents, who will continue restoring the creek long after Shaw’s crew ceases its labors. That may not be a rapid process: Though up to 600 beavers once inhabited the Kawuneeche, today it’s home to only a few colonies. As young beavers disperse throughout the Colorado drainage in search of territory, however, Shaw expects this site, and the tall willows that will eventually grow there, to entice and nurture them. “Our play here is to give them the best habitat we can, and then hopefully they build up their population,” Shaw said.

Beaver mimicry is en vogue in the modern West. The concept was pioneered on an Oregon stream in the early 2000s, where scientists constructed more than 100 analog dams and so induced the local beavers to build many new dams of their own, furnishing habitat for threatened steelhead trout. Since that success, scientists and conservationists have applied beaver-based restoration to repair mountain meadows in California, mitigate drought in Idaho and capture pollution in Washington. In Nevada’s Great Basin National Park, the Park Service has installed analog dams to support cutthroat trout, forestall erosion — and, of course, help beavers to thrive.

In the Kawuneeche Valley, the combination of human-built dams and the authentic rodents should prove equally potent. De Silva Shewell expects the future riparian wonderland to shelter migratory birds such as Cordilleran flycatchers and yellow warblers, while Kayli Foulk, water quality specialist at Grand County, which includes Rocky Mountain’s western flank, is counting on the new wetlands to settle out the nitrogen, phosphorus and sediment bleeding off the landscape, thus improving the clarity of local lakes. Kimberly Tekavec, source water protection specialist at the conservancy district Northern Water, hopes that beaver-based filtration will also protect the quality of the drinking and irrigation water that her company provides to more than 1 million Coloradans. “There are so many benefits that this project serves,” Tekavec said.

One benefit that thrilled everyone was a restored valley’s potential to fight fires. On my drive to the valley, I’d passed forests reduced to charcoal toothpicks by the East Troublesome Fire, a 2020 inferno that seared nearly 200,000 acres, including more than 20,000 within the park — the largest fire in Rocky Mountain’s history. But not everything in the fire’s path burned. When Emily Fairfax, a beaver researcher now at the University of Minnesota, surveyed the aftermath of the East Troublesome and two other Colorado megafires, she found that beaver wetlands remained lush green refuges in oceans of black hillsides.

“Everything is burnt — all the pine trees, the brush,” Fairfax told me. “Except the beaver ponds, which are completely intact.”

For all of KVRC’s promise, it faces a daunting task. Beaver Creek is one of four streams that the group has singled out for restoration over the coming half-decade, yet those creeks represent only a small portion of the valley. The Kawuneeche doesn’t lie entirely within Rocky Mountain’s borders; it also spills over onto private ranches and developments, whose owners may not embrace meddlesome beavers. The collaborative, which has garnered more than $3 million in grants, donations and other funds, thus views the park as a proving ground where landowners can observe the benefits of restoration. “Once people can see what we want to do, I think it changes their perspective on what’s possible,” Foulk said.

But even within the confines of Rocky Mountain, the Kawuneeche faces an uncertain future — for altered ecosystems aren’t easily restored. Consider the northern range of Yellowstone National Park, whose trajectory mirrors the Kawuneeche Valley’s. In the early 1900s, the Park Service eradicated wolves, leading to an overabundance of elk, the disappearance of beavers and widespread stream degradation. The reintroduction of wolves in 1995 was supposed to help, by thinning elk herds and dispersing the survivors — and along some streams, to some extent, it has. But the canids haven’t been a panacea. In a 2024 study, Cooper and others synthesized years of research to suggest that, as in the Kawuneeche, many once-lush Yellowstone drainages remain dry grasslands. “The willow-beaver state may not return to the northern range,” he and colleagues wrote, “even in the fullness of time.”

Still, Yellowstone’s much-publicized efforts helped inspire Colorado’s voters to approve a 2020 ballot initiative mandating the return of wolves to the state. In 2023, Colorado released its first 10 lobos, one of which later spent a month in Rocky Mountain, kindling hopes that they’ll eventually recolonize the park and thin its hordes of hungry moose. Given how many moose already inhabit the Kawuneeche, however, it would be unfair to ask the canids to play savior — particularly because the valley packs a lot of human visitors into a landscape a fraction the size of Yellowstone’s northern range. “Wolves don’t necessarily like that proximity,” de Silva Shewell said.

Trying to restore beavers, of course, will ultimately be for naught if moose keep gobbling the Kawuneeche’s willows — so what can the park do about its moose problem? History might be a guide. In 2008, to deal with another overpopulated ungulate, Rocky Mountain implemented its Elk and Vegetation Management Plan, a scheme that, among other actions, authorized new exclosures and a cull of 130 elk in three years. An analogous moose plan might entail hazing the animals away from the park, dosing them with contraceptives, ramping up hunting on adjacent lands or culling them inside the park — though, for now, the Park Service is merely studying the situation. Given how beloved Rocky Mountain’s moose are among its tourists, any proposal to reduce their numbers is likely to provoke controversy. “Seeing a moose is something to celebrate,” Tracy Coppola, Colorado senior program manager for NPCA, told me. “But how do these animals fit within the larger system?”

Whatever its ultimate approach, Rocky Mountain has already shown that it’s bolder than many parks. The Kawuneeche Valley Restoration Collaborative is only the latest in a line of ambitious, intensive management actions. Since the late 1980s, for instance, the park has obliterated several dams, and in 2020 it debuted a day-use access plan that requires summer visitors to make timed-entry reservations. “This park has been so courageous about taking risks, providing funding for new studies and using the information,” Cooper, who’s worked in 31 park units, told me during our tour.

Can the park continue on that bold path in the Kawuneeche? Park leaders have recognized the valley’s crisis; now its task is to communicate the problem, and the urgency of remediating it, to the public. As Aldo Leopold, a guy who knew something about the harms of excessive ungulates, famously put it, “One of the penalties of an ecological education is that one lives alone in a world of wounds.” The implication of Leopold’s lament is that environmental degradation is both subtle and ubiquitous; once you’ve seen it, you can’t ignore it. Yet wounds, once inflicted, can still heal — particularly when beavers are involved in the operation.