For millennia, the only elements to leave their mark on these red sandstone cliffs that rise 1,500 feet from the floor of the Eldorado Canyon were forces of nature.
Today, many of the scars that are now changing the face of this ancient gorge are being left behind by people who climb it.
Here, some 20 miles outside Denver, the talk of the park is climbing bolts - the hardware many climbers drill into stone walls to anchor their ascent. As a new wave of adventurers takes to climbing, mountains across the West have taken the appearance of connect-the-dots templates.
Now, a growing number of parks and forests nationwide are putting restrictions on climbers who leave bolts behind. From Joshua Tree in California to Idaho's Sawtooth Mountains, the debate over whether to limit rock climbing's impact is dividing not only park officials and environmentalists, but also the often clannish climbing community.
Indeed, the conundrum goes to the heart of the outdoor ethic: Where to draw the line when communing with nature can mean actively destroying it.
The antibolt movement hit a crescendo last summer when the US Forest Service announced a nationwide ban on climbers' use of "fixed anchors" in national forest wilderness areas. Fallout was intense. As one federal official puts it, "the climbing community came unglued."
As a result, the Forest Service has since rescinded the ban for one year, pending further study. Meanwhile, other land managers, including the National Park Service, are considering policies of their own.
Yet defining the balance between protection and appropriate recreational use has its challenges. "Do we really want to ban rock climbers from wilderness?" says Craig Mackey, public-policy liaison for Outward Bound USA. "You are lopping off a major constituency that has been supportive of wilderness."
Environmental groups are divided on the question. The Wilderness Society does not oppose climbing bolts, but Wilderness Watch does. The Sierra Club's national policy is that decisions about bolts should be site-specific. Yet some chapters are outspokenly opposed to allowing new bolts.
Even among climbers, there's no consensus as to whether it's appropriate to install permanent safety anchors on mountainsides. Those schooled in traditional mountaineering tend to eschew bolts and favor removable anchors that slide into crevices. But the latest generation of "sport climbers" prefers permanent bolts - and uses them liberally. It is primarily these climbers that account for the sport's boom in popularity in the past decade.
"Now, you have people who started climbing at climbing gyms. They're there for an activity that's not resource dependent," says Wes Henry, wilderness program manager for the National Park Service in Washington. "They don't have the same relationship to the resource."
Sally Moser, executive director of the Access Fund, a rock-climbing advocacy group in Boulder, Colo., says gym climbers don't have the wilderness ethic of traditionalists. But banning bolts is not the answer. "Climbing is a legitimate use of public lands. And if you allow climbing, you must allow some kind of fixed-anchor device," says Ms. Moser. "It's part of ensuring the safety of the sport."
FOR nonclimbers, the question is mostly one of aesthetics. "Some people are offended by a piece of metal in a rock face, and others see it as a legitimate recreational use," says Steve Muehlhauser, chief ranger here. Eldorado Canyon has struggled with this issue for decades. As one of the world's premier climbing areas, the steep canyon walls here can attract as many as 700 climbers a day. The rock is now peppered with bolts.
But six years ago, the park established a strict management plan: Anyone who wanted to create a climbing route had to apply for a permit, which then would be scrutinized by a review board based on its merit and environmental impacts. Since then, the park has approved an average of only one new route per year.
To Matt, a climber here who declined to give his last name, an approval process is needed. "Without it, it would be a free-for-all," he says.
Similar plans are being implemented at Joshua Tree and Colorado National Monument. But National Park Service officials don't support blanket bans on climbing bolts. Instead, they hope to issue general-policy guidelines in the coming year, and believe specific decisions about bolt use should be made on a case-by-case basis. "There's nothing wrong with fixed anchors, per se," says Mr. Henry. "But when there is a problem, deal with it on a local level."