Peter Clark was dangling off the edge of a cliff in New River Gorge when he spotted something that looked like a clump of rotten, peeling wallpaper on the side of the cliff. Most rock climbers would have moved right past it. But Clark was a master's student in ecology at West Virginia University, and surveying the cliff was his job.

The thing that looked like wallpaper was actually, on closer examination, lichen. Identifying it while hanging from a rope was practically impossible, so Clark took a sample back to the lab and examined it under a microscope, finally identifying it as a species with the evocative name of Frosted Rock Tripe. It was not only rare, it was believed to be extinct in the southeastern United States. “This is a testament,” Clark says, “to the fact that there just aren’t folks out there on the cliff looking for these small organisms.”

Or rather, there are plenty of people out on the cliffs. It’s just that they’re there for the climb, not for lichen-gazing. Cliff ecosystems are home to some of the oldest and rarest plant species in the world. Their verticality may have spared them logging and agriculture, but it’s made them irresistible for an entirely different kind of human activity. John Perez, a botanist at New River Gorge National Park, estimates that the amount of rock-climbing activity at New River Gorge has nearly doubled in the last two decades. But because there’s no data on cliffside biodiversity from before rock climbing’s popularity began to skyrocket, it’s hard to quantify climbing’s effects. The vast majority of cliffs have never been inventoried.

There are many reasons for this. Few ecologists have enough climbing experience to do the work. Even the simplest cliffside biodiversity survey requires extensive climbing skills and a willingness to dangle from a rope for hours at a time while scrutinizing plants. Digital cameras have made it easier to gather data about hard-to-reach places, but in the past many studies have used literal magnifying glasses and rulers to identify species and to measure the amount of lichen cover and the depth of crevices. “You have to be an expert with mosses and lichens, an expert with ropes, and an ecologist,” says Michael Tessler, an ecologist at the American Museum of Natural History. “How many people have that combination of skills? Almost nobody.”

There’s also a lack of interest in some scientific circles. Physical geographer Amy Hessl, one of the senior scientists on the New River Gorge cliff biodiversity survey, noted that when she and Clark were trying to publish their analysis on rock climbing in the park, one journal editor dismissed cliff faces as “a boutique ecosystem” that few ecologists would be interested in. Even Joshua Tree National Park—one of the most popular climbing sites in the world—has trouble cobbling together the resources to inventory the biodiversity and cultural resources—such as petroglyphs—on the park’s cliff faces, even though park staff is on good terms with local climbers, says Joshua Tree’s chief of resource management, Jane Rodgers.

Despite the obstacles, rock-climbing ecologists still manage to get a few studies published here and there. Last year, Tessler and a colleague, Theresa Clark of the University of Nevada, published the first-ever study on the effects of “bouldering”—a variant of rock climbing where climbers scale giant boulders. Tessler is quick to point out that for him and for many others, the climbing research is a side project and there aren’t many labs that are fully devoted to cliff ecology. “Anecdotally, I do think that climbers have an impact on vegetation,” he says. “The science is not 100 percent there yet.”

In a recent rock-climbing study published in the journal PLOS One, two botany grad students from the University of Granada in Spain systematically rappelled up and down 34 routes—17 climbed and 17 unclimbed—at three sites in the Spanish Sierra Nevada, taking photos and collecting samples of plants as they went. When the Granada team compared climbing routes to unclimbed sections of the cliff, they found that climbing routes had less plant cover and lower biodiversity than their unclimbed counterparts. They also noted that the effect was most dramatic on the climbing cliffs with higher traffic.

“This work is only a first step,” study coauthor Juan Lorite of the University of Granada wrote in an email. “Only when we get data from many case studies will we be able to evaluate the impact of existing climbing routes and to foresee the impact of new ones.”

Though the Granada project was just one study, its results line up with previous findings. Hessl said the Granada results were “surprisingly similar” to what she saw in New River Gorge. In both cases, climbing routes had fewer plants, and scraggly trees and shrubs were most likely to be missing.

The effects of rock climbing on plants are often subtle but can be spotted by attentive climbers. Turning a cliff into a safe climbing route often entails the removal of slippery lichens and plants that occupy chinks in the rock. “Most of those cracks and crevices would have vegetation growing in them,” says Hessl, “but climbers will clean those out.” If there’s nothing growing in a crevice, that’s a sign that it’s probably been affected by climbing.

Since many cliff-dwelling species only exist within a very small area, even small changes to cliffside ecologies could put an entire species at risk. At New River Gorge, Hessl and Clark found that plants at the bases of the cliffs and the clifftop vegetation bear the brunt of the damage, possibly because of climbers spreading out their gear below climbing routes and straying from designated access paths. Climbers have also been known to tie their ropes to trees when they can’t find a stone or man-made anchor point for their ropes.

Walk-offs or “top-outs”—where climbers clamber onto the clifftop and find a way to hike down can also harm plants. “That kind of damage is very noticeable,” says botanist John Perez, describing clifftops in New River Gorge. “Some of the lichens up there are very fragile. You step on them and they crunch. . . . Intuitively you know, ‘I shouldn’t be doing this. I’m crunching something.’”

Rappelling down a cliff affects fewer plants, but it also requires more climbing expertise. “Rappelling’s more dangerous than walking off, but walking off has a greater ecological impact,” says Hessl. “So you choose your evil there, I guess.” And at the climbing level, Tessler suggests adopting a “leave no trace” ethic. “Respect the plants and animals around you," he says. "Don’t pull out the plants if you don’t have to. Get stronger at climbing rather than making extra holds for yourself.”

The New River Gorge study found that cliffs where climbing route developers had installed permanent anchor points a few meters below the cliff’s summit had far less walk-off-related damage than cliffs without, because climbers who use these anchors never set foot on the clifftop, leaving the plants there undisturbed. However, these anchors are controversial additions to parks. A 2013 order from the director of the National Park Service specifies that “Climbing management strategies will address ways to control, and in some cases reduce, the number of fixed anchors to protect the park’s wilderness resources or to preserve the ‘untrammeled,’ ‘undeveloped,’ and ‘outstanding opportunities for solitude’ qualities of the park’s wilderness character.”

Some researchers and natural resource managers point to rock-climbing organizations as potential partners in cliff-ecology studies. The Access Fund, a national rock-climbing advocacy association, works with over a hundred climbing groups to organize trail clean-up days, raise money for climbing and conservation, and distribute information about best practices for climbers. “I think if you assume that all people are not going to be attentive and not care, then the battle’s kind of lost then,” Tessler says. “For every one person who is ripping out plants and not really caring, there are probably a number of other people who would have been more careful.”

At Joshua Tree National Park, volunteers help rangers keep an eye out for where peregrine falcons and other cliff-dwelling birds are nesting, Rodgers says. When resource managers such as Rodgers do close certain routes during nesting season, most climbers cooperate without complaint. Rodgers attributes the good relationship between Joshua Tree park staff and local climbers to outreach efforts, and to the fact that Joshua Tree has over 8,000 climbing routes. “If there’s two closures a year, there’s 7,998 other climbs to go to,” she says.

Some researchers and park managers are optimistic about the possibility of training climbers to look out for certain rare plants and help rangers collect data. Others counter that including climbing organizations in biodiversity studies could introduce bias into the results. All agree that cliff ecology is riddled with unknowns and that more cliffs need to be studied. A before-and-after study of a cliff in development as a climbing route might be a good first step, but cliff ecosystems vary widely. What applies to limestone cliffs may not apply to sandstone cliffs, and climbing may have more of an effect on some ecosystems than others. The angle of a rock face can affect the amount of moisture and light plant communities receive as well as the climbing techniques climbers use. In some places, climbers only scale a relatively narrow sliver of a large cliff, while other cliffs are covered with dozens or hundreds of climbing paths. The effects that rock climbing can have in deciduous forests such as New River Gorge may be nonissues in drier or rockier locales.

It’s also possible that the differences in biodiversity on climbed and unclimbed cliffs could be due to climbers deliberately choosing stretches of cliff with fewer plants when they first develop routes. Clark likens the problem to assessing the effects of a road through a forest. Researchers would have to ask, “Is the impact from the cars, or is the impact from the initial development of the road?” he says.

Scientific uncertainty can frustrate climbers who want to scale cliffs and park staff who want to protect a still-mysterious ecosystem. When Perez, the New River Gorge botanist, closes cliffs, climbers’ response is often “Why? Where’s your research?”

The answer is, it’s coming. Perez and other park staff are carrying out a long-term follow-up to Hessl and Clark’s initial survey at New River Gorge. They will be measuring biodiversity on 18 cliffs over the course of years (and hopefully decades). “We won’t be able to draw any cause and effect for years,” says Perez. “But we’ll be monitoring.”