"In the '70s, people used to teach each other how to climb outdoors," said McGahey, 29. "Now a lot of people come out of the gym and head straight for the woods, with no idea of what they'll find there."

Other popular climbing destinations are also struggling to keep a balance between preserving the backcountry and helping gym rats aspire to something higher.

An Outdoor Industry Association survey showed the number of climbers grew from 7.5 to 9.2 million people from 2004 to 2005. The percentage of people climbing on an artificial wall rose 30 percent.

Many newcomers don't learn the traditional climbing style developed in the 1960s, but instead learn in a gym, where man-made walls feature bolts every three feet.

Young climbers often start out bouldering, a ropes-free style that helps build strength but can also leave forest floors strewn with chalk and abandoned crashpads.

"There are lots of people out cruising around the woods looking for really fun boulders to climb on," said Phil Powers, executive director of the Golden, Colo.-based American Alpine Club. "But one of the biggest concerns that we have is that gym-to-outside transition."

In Southern California's Joshua Tree National Park, boulders are riddled with holes and stakes marking climbing routes. Rangers say the problem is twofold: It alters the landscape for nonclimbers visiting the park and accelerates erosion of the rock formations.

At Arches National Park in Utah, officials feared climbers would damage delicate sandstone formations, so last year they banned slacklining, a strength- and balance-building exercise that requires walking on a nylon rope strung between natural features.

They also banned climbing on any arch named on a topographical map of the park, a U.S. Geological Survey guide climbers follow like a Bible.

Red Rock Canyon National Conservation Area, near Las Vegas, is considering placing a 10-year cap on the number of bolts and anchors climbers can wedge into the sandstone, hoping to encourage climbers to use natural protection instead of the quick approach favored by novices: drill more gear into the wall.

"People are looking for weekend escapes," said Rick Potts, the former conservation and outdoor recreation chief for the National Park Service. "Trips are getting shorter, and trips into the backcountry are getting less and less common."

McGahey approaches Yosemite's visitors — many of whom visit the park on weekend pilgrimages — his own way.

To prevent erosion near Cathedral Peak, he's working with volunteers to block the braiding trails with dead logs. He and the nonprofit Yosemite Climbing Association recruited eco-friendly climbers to remove 21 tons of garbage throughout the park in last month's annual trash-pick up.

Each Sunday morning he offers climbers free coffee in exchange for participating in rap sessions about community responsibility.

Rock climbers don't need a backcountry permit even if they spend the night slung off the side of El Capitan, the park's famed granite monolith, so McGahey stresses leave-no-trace camping techniques.

Kay Okamoto, a Los Angeles-based urban planner who climbs at a gym during the week, soaks in all the tips she can.

"More people keep coming up here and getting stoked about going cragging," said Okamoto, 26. "What you learn about the environment is really all in who you meet."