Some 800 or so years ago the smooth face of the Navajo sandstone provided a limitless canvas for ancient inhabitants who pecked and painted their unique culture onto the canyon walls.

Now that canvas has become a virtual mecca for rock climbers from around the world, attracted by the challenge of the slick, red-rock surfaces and the sheer beauty of the canyon walls.And the result, Bureau of Land Management officials say, is that Utah's priceless heritage is, in many cases, now crumbling under the onslaught of rock climbers.

"It seems the popular thing is to climb right over the top of ancient petroglyph panels," says Julie Howard, an archaeologist for the Moab District of the BLM. "And in the process, the rock art itself is being destroyed."

Howard even cites an advertisement in a rock-climbing magazine inviting climbers to challenge the Utah canyons. The color photograph for the advertisement features a climber working his way over the top of an Anasazi petroglyph.

"It's tragic," Howard said. "And it's also illegal to damage or deface rock art in any way."

The BLM has posted signs prohibiting rock climbing in areas with high concentrations of rock art, but it has done little good. Someone has removed the signs.

"Another (sign) was found floating in the Colorado River just the other day," Howard said. "The first two signs we put up disappeared within the first week."

Ironically, two areas that are particularly popular with rock climbers are also two areas with the richest concentration of rock art: the Potash Road area just west of Moab and the Indian Creek area just east of the Needles District of Canyonlands National Park.

Other areas like the Kane Springs Road and Flower Canyon have also been heavily abused, she said.

"They think it's neat to climb next to it or over it," Howard said. "What they don't realize is they are climbing through it, and that it's being lost forever. It's a problem of ignorance more than of intentional abuse."

Because the sandstone is very soft, it deteriorates quickly under any kind of pressure. That pressure is accentuated by rock climbers who drive pitons, or wedges, into existing cracks in the sandstone, to which they tie their climbing ropes.

"When you drive those pitons into the cracks, the soft sandstone peels off in layers. And with it comes the rock art," Howard said.

Another problem, she adds is the aesthetic damage to the canyon walls caused by climbing equipment left behind and by chalk used by climbers in gripping the ropes.

Howard is particularly concerned about the damage to the Potash Road rock art - panels she describes as some of the most pristine anywhere in Utah. She adds there are 70 different climbs on the Potash Road where rock art will not be damaged.

Howard emphasizes that Utah rock climbers have been sensitive to the problem. Those who abuse the rock art the most seem to come from outside Utah and bring with them no real appreciation for Utah's native heritage.