But one morning, on a hillside speckled with those prehistoric petroglyphs, he was also finding signs of a younger civilization: Shotgun shells. Bullets. Shredded juniper trees. Exploded cans of spray paint.

"It's all been shot," he said. "It's just destroying everything."

America's cultural divide over guns has gone into the woods. As growing numbers of hikers and backpackers flood national forests and backcountry trails searching for solitude, they are increasingly clashing with recreational target shooters, out for the weekend to plug rounds into trees, targets and mountainsides.

Hiking groups and conservationists say that policies that broadly allow shooting and a scarcity of enforcement officers have turned many national forests and millions of Western acres run by the Bureau of Land Management into free-fire zones. People complain about finding shot-up couches and cars deep in forests, or of being pinned down by gunfire where a hiking or biking trail crosses a makeshift target range.