Environment / Mountain, Desert, & Forest

The waters of the Middle Fork of Idaho's Salmon River are pristine because the watershed is protected from development.

Just three gutted shacks remained in Forney, a ghost town on the eastern edge of the Frank Church–River of No Return Wilderness in central Idaho. When I step out of the car to look around, nothing stirs but a grasshopper buzzing in the hot breeze. On the dry foothills, scattered conifers come together in dark lines of vegetation where the water runs down in the draws in the springtime. "If there is anyplace in this guide where you are truly on your own," I read in my traveler's handbook, "this is the place."

At 2.4 million acres, "the Frank" is the largest undivided wilderness area in the Lower 48 states. An additional 10 million acres of national forest surround the Frank, making central Idaho the least developed tract outside of Alaska. Wilderness, by definition, is supposed to be uninhabited, uncultivated, unspoiled terrain. The National Wilderness Preservation System has 680 chunks of such terrain, varying in size from a six-acre island in Florida to a nine-million-acre park in Alaska. About 2.5 percent of the land of the Lower 48 is designated as wilderness, the great majority situated in the West.

If I'd arrived a century ago, miners and ranchers would have been pecking and nibbling at the basins and ridges. Central Idaho's forest is wilder now than it was in 1900 or 1940 and is actually getting wilder as the landscape recovers from exploitation. The danger to places like the Frank has shifted from low-tech and dispersed human activity to high-tech, focused fascination. In the vision of the 1964 Wilderness Act, human beings are temporary visitors. As more Americans take advantage of better gear to travel deeper and stay longer, though, they threaten to overwhelm the crown jewels of the backcountry. "Even the largest wilderness areas become partially deranged," wrote Aldo Leopold, who helped found the conservation movement in the United States in the early part of the 20th century. In the Frank Church–River of No Return, the derangements include nonnative plants, missing fish, and the tremendous and growing popularity of rafting trips on the Salmon and Middle Fork rivers. Wilderness managers—the oxymoron suggests the delicacy of the problem—have turned to science for help. While one body of researchers analyzes damage to the wilderness, another looks to its pristine aspects for tips about restoring natural systems elsewhere. Still, there's a paradox inherent in such work: Landing in this unique place with their stakes, scopes, shovels, and laptops, the researchers help change the very phenomena they wish to preserve. I imagine the Frank, despite its gigantic size, becoming entangled like Gulliver in the snares of teams of well-meaning Lilliputians.

The road into the Frank climbs through steep forest on a single lane of scraped rock. On this August day, at the height of tourist season, there is no other traffic. South of Cobalt, I pass Porphyry Creek coming down Quartzite Mountain—proof of prospectors past. The raw volcanic material of central Idaho lies over the slopes in haphazard heaps. Called talus, the jagged, burnt-colored slabs look like tailings from a massive mine. As I go higher, big-bellied ponderosa pines give way to slim lodgepole pines and firs, and blooms of white yarrow and blue larkspur border the roadway.

At the ridgeline, the mountaintops of the Frank roll on and on, their canyons folded deeply between them. When Lewis and Clark came here in 1805, they stared glumly at the "immense ranges of high mountains still to the west" and decided to alter the route of their expedition to the north. Today almost 2,500 miles of trails traverse the preserve, but many are scratchy and treacherous, and 1.5 million acres of wilderness have no trails at all. "Tons of wilderness never see a soul," says Sheri Hughes, who manages the Middle Fork of the Salmon River for the U.S. Forest Service.

Second only to the white-water rivers, the alpine lakes and granite outcrops of the Bighorn Crags are probably the most striking features of the Frank Church–River of No Return Wilderness. When I arrive at the Crags Campground, having traveled through Forest Service land to the official border of the wilderness, I am dismayed to see a dozen cars parked at the trailhead. The campground is flush with brightly colored tents.

A couple of years ago, the Forest Service, the agency in charge of the wilderness, commissioned Randy Gimblett, a professor at the School of Natural Resources at the University of Arizona, to analyze the stresses on the Crags environment. In 2003 Gimblett's assistants offered surveys to parties of hikers and riders entering the Crags at the main trailhead. The participants were asked to drop off or mail in "trip diaries" that noted their daily whereabouts in the wilderness, the paths they took between lakes, and the number of other people they ran across.

For a broader gauge of tourist traffic in this area, the researchers implanted battery-powered counters just outside the wilderness boundary, a few hundred yards from the campground. Hikers and horse parties were chronicled coming and going all summer. Gimblett's team then went out and rated the compression of the soil, amount of erosion, loss of vegetative cover, damage to trees, volume of litter, and the like.

"We're asking, which areas are getting hit?" Gimblett says. "How do people distribute across the landscape? We modeled between 400 and 500 trips—simulated parties of backpackers moving in and out of the landscape." His software can even predict how often a hiker will encounter another hiker on a given trail or at a given lake on a particular day. The model is not meant to be a tool to limit hiking, but it might help the Forest Service respond to changes in traffic patterns without having to be out in the field verifying the impacts.

At dusk I reach the top of a ridge; the altitude at 8,000 feet affects my breathing. Through the pines I can see silhouettes of the famous Crags, a troupe of cones and knobs sculpted against the sky. The next day I head for nearby Wilson Lake, one of the most heavily frequented overnight spots in the Crags. On any night during the summer, an average of 1.2 parties stop there, according to Gimblett's data. Unwittingly I decide to make camp at a location where his computer predicts I will have an "encounter"—that is, I will hear or see or meet other people—approximately six times during my stay. That turns out to be a good call. I have repeated encounters with a middle-aged couple who are hiking with their dog. Their tent is located across the lake, and we end up disturbing each other's solitude for 12 hours.