DENNY DAVIES pulls his car over in the heart of the spectacular canyon for which Utah's Zion National Park was first set aside 84 years ago. Walls of salmon sandstone rise on both sides, while the Virgin River, the geologic Ginzu knife that carved this grand corridor, slithers nearby.
The scene is idyllic - murmuring stream, wind whisk-brooming through the cottonwood, 2,000-foot temples of rock. There is only one problem: the sound of traffic. Cars taking the 6.5-mile journey through this hallway of stone pass by every few seconds.
"Here are the two points of the dilemma we face right here," says Mr. Davies, a National Park Service ranger, enjoying nature's handiwork but listening to the traffic. "It's use versus preservation."
The crush of visitors at Zion raises an enduring question: Are people loving America's national parks to death?
It is a question usually reserved for places like Yosemite, where Half Dome-sized crowds frequently clog the famed valley floor, or popular haunts such as Yellowstone and the Grand Canyon.
But other parks are increasingly feeling the pressure of more hikers in the back country and Winnebagos in the fore country. Coming in an era of lean Park Service budgets, the rise in visitation threatens to imperil park resources and despoil the solitude that people flee to the sanctuaries to find.
"It has become a very serious issue," says Donald Falvey, superintendent of Zion. "I think our ability to provide a quality experience with the number of visitors coming in is really being hampered."
Southern Utah is on the cusp of the problem. The state harbors more national parks (five: Arches, Bryce Canyon, Canyonlands, Capitol Reef, and Zion) than any place in the United States other than Alaska or California. Its southern flank, which features various magnificent rock manifestations of the Colorado Plateau, has become a magnet for tourists.
The parks are an easy drive from some of the region's largest cities - Los Angeles, Las Vegas, and Denver - and southern Utah has become a popular retirement area. While visitor growth in the park system averages 3 percent a year, consider these numbers from Utah's outdoor sanctuaries:
r Zion has seen more than an 8 percent increase in visitation in each of the past 10 years. It will approach 3 million visitors this year - more than double the number in 1983.
r Visits to Canyonlands are growing 15 percent annually. Though only 400,000 people go through the park each year, enough bikers, hikers, rafters, and jeep enthusiasts are using its back country that fragile high-desert terrain is being marred. Thus the park is revising its management plan for the area - and may limit access.
r Visitation at Arches and Capitol Reef National Parks has more than doubled in recent years. Arches is undertaking a special visitor-impact project as a result.
"Southern Utah's problems are more intense than other park regions," says Rod Greenough of the National Parks and Conservation Association, an environmental watchdog group. "What we're seeing is the discovery of southern Utah, and if we don't get control of visitation at the parks now, they are going to turn into the sort of Disney[land]-like experience of the older flagship parks."
Zion offers a template for the challenges of trying to keep pristine areas from turning into playgrounds. Though visitation here is still far less than at some other parks, Zion has less than 30 miles of paved road, making them heavily used.
This visitation focuses in particular on the short trip up and down Zion Canyon, the sleeve of stone that caused the area to be designated a national monument in 1909 at the urging of a government surveyor.
It's easy to understand why. The canyon rises precipitously and cloisteringly close on both sides. Its walls are a prism of colors: ocher Navajo sandstone, capped in places by gray rock dimpled with green puffballs of pinon, juniper, and ponderosa pine.
It is also a laboratory of geology - how oceans, desert winds, earthquakes, and volcanoes first molded the area, and then the Virgin River cleaved a canyon out of petrified sand dunes.
On peak summer days, 5,500 cars course through the park. The line of vehicles at the main entrance, in tiny Springdale, Utah, can extend a half mile, past Oscar's Deli down to Electric Jim's burger stand. More than half the visitors surveyed by university researchers last year considered traffic in the park "moderate to extremely heavy."
As a late afternoon sun burnishes the "court of patriarchs," the "pulpit," and other fingers of stone, Ranger Davies wheels his vehicle into Weeping Rock, a popular turnout along the canyon drive. Here visitors are training their Nikons on a series of hanging gardens - moss and maidenhair ferns clinging to the red rock that are nourished by water that has percolated down through the porous stone, in one of those patient and primal processes of nature, for 80 years.
All 31 parking spaces are filled, so people have pulled over along the main road, denuding the shoulder of grasses, cactus, and wildflowers and altering erosion patterns. "See, there is no vegetation there," Davies says, pointing.
Further down the road, where the canyon drive ends in a horseshoe of stone, the scene is similar. This is the starting point for the Gateway to the Narrows Trail, a one-mile walk to a gap in the rock small enough to squeeze a rucksack, which it does for nearly 700,000 hikers a year. Cars circle, looking for parking spaces as if they were at Wal-Mart.
To alleviate congestion, the Park Service wants to start a shuttle-bus system in the canyon. The road would likely be closed to all but staff vehicles. Park Service officials say, and environmentalists agree, that busing is the best way to handle visitor growth while preserving wilderness values.
"What I see it doing is allowing people to come in and see the scenic qualities without destroying the experience of the park," Mr. Falvey says.
If the Park Service solves the riddle of the roadways, it may then have to look to the skies. A few enterprising folks want to begin scenic helicopter flights over Zion. Park Service officials hope to get minimum-altitude rules set so canyon walls don't echo with the rap music of rotor blades.
Even with all the human intrusions, Zion is no Central Park. The views remain the same as when Isaac Behunin, an early Mormon settler, gazed across the canyon at twilight and recalled a passage from the Bible about "Zion," a place where "the Lord's house shall be established in the top of the mountains" (Isaiah 2:2), thus naming the park.
Back along the Virgin River, Davies, in his gray-and-green uniform and Smokey Bear hat, looks across the rocky expanse and comes to his own conclusion.
"Even though a fair number of cars are going by," he says, "this is still a pretty nice experience."