STANDING on the lip of the world's most famous abyss, Carl Bowman looks out at temples of stone that, in a moment's view, reveal 2 billion years of geologic time.
It is a pluperfect day: wind hissing through the pinon pine, the Grand Canyon dressed up in O'Keefean colors of ocher and gold, and the Colorado River lugeing through desert rock a mile below.
Yet Mr. Bowman, a National Park Service ranger, is not taking in the splendor in solitude. Nearby, a popular hiking trail courses with backpackers and mule trains. Camera-clicking tourists congregate on an overlook. Tour buses wheeze past. ``In some ways, it definitely does have an amusement park feel,'' Bowman says.
The two views encapsulate a dilemma facing national parks in the 1990s: how to preserve the resources and wilderness values of the country's outdoor sanctuaries and still maintain access to a public ever more eager to enjoy them.
Americans may or may not be loving their national parks to death, but they are, by many accounts, loving them to deterioration.
The result is that many of the woes they are fleeing cities to avoid are showing up in the wilderness areas where they seek refuge: overcrowding, traffic jams, dirty air.
The result may also be a change in the way the parks are run. In May, Interior Secretary Bruce Babbitt signaled a desire to return the parks to a more natural state. No longer, he vowed, will new hotels and roads be built inside park boundaries. Park planners are fashioning a new management plan that will govern the operation of the Grand Canyon into the next century - everything from transportation to trail networks.
Thus, as it marks its 75th year, the park is once again on the cusp of defining what humans' relationship should be to their most treasured landscapes.
``The Grand Canyon and Yellowstone are fishbowl parks,'' says David Simon, southwestern director of the National Parks and Conservation Association, an environmental group. ``Everything that goes on is scrutinized. What works is replicated. What doesn't is magnified.''
A stadium feel
The park has experienced something of a respite this year. Visitation is off 1 percent. July has been a busy month, however, and even though it is still not like last summer, when fistfights broke out over parking disputes, standing on an overlook can have a stadium feel.
Moreover, the trends look inexorable. Visitation has doubled in 10 years to nearly 5 million annually, and planners expect it to reach 8 million by 2010.
``Last year there was a sense this wasn't a park,'' recalls Gary Cummins, acting superintendent. ``It was the feeling I had when I took my kids to Disneyland. This year we're crowded but not uncomfortable.''
During the summer, some 6,000 cars daily jockey for 1,600 parking spaces on the south rim. About 100 bus tours roll through the park daily. In preparing for the crowds of the future, park officials don't expect to have to limit the number of visitors. Instead, they want to upgrade facilities, many of World War II vintage.
``We think we can accommodate everybody who is projected to come through 2010 - if we can change the infrastructure,'' says Brad Traver, a park planner.
The biggest change could be an urban-style mass-transit system to shuttle people around - one of the first parks to do so. Park custodians are studying taking most private cars off the roads and forcing visitors onto buses or a rail system.
Restricting access too much, though, would bring protests from Arizona's congressional delegation.
Ultimately, any new transportation network will pivot more on money than on politics. Trams and trains are expensive. Thus, one possible solution being explored is tapping the private sector.
While park stewards mull how to handle people on the ground, an enduring dispute is resurfacing over sightseeing from the air. Some 800,000 people flew over the canyon last year in a helicopter or plane. On busy routes, an aircraft drones by as often as every two minutes.
Critics find the noise irksome to people and harassing to animals. Air-tour operators consider the flights an economic - and environmental - boon.
``Eight hundred thousand people got to see the canyon last year without one leaving one drop of oil in the river or killing one plant,'' says Dan Anderson of the Grand Canyon Air Tourism Association. Federal regulators are weighing whether to further restrict flyover areas, now confined to 55 percent of the canyon's airspace.
Progress has been mixed in one other area of concern: air quality. Though one regional utility is installing scrubbers on its stacks, wind-borne pollutants still drift in from as far away as Las Vegas and Los Angeles. Summer visibility averages 100 miles - enviable, by most standards, but not the 250 miles it could be.
Despite all the encroachment of humans, most people, when gazing across what one poet has called the ``womb of the ages,'' only see nature's majesty.
``I've never really seen anything quite like it,'' says Australian Ruth Barnes.
She is sitting on the south rim at sunset, beneath a tangerine sky. The walls of the canyon are cloaked in black. The Colorado slithers silver below.
Her friend Marzia Salvanescia of Milan, Italy, apologizes for not speaking much English. The words come anyway.
``There is,'' she says, ``a feeling of infinity.''