Rocky Mountain National Park

SALT LAKE CITY» It would be a first for a U.S. national park: requiring reservations to get in. But it’s an option that Zion National Park is considering to manage an overwhelming surge of visitors to its sweeping red-rock vistas and canyons in Utah.

Zion, which welcomed 4.3 million people last year, is weighing online reservations for those who want to explore its main canyon. National Park Service rangers struggle to cope with overcrowded tour buses and alleviate damage to Zion’s natural wonders, including soil erosion and human waste near trails.

People without reservations could pay an entrance fee and drive through the park, but they couldn’t stop to hike or picnic.

“We have to do something,” said park spokesman John Marciano. With limited budgets, Zion’s Park Service rangers routinely see long lines and plants trampled by visitors who also have cut some 30 miles of their own trails.

Zion isn’t the only U.S. national park with swelling numbers of tourists, and at least two national parks, in California and Hawaii, are testing more limited reservation systems for parking.

More than 330 million people visited U.S. national parks in 2016, a record. Visits were bolstered by the improving economy, cheap gas and marketing campaigns for the National Park Service’s 2016 centennial.

Zion is the fifth-most-visited national park. It’s particularly susceptible to overcrowding because its iconic cliffs and trails are located in the narrow, 6-mile-long Zion Canyon. The park urges visitors to take shuttles between March and November.

After a series of public meetings, Zion rangers are proposing an online reservation system, similar to the way campsites are reserved now. While certain hikes and activities require permits or reservations, the new system would apply to the park’s main corridor.

The number of reservations would be based on capacity, With more than 4.5 million visitors in 2016, Rocky Mountain National Park was the fourth-most-visited national park in the country. From late June through September, the 415-squaremile park is crowded — especially on weekends when rangers restrict traffic to popular areas. would vary by season, and could fall somewhere between a manageable 10,000 people a day and an overpowering 30,000 people a day, Marciano said.

One option would require a single reservation to enter and explore the park. A second would allow tourists to enter the park at a specific time and visit specific trails, like Angel’s Landing, a popular