Most national parks have failed to set carrying capacities as required by the National Parks and Recreation Act of 1978, according to PEER/Patrick Cone

Editor's note: This updates with National Park Service officials declining to comment on the report.

Nearly four decades have passed since Congress directed the National Park Service to establish visitor carrying capacities for the National Park System, yet few parks have done so, according to a review by Public Employees for Environmental Responsibility.

Zion National Park officials, who lament the crowds that overrun the park at times, have embarked on a visitor use study that could lead to a carrying capacity, and other superintendents have commented about crowding. A Traveler survey of parks late last year pointed to some of the issues:

* At Zion in Utah, the shuttle service in Zion Canyon that was supposed to end in late October had to start back up to handle early November's crowds. During the Labor Day Weekend, it took some visitors 45 minutes to enter the park at Springdale, and then another 45 minutes waiting in line to board a shuttle to Zion Canyon. "And if you parked in town or you could find a place to park in town and took the shuttle bus to come to the park, it could be 45 minutes on top of that," said Superintendent Jeff Bradybaugh.

* In Acadia National Park in Maine, cruise ships that disgorge thousands of visitors during fall stops at Bar Harbor have created problems as passengers try to get to the top of Cadillac Mountain.

* In Montana, Glacier National Park managers weren't overwhelmed so much last year by greater visitation, but rather by an early spring that saw crowds heading into the park, and damaging facilities, before the seasonal ranger force was in place for the busy summer season.

* At Grand Teton National Park in Wyoming, a proposed management plan for the Moose-Wilson Road corridor to control traffic has drawn complaints from the governor.

* Great Smoky Mountains National Park Superintendent Cassius Cash has received written complaints from visitors irate that it can take five hours to drive the 11-mile loop through Cades Cove.

* At Arches National Park in Utah, crowds trying to get into the park during the 2015 Memorial Day weekend were backed up to U.S. 191, prompting the Utah Highway Patrol to temporarily close the entrance.

* At Yellowstone National Park, during the height of the 2015 summer it took some visitors up to three hours to get through the entrance at West Yellowstone, and then another hour to travel 14 miles to Madison Junction. "If you speed up the entrance station, there's no place to go, as four entrance lanes go down to one lane of traffic," said Superintendent Dan Wenk. "And then there's a bison three miles down the road. What do you do? Because if it's the first bison these people have seen, everybody thinks it's the last bison they're going to see. They all stop to take a picture."

PEER on Thursday said that "very few parks have required carrying capacities to prevent the crush of humanity from damaging natural resources or the quality of visitor experience." That despite a requirement in the National Parks and Recreation Act of 1978 that park superintendents "will identify visitor carrying capacities for managing public use. Superintendents will also identify ways to monitor for and address unacceptable impacts on park resources and visitor experiences."

Among the parks that PEER found have established some form of carrying capacity regulations are:

* Channel Islands National Park set use limits by alternative in their 2015 GMP. The preferred alternative (alternative 3) lists day use and overnight use limits for the following park areas: East Anacapa Island, Middle Anacapa Island, West Anacapa Island, East Santa Cruz Island including Scorpion Harbor and Smugglers Cove, and Santa Cruz Island’s Prisoners Harbor and Rancho del Norte.

* Dry Tortugas National Park set preliminary limits, subject to testing, of 330 people per day in Garden Key and 24-36 per day in Loggerhead Key. The proposed action (alternative C) set the maximum campground capacity to 68 campers overnight on the island, which would be regulated via a reservation system.

* Everglades National Park has a GMP that employs indicators and standards to address user capacity. The only standard that could be found in the GMP that limits the number of people in a park area is the number of people on a 15-mile loop road, waiting for a tram, in the parking or restroom area at Shark Valley (400-500 people).

* Golden Gate National Recreation Area has a GMP which also employs indicators and standards to address user capacity. On Alcatraz Island, the Golden Gate GMP sets a limit of 0-43 people per view on Michigan Ave. 90% of the time, and 0-74 people at one time on C-D St. 90% of the time. The GMP also sets limits on the encounter rate on trails to “no more than 40 encounters with other visitor groups traveling in the opposite direction, 90% of the time during park operating hours.” The number of visitors in Muir Woods National Monument is restrained by the capacity of the parking lot. In Muir Woods, no more than 18 people per view per 50-meter trail section along valley primary trails 90% of the time during park operating hours, and no more than 30 people at one time at the Pinchot Tree and Redwood Crosscut 90% of the time during park operating hours.

* Saguaro National Park utilizes indicators and standards to address user capacity. Only one standard that limits the number of people in an area could be found in their 2008 GMP: “no more than 90 people in any given month for at least 11 out of the 12 months of the year” in the Madrona Pools area.

* Zion National Park in its 2001 GMP stated it would use “preliminary carrying capacities” (i.e., 80 day hikers and 70 overnight users in the Narrows from the northern park boundary down through Orderville Canyon, and 50 people in the Left Fork of North Creek (p. 36)) until a wilderness management plan and carrying capacity studies were completed. The GMP also stated that visitor use levels are somewhat regulated by the shuttle system. The GMP also set “interim carrying capacities, pending further research, for hikers and saddle stock groups in the primitive and pristine zones.” They include hiker group size limits of 12 individuals, and saddle stock group size limit of six people per group with six saddle stock.

National Park Service officials would not respond to the report, said Thomas Crosson, who this month took over as the agency's new chief of public affairs.

At the National Parks Conservation Association, officials said the Park Service needs to take a closer look at the impacts caused by the record visitation levels.

“Many popular national parks are seeing a sharp increase in visitation, and there is no ‘one size fits all’ solution for how to handle the influx. More analysis of impacts to the parks’ resources must be done to really understand these park-specific challenges. This careful research, combined with public engagement, will be essential to help identify solutions, to ensure that visitors continue to have incredible experiences and adventures in our national parks," said Kristen Brengel, NPCA's vice president of government affairs.

PEER Executive Director Jeff Ruch said “(T)he safeguards Congress enacted to prevent national parks from being loved to death have become dead letters." He also noted that in a campaign called “Find Your Park” to promote its centennial, the Park Service is pushing to increase visitation--which in 2015 was already at an all-time high.

“Instead of ‘Find Your Park,’ this summer the challenge should be called ‘Find a Place to Park’," said Mr. Ruch in a release.

In reaching its conclusion that "almost no major national parks have carrying capacities," PEER reviewed the management plans of 59 national parks, 19 national preserves, two national reserves, 18 national recreation areas, and 10 national seashores in the park system. "Of these 108 major units, only seven have established carrying capacities and all but one of those only cover only certain areas or facilities," the group said.

The PEER analysis found that of the ten most visited national parks, only Yosemite had carrying capacities for its wilderness zones. In a 1995 plan, Grand Canyon set numeric caps on visitors to specified areas but that plan lapsed and has not been replaced. In 2001, Zion adopted “preliminary carrying capacities” which it has yet to finalize. Encapsulating this posture was the reply Yellowstone Superintendent Dan Wenk gave a reporter asking about this topic: “The words ‘carrying capacity’ will be attributed to you and not to me because they are words I don’t say.”

PEER noted that among the parks that have established carrying capacities of some fashion:

* Everglades has standards for crowding at boat launches, for road traffic, and on trails.

* In 2014, Golden Gate National Recreation Area, the second-most-visited place in the park system, promulgated a set of concrete user limits for identified “management zones” as does the management plan adopted that same year by Gulf Islands National Seashore.

“While not all parks are the same, the ability of a handful of parks to do thoughtful planning while most others do none suggests that it is not a priority in today’s Park Service,” said Mr. Ruch. “Contrary to the clear dictates of law and official policy, the Park Service appears to be evolving to the position that there can never be too many visitors – a position with which many visitors in long lines would disagree.”