The smell of bacon mixed with wood smoke. The sight of a spectacular waterfall or field of wildflowers. The sound of a bugling elk ... or nothing at all in the backcountry wilderness.

National parks are meant to be laid-back places where the stress and strain of work and home are left behind for a more mellow experience.

But increasingly, those rangers in their Smokey Bear hats who give talks on nature and lead campfire singalongs - especially the ones trained in law enforcement - are facing crime and violence.

A watchdog group last week warned that law enforcement work in national parks is the most dangerous in federal service.

"National Park Service officers are 12 times more likely to be killed or injured as a result of an assault than FBI agents," the group Public Employees for Environmental Responsibility reported. "National Park Service commissioned law-enforcement officers were victims of assaults 111 times in 2004, nearly a third of which resulted in injury. This figure tops the 2003 total of 106 assaults and the 2002 total of 98."

"The National Park Service has an astoundingly poor safety record for its officers," says Randall Kendrick, who represents park rangers as part of the Fraternal Order of Police. "If anything, these assaults against park rangers are undercounted. If there is not a death or injury, pressures within a national park can cause the incident to be reported as being much more minor than it is in reality, and it is not unheard of for an assault to go unreported altogether."

So why all this violence and crime in places that are supposed to be tranquil and relaxing? Alcohol or drugs are part of most violent incidents. Hideaway methamphetamine labs and marijuana fields in rural park areas (some of them run by drug cartels) and illegal aliens crossing through parks near the US- Mexico border are part of a growing crime scene.

But like increasing incidents of road rage, the stress of modern urban life, especially in the post-9/11 world of terrorism, may have something to do with it as well.

"We're suffering from the same societal problems that most urban areas are," says park service spokesman David Barna, who notes that park rangers interact with 1 million visitors a day and a lot more than that during the summer months.

FBI agents "are not face to face with the public the way we are," says Mr. Barna. "We're more like cops - metropolitan police organizations."

Here in Oregon recently, two rangers at Crater Lake National Park attempted to calm a man at the Mazama campground who had been involved in a domestic disturbance, loudly threatening people, disrupting an evening program, and leaving campers cowering in their tents. Undeterred by pepper spray, he came at the rangers with a club. They finally fatally shot the man.

The National Park Service (NPS) is a huge organization whose 20,000 professionals and 125,000 volunteers oversee 388 parks, monuments, battlefields, historic sites, lakeshores, recreation areas, scenic rivers and trails, and the White House. Their security and law-enforcement responsibilities include more than 18,000 permanent structures, 8,000 miles of roads, 1,800 bridges and tunnels, 4,400 housing units, 700 water and wastewater systems, 400 dams, and 200 solid-waste operations.

While Yellowstone National Park had the biggest number of violent incidents directed at park service officers last year (16), nearly half the total took place in urban areas where US Park Police patrol: the National Mall, the Statue of Liberty, Golden Gate Bridge, the Camp David perimeter, and dozens of parks and parkways in the Washington, D.C. area.

For some critics, this raises questions about why there are fewer US Park Police today than there were before 9/11, even though the park service's law enforcement budget has increased $42 million in the last three years and officers now get more training.

Last year, US Park Police Chief Teresa Chambers was fired for speaking out against the dangers of understaffing at places like the Lincoln Memorial and the Washington Monument. With help from whistle-blower organizations, she is fighting her termination.

In a report last summer, the National Parks Conservation Association, a private organization, noted that the number of commissioned permanent and seasonal rangers had been declining in recent years while the number of park visitors was rising.

Noting incidents of vandalism, arson, burglary, and theft, including stealing old-growth redwood trees and poaching of black bears for use in Chinese medicines, NPCA warned that "a shortage of law enforcement rangers has a direct impact on park resources."

"The Park Service's on-the-ground law enforcement capacity has been further eroded by the demands of homeland security," the group stated in its report, titled "Endangered Rangers."

"The agency has estimated that it spends $63,500 each day that the nation is at orange alert," according to NPCA. "This diverts funds from the parks' operating budgets, and when rangers from parks such as Rocky Mountain and Shenandoah are sent to guard dams and icon parks, their positions remain unfilled."

More recently, the Government Accountability Office (GAO) expressed concern about the ability of the Interior Department - of which the National Park Service is part - to maintain adequate security in the post-9/11 world of heightened alerts due to potential terrorist attacks.

Based on interviews with Interior and Park Service officials, GAO reported that "the department's law enforcement staff is already spread thin ... averaging one law enforcement officer for about every 110,000 visitors and 118,000 acres of land."