As part of its push to privatize federal workers, the Bush administration has identified about 70 percent of full-time jobs in the National Park Service as potential candidates for replacement by private-sector employees.

Interior Secretary Gale A. Norton, who oversees the Park Service, has earmarked 11,807 of 16,470 full-time positions for possible privatization. They range from maintenance and secretarial jobs to archeologists and biologists.

Interior Department officials stressed, however, that the number of people replaced would not be nearly that high. Moreover, they said that law enforcement personnel, managerial positions and most park rangers would keep their jobs.

But some of the people who have come to embody the institution's 86-year-old tradition of public service, as they greet visitors and lead them on nature walks, could be replaced by volunteers.

Critics fear that the outsourcing of federal positions, including the Park Service's entire corps of scientists, could undermine protection of the nation's vast inventory of archeological and paleontological sites within parks and hand over the care of forests, seashores and wildlife to private companies not steeped in the Park Service culture of resource protection.

"This is about respect for professionals. It is about a recognition that people spend a lifetime learning their profession and how to resist pressures -- political or commercial -- in the public interest," said Roger Kennedy, who directed the Park Service during the Clinton administration.

"The public understands that parks are not parking lots -- they are places that require a high degree of professional skill to manage. Not just anyone can do it."

The potential cuts are part of the Bush administration's effort to identify as many as 850,000 federal jobs that could be performed by private-sector employees.

Park Service Director Fran Minella said she wants to maintain uniformed personnel in the parks as a "public face" to visitors. Still, some duties performed by rangers, such as nature walks, could be conducted by volunteers, Park Service officials said.

Interior Department officials say there is little likelihood that all of the jobs identified by Minella will be outsourced.

Deputy Assistant Interior Secretary Scott Cameron said he anticipated that no more than 4 percent of the current workers would lose their jobs.

He said much of the change would occur as employees retire. Cameron estimated that about 20 percent of the Park Service staff will reach retirement age in the next five years.

The positions identified by Norton will be examined to determine whether they can be eliminated or filled more cheaply and efficiently with nongovernmental contract employees.

Park Service employees would be given a chance to argue why they are better equipped to perform their jobs than private-sector workers.

Officials say the injection of free market-style competition would bring out the best in employees.

"This is a way to capture the benefits of competition to produce better performance and better value," Cameron said. "Competition makes for a much more exciting Lakers game than if only one team were on the court."

But critics say the responsibility of overseeing the country's 388 parks and monuments is too important to entrust to people with little or no preparation for working in the nation's park system.

"The Park Service is not a business enterprise," said Frank Buono, a former assistant superintendent of Joshua Tree National Park and a former manager of Mojave National Preserve. "There is a fundamental ideological binge that the free enterprise system will heal all wounds and solve all problems. Ask Enron about the efficiency of the unregulated private marketplace."

National Park Service rangers, like this one at Pennsylvania's Valley Forge National Historical Park, might be cut in a plan to turn over some functions to the private sector.