WHAT WE have here is another widely popular federal agency taking it on the chin. The F.B.I. had the Watergate cover-up, the Pentagon has its $600 ashtrays, NASA has the Challenger explosion, and now the National Park Service has Alston Chase.

Chase's rambling, angry expose' about the "destruction" of Yellowstone National Park has already become something of a cause celebre in conservation circles because the bad guy in this melodrama is none other than the familiar park ranger -- that friendly naturalist in the green suit and broad-brimmed mountie hat. As Chase sees it, a combination of evil and incompetence on the part of the park rangers and their superiors in the bureaucracy of the National Park Service has pretty much ruined the flora and fauna of Yellowstone.

"As a wildlife refuge, Yellowstone is dying," Chase says at the start of his book, "and the story of its decline is perhaps one of our government's best kept secrets."

Chase argues that park managers are responsible for the decline in numbers of some native Yellowstone species (such as antelope, mountain lions, and grizzly bears) and also for the serious problem of overpopulation in the park's elk and bison herds. The book does not mince words. The reduction in numbers of black bears in the park is called a "holocaust"; the Park Service is compared to the Johnson Administration during Vietnam and the Nixon Administration during Watergate.

Chase, a former philosophy professor who moved to the splendidly scenic country just north of Yellowstone 14 years ago, has no shortage of criticisms of the Park Service. Most of his vexation, though, is aimed at a fundamental management principle that governs all U.S. National Parks today: the concept of "natural regulation," in which natural developments are permitted to take their course with minimal human interference.

The book explains that "natural regulation," instituted in the early 1960s when Stewart Udall was running the Interior Department, had its roots in the same "back to nature" philosophy that spawned the modern environmental movement.

A simple example of natural regulation at work can be found in a story Chase relates about a buffalo that was walking atop the frozen Yellowstone River one winter's day. The ice cracked; the buffalo fell into the river, struggled pathetically for a while, and drowned. A park employe watched the animal's death throes but did nothing to help. To the Park Service, this is precisely what is meant by leaving nature alone; to Chase, it is an outrage.

Chase protests that the Park Service has adopted its minimal intervention policy as a cop-out: "natural regulation, dressed in the trappings of a biological theory, gave policy the patina of academic responsibility while real science was carefully prohibited." BUT HIS criticism of natural regulation goes further than that; Chase suggests that nature might be a lousy regulator. "Why should we believe that nature always knows best?" he writes. "Why should we believe that some invisible hand always guarantees that natural systems, if left undisturbed, will, despite continual fluctuation, remain roughly stable?"

Chase scores some points, but the relentlessly negative tone and a tendency toward repetition make his book tedious at times. The book is most interesting during the interludes when Chase lets up on the park rangers. There's a fine chapter about Yellowstone's geothermal features -- the geysers, mud volcanoes, hot springs, and fumaroles. Since Chase can't argue that the Park Service has wrecked these natural wonders, he just discusses what they are and how they work, with fascinating results.

The big flaw with this book, though, is that the author is so busy denouncing Park Service policy that he never tells us what he thinks should have been done instead. He suggest, vaguely, that the alternative to natural regulation is intensive human management of individual species; but the book says that approach was a disaster when it was tried in the early years of park management.

He offers no comparison to private parks or to national parks in other countries. Although his criticism of the Park Service has made Chase a darling of the emerging cadre of "free market environmentalists" -- scholars who argue that the private sector could run national parks better than Uncle Sam -- his book never mentions these thinkers or their interesting ideas.

Playing God in Yellowstone is a screed that accentuates the negative about the National Park Service and its policy of relying on natural regulation with minimal human control. But the book never gets around to answering a key question: If you can't trust nature, what should you trust instead?