When it comes to basing park management on science rather than the needs of tourists, the National Park Service is a bit like an old drunk: It's constantly promising to go on the wagon but forever reaching for the bottle.

Since its creation 83 years ago, the service has faced an enduring conflict embodied in its founding legislation, which declared that the fundamental purpose of the park system was "to conserve the scenery and the natural and historic objects and the wild life therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations."

More often than not, reported Park Service historian Richard West Sellars in his 1997 book "Preserving Nature in the National Parks," the conflict between preservation and enjoyment has usually been won by enjoyment.

"Nature preservation-- especially that requiring a thorough scientific understanding of the resources intended for preservation--is an aspect of park operations in which the Service has advanced in a reluctant, vacillating way," Sellars wrote.

In Yellowstone National Park alone, the service has introduced non-native fish, fed grizzly bears like so many zoo animals and raised hay for the winter feeding of deer and antelope. In Yosemite, the Park Service set up a zoo.

In part because of demands of the public and Congress, Sellars wrote, the service has concentrated on "facade management"--that is, "protecting and enhancing the scenic facade of nature for the public's enjoyment but with scant scientific knowledge and little concern for biological consequences."

Now, partly in response to Sellars's criticism, the Park Service has embarked on an initiative to shift the balance back toward protecting the natural world. In announcing the "Natural Resource Challenge" during a visit to Mount Rainier National Park earlier this month, National Park Service Director Robert Stanton promised a new commitment to protect resources for future generations. "Preserving our natural resources far into the future now requires active and informed management based on sound science," he said.

PARK PROMISES: Among the promises in the new initiative are that the Park Service will:

* Assume more of a leadership role in protecting threatened and endangered species and in controlling invasive, non-native species.

* Do a better job of enforcing existing environmental laws within parks, particularly clean air and clean water mandates.

* Make natural resource protection an integral part of long-range park planning and make parks centers for scientific research and education.

* Ensure that employees who specialize in natural resource protection rise to positions of senior leadership.

If those promises sound familiar, they are. Over the years, in numerous internal and external reports, the Park Service has been criticized for inattention to science-based management and has pledged to do better.

In 1963, a report by biologist A. Starker Leopold commissioned by then-Interior Secretary Stewart Udall urged that scientific research "form the basis for all management programs." Later that year, a National Academy of Sciences report called the Park Service's science programs "anemic." A 1980 "State of the Parks" report noted that the service paid far more attention to maintenance of visitor facilities than to developing sound information on resources. And in a 1991 assessment, the Park Service criticized itself for "sporadic and inconsistent" support for science.

So, is there any reason to believe this new commitment to science and ecologically sound management will be any more fruitful?

Deputy Director Denis P. Galvin thinks so. Not only does the plan have serious backing by the agency's top leadership, but it will--Congress willing--have a major budgetary commitment of up to $100 million over five years.

"The default position in the Park Service is visitor services," Galvin said. "We have to keep the roads in reasonable shape. If we have a sewage plant that's not up to snuff, we have to do something about it. If you are making budget decisions, you are constantly pushed in the direction of visitor services. This initiative is a recognition that we have to carve out something in our budget that protects the natural resources program from being decayed by that default mode."

Sellars agrees: "It's a pretty strong proposal."