A Woman Who Guards a Wilderness. Margaret Nygard is the guiding force in preserving North Carolina's Eno River Valley. NATURE: ENVIRONMENTAL ACTIVIST

HER gray hair swinging, Margaret Nygard climbs nimbly down a granite ledge slick with fallen leaves. Steadying herself with her dogwood walking stick, the elfin 64-year-old hikes briskly down the gorge. ``This is the crane-fly orchid,'' she says, pausing briefly to point out green and purple leaves that spring from the forest floor. ``It blooms in the summer, tiny little orchid flowers, but the leaves die back then. If you don't know where to find it, you miss it.''

By a clump of green she stops again. ``This is trailing arbutus. It's rare, because its ecology requires a fungus plus granite.'' She leans forward on her stick, her round face crinkling with satisfaction. ``We've been watching that patch for 25 years.''

For longer than most of the nation's environmental protection laws have been written, Margaret Nygard has been watching over the wild and delicate beauty of the Eno River Valley, 40 miles of wilderness meandering through the rapidly urbanizing piedmont of North Carolina.

When she and a group of neighbors first protested the river damming and development of the valley back in 1965, local newspapers and businessmen called her a Rip van Winkle, too out of step with modern times to understand that progress requires the destruction of wilderness.

Now they call her a visionary, a pragmatist who acted while there was still time, back when land prices were reasonable and nature lay pristine in big blocks that could be strung together into a major public reserve.

As the driving force behind a citizens' group called the Association for the Preservation of the Eno River Valley, Mrs. Nygard helped design, promote, and fund the creation of the 2,028-acre Eno River State Park. The park links federal and local reserves to form a greenbelt 40 miles long.

The Eno River Association now includes 700 dues-paying members. They have raised $227,000 to buy parkland, negotiated creative compromises with developers and politicians, and for 10 years have held an annual fund-raising festival. The most recent one was attended by 35,000 citizens.

Last year the association received a national ``Take Pride in America'' award at the White House. This year they are launching a major land drive to bring 885 more acres - including rare plant habitat - into the park.

Most of these activities have been organized from Nygard's kitchen, where the association maintains its telephone. She has been the group's executive vice-president for 20 years.

``She is a role model for other groups,'' says Donald Reuter, public information officer with the North Carolina Division of Parks and Recreation, which nominated the association for last year's Take Pride award.

``She exhibits a genuine concern for the environment and somehow reaches the right people. She is an extremely valuable person to North Carolina.''

Soft-spoken and modest, Nygard seems an unlikely mastermind behind the actions of thousands of citizens. If not a Rip van Winkle, she is clearly a person unbound by the conventions of this modern age.

With Holger, her husband of 45 years, she lives in a 175-year-old house in the woods above the river. She doesn't drive a car. Except in the dead of winter, she is usually barefoot.

But in her own unassuming way, she has been able to reach a range of citizens rarely united by more conventional leaders. ``We didn't say, `Don't, don't, don't,''' she says of the association's efforts. ``We said, `Do, do, do.'''

Her ability to rally the business community to her cause netted her a $5,000 award last year from the Conservation Fund of Alexandria, Va., which annually recognizes an environmentalist who achieves significant conservation by cooperating with business groups.

A coalition with the Washington, D.C.-based Nature Conservancy first gave the Eno River Association tax-exempt status for landowners' donations.

BY talking with elderly people and researching old letters, deeds, genealogies, and newspapers, the association was able to publish the river valley history and gain the support of the area's older families.

The group once persuaded some Green Berets to take citizens on raft trips down the river. Another time it organized National Guardsmen and high school students to move an old gristmill down from Virginia to re-create a historical site.

So many people have been so involved in helping create the park that Nygard now laughs off her leadership image as ``mythmaking.'' She routinely refers to her efforts as ``us.'' But others credit her with providing the strategy behind all the diverse and disparate elements.

``Someplace in her head all of this is synthesized into a whole,'' says Carol Charping, a member of the Eno River Association for 15 years. ``It's Margaret who has the fine sense of purpose.''

Her love of nature has been a lifelong passion, a fundamental bond she shares with Holger. As a young couple (they married when she was 19), the two cycled up Canada's precipitous Fraser River Canyon on bicycles that would horrify today's high-tech cyclists.

Her chosen field of study was English language and literature, in which both she and Holger received doctorates from the University of California at Berkeley. But she was raising four children in the old house above the river when the city's plan to dam the river and flood the valley for a reservoir ignited her activism.

``There's something very stagnant about a man-made lake,'' she now muses. ``To us a river is a very vibrant thing. Changing moods, changing seasons. It's kind of a restorative, if you go walking along the river. It replenishes after walking on pavement and being under city lights. It's very genuine.''

Her family was swept up in Margaret's environmental work. Holger, a founding member of the Eno River Association, has worked beside her for more than two decades. His photographs are among those in the association's exhibitions of Eno River scenes displayed around the state.

Their oldest daughter, Jenny, is an artist whose work includes botanical drawings and posters for the annual Festival for the Eno. Their youngest son, Erik, is a state park ranger.

NYGARD herself manages an astonishing array of activities. As vice-chairman of the Durham County Open Space Committee, she is working to preserve other undeveloped lands for public hiking and recreation. Last summer she spoke before a US House subcommittee on the importance of federal funding for conservation.

One recent week she spent several days lobbying against a new road that would fragment the greenbelt along the lower Eno. Another day she organized public pressure on the state Division of Environmental Management to stop a textile mill from discharging dyes that color the river.

``We're trying to work it out as nonconfrontationally as possible with industry and government,'' she says of the dye dispute, speaking with the gentle courtesy that is her hallmark. But her voice holds a note of unwavering commitment that has led some to describe her as relentless. Confrontation is not her style. But neither is surrender.

Her biggest task at the moment, she says, is to try to help fill in the state park's ``missing links'' - 885 acres still privately owned and subject to development.

``Yesterday we bought outright a piece of property for $100,000,'' she says. She seems slightly in awe of the accomplishment, but she is already brainstorming about the possibilities.

The land, with the former Girl Scout camp next to it, has ``the potential of holding a youth hostel and a ranger, possibly an educational center,'' she says, noting that a new high school is planned nearby. ``We've got to get the kids involved.''

``I see the whole effort as unending,'' she explains. Then she picks up a soft drink can beside the river and hikes rapidly down the trail.