The road from Northwest Washington to Cinda Sebastian and Scott Williams's farm in Carroll County, Md., passes first through Chevy Chase, one of the earliest of the suburbs that slowly and concentrically extended the metropolitan area. From there, it goes through Montgomery County, where six-lane avenues slice through relatively dense housing and commercial real estate. On it travels, northeast to Howard County and then, finally, to Carroll County, where developments of one- and two-acre "estates" begin to give way to rich farmland, with fields of corn and grazing horses.

Sebastian and Williams's farm is just past a stretch of road lined with developments with names like the "Greens of Westminster" and "Whispering Meadows."

There, the couple works about 35 acres on the 300-acre farm where Sebastian grew up. Their operation, called Gardener's Gourmet, produces organically raised herbs, tiny greens and heirloom and specialty fruits and vegetables such as chiogga beets, bronze fennel and Charentais melons for Baltimore and Washington markets and restaurants. Along with several nearby farms, they are protected from development by an agricultural easement sold to the state of Maryland. But just beyond this small oasis, the landscape is changing.

Now some agricultural advocates are warning that metropolitan sprawl could jeopardize access to high-quality, locally produced fresh fruits, vegetables, meats and dairy products. Two nearby areas--one in Virginia and one in Maryland--are at risk, along with their dairy farms, apple and peach orchards and fields of sweet corn.

"When I moved up here 20 years ago, between our house and Westminster there were about 15 houses," said Williams. "It was all farmland. It was just beautiful, and now it's like a gazillion houses."

In the past several years "sprawl" has become a hot political issue, blamed by environmentalists for a variety of ills and taken up by politicians as an issue of consumers wanting choice and "livability."

Sprawl represents a change in the traditional patterns of development, according to opponents. People are rapidly moving farther away from urban areas into bigger houses on bigger lots surrounded by bigger stores. In the area surrounding Chicago, for instance, land has been developed for housing at a rate 11 times faster than the population growth, and the amount of retail space per capita increased by 30 percent between 1986 and 1998, according to F. Kaid Benfield, a senior attorney with the Natural Resources Defense Council, and co-author of "Once There Were Greenfields: How Urban Sprawl Is Undermining the Environment, the Economy, and Social Fabric" (NRDC, $20)

There's no danger of a food shortage in the United States. And there's plenty of land, noted Keith Collins, chief economist at the U.S. Department of Agriculture. "For a nation with 2 billion acres in the contiguous 48 states and 1 billion acres in farms, a million acres a year being converted [to housing] is dwarfed by the land available for crop production," he said. In addition, crop production per acre has gained steadily over the years, he said.

But not all land is created equal, say those who want to control sprawl. "Most of the good farmland is around major cities, and that makes sense, because that's where people settled," said Ann Harvey Yonkers, who manages the American Farmland Trust's FreshFarm Market program. The program is designed to put consumers in direct contact with producers of agricultural products by setting up farmers' markets, including one at Dupont Circle in Northwest Washington and another in St. Michael's, Md., on the Eastern Shore.

American Farmland Trust, a private, nonprofit organization founded in 1980 to stop the loss of productive farmland and to promote environmentally friendly farming practices, has compiled a list of the 10 most endangered agricultural areas, including two near the Washington metropolitan area. Second on the list is the Northern Piedmont, which includes parts of Maryland and Virginia; ninth is the Mid-Atlantic Coastal Plain, which includes parts of Maryland, Virginia and Delaware. The most endangered area on the list is California's Central Valley.

According to the American Farmland Trust, 79 percent of U.S. fruits, 69 percent of the vegetables and 52 percent of the milk are produced near urban areas on land in danger of falling to development. According to the USDA, urban-fringe agriculture produces 2 1/2 times as much revenue per acre as does rural agriculture. In part, says the USDA, this may reflect "innovative marketing techniques, such as 'pick-your-own' operations that also provide recreation and a connection to the land for urban and suburban residents." Those techniques also include marketing varieties of fruits and vegetables that don't lend themselves to large-scale, corporate farming.

That's the kind of approach that allows Sebastian and Williams and others to operate profitably as farms around them disappear.

Jim Crawford and his wife, Moie Kimball Crawford, run New Morning Farm in Huntington County, Pa., a location they chose in part because it was remote. "There're not that many places in the East that are 125 miles from any major city," he said. Crawford sells organically grown fruits and vegetables and eggs and dairy products at markets in Washington and through a marketing cooperative called the Tuscarora Organic Growers Cooperative.

Many of the farmers in his area have tried to survive by buying or leasing more acreage in order to benefit from economies of scale--reducing the cost of production by spreading it over more land.

"We've gone in a very different direction into much more intensive production of much higher value crops and with specialized marketing," he said. "Doing that has changed the whole economic equation completely and made it possible to hang on longer," said Crawford. "It's still not a living that many people would be willing to accept, but there's some profit to it."

Crawford has watched the landscape around him begin to change, although much of the change has been prompted not by sprawl as much as by other hardships of farming, such as low prices and scarce rain.

"There's an awful lot of land up here that used to be productive cropland . . . that basically is just sitting there idle," he said. Some of the land is owned by families now working elsewhere for a living and some of the land is tied up in the settlement of estates.

On the other hand "there are an awful lot of people who are farming who are doing it kind of out of habit and love because they grew up doing it," he said. "They're not investing heavily in equipment. They're taking whatever equipment they have and planting corn or making hay, and this stuff is not worth anything," he said. "People are going through the motions. It's just really sad."

But small expeditionary forces are moving out from the cities, even as far as McConnellsburg in Huntington County, 175 miles from Washington, Baltimore and Philadelphia. "There are weekenders on all sides of us and, of course, they're pushing up the price of land all the time," he said. "Our taxes are much higher than they were. They're still relatively low, but they've gone up by about 20-fold since we've been here."

Eric Rice, an organic farmer who has operated in Middletown, Md., for about 12 years, said that, in addition to putting pressure on farmers by raising property values, sprawl also results in the loss of the infrastructure that served farming communities. Commercial kitchens, which once bought tomatoes for tomato paste or apples for applesauce, have disappeared from the state, he said.

Farmers also must travel farther to buy or maintain farm equipment. "We used to have everything we needed right in Waldorf," said William Alton Gallahan, who runs a pick-your-own farm called Cherry Hill in Prince George's County. "That's become citified, and now you couldn't buy any farm supplies," said Gallahan, who drives an hour for what he needs.

Farmland is particularly vulnerable to sprawl because it typically comes in large parcels--making the developers' job easier because they won't need to assemble a lot of small pieces of land. And some of the attributes that make the land attractive for farming--being relatively level, for instance--also make it easier to develop.

Maryland was the first state in the nation to adopt a program of buying easements--essentially paying farmers to keep their property as farmland in perpetuity as an alternative to cashing out by selling to developers. In contrast, Virginia has no program and no plan to prevent farmland from disappearing, according to Mary Heinricht, director of American Farmland Trust's Mid-Atlantic Region.

Sprawl takes its toll not just on agricultural produce, but also on the Chesapeake Bay and the oysters, crabs and fish it produces, said Lee Epstein, director of the lands program for the Chesapeake Bay Foundation. According to Epstein, approximately 90,000 acres in the bay's watershed are converted from farmland, forestlands or wetlands every year. That's an area twice the size of Washington, he noted. That means a loss of land that helps filter out contaminants before the water runs into the bay, and more air pollution, which also has an impact. Epstein said that approximately a quarter of the nitrogen that has contributed to choking the bay is from airborne sources such as motor vehicles.

Anne Arundel County--where developers broke ground in July for a mega-mall whose potential attractions include a sporting goods store with an indoor fishing stream--has lost 20 percent of its productive land to urban growth over five years, according to Epstein.

"Growth per se isn't bad. It's the way it's arranged on the land," he said. It's what happens on land, both farmland and urban land, that probably is the ultimate challenge for restoring the Chesapeake Bay.

Some farmers say they see benefits from development moving closer. It helps bring new customers to farm-based markets, for instance. Still, many of them say they regret the loss of farmland around them, whether the culprit is death in the farm family, drought or development.

Once those farms are lost, they aren't likely to ever be restored. American Farmland Trust's Heinricht said that the United States could lose the opportunity to sell fruits and vegetables to growing markets in China and India, where agricultural production can't keep up with population growth. The vast U.S. agricultural areas that are remote from urban sprawl tend to be more suitable for producing food grains and livestock grains than for fruit and vegetable production, she noted.

Jim Crawford, contemplating the disappearance of dairy farms and orchards since he moved to McConnellsburg, spoke of another kind of loss. "The next generation of kids is not going to know what a good peach is. If you take a peach 3,000 miles, it is just not the same peach. The whole thing of losing agriculture and smaller-scale family farms in the East has had a big impact on the quality of food that people have available to them."

CHANGING FARM PROFILE:

MARYLAND

* 1969

Number of farms: 17,181

Acres of farmland: 2.8 million

Average farm size: 163 acres

Average farm value: $640/acre

* 1997

Number of farms: 12,084 (30% loss)

Acres of farmland: 2.154 million (23% loss)

Average farm size: 178 acres

Average farm value: $3,176/acre

VIRGINIA

* 1970

Number of farms:76,000

Acres of farmland: 11.4 million

Average farm size:150 acres

Average farm value:$286/acre

* 1997

Number of farms: 47,000 (38% loss)

Acres of farmland: 8.5 million (25% loss)

Average farm size: 181 acres

Average farm value: $2,030/acre