Flying high above western Rhode Island, conservationist Kevin Essington points to a bit of Eden below. Pointy white pines and red oaks stretch from the shadow of a swooping Cessna to the hazy blue horizon.

The jagged tops, in Coventry and West Greenwich, include a 1,647-acre forest purchased by The Nature Conservancy and others this year and last. The deal, the agency's biggest in 20 years, stopped developers from building new roads and houses in a wilderness pawed by beavers, black bears and deer.

To the north, however, new houses skirt a small reservoir. In nearby Hopkinton, a looped road splits the forest, the early footprint of a stalled subdivision. And just across the state line, in Sterling, Conn., new rooftops glint along the winding Moosup River, part of a key watershed that includes part of western Rhode Island.

Conservationists tried to buy the Sterling parcel a few years ago, but a developer outbid them, says Essington, who has been with The Nature Conservancy since 2001. The developer left trees on the perimeter to meet a local zoning requirement, "but the house lots were left bare," says Essington. "The owners had to buy new trees from Home Depot."

According to the U.S. Department of Agriculture's Forest Service, Rhode Island has been losing forest land since 1963, when the tree cover peaked at 434,000 acres, or about two-thirds of the state. In 2005, the amount of forest land fell to around 358,000 acres, or a little more than half the state, which is around 671,000 acres.

The same thing is happening across New England. From Canaan, Conn., to Caribou, Maine, developers from 1987 to 1997 have chewed up 60,800 acres of forest land a year. That's 167 acres a day, or 7 acres an hour, says Brett J. Butler, a researcher with the USDA Forest Service. "It's happening all along the east coast, along the I-95 corridor definitely."

Much is at stake. According to the Massachusetts Office of Travel and Tourism, the state's $13.1-billion tourism industry relies heavily on forests, including fall foliage trips, camping and other outdoor recreation. The same is true for other New England states, where nature lovers hike the White Mountains or wander through thick woods in the Arcadia Management Area.

But if growth trends from the past decade continue, Rhode Island could lead the nation in forest loss, followed by New Jersey, Massachusetts and Connecticut, say researchers David J. Nowak and Jeffrey T. Walton, who painted a bleak picture of the region in a Journal of Forestry article more than a year ago.

By 2050, Rhode Island could be 70 percent urban, they say. And Connecticut and Massachusetts - where Thoreau built a cabin in the woods to live deeply - could be 61 percent urban. Rhode Island stands to lose a greater percentage of trees because of its small size. Says Nowak, "Rhode Islanders may have to drive to New Hampshire" to find large swaths of pristine forest.

Other researchers offer similar forecasts. According to the U.S. Forest Service, four watersheds in Maine and New Hampshire are threatened by development. Elsewhere, Eastern Connecticut and south-central Massachusetts - an area known by conservationists as "The Last Green Valley" - could lose 64,000 acres of forest in the next 17 years, researchers say.

URBAN FLIGHT AND changing lifestyles are remaking the New England landscape. In Massachusetts, buyers are building big vacation or retirement homes, says James DiMaio, chief forester for the Massachusetts Department of Conservation and Recreation. At the same time, people are fleeing the cities. Although just over half of the state is forest, Massachusetts is losing an estimated 40 acres a day to sprawl, he says. "It's moving out from Boston and heading in all directions, from Cape Cod to the Berkshires."

Houses, too, are getting bigger. According to the National Association of Home Builders, nearly 40 percent of all new houses boast four or more bedrooms. The average size of a new home two years ago reached an all-time high of 2,434 square feet, up from 1,645 square feet in 1975. The area with the biggest homes? The Northeast.

While houses are getting bigger, forest lands are getting smaller. Much of the forest in New England is privately owned, and those parcels are shrinking as owners subdivide the land and sell it, often to developers.

Between 1973 and 1993, the average size of a privately owned Rhode Island forest parcel decreased from 26 acres to 13 acres. In Connecticut, parcel sizes have fallen from 43 acres in the 1950s to about 12 acres today.

The breakup of pristine forests - called fragmentation - is taking a toll on wildlife. Roads and houses can block the routes animals use to find food and water. In addition, some song birds will only mate in deep woods. Black bears, too, need hundreds of acres to live, says David B. Kittredge Jr., a University of Massachusetts professor and state forester. But other animals - squirrels, raccoons, deer and blue jays - thrive better on forest edges. Bird feeders, compost heaps, trash cans and gardens encourage wild animals to live in and around subdivisions. Some, like deer and mice, help spread Lyme disease among home owners with yards that abut forests.

Changing habitats are only one problem. Forests, which act like big sponges, also keep the air and water clean. They slow runoff, prevent erosion and filter pollutants before they enter reservoirs, rivers and streams. "A forest is a big natural filtration plant," says Kittredge. Without forests, officials must build expensive plants to treat their drinking water.

Trees also cool cities, capture storm water and remove carbon dioxide from the atmosphere. Without them the air will be dirtier, cities will get hotter, and there will be more flooding, experts say. There will be more damaging forest fires, too, because homes are closer to the woods. Hikers, campers and bikers will have fewer places to explore, and those who make a living in the forest, including loggers and syrup makers, will have fewer places to work.

"When you cut 300 acres of forest into roads and 8- or 10-acre lots, people care less about the forest," says Rhode Island's Sparks. "They put in street lights, sewers. People change the oil in their cars, and the lawns come with Chemlawn." Individually, the impacts are small. But together, she says, "they change the character of the land. Those areas that felt remote no longer are."

AWAKENING TO THE problem, conservationists are fighting back, often with money.

Last year, The Nature Conservancy of Rhode Island agreed to pay $26 million for more than 1,600 acres of woodlands in West Greenwich and Coventry. To close the deal, the Conservancy sought help from the Rhode Island Department of Environmental Management, the Champlin Foundations and West Greenwich voters, who agreed to borrow $8 million to help buy the land.

The Conservancy, which owns more than 7,600 acres of forest, farm and other land, is now looking to protect land in Foster, Glocester, Burrillville and Scituate. "We're looking at watersheds we haven't looked at before," Essington says.

Local land trusts are scooping up parcels, too, from Westerly to Glocester. Although conservation officials don't track those purchases, there are more than 40 private, town and state land trusts in Rhode Island. Nationally, private land trusts doubled the amount of land they protect to 12 million acres from 2000 to 2005.

But such deals aren't easy.

The West Greenwich purchase took years to complete. And the Nature Conservancy must still raise about $2 million from private donors to pay for the land.

"It's hard to stretch the dollars," says Essington, who barely outbid a developer for a 78-acre family forest in West Greenwich more than a year ago. "There are a lot of interested buyers now. There's always someone knocking on the door, willing to convert raw land into houses pretty quickly."

BUYING LAND is only one approach. Some sprawl foes want to save trees by making cities more attractive.

In Rhode Island and elsewhere, state and city officials are using tax credits and other incentives to lure developers back to New England's crumbling mills, shuttered factories and urban lots, dubbed "brownfields" by planners.

In Rhode Island, historic tax credits have spurred nearly 300 projects in 23 towns and cities, says Scott Wolf, executive director of Grow Smart Rhode Island. Developers are planning new offices, stores and homes in old mills and factories in West Warwick, the Olneyville section of Providence, Cumberland and Pawtucket.

States could go further, Wolf says. They could designate growth centers and make it easier for developers to revive abandoned landscapes, which often contain chemicals and industrial debris.

"Buying land isn't the whole ball game. There will always be pressure on our farm and forest lands." Planners must stop residents from fleeing cities by investing in urban schools, housing and transportation, he says. "If we want to save forests in Glocester, we need to rebuild the factories and mills in Pawtucket. Those two things are inextricably linked."

Some experts point to the examples of crowded Europe and Japan, where sprawl is managed better.

Rhode Island could also mimic Maryland's aggressive approach to conservation. Developers there must plant trees when they build, says John T. Campanini Jr., an adviser to the Rhode Island Tree Council, a nonprofit group. "The state needs to pass a law that makes people march to the same drummer. You're going to need a statute that helps protect forests. Too many towns are afraid of developers. They're worried they'll end up in court," he says.

"People don't realize the importance of our forests. So many people are tied into Narragansett Bay they don't realize we're a land people."

A SLOWDOWN IN new home construction could give conservationists a break. In Rhode Island, the number of single-family building permits - a harbinger of future building activity - fell 17 percent in the first quarter, in part because of market worries, rising foreclosures and tightening credit. In July, the number of Northeast permits fell 1.3 percent.

But historically, such lulls are often followed by hot markets. And conservationists have another concern.

In southern New England, more than half the forest is in private hands. In Rhode Island, individuals and families own nearly 60 percent of the state's forest land. Of the owners, nearly 70 percent are 51 years or older.

Conservationists worry that, as owners age or die, the land will go to children who may sell to developers.

"A lot of big decisions will be made in the next two decades," says Janet Coit, director of The Nature Conservancy's Rhode Island office. "We're concerned that as urban centers continue to sprawl we could lose more pieces of the forest."

Another problem is forest management. States are working with less money and fewer employees than 20 years ago, says Thomas A. Dupree, a University of Rhode Island forestry professor and former chief of DEM's Division of Forest Environment. "What the future holds remains to be seen," he says. "It's vitally important that Rhode Island, Connecticut and Massachusetts join together" to preserve New England's forests, he says.

Meanwhile, other states are looking to see what Rhode Island does next, says Wolf at Grow Smart. "In national land-conservation circles, Rhode Island and New Jersey are called end game states, because we're in the last innings of the battle."