Thousands of acres along the shore of the Chesapeake Bay and five of its largest tributaries in Maryland have been targeted by a national land conservation group as part of a long-term plan to buy individual parcels and turn them into one of the nation's largest systems of open spaces, public parks and water-access points.

The Trust for Public Land, which has preserved more than 8,000 acres of open space in the state since 1985 and played a key role in the recent creation of the 14-mile Gwynns Falls Trail in Baltimore, has identified miles of undeveloped land along the western shore of the Chesapeake and throughout the Gunpowder, Patuxent, Patapsco, Potomac and Susquehanna river systems that it wants to help state and local governments, conservation groups and private donors to preserve.

"The concept is parks for people that will in turn protect the bay," said Rose Harvey, the trust's Mid-Atlantic regional director. "We call it green-printing."

The ambitious plan comes at a time when dropping property values and stalled development have made such initiatives more likely to succeed, she and others said. In addition, state environmental officials have said they plan to focus more on water quality and habitat in deciding which land to purchase.

"When the market is red hot, we have a hard time competing," said Russell Shay, director of public policy at the Land Trust Alliance, a group that represents 1,700 land trusts nationwide. "When the market slows down, we have a little better chance."

In most cases, The Trust for Public Land plans to buy parcels that state or local government agencies have agreed to acquire, and then sell them to the agencies when they can pay for them, Harvey said. This prevents potential parkland from going to a private buyer just because public money isn't available right away, she said.

The trust's plan also could put it in competition with Maryland's home building industry, which says developable land will be needed to accommodate expected population growth in the next 20 years.

The trust hopes that by 2020 it will have helped purchase and preserve one-third of the shoreline identified in its new Parks for People-Community Rivers program. While all shoreline woods, farms and recreational areas such as camps or trail systems are on the group's radar, the ultimate goal is to expand and connect state and local parks that now dot the region, Harvey said.

"We're going to be extremely strategic to pick those lands that will link greenways, on the notion that the longer and more linear the park the better," she said.

The nonprofit trust says it has protected 2.5 million acres in 47 states since its inception in 1972. Its funding comes largely from grants from corporations and foundations, contributions of land and money from groups and individuals, and its own investments.

Because it does not buy land speculatively, the trust is able to maintain a high level of capital that allows it to compete for real estate at market value, said Susan David, the trust's director of public affairs. The trust reported having more than $223 million in net assets in 2007. David declined to identify properties that the trust is pursuing, saying the negotiations are confidential.

While the economic picture for such trusts isn't completely rosy - contributions are down, government agencies are strapped for cash and some people aren't selling their land in hopes its value will eventually increase - many developers who bought land at high prices a few years ago are now selling it for less because their building projects have been canceled.

The poor housing market also leaves Program Open Space, the major land acquisition and conservation funding arm of the state Department of Natural Resources, with less bargaining power. Its funding comes from the state real estate transfer tax, and when the housing market slows, the program receives less money.

"Sometimes the trust can act quicker than us, and that's one of the benefits of the partnership to the state," said Shaun Fenlon, director of land acquisition and planning for the Department of Natural Resources. "It just becomes a question as to what extent their interest and their focus overlaps with our focus."

Because of recent changes in the state's strategy for determining lands to purchase, such overlap is likely. Last summer, the department's land acquisition strategy was questioned by state officials, including Gov. Martin O'Malley, who thought it was not picking particularly ecologically important land. In response, Natural Resources Secretary John R. Griffin said water quality and habitat would become more important in land acquisition deals.

Although Maryland has a Critical Area Act that restricts development within 1,000 feet of tidal waters or wetlands on the bay and parts of tributaries and largely prohibits it within 200 feet of the water, local governments can grant variances to landowners that allow them to build in the area, and development along the shorelines has continued at a steady pace.

Marsh grasses, wetlands and trees act as "natural kidneys" for the rivers and bay, absorbing unwanted nitrogen and phosphorus and serving as a place for sediment to settle, said William Dennison, a vice president at the University of Maryland Center for Environmental Science, who oversees bay and river research.

The current project was conceptualized during the work the trust did on the Gwynns Falls Trail, when Harvey and her colleagues realized the vast potential for conservation around Baltimore and its river systems, she said.

The trust's research showed that 28 percent of the Chesapeake Bay's western shoreline, 41 percent of Maryland's Potomac shoreline and 29 percent of the Patuxent shoreline - more than 170,000 acres within a one-mile corridor of the waterways - is undeveloped, making it prime real estate for the conservation group to turn into parks. More than 230,000 acres are undeveloped in the entire targeted area, research found.

On top of that, the population of the Baltimore-Washington metropolitan area is expected to increase by 1 million people by 2030, Harvey said.

The combination of vacant land and population growth sent a chilling message as to the vulnerability of the shorelines, Harvey said.

"It's now or never," she said. "Without a doubt, this is where the influx of the population is going to come in."

But developers say the additional people will need places to live, work and shop.

"We do know that despite the downturn in the housing market and the economy and the increase in fuel costs, people are still going to migrate to Maryland over the next 20 years," said Susan Stroud, director of government affairs for the Home Builders Association of Maryland. "Once we get through this period of time - however long it's going to take - and rebound and start addressing the needs of the marketplace, there still will be, at the end of the day, a large expectation of growth in the state of Maryland, and we will need land to be available."

According to Harvey, parklands will help developers by adding "nearby, recreational space" to their lists of amenities.

"It's symbiotic," she said. "If we get in ahead and create contiguous parkland around the waterways, it will benefit the development."

Harvey said she's not sure when the first land will be bought but is encouraged by the amount of land identified as preservable. By the time the trust gets to many metropolitan areas, there isn't much natural land left, she said.

"You're always picking up the leftovers," she said. "Not here. I think we're ahead of the curve in terms of growth and identification of lands for protection, before they become the leftovers."

kevin.rector@baltsun.com