What would Frederic Church think?

The Hudson Valley School painter who glorified the great green sweep of the valley in the 19th century would paint a very different picture today.

Trophy homes, townhouses, and strip malls have popped up around the river, a signal that the valley is prime real estate. Development is so fast and heavy that conservationists want to step up land purchases and preservation efforts before more woods and farms are built over.

“It’s almost a race now between ‘Will we be able to preserve what makes the Hudson Valley special?’ versus ‘Will the Hudson Valley become one vast bedroom community for New York City?'” Jeff Jones of Environmental Advocates said.

To get a sense of development patterns in the Hudson Valley, imagine a map with concentric rings radiating from New York City. Suburban areas in the inner circles, like Westchester and Rockland counties, are tightly developed, with home prices routinely topping the half-million-dollar mark.

That, in turn, pushes people looking for bigger lawns and cheaper housing to outer circle areas, like Orange, Ulster, and Dutchess counties.

Those three counties are among the fastest growing in the state. Many new arrivals are New York City residents, some looking for more security in the post-September 11 era. The lion’s share of the residential growth has occurred outside the valley’s cities and villages.

Developers have proposed construction along the Kingston waterfront, the Shawangunk Ridge, and the sprawling grounds of an old psychiatric center in Poughkeepsie, among other places. There also is a proposal to build a $353 million cement plant down the road from Church’s old hilltop home, Olana.

The New York and New Jersey Highlands, which includes parts of Orange, Putnam, and Dutchess counties, could be built out in the next 20 to 30 years, according to an estimate cited by Thomas Gilbert, executive director of the Highlands Coalition.

“What is not protected in the next couple of decades is going to be developed,” he said.

While not against all development, conservationists advocate “smart growth” – that is, planned development around population centers that avoids sprawling construction. Unchecked sprawl is blamed for loss of land and degraded air and water quality.

There are a number of groups buying land and conservation easements in the Hudson Valley, including local trusts, governmental entities, and larger players like the Open Space Institute and Scenic Hudson.

Scenic Hudson tries to protect crucial parcels while working with towns under pressure like Red Hook, a once-rural haven about 90 miles north of New York City that is now popular with commuters and weekenders.

Scenic Hudson acquired conservation easements for nine farms in Red Hook, and the town approved its own $3.5 million bond to protect farmland.

Town officials also have a detailed plan for addressing open space issues and are looking at tax incentives and other means to regulate development. Town officials and environmentalists both say policies encouraging smart growth are necessary because there is not enough money to go around to protect everything.

“Neither we nor the town can buy up all the farmland there, or all the open space that community members are interested in protecting,” said Scenic Hudson’s president, Ned Sullivan.

Open Space Institute’s president, Joseph Martens, said the red-hot real estate market of recent years has made purchases and easements, already a pricey proposition, even more expensive. He said land-owners have a sense that they can get extraordinarily high prices, even higher than the market has been bearing lately.

State and federal governments also contribute.

President Bush recently signed a bill authorizing $110 million to preserve open space in the Highlands, a swath of the Appalachians that cuts across the Hudson Valley from Pennsylvania to Connecticut.

New York routinely purchases sensitive lands through its Environmental Protection Fund, though conservationists complain the fund has been stuck at a $125 million funding level for several years.

They claim New York lags neighboring New Jersey and Massachusetts in per capita spending on open space acquisition.