Scientists have identified and begun computer-assisted research on 17 environmentally sensitive sites in Loudoun County in the first year of the Loudoun Environmental Indicators Project, researchers from George Washington University reported Thursday.

The $1 million project, which will stretch over five years and involve the work of a team of George Washington faculty and students from several academic departments, was organized last year to research potential environmental changes caused by rapid growth in Loudoun.

Researchers are monitoring the condition of forests and farmland; the quality of air and water; the amount of land covered by asphalt, shopping centers and other development; the location and condition of rare and endangered plants; and the status of cultural and historic landmarks.

Dorn C. McGrath Jr., director of the Institute for Urban Environmental Research and professor of geography at George Washington, said the mission of the project is to raise public awareness of the ways that rapid urban growth can change the environment and to present data on these changes that can be monitored and used by county leaders.

The project received funding from the Virginia Environmental Endowment, the Canaan Valley Institute of West Virginia, the Loudoun County Board of Supervisors and many Loudoun businesses and private citizens. It will include color satellite images and aerial photographs of forests, creeks, roadsides and landmarks as a tool for county planners in making development decisions.

"Experience strongly suggests the need for continuing public discussion of environmental pressures and changes in the county as the key to enlightened governance and use of the county's delicate resource base," McGrath said at a forum at the university's campus near Leesburg, where the project's first annual report was released.

"The indicators project will provide information for Loudoun County leaders and citizens in guiding the process of inevitable urbanization in much of the county," McGrath added.

In the project's first year, researchers began to quantify the amount of impervious surfaces--asphalt and other ground covers that do not absorb rainwater and that alter the natural flow of water--in Loudoun, beginning with shopping centers in Cascades, Potomac Run and Dulles Town Center.

The aim is to show the extent to which widespread paving can change surface temperatures and lead to the creation of "urban heat islands," McGrath said. The existence of such "islands" can lead to more air conditioning use, greater energy consumption and the need for more watering in landscaped areas, McGrath said.

To measure the acreage of impervious surfaces in Loudoun, the researchers obtained aerial photographs of the three malls, scanned the images into a computer to produce digital images, and used a computer program to analyze the images and to identify buildings, parking lots, water features, streets, roads and grassy areas.

The information went through another round of computer analysis to produce calculations of the percentage of each of the three sites that is covered by impervious surfaces--229 acres, or 43 percent of the 537-acre total for the three sites.

The researchers also analyzed impervious surfaces at Washington Dulles International Airport--1,436 acres, including runways, ramps and access roads--and Leesburg's municipal airport--30 acres.

Researchers also began to compile data on other county land uses.

The first-year report concluded that 71 percent of Loudoun's 138,000 acres of agricultural land is in tracts of 100 acres or more. In coming years, through a review of county land use files and aerial photographs, the researchers hope to determine how much farmland has been assembled for eventual development.

"It is clear that many farms, especially dairy farms, have disappeared from the county in the past decade," the researchers said.

Aerial photographs also will be used to document the extent to which forests and wetland buffer areas have been removed to accommodate development. The researchers found that "the most significant" buffers in Loudoun, which lie along the Potomac River and Goose Creek and its tributaries, have been largely untouched in the past decade.

These and other buffers have become the focus of a special task force appointed by the county's Open Space Advisory Committee, which eventually could decide to protect these areas from development, the report said.

The researchers found that the amount of forested land in Loudoun actually has increased in the last 25 years but that many of the remaining forests are fragmented into islands. They also found that those that were cut down have been replaced by fast-growing "trash trees" such as junipers instead of the hardwoods that originally were there.

The researchers used satellite images obtained last summer to map forested land in Loudoun. The images were subjected to an analysis using a computer program known as a geographic information system that can track the fragmentation of forest cover.

The results showed that from 1973 to 1999, Loudoun experienced a net gain in forest cover--from 30,281 forested acres to almost 38,000 acres--primarily because patches of juniper trees have taken root in recently developed areas and in parts of central and southeastern Loudoun that once were used for agriculture.