Remote sensing on the range.

• Position: Monitoring

Ranchers, farmers, loggers, and recreationalists throughout the nation's western region are being asked to share rangelands. With more groups using them, it has become increasingly important to monitor the land to maintain it and to guard against overuse.

The Bureau of Land Management (BLM) has been tasked by Congress with reporting the conditions and changes on the land it manages--all 262,000,000 acres of it. Pacific Northwest National Laboratory (PNNL), Richland, Wash., researchers have developed a unique way of applying remote sensing capabilities to monitor these range-lands.

PNNL was asked to find a cost-effective and easy-to-use way to sample BLM lands, locating areas of management concern such as bare soil. Remote sensing tools, including low-level aerial photography and digital imagery from satellites, were the logical choice for cost-effective monitoring. "Each pixel of a remote sensing image gives a spectral signature for that area on the ground, and when you have a change in vegetation cover resulting from some disturbance, that change is reflected in the spectral signature," says Larry Cadwell, project manager. Finding where the spectral signature differs from the expected or normal pattern of the site helps identify areas of overgrazing, weed invasion, or fire damage.

Researchers...