A fire set under controlled conditions is an important tool in managing the national forests of the United States. These fires are used to clear away forest residue that might otherwise turn a minor fire into a major conflagration. A prescribed burn might be used to clear an area as small as 15 acres in the Tahoe National Forest in Nevada or as large 2000 acres in the Prescott National Forest in Arizona. They are also utilized to enhance wildlife habitat and prepare a site for seedlings. However, planning and executing a controlled fire is a complex and risky process. The spread of a fire is affected by uncertainty surrounding the environmental conditions and the fire's behavior once it is started. Decision makers must decide under what conditions to start a fire and the level of resources to made available on-site as the controlled fire is initiated. The final outcome is also uncertain as to its effects on vegetation, soil, timber, hazards, and wildlife.
Once a fire plan has been established, decision makers still must make a careful assessment of current and forecasted weather conditions before going ahead. The decision elements (rectangles) and the uncertain variables (circles) are represented in a schematic decision tree below. The article describes three case studies in the early 1980s. The primary goals with regard to Tahoe National Forest were to prepare the land for planting new trees and reduce the hazard of wildfire. In the Prescott National Forest the main goal was to improve the wildlife habitat. Another decision tree study was prepared for planting and wildfire reduction in the Gifford Pinchot National Forest that straddles the border between Washington and Oregon.