Fuel treatment tradeoffs – Protecting the wildland urban interface vs. restoring fire resilient forests

Project Description

Large investments in wildland fuel reduction projects are being made on federal lands in many regions in the United States in an ongoing effort by land management agencies to control human and ecological losses from wildfire. The implementation of these projects continues to challenge planners as they attempt to reduce fuels over extensive areas while addressing multiple and often conflicting federal planning regulations, management objectives, public expectations, and finite budgets. Policies, constraints, and regulations that restrict treatment location, type, and total area treated can significantly degrade the performance of a landscape fuel treatment strategy. For instance, focusing treatments in and around highly valued areas, such as the wildland urban interface (WUI), is less efficient and perhaps not compatible with landscape restoration goals to change large fire behavior. The long term compatibility of these divergent management objectives to protect relatively small WUI’s while also meeting large landscape forest restoration goals is not well understood. Simulation modeling was used to examine tradeoffs between investments in fuel management activities in a WUI in Oregon’s Blue Mountains versus treating fuel in the surrounding National Forests, where fire management objectives are to restore fire resiliency. As expected, fuel treatment in the WUI had the largest reduction in wildfire risk to structures. However, fuel treatment in the WUI also resulted in substantial wildfire-caused mortality of large trees in the surrounding forest, and thus did not contribute to broader forest restoration goals. Treatment strategies to meet forest restoration goals outside the WUI decreased wildfire risk to large trees, and also reduced the incidence of wildfire in the WUI. The results suggested that fuel treatments well outside the WUI can significantly reduce wildfire threats to property and help meet broader forest restoration goals.

Maps depicting two spatial treatment scenarios used in the wildfire behavior simulations. The green areas indicate where fuel treatments would most likely be effective, given a specific objective. In the figure, the left-hand objective was to protect and preserve large trees and the right-hand objective was to protect structures.

Purpose and Scope

Federal policies direct public land managers to reduce wildfire risks for urban areas close to wildlands, while broader agency goals call for landscape restoration to create fire resilient forests. This research explored treatment effectiveness to (1) protect structures and (2) preserve old-growth trees by concentrating treatments close to the WUI vs. in the surrounding National Forests.

Methods

We simulated thousands of wildfires using RANDIG, a landscape wildfire behavior simulation system, to test multiple fuel treatment strategies. Fuel treatment strategies varied in their objectives; to protect structures or promote fire resiliency. Multiple alternatives for each were simulated to determine the most ideal proportion of land treated to result in desired changes to fire behavior.

Key Findings

• Results from wildfire simulations suggest that fuel treatments on 10 to 15% of the forest landscape outside the wildland-urban interface (WUI) could dramatically reduce the expected wildfire loss of large, fire-resilient trees.
• Fuel treatments simulated at distances of 3 to 6 miles from the WUI substantially reduced burn probabilities around structures.
• Objectives for fire protection of WUIs and forest restoration can be compatible if fuel-treatment designs consider landscape features and other factors significant to wildfire behavior in relation to the spatial arrangement of human property and ecologically valuable resources.