Analysis of fire suppression and increasing environmental variability on wildfire intensity

Wildfires are burning at scales and intensities not seen in generations with potentially devastating impacts on watersheds, ecosystems, and human communities. Investigators plan to analyze 400-years of tree-ring fire records and 1,000-years of heat sensitive archeological artifacts to determine if fires today are burning hotter than they have historically.

After more than a century of fire suppression, forests are full of undergrowth, dead fuel, and overly dense stands of trees. Warmer temperatures and severe drought make these forests explosively combustible. It is difficult to disentangle the relative contributions of environmental change and of fire suppression to wildfires because of these confounding factors.

Comparing recent fires under cool weather conditions versus those that only burned in pre-fire suppression fuels will enable these scientists to separate the influences of environmental change from those of fire suppression. This project trains Native American students and enables land managers to better allocate resources to activities that mitigate wildfires.

As a result of a century of fire suppression, many forests have accumulated fuels in the form of leaf litter, dead and down branches and trees, and an increasing density of young trees and shrubs. Hotter temperatures and pervasive droughts make these accumulated fuels more combustible and are driving extreme fire behavior including fire tornados. Increasingly large "megafires" have impacted water supplies, ecosystems, and destroyed thousands of homes.

It is difficult to parse the relative contributions of environmental change and fire suppression in these contexts because they are operating simultaneously. However, knowing the relative importance of each would aid land managers and policy makers to allocate resources to mitigate the situation. In this project researchers use an innovative integration of heat sensitive archaeological proxies in artifact dating and charcoal analysis, and tree-ring science to determine if fuels accumulated from a century of fire suppression alone are enough to drive increases in fire intensity that are unprecedented in last 500-1,000-years.

They investigate sites that burned frequently prior to fire suppression to establish a baseline for historical conditions (pre-suppression sites) and sites that burned in cool-season conditions after a century of fire suppression (post-suppression sites). By focusing on cool-season post-suppression fires, the impact of environmental change can be reduced by isolating the impacts of fire suppression and fuels on the temperature and duration of fire events.

The results of this study contribute to land-use and fire planning by allowing policymakers to better weigh the opportunity costs of intensive forest thinning and prescribed burning versus. environmental mitigation and home protection.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.