Wildfires are Burning Less Frequently and More Severely than Historically in the Western US: A Novel Approach to Calculating Fire-Regime Departures

Author

Jeffrey Ryan Chandler, University of Montana - MissoulaFollow

Year of Award

2024

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Systems Ecology

Department or School/College

Forestry

Committee Chair

Solomon Z. Dobrowski

Commitee Members

C. Alina Cansler, Sean A. Parks

Keywords

fire-regime departure, fire frequency, fire severity, earth mover's distance, forest ecology, fire ecology

Subject Categories

Forest Management | Other Forestry and Forest Sciences | Research Methods in Life Sciences | Systems Biology

Abstract

Changing climate, vegetation, and fire exclusion are altering and homogenizing fire-regime attributes compared to historic conditions. Fire-regime changes are commonly quantified using departure metrics, which are often based on measures of central tendency (i.e. changes in the mean). These metrics can mischaracterize complex changes to the distributional characteristics of fire-regime attributes. Here we develop a fire-regime departure metric that quantifies nonparametric distributional changes to fire-regime attributes over time. We use this metric to compare fire frequency and severity between historical (~1600-1880) and contemporary (1880- 2021) time periods in western US forests. Our analysis revealed that 89% of Western US forests are experiencing less frequent, more severe wildfires, and these departures increase with human land use intensity. We also evaluated management prioritization within the Wildfire Crisis Mitigation plan and found that priority landscapes are, on average, more departed than nonpriority landscapes. Our results suggest that existing fire-regime departure metrics differ from our distributional approach by underestimating departures in frequent fire forests while overestimating departures in infrequent fire forests.

Recommended Citation

Chandler, Jeffrey Ryan, "Wildfires are Burning Less Frequently and More Severely than Historically in the Western US: A Novel Approach to Calculating Fire-Regime Departures" (2024). Graduate Student Theses, Dissertations, & Professional Papers. 12340.
https://scholarworks.umt.edu/etd/12340