Warming enabled upslope advance in western US forest fires

Area of Science:

• Ecology
• Climate Science
• Forestry

Background:

• Forest fires have increased in the western US over the past 50 years.
• Elevational fire distribution is critical for understanding montane ecosystem dynamics.

Purpose of the Study:

• To analyze the elevational distribution of forest fires in western US mountains.
• To investigate the relationship between fire spread and climate variables.
• To assess the impact of climate change on high-elevation fire regimes.

Main Methods:

• Analysis of burned area data from 1984 to 2017 in mountainous western US ecoregions.
• Statistical analysis of fire-elevation relationships and vapor pressure deficit (VPD).
• Modeling the impact of climate trends on high-elevation forest flammability.

Main Results:

• The largest increases in burned area occurred above 2,500 m.
• High-elevation fires advanced upslope by a median of 252 m.
• A strong correlation was found between high-elevation fires and warm season VPD.
• Climate warming has reduced the high-elevation flammability barrier, opening 11% more forests to fire.

Conclusions:

• Climate warming is the primary driver of upslope fire advancement in western US mountains.
• Weakening of the high-elevation flammability barrier has significant implications for ecosystems and watersheds.
• Continued warming may transform montane fire regimes, necessitating adaptive management strategies.