Climate‐Driven Tree Mortality and Fuel Aridity Increase Wildfire's Potential Heat Flux

Wildfire is capable of rapidly releasing the energy stored in forests, with the amount of water in live and dead biomass acting as a regulator on the amount and rate of energy release. Here, we used temperature and fuel moisture data to examine climate‐driven changes in fuel moisture content over th...

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Bibliographic Details
Published in:Geophysical research letters Vol. 48; no. 24
Main Authors: Goodwin, Marissa J., Zald, Harold S. J., North, Malcolm P., Hurteau, Matthew D.
Format: Journal Article
Language:English
Published: Washington John Wiley & Sons, Inc 28.12.2021
Subjects:
Aridity
Availability
Bark
Biomass
Climate change
Drought
Energy
Fires
Forests
fuel
Fuel combustion
Fuels
Heat
Heat flux
Heat transfer
Moisture content
Mortality
Positive feedback
Temperature rise
tree mortality
Trees
Water content
wildfire
Wildfires
ISSN:0094-8276, 1944-8007
Online Access:Get full text
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Summary:Wildfire is capable of rapidly releasing the energy stored in forests, with the amount of water in live and dead biomass acting as a regulator on the amount and rate of energy release. Here, we used temperature and fuel moisture data to examine climate‐driven changes in fuel moisture content over the past three decades. We then calculated the changes in energy release (energy release component and fire radiant energy) for two forests that experienced drought and bark beetle mortality and were subsequently burned by wildfires. We found that mortality transitioned substantial amounts of biomass from live to dead pools. Coupled with climate‐driven decreases in fuel moisture content, this change in fuel availability increased the amount of energy that could be released as heat during wildfire in these forests. Our results demonstrate that climate‐driven tree mortality and fuel aridity may be increasing the amount of energy that is released during wildfire. Plain Language Summary Assuming sufficient biomass and fuel continuity, the amount of water stored in the woody fuels of fire‐prone forests regulates wildfire ignition and spread. Rising temperatures and widespread tree mortality are making fuels drier and increasing the ease of fuel combustion. While, previous research has focused on the relationship between increasing fuel aridity and wildfire activity, we propose that future research consider the combined effects of tree mortality and fuel aridity on fuel availability. We present a potential pathway for how climate change is increasing the energy that is released as heat during wildfire. This increase in the heat flux of wildfires creates a positive feedback for fire spread and may be a significant contributor to the unprecedented wildfire behavior we have seen in recent years. Key Points Tree mortality is increasing fuel availability by transitioning large amounts of biomass from live to dead pools The fuel moisture of dead biomass is more responsive to increasing temperature than live biomass Changing climate is increasing the amount of energy stored in biomass that can be released as heat during wildfire
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ISSN:0094-8276
1944-8007
DOI:10.1029/2021GL094954