[MCN] Insect-killed forest at less, not more, risk of fire
lance at wildrockies.org
Fri Apr 29 11:21:28 EDT 2016
UNIVERSITY OF VERMONT PUBLIC RELEASE: 28-APR-2016
Insect outbreaks reduce wildfire severity
Pine beetle, budworm outbreaks dampen forest fire impacts
Forest scientists have found an unexpected 'silver lining' to the
insect outbreaks that have ravaged millions of trees across western
While insect outbreaks leave trees looking like matchsticks, a new
University of Vermont-led study finds these hungry critters
significantly reduce wildfire severity.
The findings contrast sharply with popular attitudes - and some U.S.
forest policies - which connect tree-eating insects with increased
"This is surprising," says UVM forest scientist Garrett Meigs, lead
author of the study. "Forest fires and insect outbreaks have
increased in recent decades, causing some people to link the two in
"Our findings clearly show that insect outbreaks can reduce burn
severity," says Meigs, a researcher at UVM's Gund Institute and
Rubenstein School of Environment and Natural Resources. "So there is
a connection, but just not the way most people thought."
The study, by scientists at UVM and Oregon State University, is
published in the journal Environmental Research Letters. OPEN ACCESS
LARGEST STUDY OF ITS KIND
Analyzing 81 fires over 25 years, the study is the largest to date on
forest fire severity following insect outbreaks. Researchers focused
on sites in Oregon and Washington State with past outbreaks by the
mountain pine beetle or western spruce budworm, two of North
America's most destructive insects.
Wildfires in areas that experienced greater insect damage in the past
burned with significantly less severity, regardless of fire size,
season or drought conditions. The researchers measured burn severity
- or vegetation loss - using satellite imagery taken before and after
"There is huge concern that insect outbreaks and forest fires will
continue to increase with climate change," says UVM forest ecology
professor Bill Keeton, a study co-author. "These threats remain
significant, but our study suggests that major insect outbreaks,
contrary to current thinking, can dampen future fire impacts - and we
can use that knowledge to improve forest management."
NATURAL THINNING EFFECT
The researchers say the findings can be explained by "forest
thinning," which occurs when insects kill some trees and leave others
to survive. This lowers forest density, which reduces the amount of
fuel available for subsequent fires.
The study builds on previous research by Meigs and colleagues, which
found that insect outbreaks in the Pacific Northwest did not increase
the likelihood of wildfires.
FOREST POLICY APPLICATIONS
The results give new insights to communities and forest agencies
dealing with the effects of insect outbreaks on forestry, tourism and
For example, the 2014 U.S. Farm Bill included fuel reduction
provisions for forests with insects and diseases. The study suggests
that forest managers may be able to factor in the natural "thinning
effects" of insects into these efforts.
And while both insects reduced fire severity, each critter exhibited
unique patterns that require different approaches by forest agencies.
"These findings will help forest managers to better prioritize
restoration efforts designed to reduce fire risks," says Keeton,
chair of UVM's Forestry Program.
TREASURE TROVE OF DATA
While previous studies explored a handful of fires for shorter
periods, recently released satellite imagery and data enabled the
researchers to analyze a much greater number of fires over longer
periods. The team used advanced spatial statistical analyses to
decipher insect-fire interactions in areas with past outbreaks of
these two key insects.
"Together, these studies tell us that not only can insects reduce
forest fire likelihood - they also reduce potential forest fire
impacts," says Meigs, summarizing his two recent papers on fire risk
"We can reduce our risks by disincentivizing housing development in
fire-prone areas, better managing public land and rethinking the
effectiveness of our current firefighting approach."
Incorporating Anthropogenic Influences into Fire Probability Models:
Effects of Human Activity and Climate Change on Fire Activity in
Michael L. Mann, Enric Batllori, Max A. Moritz, Eric K. Waller, Peter
Berck, Alan L. Flint, Lorraine E. Flint, Emmalee Dolfi
Research Article | published 28 Apr 2016 | PLOS ONE (open access)
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