10 common questions on how to mitigate against
wildfires in the northwest
Summary by
Mira Behn
As the climate warms, forests face amplified risks of rapid and extensive ecosystem changes. These can include severe, large-scale disturbances such as persistent droughts, insect outbreaks, disease epidemics, and high-severity fires. Risks to forests are increasing due to not only drought, but also changes in fire management, such as proscribed burning practices by Indigenous people. A group of researchers from the Northwestern USA asked 10 important questions about wildfire mitigation in western North America. In 2021, they found that a range of proactive management actions are both justified and necessary to keep up with the changing climate and to preserve the diversity in these ecosystems after severe wildfires.
The 10 questions they asked were:
1. Are the effects of fire exclusion overstated?
a. If so, are treatments unwarranted and even counterproductive?
2. Is forest thinning alone sufficient to
mitigate wildfire hazard?
3. Can forest thinning and prescribed
burning solve the problem?
4. Should active forest management,
including forest thinning, be concentrated in the wildland urban interface
(WUI)?
5. Can wildfires on their own do the work of
fuel treatments?
6. Is the primary objective of fuel
reduction treatments to assist in future firefighting response and containment?
7. Do fuel treatments work under extreme
fire weather?
8. Is the scale of the problem too great?
Can we ever catch up?
9. Will planting more trees mitigate climate change in wNA forests?
10. Is post-fire management needed or even ecologically justified?
In many of the forests studied, past forest management inadvertently
caused tree infilling, in part because fire exclusion practices resulted in denser
forests with continuous layered canopies, uniform structure, more
fire-intolerant species, and more persistent crown fires a pattern of floor
growth which provided easy transfer of fire to tree crowns. In some cases, the
advancement of grassland and changes to forest growth patterns are nearly irreversible
because of the change to the internal canopy structure of the forests. As
warmer and drier conditions prevail, managers may alleviate risk to a certain
extent by using variable density thinning and prescribed fire processes. These
methods increase the likelihood of low- to moderate fire effects as an
alternative to high severity fires because they encourage tree clumping, gaps
in vegetation, and deliberately creating openings in the forest canopies where they
were previously quite uniform.
No. the researchers noted that Stephens et al. (2010)
recommends four strategies for hardening western forests.
These four directives are:
·
Resistance work mitigates expected
wildfire effects and protects valued resources.
·
Realignment work modifies existing
conditions to restore key ecosystem patterns and the processes they drive.
·
Resilient conditions, such as native
plant growth after fire, encourage these ecosystems to recover their balance
when unplanned or unanticipated disturbances occur.
·
Response work to encourage
culturally or ecologically desirable results.
In all cases, fuel reduction treatments can be effective at
mitigating subsequent wildfire behavior for at least a brief time while the
undergrowth returns.
It’s difficult to accomplish some of the proscribed burns
due to variances in forest ownership, however, treating dry and moist
mixed-conifer forests at a deeper level can modify fire behaviors and may act
to decrease the intensity of wildfires arriving at communities
Natural wildfires can burn at extreme temperatures, and they can
leave a landscape that is uninhabitable for all but a few species. However,
prescribed burns usually burn at lower temperatures as a result of being
intentionally started under more moderate weather conditions. These fires have
more variable effects and tend to rebound quickly, with more diverse ecosystems,
and tend to result in less intensity in future fires.
The goal of adaptive treatments in fire-adapted landscapes is
to restore the ecological process of ‘patch to landscape’. This can reduce fire
effects and the need for aggressive suppression when the fire next occurs.
Scientific evidence on effects of fuel treatments in relation
to dry and moist mixed conifer forests shows that fuel treatments are effective
at mitigating severe burns, often even under extreme fire weather conditions
More resources are needed, but evidence strongly supports the
expanded use of fuel reduction treatments as an effective strategy toward effective
forest management.
It’s important to recognize that planting to increase tree
density and continuity in fire-prone forests is unsustainable because of higher
fire risk due to anticipated climatic water deficits and drought stresses that
turn undergrowth into fuel.
Post-fire management may be needed after the initial fire
response to encourage future forest resilience to disturbance and hardening
against climate change. As a result of incomplete burns during forest fire, unusually
dense patches of dead trees can contribute to high-severity reburns. This is
because when these trees fall, they create heavy surface fuel accumulations by
feeding new undergrowth.
A link to the
full research paper:
Prichard, S. J., et al. 2021. Adapting western North AMerican forests to climate change and Wildfires: 10 common questions
Ecological Applications 31( 8):e02433. 10.1002/eap.2433
