[Vision2020] Western US Wildfire & Land Use Impacts

[Ted Moffett]

All-

The truth is often more complicated than what is presented with political or
ideological bias.  Both climate change and "overabundant fuels" are
considered as variables contributing to the dramatic increase in Western US
wildfire activity in the article below:
 Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity *A.
L. Westerling,1,2*<http://www.sciencemag.org/cgi/content/full/313/5789/940#COR1>H.
G. Hidalgo,
1 D. R. Cayan,1,3 T. W. Swetnam4 *


http://www.sciencemag.org/cgi/content/full/313/5789/940

We compiled a comprehensive database of large wildfires in western United
States forests since 1970 and compared it with hydroclimatic and
land-surface data. Here, we show that large wildfire activity increased
suddenly and markedly in the mid-1980s, with higher large-wildfire
frequency, longer wildfire durations, and longer wildfire seasons. The greatest
increases occurred in mid-elevation, Northern Rockies forests, where
land-use histories have relatively little effect on fire risks and are
strongly associated with increased spring and summer temperatures and an
earlier spring snowmelt.
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Robust statistical associations between wildfire and hydroclimate in western
forests indicate that increased wildfire activity over recent decades
reflects sub-regional responses to changes in climate. Historical wildfire
observations exhibit an abrupt transition in the mid-1980s from a regime of
infrequent large wildfires of short (average of 1 week) duration to one with
much more frequent and longer burning (5 weeks) fires. This transition was
marked by a shift toward unusually warm springs, longer summer dry seasons,
drier vegetation (which provoked more and longer burning large wildfires),
and longer fire seasons. Reduced winter precipitation and an early
spring snowmelt
played a role in this shift. Increases in wildfire were particularly strong
in mid-elevation forests.
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However, the same study states:

We describe land-use history versus climate as competing explanations, but
they may be complementary in some ways. In some forest types, past land uses
have probably increased the sensitivity of current forest wildfire regimes
to climatic variability through effects on the quantity, arrangement, and
continuity of fuels. Hence, an increased incidence of large, high-severity
fires may be due to a combination of extreme droughts and overabundant fuels in
some forests.
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Thus, although land-use history is an important factor for wildfire risks in
specific forest types (such as some ponderosa pine and mixed conifer
forests), the broad-scale increase in wildfire frequency across the
western United
States has been driven primarily by sensitivity of fire regimes to recent
changes in climate over a relatively large area.

The overall importance of climate in wildfire activity underscores the
urgency of ecological restoration and fuels management to reduce wildfire
hazards to human communities and to mitigate ecological impacts of climate
change in forests that have undergone substantial alterations due to past
land uses. At the same time, however, large increases in wildfire driven by
increased temperatures and earlier spring snowmelts in forests where
land-use history had little impact on fire risks indicates that ecological
restoration and fuels management alone will not be sufficient to
reverse current
wildfire trends.
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Vision2020 Post: Ted Moffett
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