IEEE Power & Energy Magazine - January/February 2022 - 21

A 2009 study found a close correlation between drought
indexes and the area burned by wildfires. The study also
found that areas experiencing extreme drought periods have
been expanding over Eurasia in the 20th century. Climate
change can cause longer or more intense drought conditions
punctuated by events of more significant rainfall. This poses
the risk of allowing fine ( " flash " ) fuels to grow and then dry.
The Mediterranean region constitutes an interesting exception
in that sense, as the burned area has decreased slightly since
the mid-1980s. There is also evidence that the global wildfire
weather season is lengthening as a consequence of climate
change, i.e., the number of days in the year with weather conditions
favorable to sustain wildfires has increased.
While the burned area has increased during the last
decades in many ecoregions around the globe [Figure 4(b)],
the overall number of fires follows a less intuitive trend.
Data from Cal Fire indicate that wildfires have decreased in
numbers since 1985, although the trend has been reversed in
the past 15 years [Figure 4(a)]. This leads to the conclusion
that individual fires are, on average, increasing in size, i.e.,
wildfires are burning larger areas.
There are, of course, other factors that contribute to
increased wildfire activity. Some of them are also triggered
by climate change, including altered wind patterns, longer fire
seasons, earlier snow melt, and longer snow-free seasons. But
humans can also have a more direct impact on changes in wildfire
activity. Growth in population at the wildland-urban interface
(WUI) increases the probability of accidental wildfire
ignition and exposes a larger number of people to the consequences
of wildfires. Changes in land use and forest management
also impact both wildfire numbers and total area burned
(see " Fire Paradox " ). Invasive vegetation altering the natural
ecosystem constitutes another factor of importance in terms of
wildfire frequency and extension (e.g., invasive annual grasses
in the Mojave Desert in the western United States, or increased
tree density due to timber production in Chile).
Whether the risk wildfires pose to power networks has
increased due to climate change is difficult to establish.
There is a lack of indicators and data about the risk of wildfires.
Wildfire frequency and area burned (such as those
for California shown in Figure 4) are the proxies typically
invoked to describe the risk, but it is unclear whether these
indicators translate into actual risk to power networks.
Information regarding fire severity would provide more
insight into the potential for wildfires to damage power
infrastructure. Observations of flame length, the estimated
rate of heat release, or the presence of flames in the canopy
of trees would be more telling indicators, but these are not
reported consistently and are difficult to measure. Other
indicators, such as flammability and fuel load, however,
could be included in climate change studies related to wildfires
for a better understanding of the link between climate
change and wildfire activity.
Furthermore, no published studies were found discussing
the relationship between the risk posed to power networks
january/february 2022
by wildfires and climate change directly. However, an
increased Forest Fire Danger Index (based on temperature,
wind speed, drought, and relative humidity) positively correlates
with an increased loss of houses due to wildfires. This
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6,000
Linear Fit
1985 1990 1995 2000 2005 2010 2015 2020
Year
(a)
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Linear Fit
1985 1990 1995 2000 2005 2010 2015 2020
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figure 4. The evolution of frequency and burned area over
time in California. (a) Note that the number of fires is generally
decreasing with time, but there may be a slight increase with
time over the past decade. (b) National U.S. trends also do not
show increases in the number of fires but increases in the area
burned. (Source: Cal Fire.)
Fire Paradox
One of the many explanations for the increase in the burned
area even with lower fire frequency is " the fire paradox. " To
prevent catastrophic wildfires in the past, an effort (particularly
in the United States) was made to aggressively suppress
all fires. Without periodic burning, dead plant material (solid
fuel) accumulated over the years. The increased fuel load
caused wildfires to be more likely to grow out of control and
more severely affect the ecosystem. From that grew a shift in
fire control efforts. Now, allowing low-intensity fires to burn
and using controlled burning have become important wildfire
management strategies.
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21
Area Burned (km2)
Number of Fires
IEEE Power & Energy Magazine - January/February 2022

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