WILDFIRE

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WILDFIRE

• fire has been a natural part of many ecosystems
  for
• as long as trees have been on the earth

NPS
SIU
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• while most fires are ignited by lightning, a
  number of
• different factors affect the behavior and
  severity of fires

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3 factors that affect wildfire behavior

• the build up of fuel is affected by windstorms,
  tree diseases,
• insect outbreaks, and natural tree mortality

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under normal conditions, fires will
narrow canyons in mountainous areas can be
hazardous
dry out vegetation and can lead to
fires winds also drive fires and can even cause
flames to jump into unburned areas spreading the
fire
low rainfall and low humidity increase fire
chance
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Fires are classified by size and by the area in
which they occur
NPS
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NPS
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driven by strong winds these fires can jump
from one tree to another independent of surface
fires
NPS
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• In the US over 250,000 forest fires burn over
• 5 million acres of forest each year

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Since 1900 (US) Deaths from
1700 Deaths from 2400
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1925 average fire size 120 acres 1970 average
fire size 20 acres
Fire suppression bulldozers, trucks, roads,
air tankers, smoke
jumpers, Smoky the
bear
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a tendency towards fewer, but larger fires
(as opposed to the more natural smaller,
frequent fires)
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Tree cross-sections showing fire scars note the
effect of in the tree on the right
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deliberate fires set to reduce fuel build
up

• If done under proper conditions, prescribed
  burning is
• an effective way to lower fuel levels.
  Occasionally, prescribed
• burns have gotten out of control. Another way to
  lower fuel
• levels is salvage loggingbut this is
  controversial also.

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Clemson Univ.
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• park policy is to let all natural fires burn, as
  long as they
• dont threaten people or property this policy
• was temporarily rescinded during the 1988 fires,
  but remains
• in effect today

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Perhaps the most dangerous area for fires is the

• these areas are increasing in
• population

• city firefighters may not be
• trained to fight forest fires

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• some suburban areas may be
• out of the jurisdiction of cities and
• may have to rely on seasonal fire
• fighting crews

• difficult to set back-fires
• due to residential areas

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Southern California fires often fueled by
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• Fires can destroy the water holding capacity of
  soils
• leading to the threat of

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• canyon in California
• subject to wildfire,
• followed by debris flow

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• thousands of
• cases of repertory
• illness, deaths

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Example of a wildfire hazard map