Environmental Engineering Reference
In-Depth Information
germination of certain tree seeds (such as those of the
giant sequoia and jack pine), and help control
pathogens and insects. In addition, wildlife species
such as deer, moose, elk, muskrat, woodcock, and
quail depend on occasional surface fires to maintain
their habitats and provide food in the form of vegeta-
tion that sprouts after fires.
Some extremely hot fires, called
crown fires
(Fig-
ure 8-16, right), may start on the ground but eventu-
ally burn whole trees and leap from treetop to treetop.
They usually occur in forests that have not experi-
enced surface fires for several decades, which allows
dead wood, leaves, and other flammable ground litter
to accumulate. These rapidly burning fires can destroy
most vegetation, kill wildlife, increase soil erosion, and
burn or damage human structures in their paths.
Sometimes surface fires go underground and burn
partially decayed leaves or peat. Such
ground fires
are
most common in northern peat bogs. They may smol-
der for days or weeks and are difficult to detect and
extinguish.
forests and people. One approach is to set small, con-
tained surface fires or clear out (thin) flammable small
trees and underbrush in the highest-risk forest areas.
Such
prescribed fires
require careful planning and moni-
toring to keep them from getting out of control.
Another strategy is to allow many fires in national
parks, national forests, and wilderness areas to burn
and thereby remove flammable underbrush and
smaller trees as long as the fires do not threaten human
structures and life. A third approach is to protect
houses or other buildings in fire-prone areas by thin-
ning a zone of about 46 meters (200 feet) around them
and eliminating the use of flammable materials such as
wooden roofs.
In 2003, the U.S. Congress passed the
Healthy
Forests Restoration Act
. Under this law, timber compa-
nies are allowed to cut down economically valuable
medium-size and large trees in most national forests in
return for clearing away smaller, more fire-prone trees
and underbrush. The law also exempts most thinning
projects from environmental reviews and appeals cur-
rently required by forest protection laws.
According to biologists and many forest fire scien-
tists, this law is likely to
increase
the chances of severe
forest fires for two reasons.
First
, removing the most
fire-resistant large trees—the ones that are valuable to
timber companies—encourages dense growth of
highly flammable young trees and underbrush.
Sec-
ond,
removing the large and medium trees leaves be-
hind highly flammable slash. Many of the worst fires
in U.S. history—including some of those during the
1990s—burned through cleared forest areas containing
slash.
Fire scientists agree that some national forests
need thinning to reduce the chances of catastrophic
fires, but suggest focusing on two goals. The first goal
would be to reduce ground-level fuel and vegetation
in dry forest types and leave widely spaced medium
and large trees that are the most fire resistant and thus
can help forest recovery after a fire. These trees also
provide critical wildlife habitat, especially as standing
dead trees (snags) and logs where many animals live.
The second goal would emphasize clearing of flamma-
ble vegetation around individual homes and buildings
and near communities that are especially vulnerable to
wildfire.
Critics of the Healthy Forests Restoration Act say
that these goals could be accomplished at a much
lower cost to taxpayers by giving grants to communi-
ties that seem especially vulnerable to wildfires for
thinning forests and protecting homes and buildings
in their areas.
Solutions: Reducing Forest Damage
from Fire
To reduce fire damage, we can set controlled
surface fires to prevent buildup of flammable
material, allow fires on public lands to burn
unless they threaten human structures and lives,
and clear small areas around buildings in areas
subject to fire.
In the United States, the Smokey Bear educational
campaign undertaken by the Forest Service and the
National Advertising Council has prevented countless
forest fires. It has also saved many lives and prevented
billions of dollars in losses of trees, wildlife, and hu-
man structures.
At the same time, this educational program has
convinced much of the public that all forest fires are
bad and should be prevented or put out. Ecologists
warn that trying to prevent all forest fires increases the
likelihood of destructive crown fires by allowing accu-
mulation of highly flammable underbrush and smaller
trees in some forests.
According to the U.S. Forest Service, severe fires
could threaten 40% of all federal forest lands, mainly
through fuel buildup from past rigorous fire protec-
tion programs (the Smokey Bear era), increased log-
ging in the 1980s that left behind highly flammable
logging debris (called
slash
), and greater public use of
federal forest lands. In addition, an estimated 40 mil-
lion people now live in remote forested areas or areas
populated by dry chaparral vegetation with a high
wildfire risk.
Ecologists and forest fire experts have proposed
several strategies for reducing fire-related harm to
x
H
OW
W
OULD
Y
OU
V
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?
Do you support repealing or
modifying the Healthy Forests Restoration Act? Cast your vote
online at http://biology.brookscole.com/miller11.
