Delanceyplace: Unexpected Consequences
"Due to the increasing frequency of large forest fires that were essentially impossible to extinguish unless rain and low winds combined to help. People began to realize that the U.S. federal government's fire suppression policy was contributing to those big fires, and that natural fires caused by lightning had previously played an important role in maintaining forest
structure,'' writes Jared Diamond.
The U.S. Forest Service in the first decade of the 1900s adopted a policy of fire
suppression (attempting to put out forest fires) for the obvious reasons that it
didn't want valuable timber to go up in smoke, nor people's homes and lives to
be threatened. The Forest Service's announced goal became, 'Put out every forest
fire by 10:00 A.M. on the morning after the day when it is first reported.' Firefighters
became much more successful at achieving that goal after World War II, thanks to
the availability of firefighting planes, an expanded road system for sending in
fire trucks, and improved firefighting technology. For a few decades after World
War II, the annual acreage burnt decreased by 80 percent.
That happy situation began to change in the 1980s, due to the increasing frequency
of large forest fires that were essentially impossible to extinguish unless rain
and low winds combined to help. People began to realize that the U.S. federal government's
fire suppression policy was contributing to those big fires, and that natural fires
caused by lightning had previously played an important role in maintaining forest
structure. ...
Take the [Montana's] Bitterroot low-altitude Ponderosa Pine forest
as an example, historical records, plus counts of annual tree rings and datable
fire scars on tree stumps, demonstrated that a Ponderosa Pine forest experiences
a lightning-lit fire about once a decade under natural conditions (i.e., before
fire suppression began around 1910 and became effective after 1945). The mature
Ponderosa trees have bark two inches thick and are relatively resistant to fire,
which instead burns out the understory of fire-sensitive Douglas Fir seedlings that
have grown up since the last fire. But after only a decade's growth until the next
fire, those seedlings are still too low for fire to spread from them into the crowns.
Hence the fire remains confined to the ground and understory. As a result, many
natural Ponderosa Pine forests have a park-like appearance, with low fuel loads,
big trees well spaced apart, and a relatively clear understory.
Of course, though, loggers concentrated on removing those big, old, valuable, fire-resistant
Ponderosa Pines, while fire suppression for decades let the understory fill up with
Douglas Fir saplings that would in turn become valuable when full-grown. Tree densities
increased from 30 to 200 trees per acre, the forest's fuel load increased by a factor
of 6, and Congress repeatedly failed to appropriate money to thin out the saplings.
Another human-related factor, sheep grazing in national forests, may also have played
a major role by reducing understory grasses that would otherwise have fueled frequent
low-intensity fires. When a fire finally does start in a sapling-choked forest,
whether due to lightning or human carelessness or (regrettably often) intentional
arson, the dense tall saplings may become a ladder that allows the fire to jump
into the crowns. The outcome is sometimes an unstoppable inferno in which flames
shoot 400 feet into the air, leap from crown to crown across wide gaps, reach temperatures
of 2,000 degrees Fahrenheit, kill the tree seed bank in the soil, and may be followed
by mudslides and mass erosion.
Foresters now identify the biggest problem in managing western forests is what
to do with those increased fuel loads that built up during the previous half-century
of effective fire suppression. In the wetter eastern U.S., dead trees rot away more
quickly than in the drier West, where more dead trees persist like giant matchsticks.
In an ideal world, the Forest Service would manage and restore the forests, thin
them out, and remove the dense understory by cutting or by controlled small fires.
But that would cost over a thousand dollars per acre for the one hundred million
acres of western U.S. forests, or a total of about $100 billion. No politician
or voter wants to spend that kind of money. Even if the cost were lower, much of
the public would be suspicious of such a proposal as just an excuse for resuming
logging of their beautiful forest. Instead of a regular program of expenditures
for maintaining our western forests in a less fire-susceptible condition, the federal
government tolerates flammable forests and is forced to spend money unpredictably
whenever a firefighting emergency arises: e.g., about $1.6 billion to fight the
summer 2000 forest fires that burned 10,000 square miles."
Author: Jared Diamond
Title: Collapse: How Societies Choose to Fail Or Succeed
Publisher: Penguin Books
Date: Copyright 2005 by Jared Diamond
Pages: 44-46
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