Wildfires are getting more severe, with more acres and houses
burned and more people at risk. This results from excess biomass in
the forests, due to past logging and grazing and a century of fire
suppression, combined with an expanding wildland-urban
interface-more people and houses in and near the forests-and
climate change, exacerbating drought and insect and disease
problems. Some assert that current efforts to protect houses and to
reduce biomass (through fuel treatments, such as thinning) are
inadequate, and that public objections to some of these activities
on federal lands raise costs and delay action. Others counter that
proposals for federal lands allow timber harvesting with
substantial environmental damage and little fire protection.
Congress is addressing these issues through various legislative
proposals and through funding for protection programs. Wildfires
are inevitable-biomass, dry conditions, and lightning create fires.
Some are surface fires, which burn needles, grasses, and other fine
fuels and leave most trees alive. Others are crown fires, which are
typically driven by high winds and burn biomass at all levels from
the ground through the tree tops. Many wildfires contain areas of
both surface and crown fires. Surface fires are relatively easy to
control, but crown fires are difficult, if not impossible, to stop;
often, crown fires burn until they run out of fuel or the weather
changes. Homes can be ignited by direct contact with fire, by
radiative heating, and by firebrands (burning materials lifted by
the wind or the fire's own convection column). Protection of homes
must address all three. Research has identified the keys to
protecting structures: having a nonflammable roof; clearing
burnable materials that abut the house (e.g., plants, flammable
mulch, woodpiles, wooden decks); and landscaping to create a
defensible space around the structure. Wildland and resource
damages from fire vary widely, depending on the nature of the
ecosystem as well as on site-specific conditions. Surface fire
ecosystems, which burn on 5- to 35-year cycles, can be damaged by
crown fires due to unnatural fuel accumulations and fuel ladders
(small trees and dense undergrowth); fuel treatments probably
prevent some crown fires in such ecosystems. Stand-replacement fire
ecosystems are those where crown fires are natural and the species
are adapted to periodic crown fires; fuel treatments are unlikely
to alter the historic fire regime of such ecosystems. In
mixed-intensity fire ecosystems, where a mix of surface and crown
fires is historically normal, it is unclear whether fuel treatments
would alter wildfire patterns. Prescribed burning (intentional
fires) and mechanical treatments (cutting and removing some trees)
can reduce resource damages caused by wildfires in some ecosystems.
However, prescribed fires are risky, mechanical treatments can
cause other ecological damages, and both are expensive. Proponents
of more treatment advocate expedited processes for environmental
and public review of projects to hasten action and cut costs, but
others caution that inadequate review can allow unintended damages
with few fire protection benefits.
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