In at least some ecosystems, logging, livestock grazing, and a century of fire suppression efforts have allowed biomass fuels to accumulate to unnatural levels. Climate change, and its impacts on drought, fire, and insects and diseases, could exacerbate these problems. Some interests are concerned that current efforts to reduce fuel levels on federal lands are inadequate, and that "environmentalist objections" to some of those efforts are unnecessarily raising costs and delaying action. Congress continues to address these issues as it considers funding and legislative proposals. Not surprisingly, crown fires are difficult, if not impossible, to control. Often, however, crown fires burn until they run out of fuel or the weather changes (the wind dies or it rains or snows). Nearly all fires are "patchy," with a mix of areas of varying fire severities, depending on site-specific fuel, moisture, and wind conditions. Treating these three elements addresses all three ways by which structures are ignited—direct contact, radiation, and firebrands. Adjacent burnable materials are items that can burn that abut the house. Finally, landscaping—the character of the vegetation surrounding the house—is critical to preventing both direct burning and ignition by radiation. Protecting Wildlands and Natural Resources

Wildlands and natural resources can also be damaged by wildfires. Wildfire damages vary widely, depending on the nature of the ecosystems burned as well as site-specific conditions. Surface Fire Ecosystems

Surface fire ecosystems are ecosystems where fires burn relatively frequently (typically 5- to 35-year intervals), with the fires consuming leaves or needles, grasses, twigs and small branches, and sometimes small trees, but generally leaving moderate and large trees unharmed by the fire. Stand-Replacement Fire/Crown Fire Ecosystems

Stand-replacement fire ecosystems are those where crown fires are normal, natural, periodic events to which the ecosystem has adapted. Depending on how it is accomplished, mechanical thinning may add to surface fuels (and increase surface fire intensity) unless the fine fuels that result from the thinning are removed from the stand or otherwise treated....
Thinning and prescribed fires can modify understory microclimate that was previously buffered by overstory vegetation.... Thinned stands (open tree canopies) allow solar radiation to penetrate to the forest floor, which then increases surface temperatures, decreases fire fuel moisture, and decreases relative humidity compared to unthinned stands—conditions that can increase surface fire intensity.... An increase in surface fire intensity may increase the likelihood that overstory tree crowns ignite. However, others caution that expedited review or limits on ESA consultation and on public oversight of proposed fuel treatments may allow treatments to include commercial timber harvests or other actions that provide little wildfire protection and exacerbate fuel accumulations in the short run, while causing other environmental damages. Conclusions

As more acres and more homes have burned in the past few years, and more people are at risk from wildfires, Congress has faced increasing pressures to protect structures and resources. To protect homes, Congress could create new programs and expand existing ones for installing non-flammable roofing, removing burnable materials adjacent to structures, and creating a defensible space of at least 30 feet around the building. Existing programs for federal lands authorize prescribed burning (intentional fires under prescribed conditions) and mechanical treatments (cutting and removing some trees), the principal means of reducing fuel levels. However, prescribed fires are risky and mechanical treatments can cause other ecological damages, and both are expensive. Proponents of more fuel treatment advocate accelerated processes for environmental analysis and public review to reduce costs and expedite action. Others caution that inadequate analysis and review can allow projects with unintended damages and few fire protection benefits. Such activities:
a. Shall be limited to areas:
(1) In the wildland-urban interface; or
(2) Condition Classes 2 or 3 [moderate or high risk of ecological damage] in Fire Regimes I, II, or III [surface fire, stand-replacement fire at 35 years or less, and mixed-intensity fire], outside the wildland-urban interface;
b. Shall be identified through a collaborative framework as described in "A Collaborative Approach for Reducing Wildland Fire Risks to Communities and Environment 10-Year Comprehensive Strategy Implementation Plan";
c. Shall be conducted consistent with agency and Departmental procedures and applicable land and resource management plans;
d. Shall not be conducted in wilderness areas or impair the suitability of wilderness study areas for preservation as wilderness; and
e. Shall not include the use of herbicides or pesticides or the construction of new permanent roads or other new permanent infrastructure; and may include the sale of vegetative material if the primary purpose of the activity is hazardous fuel reduction.
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 non-flammable 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.