Virtually every forest type has experienced fire at some point, and many types evolved with fire as the major disturbance factor, affecting the forest's successional patterns and shaping its species composition. Because of fire's importance in determining structural patterns in forests, and because people have so strongly altered the way fire operates in the forest, it merits a separate discussion as a major component of modem forest management. The impacts of fire on the forest are very complex. Although there is much scientific literature about the effects of fire, and virtually everyone has an opinion as to what fire does in the forest, every fire is a unique event. Unlike some of the other natural forest disturbances---windstorins and flooding, for example---the behavior and ultimate effects of a particular fire are strongly influenced by the condition of the forest at the time of the fire. While a forest's condition may mean a different response to a windstorm, for example, the forest does not shape the windstorm itself. The forest's condition, however, dramatically shapes the fire. Thus, the manner in which a forest has been managed may largely deterinine the intensity and ultimate damage caused by a particular fire. (right) Protecting rural homes from wildfire is costly and dangerous for firefighters. Fire is also an event that can be human-caused, in contrast to windstorms or (most) floods. People have used fire since precivilization to shape their environment, and the intentional use of fire has been a significant addition to the lightning-caused blazes that affected earlier forest development. Human fires also create different impacts and landscape patterns. Evidence suggests that Indians burned aspen groves early in the spring and late in the fall, for example, because that is when the leaves are off the trees and the ground fuels are dry. This created a very different impact than today's lightning-caused summer wildfires, which seldom bum far into the lush green aspen groves. A major change in fire conditions occurred with the advent of European settlement in the United States. Prior to that, American Indians used fire as their most powerful land management tool. Although popular myth often portrays the Indians as a limited population of nomadic people that did little to affect the environment around them, modern scholars are increasingly finding evidence of major populations that had extensive impact on the land. In addition to clearing land for agriculture, fire was used to favor plants desired for grazing or food; to reduce wildfire hazards around villages; to control dense vegetation, thereby eliminating cover for potential enemies; and to harass enemies during conflicts. Once ignited, a fire could bum for weeks or months under some conditions, because there were no efforts to suppress it. With the arrival of European settlers and their wooden homes, fences, and towns, fire became a major threat and unwanted fires were extinguished wherever possible. In many areas, clearing or plowing land for agriculture fragmented the grass, brush, or forest areas that were previously free to bum when ignited. Livestock grazing removed many of the fine fuels (grass and herbs) that previously carried ground fires from place to place. Farmers, cowhands, and loggers---who saw in fire a force that destroyed resources they wished to use themselves---were quick to suppress any small fire they could control. As the federal government began to take more of a role in western land management around the beginning of the 20th Century, fire control was one of its primary missions. Thus, in a matter of decades---an eye-blink of ecological time---many forests went from a regular fire regime to a nonfire regime. The ecological impacts were significant, and many are still not well documented by scientists. Some facts are generally agreed upon, however. Forests where regular ground fires kept brush and young trees in check began to change once fire was eliminated. Forests of massive, widely spaced oaks in the East, and pines in the South and West---the savanna structures---began to be filled in with species that could thrive in the shady conditions. As these newcomers grew larger and more competitive, the older trees often failed to survive. Forest diversity diminished as savannas gave way to dense forests. Open structures such as meadows and recovering burned areas diminished, as trees began to fill in the open spaces in the landscape. In some areas, the "edge" between forest and grassland began to shrink, as forests filled in the former open sites. Obviously, these changes affected wildlife habitat, as well as the cycling of rain, snow, groundwater, and nutrients. Several studies of the current situation suggest that the forest types and structures that were most dependent on periodic fire (such as ponderosa pine savannas) are among the most heavily impacted by fire suppression. In addition, many of these types occupy low-lying landscape positions that were the most heavily impacted by land clearing, grazing, and timber harvest after settlement began. A study in Colorado identified ponderosa pine, mixed conifer, and aspen forest types as those whose recent fire history is farthest away from the historical range identified by ecologists. The higher elevation forests in that study (lodgepole pine, spruce) were affected as well, but they were much closer to their past history. On the basis that these studies might be indicative of the wider region of general forest types in terms of the wildfire hazards that they face. This suggests that the more separated a system becomes from its historical fire regime, the greater the possibility of increased wildfire intensity and severity, which can translate into additional damage to the soil, as well as the forest biota. In a frustrating paradox, our increasing human effectiveness at fire suppression itself has led to more devastating wildfires, because not only did forests change with the suppression of fire, but fire behavior itself changed as well. Success in keeping fires out assured, in many situations, that the amount of available fuels increased. These fuels then feed the next, inevitable fire making it burn with additional heat and intensity. In forests where large trees historically survived the frequent, low-intensity ground fires, the modem fires burn at much higher temperatures, killing most or all of the trees, and affecting far larger areas. In the West, where large areas of wild lands and dry summer conditions lend themselves to significant wildfire events, the changes in vegetation support fires that modem technology is helpless to control. The average annual wildfire acreage in the I I western states has increased significantly in recent decades, in spite of continued advances in sophisticated firefighting technology. Wildfire dynamics have changed, and the most likely reason is the changed vegetative condition of the forests, particularly the increase of dense forest structures caused by a combination of fire suppression and nonmanagement. These wildfires come at enormous public expense. The Forest Service reported almost $1-billion in fire fighting outlays in 1994. The toll rises into billions of dollars for that one year alone when the costs incurred by other federal, state, and local agencies, as well as the resource damage suffered on public and private lands, are added. The public attention spurred by the costs and losses involved in the recent wildfires has focused new federal studies and policies on the need to change forest management in light of the wildfire problem. The basic question for many land managers is "what should be done to alter forest vegetation so that future fires will be less intense and destructive?" A recent policy study by the federal government says that the best approach is to use fire to fight fire through a major increase in managed fires (usually called prescribed, since they are allowed to bum as long as the weather and fuel conditions remain within "prescribed" limits) that reduce the fuels and lower the damage potential for future wildfires. But it may be easier to adopt such a policy statement than to apply it on the land A century or more of fire suppression has allowed conditions to change so dramatically, over such large areas, that simply reintroducing fire into the current situation is to invite disaster. Before fire can be safely used in many places, excessive fuels must be removed so that the fire will bum at lower heat and intensity, and with less destructive impact. In many places, that means a significant investment and effort to restore conditions that are less subject to the kind of intense wildfires that do more harm than good. Public forest managers, hit with the double whammy of an enormous amount of land to manage and cutbacks in state and federal budgets, face a daunting challenge. In addition, they face groups of skeptics who consider forest health treatment a thin veil for simply increasing old-style timber harvests to satisfy economic interests. For private land managers, the risks and costs involved with managing fire safely in an environment sprinkled with houses and other ownerships, as well as the regulations designed to reduce smoke pollution, combine to make fire a problematic management tool. In the southern states, where prescribed fire has long been a staple of forest management practice, growing populations and opposition to smoke pollution have led to public controversy. In many areas, the fragmentation of private forest land into small tracts and homesites has created a complex intermix of exurban growth and wildland that makes fire too risky for most owners to tolerate, let alone use on purpose as a management tool. In these areas, returning the ecological effects of fire to the forest is a problem that, to date, has not yielded a satisfactory answer. Such processes as nutrient and carbon recycling, or the heat pulse that helps some plants germinate, are not easy to replicate. If these ecological processes prove, over time, to be critical to the forest's future, managers and researchers are challenged to find substitute methods of producing them. There are other technical problems as well. After a forest has missed several fire cycles, the changes in vegetation may make it enormously difficult to reintroduce fire safely. In the ponderosa pine forests of the West, large pine trees that have survived dozens of fires prior to the last wildfire (which usually happened in the late 19th or early 20th Century), are now extremely vulnerable to fire. Large piles of dead needles and bark flakes have built up around their bases, and small roots have grown into the litter on the forest floor in search of water and nutrients. Where that has happened, even a well-controlled fire can do lethal damage. Since a fire-damaged tree may take months or years following the fire to die, it is difficult to know when a prescribed fire is doing its intended job or is killing the trees that the manager is trying to save. Similar challenges exist for people wishing to reintroduce fire safely in forests containing giant sequoia, oak, or other species that were fire-tolerant under the historical fuel and fire conditions. In short, the reintroduction of fire as a regular disturbance in forests creates enormous challenges for land managers. Research is underway, but may take years to produce definite results. Forests that have been without fire for decades are seriously altered and, in terms of our forest health definition---unhealthy. Their present condition also means that they are unstable and at high risk of experiencing major damage in the next few years. The fact that the forests took decades to develop this unstable condition does not suggest that they can remain unstable for an equally long time, and to delay treatment is to invite damage. Restoring healthy conditions normally requires either restoring fire as a regular process or carrying out other silvicultural operations such as thinning and timber harvest in ways that mimic fire's effects. Neither is easy, and forest scientists and managers are challenged to find ways that are acceptable under 21st Century land use and environmental conditions and which today's citizens will support.