Fire Science and Research
Fire in the Sierra Nevada
Fire is an integral, important, and inevitable part of the Sierra Nevada ecosystem. The plants and animals throughout the Sierra have developed not just to withstand fire, but in fact, many plants and animals depend on fire for their existence. The seeds of Giant Sequoia (Sequoiadendron giganteum), for instance, need fire to germinate properly. Several other tree species need the heat of fire to open up their tightly serotinous cones thus exposing the next seed crop that will grow within the soil and become the next generation of ancient trees. Native Americans used fire as part of their food gathering and hunting cycle. Over 100 years of logging old growth trees, as well as intense fire suppression policies have caused an unnatural accumulation of fuels that now threaten communities and the overall health and stability of the magnificent Sierra Nevada.
Fire Ecology
Fire ecology is a branch of ecology that concentrates on the origins, cycles, and future stages of wildland fire. It probes the relationship of fire with living organisms and their environment. Four concepts provide the basis for fire ecology:
Fire Dependence: This concept applies to species of plants that rely on the effects of fire to make the environment more hospitable for their regeneration and growth.
Fire History: This concept describes how often fires occur in a geographical area. Fire scars, or a layer of charcoal remaining on a living tree as it adds a layer of cells annually, provide a record that can be used to determine when in history a fire occurred.
Fire Regime: Fire regime is a generalized way of integrating various fire characteristics, such as the fire intensity, severity, frequency, and vegetative community.
Fire Adaptation: This concept applies to species of plants that have evolved with special traits contributing to successful abilities to survive fires at various stages in their life cycles. For example, serotinous cones, fire resistant bark, fire resistant foliage, or rapid growth and development enable various kinds of plants to survive and thrive in a fire prone environment.
The Role of Fire
From the time that forests and lightning came into existence, fire has played an essential role. As one National Park resource professional stated, “Fire is as natural to this ecosystem as sunlight and snow.” Fire creates plant and animal habitat throughout the United States. There is no question that many ecosystems would not exist in the absence of fire.
Now, after decades of fire suppression and other past management practices, the importance of reintroduction of fire to wildland ecosystems is widely accepted as essential practice. Two major events have been instrumental in turning policy and decision making around. One, scientists have observed that the recovery of forest plants and wildlife habitat since the 1980 eruption of Mount St. Helens in Oregon--now a natural laboratory for studying disturbance in western forest ecosystems--clearly demonstrates the ability of ecosystems to recover, even from devastating catastrophic disturbance. Secondly, the 1988 fires in Yellowstone National Park, where nearly 800,000 acres burned for several months and eventually were extinguished by fall rains, resulted in a robust increase in quality habitat for wildlife, and restored plant communities long suppressed by fire suppression policy. These seminal events, coupled with a growing increase in scientific research in the field of fire ecology, have informed agency decision making. This resulted in adoption in 1995 by Federal agencies of a new Federal Wildland Fire Management Policy. The policy contains direction to control the fires we do not want, while promoting those we do. However, it is also essential to understand that logging after fire--called "salvage logging"--is highly detrimental to the natural recovery processes in the post-fire environment and can reverse natural recovery processes and eliminate the benefits of fire. Read more about salvage logging here.
Few alternative treatments can compete with fire effectiveness to reduce unnatural fuel buildups, restore native plant communities, and improve fire resiliency, and fire is less costly than other types of treatments. It is also most effective at reducing long-term smoke impacts to surrounding communities. Chemicals have many environmental risks associated with their use and are expensive. Mechanical treatments have similar problems and if not conducted properly can increase fire hazards. Prescribed fire is much more affordable with much less risk to the habitat and destruction of site and soil quality.
What is Fire?
Fire is the combination of heat, oxygen, fuel and an ignition source. Fuels include grasses, needles, leaves, brush and trees. Natural ignition sources in the Sierra Nevada generally involve lightning. Fire management officials are increasingly using fire to improve forest health and to protect communities. However, sometimes people also start uncontrolled fires through carelessness or arson.
Where and how quickly a fire moves depends on the terrain, weather and types of fuel. Fires burn faster up hillsides than they do on flat ground. The heat rising from the flames pre-heats the grasses, shrubs or trees on upslope. Like sheets of paper, grasses burn quickly, up to several miles per hour under extreme conditions. Larger fuels, such as logs, may take hours or even days to burn completely. While windswept flames can leap into the crowns of trees and burn entire trees in seconds, many fires merely creep along the ground slowly burning brush and forest litter.
The diversity of plants and animals we enjoy in the forests and national parks depend upon fire. What may look at first like devastation soon becomes a panorama of new life. Fire starts critical natural processes by breaking down organic matter into soil nutrients. Soil, rejuvenated with nitrogen from ash, provides a fertile seedbed for plants. With less competition and more sunlight certain seedlings grow quickly.
About Wildland Fire
Wildland fire has great potential to change landscapes more often than volcanoes, earthquakes or even floods. Such forces of change are completely natural. Many plants and animals cannot survive without the cycles of fire or flooding to which they are adapted. If all fire is suppressed, fuel builds up and makes bigger fires inevitable. Under certain conditions, large, hot fires can threaten public safety, devastate property, damage natural and cultural resources, and be expensive and dangerous to fight.
Forest policy stresses managing fire, not simply suppressing it. This means planning for the inevitable and promoting the use of fire as a land management tool. The goal is to restore fire's role as a dynamic and necessary natural process.
Prescribed fire is one of the most important tools used to manage fire today. A scientific prescription for the fire, prepared in advance, describes its objectives, fuels, size and the ideal environmental conditions for it to burn. If it moves outside the predetermined area, the fire may be suppressed. Burning key areas in advance, thereby removing fuels from the path of future unwanted fires, can protect communities and make the forest more fire resistant.
Good Fire / Prescribed Fire
Not all fire is bad. In fact, the exclusion of naturally occurring, low intensity fire, over the last century has contributed significantly to the increased build up of surface fuels (needles, limbs, cones, brush) and increased wildfire intensity in recent decades.
On public lands, prescribed fires are used to manage vegetation instead of lightning-caused fires. Prescribed burns are ignited to reduce hazardous fuels (needles, brush, downed woody material, etc.) so that future fires do not become large, uncontrolled events that devastate the forest and threaten air quality for extended periods.
Fire management may also choose to closely monitor naturally started fires, ignited by lightning, to meet specific resource objectives like the prescribed fires. This type of fire management is called Wildland Fire Use. In the National Parks of California many lightning-caused fires have are allowed to burn and die naturally each year regenerating the forest and reducing future risks.
"Prescribed" burning is defined in A Guide for Prescribed Fire in Southern Forests as: “fire applied in a knowledgeable manner to forest fuels on a specific land area under selected weather conditions to accomplish predetermined, well-defined management objectives.” Wildland Fire Use is also considered a “prescribed” fire even though they are naturally caused (generally by lightning).
The question is, how can we better manage wildland fire so that people and communities are safe, while ecosystems are allowed to benefit from the annual seasons of flame? Most importantly, the only way fire will ever be successfully reintroduced is for the rural communities on the front lines to feel safe. Federal fire scientists have determined that it is the home and its immediate surroundings that principally determine the potential for home ignition during fires. Even so, communities will only feel safe when the land surrounding them--the community protection zone--is treated to reduce hazardous fuels through strategic thinning, brush removal, and prescribed burning.
Fire scientists have determined that mechanical thinning without prescribed fire (including fuel breaks) does not effectively reduce fire behavior under extreme conditions (Stephens 1998). They have also concluded that thinning or other mechanical treatments alone will not restore forest ecosystems (Conservation Biology, Vol. 18, no. 4, August 2004) and that prescribed fire is the most effective tool at reducing the surface fuels that contribute to surface fire spread (van Wagtendonk in SNEP 1996). The reintroduction of fire into the Sierra Nevada landscape is critical to solving the fire hazard that currently exists.
Few alternative treatments can compete with fire from the standpoint of effectiveness, cost, and reducing long-term smoke impacts to surrounding communities. Chemicals are expensive and have associated environmental risks. Mechanical treatments have the same problems. Prescribed fire is much more affordable with much less risk to the habitat and destruction of site and soil quality.
The Sierra Nevada Framework uses prescribed fire as a key management tool in reducing surface fuels and ladder fuels (brush and small trees) to protect communities and to make the forest more resilient and healthy.
Bad Fire
In recent years, fires in the Sierra Nevada have been breathlessly reported as being "catastrophic" with the entire forest being "destroyed" or burned up. On the nightly news, it is the catastrophic areas of fire that are shown because they are dramatic visual images. Unfortunately, this portrayal distorts the overall picture. On the ground, a far different picture emerges.
Within the "fire perimeter"--the farthest outside edge of the forest affected by the fire and whatever suppression efforts are being conducted--there are usually some areas that have burned so hot that all vegetation is destroyed. These are the "catastrophic" or severe areas, but within the fire perimeter are larger areas of "moderate severity," "low severity," and even areas that have not burned at all.
Fire severity and vegetation type are two variables that determine the impact a wildfire will have on the forest. Contrary to the conventional wisdom, recent wildfires in the Sierra have been primarily low-moderate in nature and are the kinds of fire we actually pay people to conduct as "fuels treatments" for forest health and fire risk reduction.
Even areas of "high severity" provide important ecological functions. The black-backed woodpecker is just one species that needs burned over areas to forage and nest successfully. In northeast Washington, black-backed woodpeckers were 20 times more abundant in burned versus unburned forests (Kreisel and Stein 1999), and often were restricted to standing dead forests created by recent stand-replacement fires (Hutto 1995, Caton 1996). More information about the increasingly threatened black-backed woodpecker can be found here.
Logging Actually Increases Fire Risk to the Forest
The Sierra Nevada Ecosystem Project Report (SNEP) in 1996 stated, “Timber harvest, through its effects on forest structure, local microclimate, and fuels accumulation, has increased fire severity more than any other recent human activity.” The August 2000 Congressional Research Service report concluded, "Timber harvesting removes the relatively large diameter wood that can be converted into wood products, but leaves behind the small material, especially twigs and needles. The concentration of these ‘fine fuels’ on the forest floor increases the rate of spread of wildfires."
A 1999 General Accounting Office Report (GAO/RCED-99-65) chastised the Forest Service for operating a fuels reduction program that focused on harvesting large, commercially valuable, fire-resistant trees, rather than concentrating on high fuel hazard areas on our national forests. The revisions to the Framework plan propose a return to the failed strategies of the past by downplaying the use of prescribed fire, while tripling the logging on Sierra Nevada forests, mostly in the larger size classes. Fire scientists have suggested that the largest portion (over 80%) of the fire hazard on our forests is in the surface and ladder fuels, rather than the over-story trees.
Glossary of Wildland Fire Related Terms
Plant Succession: In ecology, progressive change of the plant and animal life of an area in response to environmental conditions.
Forest Stand Density: The amount of trees in a forest per unit area. Can be measured in terms of basal area and crown cover.
Growth or Vigor: The ability of plants to exhibit healthy natural growth and survival.
Stand: A group of trees with similar species composition, age, and condition that makes the group distinguishable from other trees in the area.
Silvicultural: The practice of caring for forest trees in a way that meets management objectives. For example, foresters may control the composition and quality of a forest stand for goods such as timber and/or benefits to an ecosystem.
Prescribed Fire: A forest management practice that uses fire to improve habitat or reduce hazardous fuels. A plan for the prescribed burn must be written out and approved, and specific requirements must be met.
Fire-Resilient Landscape: A natural landscape featuring plants that have adapted to local wildlife conditions, or a domestic outdoor space where appropriate actions have been taken to make it less vulnerable to wildfire and certainly less prone to causing one.
Modify Fire Behavior: Using fire-safe practices such as fuel treatments, thinning, creating firebreaks, etc., to change the way a fire will behave, with a goal of slowing it down and/or suppressing it more easily.
Crown Fire: A fire that spreads from treetop to treetop, and is characteristic of hot fires and dry conditions. Crown fires are generally more complex to control than fires on the surface.
Surface Fuels: Materials on the ground like needles or low-growing shrubs that provide the fuel for fires to spread on the ground. Surface fuels are generally considered all fuels within six feet of the ground.
Ladder Fuels: Materials such as shrubs or small trees connecting the ground to the tree canopy or uppermost vegetation layer. In forests, this allows fire to climb upward into trees.
Crown Density: A measurement of the thickness or density of the foliage of the tree crown in a stand.
Biodiversity: The abundant variety of plant, fungi, and animal species found in an ecosystem, including the diversity of genetics, species, and ecological type.
Site-Specific: Applicable to a specific piece of land and its associated attributes and conditions (e.g. microclimate, soils, vegetation).
Soil Types: Refers to the different combinations of soil particles and soil composition. Soil can vary greatly within short distances.
Forest Stand Enhancement: A combination of both silvicultural thinning practices and other forest restoration activities such as prescribed fire, which aim to increase the health, resiliency, and vigor of tree communities within a forest ecosystem.
Fuel Continuity: The amount of continuous fuel materials in a fire’s path that allows the fire to extend vertically toward the crowns of trees or horizontally into the forest or other fuels.
Fire Science Research Papers
Fire Ecology
McKenzie, D., et.al. 2004. Climatic Change, Wildfire and Conservation. Conservation Biology, 18(4) 890-902 (432KB PDF).
Pyne, S. 2004. Pyromancy: Reading Stories in the Flames. Conservation Biology 18(4) 874-877 (133KB PDF).
Fire History
Syphard, A.D., Et.Al. 2007. Human Influence on California Fire Regimes. Ecological Applications, 17(5) 1388–1402 (924KB PDF).
Fuels Management
Loehle, C. 2004. Applying Landscape Principles to Fire Hazard Reduction. Forest Ecology and Management 198, 261–267 (145KB PDF).
Safford, H. 2008. Fire Severity in Fuel Treatments--American River Complex Fire, Tahoe National Forest. June 21-August 1, 2008. (3.85MB PDF).