Forests & Fire
Fire has, throughout history, always played a significant role in forests and the management of forest ecosystems. None more so than our temperate forests here in the western United States. Pre-European settlement, Natives across this continent used fire extensively to accomplish a variety of goals, from controlling shrubs and brush to improve travel, hunting, and gathering; to manage habitat for big game, to cool waters in salmon bearing rivers to promote the migration of salmon upriver- in practice, to “call the salmon home”. The use of fire as a management tool was crucial to their survival and existence. After European settlement, statutes and laws were enacted that banned the natives cultural burning and even imprisoned those who continued to implement it.
Along with European settlement came a fear of fire and a lack of understanding of the critical role of fire in native forest ecosystems. So much so that the founder of the United States Forest Service labelled fire the “greatest threat to our western forests”. And so began a legacy of fire suppression and exclusion- a Smokey Bear fire management policy that effected and changed forests throughout the west dramatically. Fire exclusion created overstocked forests of shade tolerant species more susceptible to diseases and insects. Fire exclusion also created forests of fuels easily ignitable and more prone to stand replacement crown fires. The effects of 140 years of fire exclusion are still influencing fire and forest management policies yet today.
The Smokey Bear fire management policy gave rise to a successful and long-term fire prevention and suppression effort. Indeed, the national policy for decades was “all fires out before 10:00 AM”. However, all forests are in a continual state of flux and change. They regenerate, grow, mature, deteriorate, collapse, and become fuels. A telling result of the Smokey Bear paradigm has been the accumulation of fuels in the forests to the point where what historically would be a ground fire now becomes a massive conflagration and a stand replacing, crowning wildfire over vast acres. Failure to implement prescribed fire across all landscapes- grasslands, sagelands, and forestlands has caused wildfires to burn out of control and consume vast acres and cause exponentially increasing property damage and losses, and not just locally and nationally, but globally as well.
It takes three components to make a fire: fuels, ignition, and weather. Fuels are defined by four different classes: 1 hr; 10 hour; 100 hour, and 1,000-hour categories. One-hour fuels are needles and small twigs up to ¼ inch in diameter; 10-hour fuels are ¼” to 1 inch diameter’; 100-hour fuels are 1” to 3” diameter, and 1,000-hour fuels are 3” to 8” diameter.
The 1-hour fuels fluctuate dramatically and diurnally due to air temperature, wind speed, relative humidity, and cloud cover. The 10-hour fuel moisture characteristics may fluctuate daily, but less so. These fuels offer a more stable planning component for prescription fire. Moisture content in this fuels category is critical for managing good fire. A 9% moisture content in these fuels produces a darker smoke because oils and resins are being volatized. Whereas even a slight increase to 12% moisture produces more white smoke and steam. The 1,000-hour fuels burn hotter and longer and provide a significant energy release component. More of these larger fuels are burning in recent fires due to a warming and drying climate.
Ignition sources vary and include lightning; arson; campfires; young people; trash burning; equipment use; railroads; smoking, and other unexplained sources. Most (85%) of wildfires in the United States are caused by human ignitions.
Weather is critical to wildfire extent and intensity, influencing both losses and gains. A fire that burns with too much intensity can destroy soil structure, roots, and rhizomes. A fire that burns too hot can also set vegetation succession patterns back to bare soil. A hot burning fire can also volatize nitrogen, an important nutrient element. However, planet earth’s atmosphere is about 78% nitrogen and nitrogen is cycled back into the forest environment through bacteria and fungi within three years to the pre-burn levels. Phosphorous, calcium, and potassium are more important elements for early plant growth. They promote root development. And they are released in abundance after a moderately hot fire…typical conditions after a prescribed fire.
However, there are more positive effects of fire in the forest.
Indeed, there are at minimum 17 positive attributes of fire in the forest: 1) to dispose of logging slash; 2) to increase and improve tree planting sites; 3) to reduce fuel loadings by removing excessive fuels build-up often created by fire exclusion policies; 4) to help in controlling wildfires with backburns and back-firing; 5) to prepare seedbeds for natural or planted regeneration; 6) to reduce shrubbery and grass competition for more fire tolerant, desired species (e.g. huckleberry plants); 7) to recycle nutrients to maintain and manage site productivity; 8) to sanitize sites against diseases and insects; 9) to eliminate less desirable plants; 10) to maintain early seral species on a site that would be taken over by less desirable, climax species; 11) to imitate a natural fire regime; 12) to maintain grasslands by killing invasive trees and shrubs; 13) to thin dense stands of trees to reduce moisture and nutrient stress; 14) to rejuvenate sprouting to improve deer and elk forage, and 16) to restore natural conditions and return the area to within its historic range of variability (HRV), and last, but not least (17) soil carbon recharge.
Large wildfires followed European settlement from the Maine forests to the coastal Pacific forests. Logging slash accumulations and lack of forest management policies and appropriate silviculture typically fuelled these early fires. The Miramichi fire in Maine and New Brunswick in 1825 burned 2,800,00 acres. As logging moved west, so did large wildfires. The Peshtigo Fire in Michigan and Wisconsin burned 4,000,000 acres in 1871, not long after the heavy logging in the red pine forests of the lake states. In 1902, the Yacolt fire in Washington state burned 1,000,000 acres. Fuelled by logging slash and high winds, the Big Burn of 1910 consumed 3,000,000 acres in Idaho and Montana. In the intermountain west, 1988 was a dry year and large wildfires burned over 2,000,000 acres in Idaho, Montana, and Wyoming.
Fire exclusion and a warming and drying climate provide the ingredients for the catastrophic wildfires we are witnessing now. Longer, draughtier summers are producing more bark beetles. Where historically we had two hatches of Ips pini per year, we can now have three in many areas. Moisture stress during these longer, dryer summers creates water stress in all species and especially the pine species. These species tend to fight climate stress by closing their gas exchange valves, reducing their carbon intake and thus their capacity to appropriate carbon resources where they are needed most- respiration and defense mechanisms. Increasing mortality increases the fuel loading and resulting fire intensity. It also increases the need for prescribed fire and active fuels management.
The solution and perhaps the only solution to these damaging and catastrophic wildfires is to re-introduce good fire- prescribed fire into these ecosystems. Though a mechanical pre-treatment before prescribed fire may be necessary on many sites to prevent tree mortality, mulching, chipping, and slashing fuels increases the organic and litter layer and creates a hot enough fire when burned near the root collar to scorch the cambial layer and kill the tree. It does not necessarily require a crown fire to kill a forest. Periodic prescribed fire at a landscape level is the only tool scalable and is an effective natural process to manage accumulated fuels. Like all forest treatments, long term, repetitive use of prescribed fire requires training, adequate staffing, the will, and the greater social commitment. After all, this is a recurring effort to manage the human environment and must be passed from one generation to the next. The Indians knew this.
