Learning Objectives Summarize the role of wildfire during the past 11,500 years. Explain why wildfire is a natural process that would occur with or without people. Explain why the wildfire hazard varies from region to region. Summarize how wildfires are linked to other natural hazards.

Learning Objectives, cont. Make the link between global change (warming) and the number and intensity of wildfires. List the potential benefits provided by wildfires. Evaluate the methods employed to minimize the fire hazard. Summarize the potential adjustments to the wildfire hazard and the role of human processes.

Summer 2013: Two Wildfires in the U.S. Southwest Two deadly fires occurred during summer of 2013 Black Forest fire Outside of Colorado Springs, Colorado Burned about 15,000 acres and destroyed more than 500 homes Most destructive in Colorado’s history However, past experience with fires enabled authorities to act quickly – only 2 people were killed Wildfire near Yarnell, Arizona Swift-moving like the Black Forest fire Burned at least 8000 acres and destroyed about 200 homes 19 firefighters were killed when fire overrode their position

13.1 Introduction to Wildfire One of nature’s oldest phenomena First when trees evolved and spread across the land Behavior changed when grasses evolved Changed again with an increase in charcoal in the sediment Before humans, fires would burn until they ran out of fuel naturally Allowed humans to harness fires for their uses Helped populations spread across continents Initiates plant regrowth, when the cycle restarts

13.2 Wildfire as a Process Self-sustaining, rapid, high-temperature biochemical oxidation reaction Releases heat, light, and other products Requires fuel, oxygen, and heat Plant tissue and other organic material (biomass) are rapidly oxidized and broken down by combustion Burn because they establish a balance between reproduction and decomposition Microbes alone do not decompose fast enough to balance plant growth

The Fire Triangle

13.2 Wildfire as a Process, cont. Essentially, wildfires are a way to remove vegetation Fires reverse the process of photosynthesis Carbon dioxide, water vapor, and heat released Water vapor and carbon dioxide are the most abundant gases released in fire Others (e.g., nitrogen oxides, carbon monoxide, and methane) are released in trace amounts These gases along with ash and soot comprise part of the smoke Three phases of a wildfire Preignition Combustion Extinction

13.2 Wildfire as a Process, cont. Preignition Fuel achieves temperature and water content favorable to ignition Preignition involves two processes Preheating Fuel loses water and other volatile compounds Compounds that are easily vaporized Pyrolysis “Heat divided” Processes that chemically degrade fuel Products include volatile gases, mineral ash, tars, etc. Heat, radiating from flames, causes both preheating and pyrolysis in advance of the fire These processes produce the fuel gases

13.2 Wildfire as a Process, cont. Combustion Begins with ignition Preignition absorbs energy, combustion releases energy External reactions liberate heat and light Ignition doesn’t always lead to wildfires Sufficient fuel must be present Ignitions are common on time scale relevant for mature vegetation In period of 50 to 100 years, every acre of land is struck by lightening On this time scale, human wildfires are not significant Just preceding a lightening strike fire that would happen anyway Play a relatively small role in affecting large wildfires Future wildfire chance is reduced after a wildfire passes and destroys the vegetation

13.2 Wildfire as a Process, cont. Combustion, cont. Ignition is not a single process, but occurs repeatedly as wildfire moves Flaming combustion Dominates early fire Rapid high temperature conversion of fuel into heat Characterized by flames and large amount of unburned material Hindered by blanket of noncombustible material that forms as volatile gases are removed from the fuel Smoldering combustion Takes place at lower temperatures Does not require pyrolysis for growth

Parts of a Wildfire

13.2 Wildfire as a Process, cont. Combustion, cont. Three processes control the heat transfer in wildfires Depends on the topography and wind direction Transfer heat primarily through convection Radiation, which generates radiant heat, also plays a role Convective and radiant heat increases surface temperature of fuel Gases become less dense and rise Rising gases remove heat and combustion products from zone of flaming Pulls in fresh air to sustain combustion Extinction Point at which combustion, including smoldering, ceases There is no longer heat and fuel to sustain fire

Influence of Wind and Topography on Wildfires

Fire Environment Behavior of large wildfire can be explained by three factors in its environment Fuel Topography Weather A better understanding of these three factors helps understand and predict wildfire behavior

Fire Environment, cont. Fuel Complex and differ in type, size, quantity, arrangement, and moisture content Types include leaves, twigs, decaying material, grass, shrubs, etc. Peat – unconsolidated deposit of partially decayed wood, leaves, or moss Fuel size affects ignition and movement Landslides, hurricanes, and tornadoes can arrange debris to facilitate fires Organic materials can dry out during droughts to become fuel

Fire Environment, cont. Topography Can have a profound affect on fires Fuel moisture content is affected by location Drier fuels that burn more easily are found On south-facing slopes in Northern Hemisphere Slopes exposed to prevailing winds Mountainous areas circulate winds up canyons during daytime Wildfires preheat fuels upslope making it easier to spread

Fire Environment, cont. Weather Has a dominant influence on wildfire, especially temperature, precipitation, relative humidity, and wind Fires common following droughts Can bring “dry thunderstorms” with lightning to start fires, but rain evaporates and can’t extinguish them Fires burn more when humidity is lowest Wind direction and strength help preheat unburned materials Winds carry embers to ignite spot fires ahead of front

Types of Fires Classified according to the layer of fuel that is allowing the fire to spread Ground fires Creep along under ground surface Little flaming, more smoldering Burn in Duff - decaying organic matter in the soil Drained or temporarily dry swamps and marshes Thicker peat deposits below the soil Surface fires Move along surface and vary in intensity Burn slowly with smoldering, limited flaming Burn grass, shrubs, dead and downed limbs, leaf litter, and other debris

Ground Fire

Surface Fire

Types of Fires, cont. Crown fires Flaming is carried via tree canopies Driven by strong winds and steep slopes

13.3 Geographic Regions at Risk from Wildfires Areas that are near grasslands, woodlands, shrublands, or tundra are at risk during drought Even deserts, rainforests, marsh and swamplands can experience wildfires Large wildfires most common Alaska and the western contiguous states in the United States In the Canadian Rockies Belt that extends from the Yukon Territory southeast to Lake Superior then east to Labrador The wildfire risk area tends to shift from year to year

Alaska and Western Contiguous States with Greatest Wildfire Hazard

13.4 Effects on Wildfires and Linkages with Other Natural Hazards Affect many aspects of the local environment Burn vegetation Release smoke into the environment Char soil Create favorable conditions for landslides Increase erosion and runoff Harm wildlife Important to consider changes that may occur in the geologic and atmospheric environments

Effects on the Geologic Environment Differing effects depending on type and moisture content of the soil and the duration and intensity of the fire Extremely hot fires may leave a water-repellent hydrophobic layer Increases runoff and erosion and flood events Soil erosion and landslides Removal of anchoring vegetation on steep slopes Precipitation often exaggerates the effect of fires on landslides

Effect of Fire on Water-Repellent Soil

Effects on the Atmospheric Environment Wildfires create their own clouds Release smoke, soot, and gases contributing to air pollution Significantly increase concentration of particulates Can be observed thousands of miles downwind Contribute to smog formation Release large quantities of carbon monoxide, volatile organic compounds, and nitrogen oxides Form harmful ground-level ozone

Smoke from Forest Fire Creates Clouds

Linkages with Climate Change Climate change increases intensity and frequency of wildfires Caused by changes in temperature, precipitation, and the frequency and intensity of severe storms Increases in temperature, decreases in humidity Grasslands replacing forests creating more fuel Lightning strikes increase ignitions Insect infestations make trees more vulnerable to fire The linkage will also affect human health

Effects on the Biological Environment Effects can vary from moderate to severe, depending on the fire type, size, location, duration, and intensity Can effect Vegetation Some plants are susceptible to fire, whereas others are not Can make plant vulnerable to later destruction by disease or drought Some plants use fire to propagate Important long-term control of plants Animals Most animals may flee or hide unharmed Habitats are altered Can determine the type and number of vertebrates that can thrive

Effects on the Biological Environment, cont. Can effect, cont. Humans Water quality is affected through increase of erosion potential Smoke and haze produce eye, respiratory, and skin problems Destroys personal property More and more living on the fringes of wildlands in the wildland-urban interface Naturally occurring fires surpressed resulting in longer return intervals and accumulation of fuel

13.5 Natural Service Function of Wildfires: Benefits to Soil Leave an accumulation of carbon and increases the nutrient content Can create a nutrient reservoir Reduce populations of microorganisms Benefit plants with which they compete for nutrients Some microorganisms are parasites or carry diseases

Benefits to Plants and Animals Reduces the number of species of plants Decreases competition for moisture, nutrients, and light May trigger a release of seeds or stimulate flowering in some species Removes surface litter for grasses Recycles nutrients in system Animals benefit from increased plant life and burned, decaying logs provide homes

13.6 Minimizing the Wildfire Hazard: Fire Management Task is difficult because large wildfires cannot be prevented and not all should be suppressed Primary approaches include Science Education Data collection Use of prescribed burns

Fire Management, cont. Science Education Scientific understanding is critical to fire management Fire regime for an ecosystem Types of fuel available Fire behavior described by fire size, intensity, and amount of biomass removed Overall fire history, including fire frequency and recurrence interval Fire reconstruction can be difficult where fires have been suppressed for nearly a century Education Educating people that wildfire is a hazard and how to reduce their risk

Fire Management, cont. Data collection Prescribed burns Remote sensing has become an important tool Mapping vegetation and potential fuel Moisture content FPI (Fire Potential Index) maps Prescribed burns Controlled burns to manage forests A way to counter the dangerous buildup of fuel from suppression Reduces fuel for more catastrophic fires Must have a written plan for each burn to control it

13.7 Perception of and Adjustment to the Wildfire Hazard: Perception of the Wildfire Hazard People do not adequately perceive risk of wildfires Example: California Development on brush-covered hillslopes Demand for hill property increases Insurance may give people false sense of security

Adjustments to the Wildfire Hazard Fire Danger Alerts and Warnings Alert land managers, residents, and visitors to daily changes in conditions Combine information about fuel conditions, topography, weather, and risk of ignition Red flag warnings: when extreme fire conditions are either occurring or will take place in less than 24 hours Fire Education May help reduce the fire hazard However, risk may not still seem “real” without experience

Adjustments to the Wildfire Hazard Codes and Regulations Enforce building codes that require structures to be built with fire-resistant materials Bans on outdoor burning and fireworks when conditions favorable for fire Fire Insurance Ensures those affected by fires will be reimbursed Can cause a sense of false security Evacuation Most common adjustment Ensures the individual’s safety but not their property’s

Personal Adjustment to the Fire Hazard Many things individuals can do to protect themselves Those that live or work in the wildland-urban interface should obtain more information to prepare for the inevitable wildfire

Reducing Your Fire Hazard at Home

Summer 2013: Two Wildfires in the U. S Summer 2013: Two Wildfires in the U.S. Southwest – Applying the 5 Fundamental Concepts People are moving into rural areas on the fringes of cities Affected the Front Range of the Rocky Mountains southwest of Denver, Colorado, as well as the mountains of Arizona. California, and most western states Lives of the residents of these areas was abruptly changed in June and July 2013 when wildfires grew quickly and out of control Became some of the largest and worst fires ever to occur in the region

Summer 2013: Two Wildfires in the U. S Summer 2013: Two Wildfires in the U.S. Southwest – Applying the 5 Fundamental Concepts, cont. These large wildfires are no longer thought to be surprising events Droughts also expected to be longer and more severe May be an increase in flash flooding and erosion due to fires and droughts reducing vegetation Private land in the wildlands is being developed Changes in fire policy and management will be necessary Six most serious fire seasons occurred since 1960

Summer 2013: Two Wildfires in the U. S Summer 2013: Two Wildfires in the U.S. Southwest – Applying the 5 Fundamental Concepts, cont. Large, more intense fires result from several factors Biomass fuels have increased in the past few decades as a result of fire management practices. Timber harvesting of the largest pine tress has resulted in less fire-tolerant understory. Fire suppression has eliminated the smaller, less intense fires that previously reduced the amount of biomass available. Higher temperatures and drought are widespread in recent years, perhaps related to global climate changes. Warmer winters have occurred in the U.S. Southwest with more rain than snow meaning runoff is quicker and soil dries out earlier.

Summer 2013: Two Wildfires in the U. S Summer 2013: Two Wildfires in the U.S. Southwest – Applying the 5 Fundamental Concepts, cont. Factors, cont. While climate change cannot be blamed for any one fire, the trend for larger, more intense fires is clearly expected with warming. In recent years, snowmelt is occurring earlier and, as spring growth is extended, there has been a noted increase in insect and disease occurrences that can weaken trees. The fire season has grown in length by at least two months in recent decades. Continued human use and interest in the natural, rural forest environment has resulted in more homes and other structures being built in the wildland-urban interface.

Summer 2013: Two Wildfires in the U. S Summer 2013: Two Wildfires in the U.S. Southwest – Applying the 5 Fundamental Concepts, cont. Better evacuation and warning systems are being developed Authorities during the Colorado fire moved quickly, sending out telephone messages and deputies door to door Speedy evacuations helped people move out of harm’s way as the Arizona fire got out of control Growing concern that largest and most intense fires will be too dangerous and we will have to just let them burn

Chapter 13 Summary Wildfire, one of nature’s oldest natural processes, is a self-sustaining, rapid, high-temperature, biochemical oxidation reaction that releases heat and light. Wildfire is a natural process that can be defined as a rapid, self-sustaining, high-temperature biochemical reaction that releases heat, light, gases, and other products. For a fire to burn, it must have fuel, oxygen, and heat.

Chapter 13 Summary, cont. Wildfires can be classified based on what part of the landscape burns. Wildfire behavior is influenced by fuel, weather, topography, and the fire itself. Most areas of the United States and Canada that are within or in close proximity to grasslands, shrublands, woodlands, or tundra are at risk for wildfires during dry weather or drought conditions.

Chapter 13 Summary, cont. Fire can increase runoff, erosion, flooding, and landslides. Wildfire is linked to air pollution, reduction of water quality, and vegetation changes through damage and fire adaptation. Wildfire occurrence and intensity are linked to global warming through drought, increasing surface temperature, and extended fire seasons.

Chapter 13 Summary, cont. Natural service functions of fires include increasing the nutrient content of soils, initiating regeneration of plant communities, creating new habitat for animals by altering landscapes, and potentially reducing the risk of large fires in the near future. Wildfire management is difficult because large wildfires cannot be prevented or, in some instances, even controlled.

Chapter 13 Summary, cont. In recent decades, there has been a move to suppress wildfire. As a result, natural fires that occur may become larger and more intense. Adjustments to the wildfire at the institutional level include establishing alerts and warnings, firefighting by fire crews, quick evacuation, and education. Most important in fire management is for homeowners to utilize fire-resistant construction, develop a defendable space around their homes, and be prepared to evacuate.