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CHAPTER 15. WILDFIRE <br />15-8 <br />response times to reported fires, the likelihood of injuries and casualties is minimal. Smoke and air pollution <br />from wildfires can be a health hazard, especially for sensitive populations including children, the elderly <br />and those with respiratory and cardiovascular diseases. Wildfire may also threaten the health and safety of <br />those fighting the fires. First responders are exposed to the dangers from the initial incident and after-effects <br />from smoke inhalation and heat stroke. In addition, wildfire can lead to ancillary impacts such as landslides <br />in steep ravine areas and flooding due to the impacts of silt in local watersheds. <br />15.2.7 Warning Time <br />Wildfires are often caused by humans, intentionally or accidentally. There is no way to predict when one <br />might break out. Since fireworks often cause brush fires, extra diligence is warranted around the Fourth of <br />July when the use of fireworks is highest. Dry seasons and droughts are factors that greatly increase fire <br />likelihood. Dry lightning may trigger wildfires. Severe weather can be predicted, so special attention can <br />be paid during weather events that may include lightning. Reliable National Weather Service lightning <br />warnings are available on average 24 to 48 hours prior to a significant electrical storm. <br />If a fire does break out and spread rapidly, residents may need to evacuate within days or hours. A fire’s <br />peak burning period generally is between 1 p.m. and 6 p.m. Once a fire has started, fire alerting is reasonably <br />rapid in most cases. The rapid spread of cellular and two -way radio communications in recent years has <br />further contributed to a significant improvement in warning time. Improvements in GIS mapping of <br />wildfires also increases understanding of the location and movements of wildfires, enabling more extensive <br />warning times. <br />15.3. SECONDARY HAZARDS <br />Wildfires can generate a range of secondary effects, which in some cases may cause more widespread and <br />prolonged damage than the fire itself. Fires can cause direct economic losses in the reduction of harvestable <br />timber and indirect economic losses in reduced tourism. Wildfires cause the contamination of reservoirs, <br />destroy transmission lines and contribute to flooding. They strip slopes of vegetation, exposing them to <br />greater amounts of runoff. This in turn can weaken soils and cause failures on slopes. Major landslides can <br />occur several years after a wildfire. Most wildfires burn hot and for long durations that can bake soils, <br />especially those high in clay content, thus increasing the imperviousness of the ground. This increases the <br />runoff generated by storm events, thus increasing the chance of flooding. <br />15.4. CLIMATE CHANGE IMPACTS <br />Fire in western ecosystems is determined by climate variability, local topography, and human intervention. <br />Climate change has the potential to affect multiple elements of the wildfire system: fire behavior, ignitions, <br />fire management, and vegetation fuels. Hot dry spells create the highest fire risk. Increased t emperatures <br />may intensify wildfire danger by warming and drying out vegetation. When climate alters fuel loads and <br />fuel moisture, forest susceptibility to wildfires changes. Climate change also may increase winds that spread <br />fires. Faster fires are harder to contain, and thus are more likely to expand into residential neighborhoods. <br />Historically, drought patterns in the West are related to large -scale climate patterns in the Pacific and <br />Atlantic oceans. The El Niño–Southern Oscillation in the Pacific varies on a 5- to 7-year cycle, the Pacific <br />Decadal Oscillation varies on a 20- to 30-year cycle, and the Atlantic Multidecadal Oscillation varies on a <br />65- to 80-year cycle. As these large-scale ocean climate patterns vary in relation to each other, drought <br />conditions in the U.S. shift from region to region. El Niño years bring drier conditions to the Pacific <br />Northwest and more fires. <br />The Northwestern US has experienced warming temperatures and declines in snowpack and streamflow in <br />recent decades. Average annual temperatures have risen by about 1.3 degrees Fahrenheit over the last