Fires, Forest

Wildfire Seasons and Causes

Wildfires occur across the world during all times of the year; however, they are most common during cycles known as fire seasons, which are based on seasonal weather conditions, fuel characteristics, and human activities. Some of these cycles are take years to complete, while others are completed in a single calendar year. Some countries, including the United States, have numerous fire seasons throughout the year in different geographic areas. For example, the fire season in the western United States is typically during the summer, when temperatures are highest and humidity is at its lowest point. The fire season in the Ozark Mountains of Arkansas and Missouri is traditionally in the fall and winter as the majority of deciduous trees lose their leaves, providing an abundant fuel source for fires. These fire seasons can change when a significant environmental catalyst is present, such as a drought or recent ice storm. In southern California, the fire season often coincides with Santa Ana winds, which are notorious for generating large, fast-moving scrub fires in Los Angeles County and neighboring areas.

Wildfires can be caused by numerous natural and human-made catalysts, including lightning, volcanic eruption, underground coal fires, negligent burns, dragging trailer chains, fireworks, campfires, grills, cigarette butts, and arson. Despite the variety of causes, most fires are human-made. A research study conducted by the National Interagency Fire Center in Boise, Idaho, revealed that while 88 percent of wildfires between 1988 and 1997 were caused by humans, they only accounted for 48 percent of the acreage burned. Lightning, which was responsible for 12 percent of the fires, accounted for 52 percent of acreage burned. Despite public-information campaigns urging caution with fire in wilderness areas—which have reduced the number of accidental, human-caused fires—the increased population sprawl into wilderness areas and burgeoning popularity of outdoor activities promises to sustain the trend of humans causing at least three-fourths of all wildfires.

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