Wildfire is a natural event, and many ecosystems have evolved to benefit from it. It clears underbrush and debris, adds nutrients to the soil, and opens up space for sunlight to reach grasses and herbs that generate food and shelter for animals. At low intensity, it also kills problematic insects and disease and helps trees grow and mature.
While wildfire can be caused by a lightning strike or a human-made spark (such as from a cigarette or campfire), its severity depends on the three key elements: fuel, ignition, and weather conditions. Fuel refers to dry, combustible material, and includes everything from grass and leaves to dead tree limbs and woody shrubs. Ignition comes from either a lightening strike or a man-made source such as a vehicle, a discarded cigarette, or an open flame. Weather is also crucial, as drought and heat cause vegetation to become dry and more flammable. Wind and topography can influence fire behavior as well; for example, a flame tends to burn more quickly uphill than it does downhill.
Climate change has exacerbated the risk of wildfire in many areas by warming temperatures and increasing the frequency and intensity of droughts. In addition, the historic practice of putting out all wildfires has left some ecosystems overgrown and dense with shrubs and debris that are more likely to catch fire and spread. The smoke that results from these blazes is a significant source of air pollution, contributing to respiratory problems and increasing the risk of cancer.
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