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Introduction
Fire is an event controlled by fuels, weather and topography. Regardless of significant variations, fire occurs nearly everywhere that fuel in a flammable condition is present in sufficient quantities and when an ignition source is available. Fire has existed throughout all time periods, and, prior to the appearance of humans in North America, the ingredients for fire were largely controlled by climate. Since human presence, ignition sources and fuels have been modified; people have changed their environment. As a result, the current distribution and composition of vegetation zones and land-based ecosystems have adapted to wildland fires, defined as all fires that burn in natural environments. The natural role of wildland fire, an important ecological force, cannot be ignored because fire greatly influences ecosystems. Fire's influential role as an ecological force, similar to that of other natural phenomena such as floods, earthquakes and hurricanes, will be discussed in this section.
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