What is the cause of most wildfires?

An overwhelming number of brush, grass and forest fires (between 87 and 96 percent) are caused by people, according to statistics collected by the National Interagency Fire Center (NIFC) and the National Fire Incident Reporting System.

While about 20% of all such fires are intentionally set, most human-caused fires are accidental and related to careless disposal of hot embers, ash or cigarettes.

Regardless of the cause, local fire departments in the U.S. responded to an average of 356,800 such fires annually between 2004 and 2008. See the National Fire Protection Association (NFPA) and the NIFC for more information on wildfire causes and frequency.