Ninety percent wildfires are started by humans some 90% storm lightning strikes National Park Service Ninety percent of wildfires are caused by humans Ninety percent of wildfires are caused by humans United States National Park Service The fact is United States National Park Service according to the National Park Service National Park Service wildfires are started by humans humans cause 90 percent of the fires National Park Service The fact is National Park Service wildfires are started by humans as much as 90% in the US 参照 90 percent 90% of U.S. wildfires are caused by humans National Park Service the National Park Service National Park Service 出典 deliberate ignition https://www.nps.gov/fire/wildland-fire/ ... causes.cfm