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By Anthony Cave April 19, 2016

Are 90 percent of fires in Arizona caused by humans?

As officials gear up for wildfire season in Arizona, Gov. Doug Ducey talked fire safety at a press conference April 13.

"I think it’s important to note that 90 percent of fires in Arizona are human-caused," Ducey said. "Unattended campfires, discarded cigarettes, hot exhaust pipes, any source of extreme heat or spark can result in a Wallow or Rodeo-Chediski fire."

Given Arizona’s vast land area, 113,594.08 square miles to be exact, we were curious as to whether nine out of every 10 fires in the state really are caused by humans and how that could be documented.

Sort of

Ducey’s spokesman, Daniel Scarpinato, provided us with Arizona State Forestry data that backs up the governor’s claim on the surface.

In 2015, 352 out of 404 fires, more than 87 percent, were human-caused. Of the 304 fires reported this year, 296, more than 97 percent, were human-caused.

The State Forestry maintains a database of all fires, even if they don’t respond to a blaze at first. State Forestry spokesman Bill Boyd said most fires historically are human-caused, even something as simple as parking a hot car over grass.

"If you look at it over the years, there is a large human component in there," Boyd said.

But there’s a caveat here -- the data only includes fires on state and private land, not federal land. Ducey said "in Arizona," which also includes federally-managed land. Almost 40 percent of the Grand Canyon State is federal land.

Multiple agencies, including the U.S. Agriculture Department, U.S. Defense Department and U.S. Interior Department, have fire jurisdiction over certain areas of land.

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For example, the U.S. Forest Service has fire jurisdiction over national forests and the Bureau of Indian Affairs does the same for tribal land.

"It is complex and coordinated at all levels, from local to national," said Mary Zabinski, spokeswoman for the Southwest Coordination Center, an interagency group of state and federal agencies.

All that coordination means we do have a total for the entire state for human-caused fires. According to the Southwest Coordination Center, for the entire state of Arizona -- state, private and federal land -- 61 percent of fires in 2015 were caused by humans, and 39 percent of fires were caused by lightning.

However, U.S. Forest Service spokeswoman Jennifer Jones notes that 90 percent of wildfires on all land nationwide are caused by humans.

"Typically, the majority of fires on land under the jurisdiction of state and local government agencies are human caused as those lands are closer to homes and roads," Jones said.

Our ruling

Ducey said that "90 percent of fires in Arizona are human-caused." Ducey’s claim is correct when referencing only state and private land. But he wasn’t that specific.

Fires "in Arizona" includes federally-managed land, in addition to state and private land. And the percentage of human-caused fires on all those lands combined isn’t 90 percent, it’s 61 percent.  

So Ducey has a point that human activity is contributing to wildfires, but the number he cites is a good bit off. On balance, we rate Ducey’s claim Half True.

Our Sources

Arizona Gov. Doug Ducey, "Remarks during a fire press conference," April 13, 2016

ABC15, "Firefighters plead for ‘space’ during wildfire season," April 11, 2016

U.S. Census Bureau, "QuickFacts Arizona," accessed April 15, 2016

Arizona State Forestry, "2016 Fire Season Outlook,"  April 13, 2016

Interview with Arizona State Forestry spokesman Bill Boyd, April 18, 2016

Southwest Coordination Center, "Fire and Acres (By State), Arizona," accessed April 15, 2016

TIME Magazine, "Here’s where the federal government owns the most land," Jan. 5, 2016

Interview with Ducey spokesman Daniel Scarpinato, April 14, 2016

Interview with Southwest Coordination Center spokeswoman Mary Zabinski, April 15, 2016

Interview with U.S. Forest Service spokeswoman Jennifer Jones, April 14, 2016

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Are 90 percent of fires in Arizona caused by humans?

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