Climate Models Project Increase In U.S. Wildfire Risk

"Fire is an inherently global phenomenon, and the only practical way to track large-scale patterns and changes in fire activity is with satellites," says Louis Giglio of the University of Maryland at College Park and Goddard.

As the U.S. land area burned by fire each year has increased significantly in the past 25 years, so too have the emissions. Carbon dioxide emissions from wildfires in the western U.S. have more than doubled since the 1980s, according to Chris Williams of Clark University in Worcester, Mass.

The satellite-based view allowed Williams and his colleagues to quantify how much carbon has been released from fires in the U.S. West. The team used data on fire extent and severity derived from Landsat satellites to calculate how much biomass is burned and killed, and how quickly the associated carbon was released to the atmosphere. The team found carbon emissions from fires have grown from an average of 8 teragrams (8.8 million tons) per year from 1984 to 1995 to an average of 20 teragrams (22 million tons) per year from 1996 to 2008, increasing 2.4 times in the latter period.

"With the climate change forecast for the region, this trend likely will continue as the western U.S. gets warmer and drier on average," Williams said. "If this comes to pass, we can anticipate increased fire severity and an even greater area burned annually, causing a further rise in the release of carbon dioxide."

Researchers expect a drier and more wildfire-prone U.S. in future decades. Previous research confirmed the connection between the measure of an environment's potential evaporation, or dryness, and fire activity.

From a fire and emissions management perspective, wildfires are not the entire U.S. fire story, according to research by Hsiao-Wen Lin of the University of California at Irvine. Satellite data show agricultural and prescribed fires are a significant factor and account for 70 percent of the total number of active fires in the continental U.S. Agricultural fires have increased 30 percent in the last decade.

In contrast with wildfires, agricultural and prescribed fires are less affected by climate, especially drought, during the fire season.

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