Trend of wildfire growth in western US identified by new research

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Large wildfires are getting larger and more numerous across the western United States, an escalating trend that has been linked to severe drought conditions, according to a new paper published by a UC Berkeley researcher and three University of Utah researchers.

The study concentrated on a 28-year period and found that the number and area of large fires have increased. Statistics from the report revealed that in the region that stretches from Nebraska to California, the number of wildfires burning over 1,000 acres increased by a rate of seven fires per year from 1984 to 2011.

Though cautious about the findings’ direct relation to climate change, UC Berkeley researcher Max Moritz, co-author of the study, sees some important discoveries in the research.

“(The period) is pretty short to say anything causal about a trend, especially if you want to link it to climate variables,” Moritz said. “What is surprising is that even though it wasn’t for that long, we were able to detect statistically significant trends.”

Monitoring Trends in Burn Severity, a multiyear project that maps the burn severity and perimeters of fires larger than 1,000 acres in the United States from 1984 onward, has served as the main database for the study. For the paper, researchers divided the area of study into nine “ecoregions,” ranging from forested mountains to desert areas.

Severe drought in some western states such as California and the growth of non-native species such as cheatgrass, which dries out quickly and burns very readily, have contributed over the years to the escalation of wildfires.

“We’ve had three of the driest wet seasons in history,” Moritz said. “We are starting the fire season with live fuel moistures at the same levels as they would be at the end of the fire season. We are facing a very challenging time and almost certainly an early start to the fire season.”

Without sufficient rain, states such as California are facing a tough battle ahead as conditions continue to be prone to wildfires. According to a release from the California Department of Forestry and Fire Protection, the department has responded to approximately 900 wildfires from Jan. 1 to April 5, nearly triple the average from a normal year. Fires have so far consumed nearly 2,400 acres in the state.

Moritz and Philip Dennison, another co-author of the study from the University of Utah, introduced the idea that increasing fire may not necessarily be a bad thing, describing it as a “crucial natural process in many ecosystems.” However, according to Dennison, too frequent fires could have unknown impacts and restrict the recovery of some native species.

“We’ve built our communities in these fire-prone landscapes,” Moritz said. “Now we need to take fire seriously and learn how to coexist with it.”

Staff writer Chris Tril contributed to this report.

Contact Robin Simmonds at [email protected] and follow her on Twitter @@rsimmonds_dc.