Earthsky Interviews
Private: Warming climate sparks wildfires, say scientists
10-25-2007 - Earth
(John McColgan, USDA)
That’s the conclusion drawn by environmental scientist Anthony Westerling of the University of California, Merced. He co-authored a study that looked at 34 years of government fire data since 1970. Westerling focused on large fires in western forests of over 1,000 acres.
Anthony Westerling: _What we saw very clearly was that most of the fires occurred in years with warm springs, sometimes drier winters, and early spring snow melts. And we had a much longer fire season in these years._
An early snow melt can create dry conditions vulnerable to fire. Westerling told Earth & Sky that the first 17 years of the study saw over 200 large fires. In the next 17 years, ending in 2003, there were over 900. Most of the increased wildfire activity was in forests at around 7,000 feet in elevation in the northern Rocky mountains.
Anthony Westerling: _These forests are thought to be the least effected, in terms of changes in the risk of a large fire due to a century or more of land management and fire suppression in the western United States. So we saw very clearly a climatic signal in an area where we don’t have other explanations for why the fires have increased so dramatically._
Thanks today to “NASA”:http://www.nasa.gov/externalflash/sts115_front/index.html.
*Our thanks to:*
Anthony Westerling
Assistant Professor
School of Engineering &
School of Social Sciences, Humanities, and Arts
University of California, Merced
How was the increase in arson considered in the study?
By only looking at high elevation forests, the scientists in this study were able to rule out direct impacts such as arson and land use (decades of fire suppression). Here’s what Dr. Westerling told Earth & Sky in response to this question.
“There are a lot of factors to consider on the human side of the equation. It’s not just that fuels in some forests have been increased because of fire suppression and land management. But it’s also the case that fire supression strategies vary over time. And it’s also the case that the population changes over time.
Each of these things is important, but it’s also important to keep in mind that the timing of these fires, the vast majority of them occured in early snow melt years and in places where land management and fire suppression have not greatly changed the forest structure and the risk of a large fire.
So in terms of thinking about the vegetation changes from the 20th century and the late 19th century, the areas that were most affected by the increase in large fires were least affected by those factors.
In terms of thinking about strategies for fire suppression, that’s more difficult. However, if you look at the records, it’s clear that in most of these large fires seasons, they were trying very hard to extinguish those fires. And if you look at the spending and the individual reports for those fires, it’s clear that they were not letting most of these fires just burn. So there’s no indication that the timing of these seasons and the location is governed by these human factors.”
– Anthony Westlerling to Earth & Sky.