NEVADA COUNTY, Calif. — The current condition of forests in the Sierra Nevada abets larger fires that burn more intensely and with a higher degree of catastrophic consequences, a new study has determined.
“The past few decades have seen a significant increase in the size of high-severity fires and the acreage subjected to catastrophic burn,” said the authors of the “Fire Threat study” sponsored by the Sierra Nevada Conservancy and released in September.
“A combination of over 100 years of human encroachment into the wildlands and fire suppression led to a drastic reduction in natural fire on the landscape and changed the character of the forest, much of which has filled in with heavy undergrowth, which is now much more prone to high-severity fire,” authors said.
While recent precipitation throughout the Sierra points to the end of fire season, officials continue to express concern it will not suffice to quell fire danger.
“This rain is a good thing, but by the end of the week, a warming trend is expected, and a northward wind pattern will dry conditions back out,” said Calfire spokesman Daniel Berlant. “We are keeping our staffing levels up.”
On Nov. 13, the National Weather Service noted that it had rained only 22 days in the region in 2013, while the average is 63.5 days a year.
“Another way of looking at it: If it were to rain every day for the rest of the calendar year, we would only catch up to normal,” weather officials posted on the agency’s Facebook page.
However, in California, rainfall is measured in water years, which begin in October and run through the end of September.
While the start of the 2013-14 water year has been arid, the dearth of rainfall is not atypical, said Johnnie Powell, forecaster for the NWS.
“The rain doesn’t really start arriving until late November, on average,” Powell said. “If we’re having this discussion at the end of December, then we’re worried. But just because we are starting slow doesn’t mean we won’t finish fast.”
The 2012-13 water year was well below normal, featuring a snowpack that hovered around half of normal measurements for much of the year.
The dry winter gave rise to a busy wildland fire season throughout California and particularly in the Sierra Nevada, which witnessed the largest fire in the history of the mountain range.
The Rim fire, which began Aug. 17, was caused by an illegal campfire started by an as-of-yet publicly unidentified hunter. The blaze grew exponentially, burning for two months before being listed as officially contained Oct. 24.
Approximately 257,314 acres, or about 400 square miles, were consumed in Tuolumne and Mariposa counties near Yosemite National Park, representing the third largest fire on record in the state.
From Jan. 1 through Oct. 19, 6,680 wildland fires were sparked in California, easily surpassing the 4,734 fires in 2012 and the 4,715 fires averaged from 2007 to 2012.
“We saw a 40 percent increase in fire responses due to the abnormally dry winter,” Berlant said. “There were a lot more fires.”
The Sierra Nevada Conservancy study makes the case that dry conditions are only one variable in a complex formula.
About 150 years ago, low-severity fire was a frequent occurrence in the forests of the Sierra, the study states. The frequent moderate fires were a boon to the landscape because they bolstered forest health by thinning out small trees, removing fuel accumulation and eradicating insect pests and curtailing tree disease.
Human encroachments into the wildland and an emphasis on fire suppression have fostered conditions that present an increased risk to both human habitation and infrastructure, as well as the forest ecosystem, the study states.
The conservancy conducted an in-depth investigation into all 22 counties within the SNC region, which includes nearly 25 million acres, 212 communities, more than 600,000 residents and a flourishing tourism industry that attracts more than 50 million recreation visit days per year.
Of that land, about 68 percent (17,500,000 acres) is classified as high, very high or extreme fire danger. Only 12 percent is classified as little to no fire danger.
Federal land managers own and maintain 60 percent of the land within the region, and two-thirds of that land has a fire danger classification of at least high.
The subregion encompassing Nevada County, which also includes Yuba, Placer and El Dorado counties, circumscribes 2.5 million acres, 67 percent of which contains fire danger listed as high or above, the study states.