The smoky aftermath of a controlled burn near the Mariposa Grove of sequoias in October 2006. (Photo by Jun via Flickr)

If historic fire suppression policies in the Sierra Nevada mountain range set the stage for the Rim Fire, can the modern, aggressive approach to wildfire management at Yosemite National Park help end its advance?

The Rim Fire, which has burned 187,466 acres in Tuolumne County and has been advancing deeper into Yosemite, is about to hit the scars of thousands of acres of prescribed fires set in the 1990s and 2000s along the park’s western edge.

These old fires effectively removed ready fuel in the Rim Fire’s path, meaning less damage and better control for the 4,000-plus firefighters working for containment.

The Rim Fire closes in on Ackerson Meadow at Yosemite. A 1996 fire called the Ackerson fire burned 47,000 acres within the park. (U.S. Forest Service photo by Mike McMillan)

“Yosemite is one of the biggest experimental landscapes for prescribed fire and it’s going to pay off,” Hugh Safford, an ecologist with the U.S. Forest Service in California, told The Associated Press. “The Rim Fire is starting to hit all those old fire scars.”

Additionally, firefighters are conducting large burnout operations this week along the southeastern edge of the fire in Yosemite National Park.

The perfect storm of a historic, century-old fire suppression policy that protected timber interests in the Sierra Nevada, several years of drought and smaller winter snow packs allowed the Rim Fire to double and triple in size when it was outside Yosemite and growing fast in steep, rugged terrain of Tuolumne County and the Stanislaus National Forest.

Only since the fire has entered Yosemite have crews been able to effectively slow its advance, even though it has still grown in size to be the seventh-largest fire in California history.

Yosemite was key in the development of the National Park Service’s prescribed burn program, and conducted its first prescribed burn in 1970. In the four-plus decades since, fire management units have conducted prescribed burns over 55,792 acres — including large areas directly in the path of the Rim Fire.

Firefighters work a controlled burn within Yosemite National Park in November 2008 (Photo by Rennett Stowe via Flickr)

Between 2000 and 2010, there were 401 wildfires within the park, burning 16,206 acres, and 67 prescribed fires burning 12,451 acres, according to the National Park Service.

This spring, Yosemite conducted a 150-acre fire in the south section of the park. The objective of the burn was to reduce hazardous fuels in the mixed conifer forest near to the wildland-urban interface (WUI) community of Wawona, according to the National Park Service. That burn created “a continuous area of reduced fuel by linking together multiple previous fires and treatments including the 2007 and 2008 Wawona Northwest prescribed fires, the 2007 Jack wildfires, which was caused by lightning, and a series of mechanical vegetation thinning projects in the 2000s.”

Forestry officials, going back well before the controversial 1988 fire at Yellowstone National Park, have held the belief that fires are beneficial to the ecosystem of a forest ridding it of decaying undergrowth and promoting new fertile growth.

Yosemite fire managers have an option to manage — instead of suppress — fires that occur naturally within the park, allowing those fires to burn and renew the landscape.

Yosemite has been taking this approach — the so-called “let it burn” approach — since 1974, and as experience as been gained managing the land and natural fires, the National Park Service has increased its proportion of zones it allows the option for these fires from 25 percent of the park to 87 percent of the park.Between 2000 and 2010 managed 168 “wildland fires for resource benefit” over 41,562 acres.

This has been termed “ecological restoration.” From The Associated Press:

The 350-mile-long Sierra Nevada is a unique mountain system in the U.S. with its Mediterranean climate, which means four-to-six months of drought every summer. California’s mountain flora is designed to burn and even flourish and regenerate healthier after a fast-moving fire.

Will Yosemite’s 40-year efforts with prescribed and managed fires slow the Rim Fire enough so that firefighters gain the upper hand? Possibly. The next days will tell, but that doesn’t mean similar dangers of unchecked fires aren’t lurking elsewhere in the Sierra Nevada mountains.

“We look at the Rim Fire and because it’s close to the Yosemite, we think, ‘There’s the big one.’ But that’s not really the big one,” University of California at Davis plant ecologist Mark Schwartz told CBS13 Sacramento. Davis conducts research on fire conditions in the Sierra Nevada mountain range.

“We see temperatures increasing in the Sierras, particularly warmer nighttime temperatures, and that’s resulted in decreased snowpack. That, accompanied by about a century of fire suppression has led to a lot of areas that are ready to burn in the Sierra Nevada.”

Yosemite Prescribed Fire History: 1970-2011

Sources: Yosemite National Park, National Park Service, U.S. Department of the Interior