CHRISTMAS VALLEY, Calif. – The sound of Caldor Fire embers falling from the sky and landing on windshields made a familiar noise. “It was almost like it was sprinkling, but it was sprinkling embers,” Chris Anthony remembers, then assistant deputy director with Cal Fire. He described the scene to a tour group on Oct. 11 as part of the California Wildfire & Forest Resilience Task Force’s Sierra Nevada Regional Meeting.

The multi-day meeting brought regional leaders and the public together to discuss wildfire topics. On this tour, participants stopped at numerous sites where the Caldor Fire burned while fire experts explained the successes and lessons learned from the fire.

While standing within the footprint at the Christmas Valley overlook, Anthony explained that the Caldor Fire began on Aug. 14, 2021 in Grizzly Flats, over 60 miles away. Around Aug. 30, 2021, the fire had crested the Sierra Nevada summit and dropped into the Tahoe basin.

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“At that particular point in time, I don’t think we would have even thought that a fire starting down in Grizzly Flats could have ever entered into the Lake Tahoe Basin,” he told the group, “It wasn’t part of our framework.”

Anthony said not only was the entrance into the basin a surprise, but also the manner of its entrance above Echo Lake. “What was so dramatic about that transition into the Lake Tahoe Basin was it was crowning in red fir forests at 8,000 to 9,000 feet at night, which was very, very unusual to see that kind of intense fire behavior occurring at night in that vegetation type.”

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Anthony expressed that fire agencies continue to see fire do things that surprise them.

“I think that’s also just the nature of wildfire,” he added , “and using words like unprecedented are just not even acceptable.”

Despite the magnitude and surprises the 221,000 acre Caldor Fire threw their way, many fire experts have found numerous successes, some even calling it a Christmas Valley miracle. The ability for fire crews to have the successes with the Caldor Fire are partly attributed to actions agencies took following the Angora Fire, which happened 14 years before the Caldor Fire and was at the time, one of the most devastating fires in the state of California.

Some of those actions had started before the Angora Fire when Lake Valley Fire Captain Martin Goldberg and his chief began to sense that something needed to be done. They started a small fuels program that turned into a larger program and ran through 2015. Other measures included shake roof replacements and defensible space measures.

“A lot of people will say, ‘well, it was the weather,'” Anthony says, “And although the weather was helpful, had the mitigations not been put into place, such as the shake roof replacements, the defensible space, the pre-attack planning that had occurred, the fuels reduction and mitigation activities that occurred across many, many different jurisdictional agencies, we would have had a different outcome that night, I guarantee it.”

While fighting the Caldor Fire, Goldberg found much of the area familiar. “When I was here fighting the fire and on the engine, I was literally at an area that I had done the fuel reduction work,” he remembered, “I was literally parked at a house where we had cleared several years prior.”

Anthony explained this was largely due to Caldor operations chiefs, Kyle Jacobson with the U.S. Forest Service and Brian Newman with Cal Fire, having local knowledge of where fuels reduction work had occurred and placing crews in those areas. This strategic placement gave fire crews an anchor point to be successful with their fire attack.

An example of this took place on a street off of Apache Avenue. “The fire came in and kind of came this way behind the homes here,” Milan Yeates with the California Tahoe Conservancy described while standing in the Caldor Fire footprint just behind the row of homes. The tour group had gathered in a half moon around him.

Yeates is charged with managing the conservancy’s urban parcels with fuels reductions and other mitigations.

“It’s not to fireproof these parcels,” he clarified, “it’s to make it so the first engine that rolls up, if something starts here, can just put it out essentially.”

The treatments done on the parcels near those neighborhoods were 10-12 years old at the time of the Caldor Fire, he explained.

“This opened my eyes a little bit,” Yeates expressed. He had thought the parcels would have needed more recent work to prepare them for a fire, “…but what happened was it actually functioned.”

A dozer line was placed near the treated area and a back burn started on the fire side of the line to burn off vegetation before the main fire arrived. Although spot fires had started in the treated area, the treatments had previously cleared ladder fuels, which could have provided a path for the fire to climb to the tree canopies. Personnel were able to address the spot fires simply with hand tools, not even requiring water. “That’s really what we’re going for on these parcels,” Yeates said.

As a result, no homes were lost in Christmas Valley due to the Caldor Fire.

These successes shed light on forest treatment effectiveness when it comes to fire suppression, but that’s not the only measure of fire treatment success.

Hugh Safford and Saba Saberi with University of California, Davis have conducted a study on the effectiveness of forest fuel reduction treatments when it comes to mitigating fire severity and reducing tree mortality. Safford shared insights from the study’s report which they also provided to the Tahoe Science Advisory Council, the League to Save Lake Tahoe, and The Tahoe Fund.

According to the report, reducing fire severity is important because it equates to reducing the occurrence of a crown fire, which in turn translates into lower fire intensity and flame lengths and reduced spotting distances. It also increases the potential for a successful direct attack.

His research team looked at what were treated areas and untreated areas in the wildland urban interface environments where the Caldor Fire burned.

They found that across all treatment types, trees were three times more likely to survive fire in treated areas. The majority of measures used to examine fire severity including, crown scorch percent, crown torch percent, and torch height, revealed these factors were significantly lower in treated versus untreated areas.

The study did bring about some surprises. In a number of treated areas, the research team found higher than expected fire severity and tree mortality with higher scorch height and bole char height than in neighboring untreated forest. The report says the presence of unburned fuel piles in these areas led to those results. Of the 31 forest areas with fuel piling that were hit by the Caldor Fire, only 12 had been burned by August 2021. That left 19 unburned at the time of the fire.

“We hope that the clear contribution of unburned piles to higher fire severity and tree mortality in the Caldor Fire will further underline the importance of resolving the pile burning backlog issue in the near future,” the report states.

The research team was also surprised to find the most effective fuel treatment did not include prescribed fire or pile burning. Instead, it was multiple entry mechanical and hand thinning followed by mastication. Although the report does say that hand thinning and fuel piling followed by pile burning was also an effective treatment, the time it takes for piles to cure and pile backlogs are important considerations.

This report and others suggest that forest management agencies should consider whether expansion of forest thinning is warranted to forested areas outside of wildland urban interface defense zones. This would provide thinning for forest restoration purposes rather than just for protection of human infrastructure alone.

“I know there’s a lot of public opposition to the idea of moving outside of just a little thin belt around communities,” Safford told the group, “but if you want to have forest in the Lake Tahoe basin in 50 years, you’re going to have to think really hard about how you reduce fuels on a very, very big scale and hopefully it’s not getting reduced for you by fires.”

Saffard and his team are involved in similar studies on the Dixie and Tamarack fires. Safford has conducted studies on the Angora Fire as well.

The full Caldor Fire report is available on the Tahoe Science Council’s website, http://www.tahoesciencecouncil.org/.