The Los Angeles Times has an excellent article written by Diana Marcum which tells the story of how firefighters on the Rim Fire worked to prevent the giant sequoia and old growth sugar pine groves in Yosemite National Park from being consumed by the fire. Everyone would agree that these trees are worth saving. Sequoias grow to an average height of 160 to 280 feet and 20 to 26 feet in diameter. The oldest known sequoia based on ring count is 3,500 years old.
About two weeks after the fire started it was still burning through drought-afflicted vegetation in a manner that mostly confounded and frustrated the 5,000 firefighters trying desperately to stop the spread. It was moving toward the groves that had survived many fires over hundreds or thousands of years, but this fire was not like the relatively cool, slow moving lightning-caused fires that the trees had evolved to to live with. It threatened to wipe them out.
With the Rim Fire only one or two days away from the national treasure trees, firefighters decided their only hope of saving them was to treat the groves with fire, a controlled fire under their own conditions, before the main fire got there. This relatively cool fire would remove most of the fuel on the ground and hopefully prevent the very intense main fire from roaring through the groves, possibly killing the 3,000-year old trees. It was their only hope.
But the test fire worried them when 50-foot flames leaped into the sky.
Below are some excerpts from the must-read article:
“…Inside Yosemite, officials had tried to restore the natural cycle of fire. For 40 years, lightning-sparked flames in wilderness areas had been left to burn, and specialists lighted controlled burns near tourist areas. But that might not offer enough protection.
“Hypothetically those old fire scars would slow the fire the further it moved into the park,” said Gus Smith, Yosemite’s fire ecologist. “But the Rim fire was like a flood, and it was coming. This was not the fire you wanted to test out a hypothesis.”
The sequoias evolved to face wildfire. But officials feared that this fire could kill even trees that had been shrugging off flames since before Rome burned.
[Ben] Jacobs and Taro Pusina, Yosemite’s deputy fire chief, drew up a plan. They would set three coordinated backfires and try to stop the wildfire with a “catcher’s mitt” of charred earth.
But first they would wind the fires through two of the very groves they were trying to protect. The Tuolumne and Merced groves were at the top of a ridge, in the direct line of the Rim fire, in an area that had not burned for 100 years. If the hotter Rim fire reached them, it could climb to the tops of 200-foot trees.
A lot could go wrong. If the backfires were too hot, they could cook the groves. If they did not burn enough ground in time, the Rim fire would roar through unblocked. Those two groves and the Merced Grove to the south would burn, the lookout tower and helicopter base would burn, and the firefighters would have to run.
“We knew it was a longshot,” Pusina said. “But no amount of bulldozers or planes or crews had stopped this fire. We were out of options.”
The next day, with the first grove still burning, a handful of firefighters drove into the Tuolumne grove, a mile to the east.
A fire crew from Arizona had prepared the area — raking debris away from trees, sawing snags and logs. Many of them had never seen a giant sequoia, which is native only on the western slope of the Sierra Nevada. The species dates back to the Ice Age.
“They were in awe of the trees. They kept looking up as they worked,” recalled Gary Oye, division chief of wilderness stewardship…”