Slope of fire-killed giant sequoias and other conifers in the Board Camp Grove, Sequoia National Park/NPS, Tony Caprio, 11-2-20 overflight

In the wake of the loss of perhaps 10,600 giant sequoia trees to last year's Castle Fire in California, a multi-agency coalition has formed in a bid to reduce fire risks to the towering, emblematic forests and seek solutions to crippling drought that also places the trees in jeopardy.

“The unprecedented number of giant sequoias lost to fire last year serves as a call to action,” Clay Jordan, Sequoia and Kings Canyon National Parks superintendent, said Monday when the Giant Sequoia Lands Coalition was formally introduced. “We know that climate change is increasing the length and severity of fire seasons due to hotter temperatures and drought. To combat these emerging threats to our forests, we must come together across agencies. Actions that are good for protecting our forests are also good for protecting our communities.”

But the task the group faces is daunting. Drought and catastrophic wildfires seem to be popping up more frequently, combining to produce stand-destroying fires that burn hotter and with more intensity and erratic fire behavior. The phenomena are challenges the country so far has been unable to easily overcome or contain. 

Fire data tracked by the National Interagency Fire Center noted that 35,086 fires have been reported as of midday Monday, and had burned 2,537,744 acres. Through the same date of a year ago, there had been 29,008 fires that blackened 1,809,976 acres. Both 2017 and 2018, however, showed greater acreage lost to wildfires (4,525,205 acres and 3,554,036 acres, respectively).

Announcement of the coalition was accompanied by a report estimating that 7,500 to 10,600 large giant sequoias were killed in last year’s Castle Fire. This loss represents 10-14 percent of large sequoias in the world, a press release from the National Park Service said. Against that loss, the agencies that came together to form the coalition aim to save the remaining 90 percent.

To better safeguard giant sequoias against wildfires, work already is underway to reduce understory fuels that can provide flames racing along the ground with fuels as well as ladders up into a forest's canopy, said Sintia Kawasaki-Yee, the public affairs officer for Sequoia and Kings Canyon national parks, during a phone call. Some of the work involves prescribed burns, though mechanical thinning of forests also will be utilized.

"We actually have a project happening, it already started and it might still be going on, in the Big Stump area on the Kings Canyon side of the park," she said. "So there are actually projects in place right now, helping with that."

Science also is being conducted to try to determine which of the sequoia groves are most at risk from wildfires.

"What are the groves that are highest risks right now that we should be addressing in priority order?" explained Kawasaki-Yee. "It's unrealistic to think that we're going to get to all of them in the next year, you know, get up to speed on so many decades and centuries of backlogs of these efforts."

Though Sequoia National Park was established in 1890 by President Benjamin Harrison, scientists still don't fully understand the physiological functions of the big trees. For example, what is the moisture content of their needles and stems during healthy times, what is the current moisture content of the trees, and how low can that content drop without killing a tree?

While the giant sequoias went through an extended drought from 2012-16, said Christy Brigham, chief of resource management and science at Sequoia/Kings Canyon, "none of those trees died at the time. So we weren't able to say, you know, once the water stress gets this high, then the tree dies."

What the researchers did find, she continued during a phone call, was that some trees dropped upwards of 70 percent of their canopy needles but weren't any worse off for that the following spring compared to trees that didn't shed so many.

"The conclusion that we drew from that was that the needle shedding that those trees had done was actually effective at reducing the water stress in the tree," Brigham said. The deaths of trees that did expire following those drought years, she added, was tied to both drought and being attacked by bark beetles.

Researchers also are trying to gain a better understanding of the sequoias' root and plumbing systems. While it has long been voiced that the trees have shallow root systems, which have been blamed for high winds blowing them over, Brigham said sequoias just might have a more extensive and deeply rooted network of fine roots that tap into pockets of water held in fractured rock underground.

"The current hypothesis is that many sequoias are able to get water from a wide variety of sources, from shallow water from rain and snow melts, from groundwater and other areas, and from this weird in between zone called 'SAP' rock," the park scientist said. "But that's really a hypothesis. And it's one that we're actively testing right now, by collecting water from the trees themselves and looking at its isotopic signature, to find out where that water came from."

If those deep underground water pockets are regularly tapped by sequoias, it could be one water source that allows the trees to endure droughts such as the current one and the 2012-16 drought. After all, many of these trees are 1,000 years old and older, and have no doubt endured more than a few droughts.

"When you look at tree rings, you can see past droughts," said Brigham. "We love giant sequoias for a million reasons. But as a scientist, they are an amazing record of, you know, two- to 3,000 years of droughts and wet years. They show it in the width of the tree rings. They're pretty damn tough trees. They don't show a major response (to drought), like you would see in some other species."

According to the “Preliminary estimates of sequoia mortality in the 2020 Castle Fire" report, released Monday, more than 10 percent of the entire existing population of large giant sequoias were killed by that fire. While giant sequoias require periodic low-to-moderate intensity fire to maintain healthy ecology, much of the Castle Fire burned too intensely for the trees, a park release said.  

"A history of fire suppression and hotter droughts driven by climate change has resulted in denser forests with extraordinary levels of fuel loading," the release added. "These conditions have changed how wildfire burns in the southern Sierra Nevada, resulting in large areas of high severity fire effects and massive fire events."

Coalition members will be hosting public and media events over the coming months to raise awareness and public knowledge about sequoia health and research, ongoing projects, the effects of recent fires, and more. Information about these events will be released as plans are finalized. 

The members of the Giant Sequoia Lands Coalition are: 

• National Park Service, represented by Sequoia and Kings Canyon National Parks and Yosemite National Park
• United States Forest Service, represented by Sequoia National Forest and Giant Sequoia National Monument, Sierra National Forest, and Tahoe National Forest 
• Bureau of Land Management, represented by Case Mountain Extensive Recreation Management Area 
• Tule River Indian Tribe, stewards of Black Mountain Grove 
• State of California, represented by Calaveras Big Trees State Park and Mountain Home Demonstration State Forest 
• University of California, Berkeley, stewards of Whitaker’s Research Forest 
• Tulare County, stewards of Balch Park