New research released by the Giant Sequoia Lands Coalition and conducted by the U.S. Geological Survey’s Western Ecological Research Center highlights a concerning trend for the future of giant sequoias. The studies found that some areas affected by recent mega-fires may not have enough seedlings to ensure the regeneration of these millennia-old trees. Since 2015, extreme wildfires have killed up to 20% of the world’s mature giant sequoias, with a significant portion of these losses occurring during three major fires in 2020 and 2021.
These mega-fires burned with unprecedented severity, significantly higher than historical norms. Without intervention, the affected sequoia groves could experience a long-term or even permanent loss of acreage as seed trees have died and the number of new seedlings is exceptionally low. Nathan Stephenson, Ph.D., a scientist emeritus at the U.S. Geological Survey and co-author of one of the studies, emphasized that while giant sequoias are fire-adapted and rely on fire to reproduce, recent fires have been so severe that they have killed thousands of mature trees and, in some cases, their seeds as well.
The studies also note that seedlings germinated after the 2020 and 2021 wildfires are facing new climate conditions, including higher average temperatures and the most severe drought conditions in the last 121 years. These factors are likely to reduce the survival rates of giant sequoia seedlings. In areas where mature seed trees have died, the chances of natural recovery are greatly diminished.
David Soderberg, Ph.D., an ecologist at the U.S. Geological Survey’s Western Ecological Research Center and lead author of one of the studies, pointed out that while some areas are regenerating well, other sites where seeds and seed trees were burned or where young seedlings have died from high heat and drought show little chance of natural long-term recovery. The data suggests that severely impacted sequoia grove areas may not have enough reproduction to replace the trees lost.
Giant sequoias are the world’s largest and among the oldest trees. As climate allies, they are second only to old-growth coast redwood forests in storing massive amounts of carbon per area. Their unique ecological role and iconic status draw visitors from around the world to the protected groves.
Joanna Nelson, Ph.D., director of science and conservation planning for Save the Redwoods League, emphasized the importance of these findings. The new research can help land managers determine how to best care for giant sequoia groves, especially in the critical window following fires. By using the best available science, managers can understand when and where sequoia reproduction may be too low for future success and take appropriate action. This includes prioritizing fuels reduction treatments that can change fire behavior and reduce the severity of future wildfires.
Ongoing research and monitoring supported by the Giant Sequoia Lands Coalition continue to provide a scientific basis for restoration programs across the sequoia range. So far, the GSLC has completed wildfire resilience work across half of California’s giant sequoia acres, planted more than 500,000 native seedlings in severely burned areas, and conducted scientific research to support evidence-based restoration techniques. More details are available in the GSLC’s recently published Progress Report for Saving the Sequoias.
The new research, detailed in two studies, provides valuable insights into the post-fire densities of giant sequoia seedlings and their chances of survival under current environmental conditions. The studies highlight the urgent need for targeted restoration efforts to ensure the long-term survival of these ancient giants in the face of increasingly severe wildfires and changing climate conditions.
