Two comprehensive studies conducted by researchers from the U.S. Geological Survey's Western Ecological Research Center have revealed a dire situation for giant sequoias in the aftermath of recent mega-fires. The studies, announced by the Giant Sequoia Lands Coalition, indicate that some areas affected by these extreme wildfires may not have enough seedlings to sustain the next generation of these ancient trees. Since 2015, extreme wildfires have decimated up to 20% of the world's mature giant sequoias, with the majority of losses occurring during three wildfires in 2020 and 2021. These recent fires burned at unprecedented scales and intensities, far exceeding historical norms.
The new research suggests that without intervention, some giant sequoia groves may experience long-term or permanent loss of acreage as seed trees have perished and the number of new seedlings is exceptionally low. Dr. Nathan Stephenson, a lead author of one of the papers and scientist emeritus at the U.S. Geological Survey, emphasized the severity of the situation: "Giant sequoias are the largest trees in the world. They're fire-adapted and rely on fire to reproduce. But recent fires have killed thousands of mature trees and, in some cases, their seeds too." The studies also highlight the challenging climate conditions facing newly germinated seedlings. These young trees are growing under higher average temperatures and the most severe drought conditions of the 121-year historical record, factors that will almost certainly reduce their survival rates.
In areas where mature seed trees have died, the chances of natural recovery are greatly diminished. Dr. David Soderberg, lead author of one of the studies, noted the variability in sequoia regeneration across the affected range. While some areas are showing promising recovery, others where seeds and seed trees burned or where young seedlings have succumbed to heat and drought are unlikely to recover naturally in the long term. The importance of these findings extends beyond the preservation of individual trees. Giant sequoias play a crucial role in carbon storage, second only to old-growth coast redwood forests in their capacity to sequester carbon per area. They also hold immense cultural and ecological significance, attracting visitors from around the world.
The research provides valuable guidance for land managers in determining how to best care for giant sequoia groves, especially in the critical period following a fire. Dr. Joanna Nelson, director of science and conservation planning for Save the Redwoods League and a lead scientist with the Giant Sequoia Lands Coalition, emphasized the importance of these findings in identifying the necessary seedling density for successful regeneration. In response to these challenges, the Giant Sequoia Lands Coalition has been actively working on wildfire resilience across half of California's giant sequoia acres. They have planted more than 500,000 native seedlings in severely burned areas where natural reproduction has been insufficient and continue to conduct scientific research to support evidence-based restoration techniques.
The two studies, "Post-fire reference densities for giant sequoia seedlings in a new era of high-severity wildfires" and "Assessing giant sequoia mortality and regeneration following high-severity wildfire", provide critical data and tools for assessing the impacts of wildfires on sequoia reproduction and informing restoration and management decisions. As climate change continues to exacerbate wildfire risks and alter growing conditions, the findings of these studies underscore the urgent need for proactive management and conservation efforts to ensure the survival of giant sequoias for future generations. The research serves as a call to action for policymakers, conservationists, and the public to support and engage in efforts to protect these irreplaceable natural wonders.
