Giant sequoias and their ecosystems face dramatic declines from intense, high-mortality fires caused by prolonged drought and the accumulation of heavy forest fuels; as well as other urgent new stressors, such as death or weakening from bark beetle attack and drought stress, and potential shifting of suitable microclimates outside of their existing range.
Visit this page for additional information and links related to the coalition, current research about sequoia threats, and efforts to protect giant sequoias.
Frequently Asked Questions
Sequoia Mortality in the 2020 Castle Fire
Yes, preliminary estimates are 10-14% of all large giant sequoias over 4 feet in diameter in the native range. This does not include trees smaller than 4 feet in diameter or trees planted outside of the native range.
Satellite imagery tells us that about 10-14% of all sequoia grove area in the Sierra Nevada burned at high severity in the Castle Fire. Ground-based data sets from previous high severity fires in Sequoia groves show that, on average, in high-severity burn areas most large sequoias die.
A combination of one hundred years of fire suppression along with climate change driven hotter droughts has resulted in a denser forest with unprecedented levels of fuel loading. These conditions have changed how wildfire burns in the southern Sierra Nevada, resulting in large areas of high severity fire effects and mass fire events that generate their own weather. The Castle Fire of 2020 was one of these megafires.
In some areas giant sequoia trees may not regenerate due to the incineration of cones, seeds, and overstory trees. In other areas of low and moderate severity the fire will likely have beneficial effects, reducing fuels and possibly creating conditions for giant sequoia regeneration such as bare mineral soil and small canopy gaps.
Giant sequoias and old growth mixed conifer forest provide a whole host of benefits to people and our world by taking carbon out of the atmosphere and storing it as wood (carbon sequestration); producing oxygen; stabilizing soil; helping store water as snow in forest gaps; creating wildlife habitat; generating recreation tourism dollars for our local communities; providing places of refuge and solace for people; and providing critical habitat for old-growth dependent threatened and endangered species such as California Spotted Owl and Pacific Fisher. Although final numbers will take months to verify through field surveys, the unprecedented scale of loss is clear. We are actively monitoring the forest to understand and report on changes as they occur.
History and Role of Fire
Tree ring studies of giant sequoias provide a long record of climate and fire history, helping land managers and scientists better understand relationships of climate, fire, and the giant sequoia life cycle.
These records show that frequent surface fires were the typical pattern of fire occurrence over the past 2,000 years. But this pattern changed after about 1860 when fire frequency declined sharply. This decline in fire was probably a result of intensive sheep grazing that began about this time (reducing live and dead vegetation that carries ground fire beneath the trees) and a decrease in fires set by Native Americans, followed by fire suppression by government agencies.
The threats to these special forests, irreplaceable in many human lifetimes, are centered around two main issues: a century of wildfire suppression which has contributed to unhealthy forest density across the giant sequoias’ range and the impacts of climate change which are already having a broad range of detrimental effects. As the 2021 fire year picks up nationally, California also reckons with impacts from the many harrowing fires that have characterized the early years of the 21st century, devastating in their frequency and intensity.
Fire plays a crucial role in the giant sequoia ecosystem. Fire scars in tree rings dating back 2,000 years show that widespread fires occurred naturally at intervals ranging from 6 to 35 years in these forests.
Large giant sequoias are adapted to survive repeated fires. Their thick, fibrous bark insulates them from fire’s heat. The more flammable branches typically occur high up the trunks, well above the flame height of most fires. Not only are sequoias adapted to survive repeated fires, but fire is actually necessary for regeneration. The fire’s heat opens cones, releasing tiny oatmeal-sized sequoia seeds onto bare mineral soil, where they can take root.
Threats and Strategies for Protection
Threats to giant sequoias have been exacerbated in recent years due to unusually high temperatures and the effects of low precipitation associated with drought. The following impacts are believed to contribute to the higher levels of giant sequoia mortality than ever previously observed:
In order to reduce fuels and restore wildfire resilience, we will need all available tools in the toolbox. Prescribed burning remains one of the most important management tools to reduce fuels in sequoia groves, favor regeneration, and increase resilience of these groves to climate change and wildfires. However, smaller burn windows and massive fuel accumulation means that prescribed fire is not able to keep up with the treatment needed and some areas cannot be safely treated with fire. Restorative thinning is an additional too that can be used to help protect the sequoia groves.
Prescribed burn reduces fuels and facilitates giant sequoia regeneration. Sequoia and Kings Canyon National Parks have a long history of prescribed burning in giant sequoia and other mixed- conifer forests, since the late 1960s. Prescribed burns reduce fuels, create favorable conditions for tree regeneration, and increase forest resilience to climate change impacts. However, it has not been possible to conduct as much prescribed fire as is needed in these forests. In recent years, extensive, severe wildfires in California have stretched fire-fighting resources thin and generated unhealthy levels of smoke for extended periods of time. Due to warming temperatures and drought, fire seasons are increasing in length and severity, and the window of time for prescribed burning is smaller most years.
The managers at Sequoia and Kings Canyon national parks are responding to the effects of climate change through research, planning, and coordination efforts. Research is currently underway to identify specific areas to resist, adapt, and direct ecosystem change in response to climate change. This data will inform decisions such as where we may plant different species of trees in order to ease a transition to a new forest type while maintaining forest cover. In other areas we may restore gullies in meadows to increase water availability and try to maintain critical meadow functioning under climate change.
Overall, responses to these sudden changes and threats requires coordination across organizations managing giant sequoias as well as with scientists, and non-governmental organizations. The National Park Service is partnering with other land stewards who manage giant sequoias as well as supporters to form a Giant Sequoia Lands Coalition that will seek opportunities for increased shared learning in giant sequoia management, increased efficiency of planning and execution of resilience treatments, and stronger public communications around giant sequoia conservation.
National Park Service giant sequoias and climate web page
Save-the-Redwoods League: Giant Sequoia and Fire
Yosemite National Park climate change webpage
Giant Sequoia Background Information
Giant sequoias grow only on the western slopes of the Sierra Nevada in California, in about 70 groves between 4,000 and 8,000 feet in elevation.
While not the world’s oldest trees, sequoias are known to reach ages of over 3,000 years.
Giant sequoias are among the largest and oldest living things on the planet. They sequester carbon in a warming world, and contribute to cleaner air and water. They support a bustling economy on public lands, drawing millions of visitors through local communities. They were among the first inspirations for federal-level conservation; in 1890, Sequoia National Park was the first national park created specifically to protect a living organism.