Focus on Arts and Ecology

Thick bark enables giant sequoia to withstand lower-severity ground fires. Photo by Kristen Shive

The area burned by California wildfires has been on the rise in recent years, and in many cases the fires have been burning hotter than ever before. Even beyond the directly impacted areas, smoke throughout the region leaves some people feeling as if the whole world is on fire. The fires have left devastating tragedies in their wake, with civilian and firefighter lives lost, not to mention homes and infrastructure. Our thoughts are with the affected communities and dedicated firefighters.

When the smoke settles, many of us are left wondering how the forests have fared. At Save the Redwoods League, we’ve been watching to see how recent wildfires may be affecting coast redwood and giant sequoia ecosystems. Both of these species are adapted to fire, their thick bark enabling them to withstand lower-severity ground fires. However, over a century of putting out all fires has allowed many forests to become thick with trees and woody debris, which can fuel larger, more severe fires in some areas. Climate change is also playing a significant role in recent increases in wildfire activity.

Although the historical relationships between fire and vegetation vary tremendously by vegetation type, in many forested regions of California, fire historically burned at regular intervals, which maintained open forests, clearing out woody debris on the forest floor and keeping the brush down.

Most of the remaining old-growth redwood forest is on the coast, where the cool, wet weather reduces fire risk, making the increased accumulation of woody debris and smaller trees less problematic in terms of severe fire risk. However, many important features of old-growth forests are created by fire, such as tree cavities and standing dead trees that provide critical wildlife habitat, suggesting that fire will eventually need to be restored to maintain healthy forests. Forests recovering from past logging often have very high tree densities because of both planting and redwoods’ prolific sprouting ability. In these forests, the fire risk is greater, particularly in the more southern and inland parts of the range where it’s a little hotter and drier. Some of these forests have burned in the last few years, and we expect most of the redwoods to survive, due to their prolific sprouting ability. No old-growth coast redwood forests have burned in wildfires in recent years.

Giant sequoia fire adaptations include not only their thick bark, but also their cones, which require heat to open. Their seeds germinate best on bare mineral soil cleared by fire. Without fire, giant sequoia will not adequately regenerate, reducing the assurance that the groves will persist over millennia. In addition, the lack of fire in many sequoia groves has increased tree densities and woody debris, which increases the risk of more severe fires.

Last year, the Nelder Grove in the Sierra National Forest burned in a wildfire. Many of the trees survived, thanks to the efforts of the US Forest Service. Fire severity was reduced and giant sequoia survived in areas where the Forest Service thinned small-diameter trees and conducted prescribed burning in the years before the wildfire. During the fire, they also worked hard to protect the trees that they could. One part of the grove had no past restoration and burned very hot, killing some sequoia. In the central Sierra Nevada, several mature sequoias died as a result of the interaction of fire and drought after the 2015 fire season. This summer, a wildfire threatened the Merced Grove of Giant Sequoia in Yosemite National Park. Although the park has completed impressive restoration treatments in their other sequoia groves, this one has received less attention, due to lack of adequate funding and staff. A major fire outside of the park has threatened that grove in six out of the last 10 years, raising a sense of urgency to restore it.

In California, with our hot dry summers and flammable vegetation, it’s not a question of if something will burn, but when. With better forest management and development planning, we may be able to reduce the severity and negative consequences of wildfires.

California Governor Jerry Brown’s Executive Order B-52-18 outlines key activities that will help keep communities in the wildland-urban interface safe, promote healthier forests, and improve the carbon sequestration potential of California’s forests. Save the Redwoods League will continue our science-based forest management practices within the giant sequoia and coast redwood ranges, and increase coordination with conservation partners and lawmakers to advance the goals articulated in the Executive Order. These goals include doubling the acreage of forests managed for fire resilience through thinning and prescribed burns, as well educating landowners on the benefits of fuels reduction efforts conducted on private forestlands. In addition to increasing fire resilience, these practices can also restore many ecosystem properties that are critical for the long-term persistence of these treasured forests.

You can help by supporting the League’s forest restoration work.

See Shive’s comments in The Mercury News story, “Yosemite fire: Valley to remain closed until August 3”.