Giant Sequoia Bark Shields Trees From Flames

Biological Strategy

AskNature Team

Manage Mechanical Wear

A living system is subject to mechanical wear when two parts rub against each other or when the living system comes in contact with abrasive components in its environment, such as sand or coral. Some abrasive components are a constant force, such as finger joints moving, while others occur infrequently, such as a sand storm moving across a desert. Living systems protect from mechanical wear using strategies appropriate to the level and frequency of the source, such as having abrasion-resistant surfaces, replaceable parts, or lubricants. For example, human joints like shoulders and knees move against each other all day, every day. To protect from mechanical wear, a lubricant reduces friction between the cartilage and the joint.

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Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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Protect From Fire

Depending on location, fire can be either predictable or unpredictable. In some areas, fires occur in cycles ranging from annual to hundreds of years. Where fire is cyclic, living systems must be able to not only survive fire, but to quickly recover following it. For example, pine trees that live in areas with periodic fires have thick bark that provides insulation, thereby protecting the tree’s living tissue.

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Conifers and Others (Pines, Spruce, Gingko)

Clade Gymnosperms (“naked seeds“): Conifers, cycads, Gingko, gnetophytes

There are approximately 1,000 known species of Gymnosperms. These include well known needle-bearing plants like pines, firs, and spruce, as well as some with broad leaves like the Gingko and the gnetophytes. Instead of flowers, gymnosperms produce unenclosed (“naked”)seeds exposed on the surface of cone scales. Economically, conifers make up 45 percent of the world’s lumber production. The first gymnosperms evolved over 390 million years ago in the Paleozoic Era and dominated landscapes for a quarter of a billion years before the evolution and diversification of flowering plants.

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Thick fibrous bark of giant sequoia trees protects from wildfire damage by insulating against heat and slowly charring to form a protective barrier.

Introduction

Giant sequoias (Sequoiadendron giganteum) can reach heights of over 300 feet (91 meters) and live for more than 3,000 years, making them some of the tallest and oldest trees on the planet. Native to the western slopes of California’s Sierra Nevada mountains, giant sequoias thrive in montane forests where periodic wildfires are a natural and essential part of the ecosystem. Remarkably, these trees have not only adapted to survive fire––they depend on it.

The Strategy

The bark of the giant sequoia is incredibly thick––sometimes measuring up to two feet––and plays a crucial role in protecting the tree from fire. It consists of two primary layers: a dense inner bark (bast) and a thick outer bark (rhytidome). The outer bark is characterized by a high fiber content arranged in a three-dimensional network, with fibers intersecting at various angles. This intricate layering creates air-filled cavities within the bark, which serve as insulation by dissipating heat and reducing its transfer to the tree’s vital inner tissues.

The fibrous and spongy nature of the bark further contributes to its poor conductivity, making it an effective barrier against the intense heat of wildfires. When a fire passes through, the outer bark may char, but the heat usually doesn’t reach the living tissue underneath. This means that even during intense wildfires, the tree’s cambium layer (which transports nutrients and allows the tree to grow) remains unharmed.

Another important feature is the bark’s low flammability. Unlike other trees that produce sticky, flammable resins, giant sequoia bark is dry. When exposed to fire, the bark chars slowly rather than bursting into flames. This slow charring process forms a protective crust that shields the rest of the tree from additional heat.

The cambium continuously produces new cells that differentiate into inner bark (phloem) and outer bark tissues. When the outer bark is damaged by fire or other environmental factors, the cambium responds by generating new layers of bark over time, effectively sealing wounds and restoring the tree’s defense against future threats. This natural combination of thick insulation, physical toughness, slow-burning material, and self-repair allows these trees to survive––and even benefit from––the fires that are part of their forest ecosystem.

Image: Kiel Maddox / National Park Service /

A stand of giant sequoia trees with burn scars from a previous wildfire.

Image: Kyle Bushnell / Unsplash /

Close-up image of giant sequoia bark, showcasing the fibrous external material.

Image: Sinjin Thomas / Unsplash /

Looking up at a giant sequoia, with a small burn scar.

The Potential

The fire-resistant bark of the giant sequoia offers powerful inspiration for developing safer, more resilient materials and structures. By mimicking the tree’s thick, fibrous layers and insulating air pockets, we can create building materials that slow heat transfer and resist ignition––valuable traits for homes and infrastructure in wildfire-prone regions. The concept of a protective outer layer that chars slowly and shields what lies beneath could also be applied to a variety of designs. Additionally, the tree’s ability to recover from fire damage by growing new protective layers suggests possibilities for self-healing materials that extend the life and safety of products.

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Last Updated May 5, 2025

References

Web page

Meet the Giant Sequoia, the ‘Super Tree’ Built to Withstand Fire

Scientific American | July 2022 | By Andrea Thompson, edited by Dean Visser

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Reference

Journal article

The Protective Role of Bark and Bark Fibers of the Giant Sequoia (Sequoiadendron giganteum) during High-Energy Impacts

International Journal of Molecular Sciences | May 2020 | Bold, G.; Langer, M.; Börnert, L.; Speck, T.

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Reference

Book

High Performance Structures and Materials IV.

Wessex Institute of Technology, UK | 2008 | Edited By: W.P. De Wilde, Vrije Universiteit Brussel, Belgium and C.A. Brebbia

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