Redwood

The Survivors of Pangaea

Redwoods are the trees that forgot to die. The subfamily Sequoioideae—coast redwoods, giant sequoias, and dawn redwoods—represents a lineage that dominated global forests when dinosaurs walked and continents were joined. Once spanning Europe, Asia, and North America, these trees retreated to refugia as climates changed, continents drifted, and competitors evolved. The three surviving species are living fossils, ecological anachronisms clinging to the conditions that once prevailed worldwide.

Dawn redwoods were known only from fossils until 1944, when living specimens were discovered in a remote Chinese valley. Scientists found the "extinct" tree growing next to rice paddies.

The subfamily's strategy is extreme longevity backed by catastrophic resilience. Individual trees routinely live 1,000-2,000 years. Giant sequoias reach 3,000+ years. This isn't just impressive—it's a strategic commitment. Trees this long-lived are betting that conditions will cycle back, that what was once favorable will become favorable again. The strategy fails only if environmental change is truly irreversible.

Three Strategies, One Lineage

Despite shared ancestry, the three redwood species evolved distinct approaches to the longevity game:

Coast Redwood (Sequoia sempervirens): Height maximizers. The tallest trees on Earth at 116+ meters, coast redwoods compete for light through vertical growth. They harvest fog through aerial roots and regenerate from stumps and root systems—a single genetic individual can persist for millennia through vegetative reproduction even as individual stems die.

Giant Sequoia (Sequoiadendron giganteum): Volume maximizers. The most massive single organisms on Earth, giant sequoias invest in girth rather than height. Their bark—up to 90 cm thick—provides extreme fire protection. They require periodic fire for seed germination; fire suppression paradoxically threatens them more than fire itself.

Dawn Redwood (Metasequoia glyptostroboides): Deciduousness in a conifer. The only deciduous member of the subfamily, dawn redwoods evolved to survive cold winters by dropping needles. This flexibility allowed persistence in climates that eliminated their evergreen relatives, explaining their survival in mountainous central China.

The Fog Connection

Coast redwoods exist in one of Earth's strangest climate niches: the Pacific coastal fog belt. Summer fog provides water during California's rainless season; the trees capture moisture through leaves and aerial roots, dripping precipitation that maintains understory humidity. Remove the fog, and redwoods cannot survive—they're adapted to a microclimate that exists in a narrow coastal strip.

This creates a feedback loop: redwood forests influence their own climate. The canopy creates conditions that attract fog, which waters the trees that create the canopy. The ecosystem is self-reinforcing but also fragile—disrupt the feedback and the system collapses to a different stable state.

Fire as Partner

Giant sequoias evolved with fire, not despite it. Their seeds require bare mineral soil to germinate; their thick bark protects against all but the most extreme fires; their competitors (white fir, incense cedar) are fire-sensitive and eliminated by periodic burns. A century of fire suppression created forests where sequoias are surrounded by ladder fuels—smaller trees that carry flames into the crown, killing giants that survived millennia of natural burns.

The 2020-2021 Castle and KNP Complex fires killed an estimated 10,000 giant sequoias—more than the previous 500 years combined. Fire that was once partner became enemy when fuel loads exceeded what sequoias evolved to survive.

Failure Modes

Climate velocity: Redwood habitats are shifting faster than trees can migrate. Coast redwoods require fog; fog patterns are changing. Giant sequoias require specific temperature and precipitation regimes that are moving upslope. Trees that live 2,000 years cannot adapt to changes happening over decades.

Range contraction: Each species already occupies a fraction of its historical range. Coast redwoods: 450-mile strip. Giant sequoias: 75 scattered groves. Dawn redwoods: one valley in China (wild population). Further contraction threatens population viability.

Reproductive limitations: Giant sequoias produce millions of seeds but seedling establishment requires specific conditions (bare soil, adequate moisture, light gaps) that are increasingly rare. Even in protected groves, recruitment often fails to replace mortality.