The Trees That Needed Fireproof Blankets

Giant sequoias evolved with fire. Their cones require heat to open and release seeds. Low-intensity fire clears the understory competition that would otherwise shade out sequoia seedlings. Their thick, fibrous, tannin-rich bark resists flame better than almost any other tree species on the continent. They did not need protection from fire. They needed fire.

In July of twenty twenty-two, the Washburn Fire started near the southern entrance to Yosemite and pushed toward the Mariposa Grove, the park's largest concentration of giant sequoias and the grove that anchored Lincoln's eighteen sixty-four preservation act. NPS fire crews made a calculation: the sequoias could probably withstand a fire of historical intensity, but the fire coming toward them was not of historical intensity. Decades of suppression had loaded the surrounding forest with fuel. The burn might exceed what the trees had evolved to survive.

Crews wrapped the bases of the grove's largest trees, including some that had been standing for two thousand years, in aluminum-foil-lined fire-resistant blankets. They conducted prescribed burns ahead of the fire's path to reduce fuel loads. They held the line.

The grove survived.

The incident condensed the central ecological problem of the modern Sierra into one image: trees that evolved with fire, that require fire, that spent two millennia surviving fire, now requiring human intervention to survive a fire of the kind that human land management created. The sequoias were not fragile. The conditions were extraordinary.

Those conditions are becoming ordinary. That is the change.