On a rolling granite hill in the Sierra Nevada Mountains, on a hot August night, tree scientist Kristen Shive camped beneath a giant sequoia tree she estimated could be a thousand years old.

Her employer, the nonprofit Save the Redwoods League, had just bought the property on which the tree stood, a 530-acre forest outside Sequoia National Park packed with ancient trees. Plans for how to preserve them spun through her head as she stared up at the stars through the tree’s frilly foliage.

A few months later, in October, she stood ankle-deep in ash at the foot of that same tree. But this time, the foliage overhead was charred to a crisp.

This giant sequoia—and likely hundreds of others—had fallen victim to