The State of the Trees · Episode 3 of 13 · 21 min
The Fire Debt: Why Fire Now Kills the Forests That Need It
The giant sequoia needs fire to reproduce, yet fire killed up to a fifth of the world's big sequoias in two seasons. A century of fire exclusion built ladder fuels, and hot, dry weather now drives crown fires that kill mature seed trees and increasingly stop forests from regrowing, converting conifer forest to shrub and grass. The episode follows the seedlings and the reforestation backlog rather than the fire regime.
Where it happens
- Sierra Nevada, California+6 more episodesGiant sequoia groves where most grove acreage burned in 2015-2021
- Castle Fire area, Sierra Nevada2020 fire killed an estimated 7,500 to 10,600 large sequoias
- National forests, western United StatesReforestation backlog of roughly 4 million acres
Timeline
- 1910-2010Fire is systematically excluded from western conifer forests
- 2015-2021More than 85 percent of sequoia grove acreage burns
- 2020Castle Fire kills an estimated 10 to 14 percent of large sequoias
- 2021KNP Complex and Windy Fires kill thousands more large sequoias
- 2021Reforestation backlog roughly doubles after the 2020-21 fires
Still debated
Whether post-fire 'conversion' is loss or transition is argued. Some failed-conifer sites become aspen, oak or shrubland, a functional shift in ecosystem type rather than a dead zone.
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