This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Tall trees are generally associated with high-biomass forests. This is particularly true for forests dominated by Sequoia sempervirens (hereafter redwood), the world's tallest tree species.
Extreme decay resistance, the ability to survive high-severity fires, shade tolerance and prolific trunk reiteration (resprouting) make the species unique, allowing tall redwood forests to accumulate more biomass and store more aboveground carbon than any other vegetation type. California's Redwood National and State Parks (RNSP) protect nearly half the global population of living trees more than 100 meters (328 feet) tall across 16,402 hectares (40,500 acres) of high-biomass primary (old-growth) forests, plus 38,379 hectares (94,800 acres) of much shorter, low-biomass secondary forests regenerating from 20th-century logging. Understanding tall-tree and forest-biomass dynamics is essential for long-term conservation, especially since reserves like RNSP are increasingly threatened by extreme weather.
Tall forests typically occur in regions with a low frequency of strong winds, but powerful storms do occur. After years of exceptional drought, California experienced hydroclimate whiplash, with nearly a dozen consecutive landfalling atmospheric rivers between December 2022 and March 2023. Northwestern California received the most rain, accompanied by high winds and a rare canopy snow load.
More apparent damage to the RNSP forest canopy occurred during these storms than at any time in the past 30 years. A new study published in Forest Ecology and Management combined ground-based measurements and repeated (2007–2025) airborne laser scanning (ALS) to inventory the tallest redwoods and quantify forest biomass. How is live-tree biomass currently distributed in primary and secondary forests across RNSP?
How did winter 2022–23 storms affect tall-tree populations and per-hectare biomass distribution in primary forests relative to the preceding 15 years? While ALS is a powerful tool for measuring tree heights over large areas, biomass mapping may be less intuitive. To do this, ALS data sets are segmented into tree objects, each corresponding to a dominant tree crown plus any subordinate crowns hidden underneath.
Field measurements of 1,076 trees associated with 400 such objects were used to develop equations for biomass estimation across RNSP, and repeated ALS sampling was used to quantify changes in primary forests before and after the storms. Winter 2022–23 storms inflicted substantial damage on the tallest redwoods. The number of trees more than 100 meters tall peaked at 950 in 2022, decreasing to 825 after the storms.
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