Drought, then a dozen atmospheric rivers: 125 of California's 100-metre redwoods dropped out

The 100 metre line is a measuring tape's verdict, not a mortality count. Between the 2022 peak and the post-storm survey, 125 trees dropped out of the class, about 13 percent of the tally ^[1]. The study attributes only 11 percent of documented losses to treefall ^[8], which puts roughly 14 trees on the ground and around 111 still rooted and simply shorter ^[2]. Redwood answers damage by resprouting, and the authors expect damaged crowns to recover into vigorous reiterated tops ^[9].

The biomass side is harder to shrug off. Priced in tonnes rather than years, the Humboldt County losses come to roughly 20 to 104 tonnes per hectare ^[5], against a pre-storm accumulation rate of 10 to 13 tonnes per hectare per year through 2007 to 2022 ^[10]. On the worst hectares the estimate exceeded 500 tonnes per hectare, more than the entire standing biomass of forests counted as high-biomass elsewhere ^[12]. At the pre-storm growth rate, that is 38 to 50 years of accrual gone in one winter ^[3].

The wood did not leave the site. What came down was mostly decay-resistant heartwood, which keeps storing carbon as woody debris on the forest floor, and the authors reckon the crown damage roughly rivalled the live-tree biomass lost to whole trees falling ^[14]. That is the useful distinction: the maps lost a lot of live biomass, the atmosphere gained much less, and the carbon mainly changed pools.

Then there is siting. Tall forests exist where they do partly because strong winds are infrequent there ^[16]. The traits that let this species reach such heights, extreme decay resistance, survival of high-severity fire, shade tolerance and prolific trunk reiteration ^[17], are answers to rot, flame and competition for light. None of them is an answer to sustained wind on a crown carrying a rare snow load after a run of atmospheric rivers ^[3]. Fire and logging shaped how these reserves were drawn and defended; wind loading on a saturated slope was treated as background noise.

The geography leaves no room to spread the risk. Primary forest inside the parks covers 16,402 hectares against 38,379 hectares of secondary forest regrowing from 20th-century logging ^[2], roughly 30 percent of the wooded area ^[4], and nearly half the world's living trees over 100 metres stand inside that fraction ^[1]. A hazard that arrives from the sky and lands on the tallest crowns hits the concentrated part first, which is the opposite of how a fire perimeter or a timber sale boundary behaves.