2020 And 2021 CA Megafires Essentially Wiped Out Reproduction In Hardest-Hit Giant Sequoia Groves

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Last edited Fri Jul 26, 2024, 07:51 AM - Edit history (2)

Giant sequoia groves in California’s Sequoia and Kings Canyon National Parks that were extensively burned in the megafires of 2020 and 2021 produced numbers of seedlings that were so “drastically low” in some areas that they may not naturally regenerate, according to two new studies by government scientists. One of the studies, by researchers with the U.S. Geological Survey’s Western Ecological Research Center and published in the journal Ecosphere in March, tried to assess the “likelihood of natural recovery” in four Sequoia groves and found that “seedling densities fell far below the average density measured after prescribed fires” that were intentionally set to maintain grove regeneration and health.

In the second study, published last month in Forest Ecology and Management, the researchers developed “seedling reference densities” based on post-fire data from eight groves that burned in 26 different fires in the national parks from 1969 to 2016 to identify areas that might require planting by forest managers. In one “case-study sequoia grove” burned in one of the recent high-severity wildfires, the study found seedling densities that were “significantly (and dramatically) lower” than historic norms, “suggesting inadequate post-fire reproduction.”

The studies found that extreme wildfires have killed up to 20 percent of the world’s mature giant sequoias since 2015, with a majority of the trees dying in three wildfires in 2020 and 2021. The sequoias are the largest trees in the world and among the oldest, and only grow on the western slopes of the Sierra Nevada in California, according to the National Park Service.

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Under the constant threat of wildfires, the giant sequoia tree evolved to be more resilient to wildfire by growing thick bark that protects their trunks from flames and branches that rise far above fires burning on the ground, as well as using fires to reproduce. Yet, their adaptations are not enough anymore. “Recent fires have killed thousands of mature trees and, in some cases, their seeds too,” said Nathan Stephenson, lead author of the June study and a Ph.D. scientist emeritus at the USGS western research center. “What we used to call high-severity fire does not compare to the unprecedented scale and severity of the wildfires we’ve experienced in recent years in the Sierra Nevada.”

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https://insideclimatenews.org/news/23072024/california-sequoia-groves-impacted-by-wildfires/