New research shows giant sequoia seedlings are growing under new climate conditions
Extreme wildfires have killed up to 20% of the world's mature giant sequoias since 2015, according to researchers with the U.S. Geological Survey's Western Ecological Research Center (WERC).
Researchers also found that some areas affected by recent megafires may not have enough seedlings to grow the next generation of millennia-aged trees.
"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," said one of the paper's lead authors, Nathan Stephenson. "Giant sequoias are the largest trees in the world. They're fire-adapted and rely on fire to reproduce. But recent fires have killed thousands of mature trees and, in some cases, their seeds too."
A majority of sequoias perished from three wildfires in 2020 and 2021, Giant Sequoia Lands Coalition (GSLC) announced on July 15. The 2021 KNP Complex fire alone killed between 3% to 5% of the world's mature sequoia population.
The coalition reported that the recent megafires burned at a size and severity far more extreme than the historic norm, and the new studies show that without intervention, some giant sequoia groves may experience a long-term or permanent loss of acreage as seed trees have died, and the remaining number of new seedlings is exceptionally low.
Researchers also noted that the seedlings that germinated after the 2020 and 2021 wildfires are growing under new climate conditions, including higher average temperatures and the most severe drought conditions of the 121-year historical record.
“These conditions will almost certainly reduce the survival of giant sequoia seedlings,” stated the coalition in a press release. “In areas where the mature seed trees have died, chances of natural recovery will almost certainly be greatly diminished.”
Sequoia regeneration has varied across the range since the recent mega-fires, lead author David Soderberg said. The data goes on to suggest that sequoia grove areas that were severely impacted by the fires may not have enough reproduction to replace the sequoias lost.
"Some areas are doing well, but in other sites where the seeds and seed trees burned, or where young seedlings have died from high heat and drought, natural long-term recovery appears to be unlikely," Soderberg said.
Joanna Nelson, director of science and conservation planning for Save the Redwoods League, says these new findings could help land managers determine how to best care for the giant sequoia groves, especially in emergency-response windows post fire.
"We can better understand when and where sequoia reproduction may be too low for future success – and be equipped to take action," she said. "At the same time, we continue to prioritize fuels reduction treatments that favorably change fire behavior and reduce the severity of potential future wildfires."
This article originally appeared on Visalia Times-Delta: Giant sequoia seedlings are growing under new climate conditions
