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Up to 19% of the world's 'irreplaceable' giant sequoias lost to fire in about a year, study finds

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  • Between 2,200 and 3,600 adult sequoias were killed this year.
  • Wildfires have killed up to 19% – nearly a fifth – of the world's sequoia trees in just over a year.
  • California has seen its largest fires in the past five years, with last year setting a record for most acreage burned.

2021 was another disastrous year for California's giant sequoias, as wildfires killed thousands of the iconic trees, federal officials announced in a report released Friday.

Between 2,200 and 3,600 adult sequoias were either killed by the KNP Complex and Windy Fires or are expected to die within the next five years – amounting to 3% to 5% of the Earth's sequoia trees, according to National Park Service estimates. Scientists used satellite imagery, overhead flights, and on-the-ground surveys to arrive at the figure.

The destruction comes on the heels of last year's Castle Fire, which torched between 10% to 14% of the world's sequoias – some 10,000 trees – in the same region of the southern Sierra. 

In the worst-case scenario, that means wildfires have killed 19% – nearly a fifth – of the world's sequoia trees in just over a year. 

There are only about 75,000 giant sequoia trees in California, which are located in about 70 groves scattered along the western side of the Sierra Nevada.

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Watch: New sequoias take root after fire guts giant trees

“The sobering reality is that we have seen another huge loss within a finite population of these iconic trees that are irreplaceable in many lifetimes,” said Clay Jordan, superintendent of Sequoia and Kings Canyon National Parks.

Since 2015 there has been a dramatic increase in area burned and amount of high-severity fire in sequoia groves, "resulting in significant mortality of large, legacy sequoias," the park service said. 

In total, 28 giant sequoia groves were affected by the fires. While giant sequoia rely on low-to-moderate severity fire to burst their pinecones and reproduce, the recent mega-blazes that have hit the west can spread to the trees' crowns and incinerate them.

California wildfires: Fire may have killed hundreds of giant sequoias, burning through Earth's largest grove

These uncharacteristically hot and ferocious fires follow a century of fire-suppression policies that saw forest managers stamping out flames as quickly as they erupted, even those that posed little threat to property or the public. The result: Forests today are much denser than they have been at any other point in history.

Climate change has played a role in wildfire seasons in the West. 

The increase in high-severity fires in the Sierra "is consistent with increases in high-severity fire throughout the western US, which has been linked with warmer, drier fire seasons and increasing fuel aridity linked with climate change," the park service said. "The warming climate is also directly impacting forests via 'hotter droughts.'" 

California has seen its largest fires in the past five years, with last year setting a record for most acreage burned. So far, the second-largest amount of land has burned this year.

"Because of their great size, age, and limited distribution, (sequoias) have captured the public’s imagination and have been central to the origin of many state and national parks," the park service said.

“As spectacular as these trees are we really can’t take them for granted. To ensure that they’re around for our kids and grandkids and great grandkids, some action is necessary,” Jordan said.

Contributing: The Associated Press. Yeager reports for the Visalia Times-Delta.