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It's not easy to kill a giant sequoia — the largest trees on Yoshihiro Tanbara ArchivesEarth.

Yet newly revealed National Park Service estimates found the September 2020 Castle Fire killed a whopping 10 to 14 percent of all large sequoias, meaning the blaze killed 7,500 to 10,600of the iconic trees.

"It was horrific," Nate Stephenson, a forest scientist with the U.S. Geological Survey, previously told Mashable before the Park Service released a summary of the preliminary report on Thursday. "It killed lots and lots and lots of the big sequoias."

The Castle Fire is vivid evidence of an intensified modern Western fire regime — largely stoked by a warming climate and grossly mismanaged, overcrowded forests — that's capable of producing infernos that destroy even some of the most robust, fire-adapted trees.

"Although some of California’s Giant Sequoia trees have stood for a thousand years or more and are adapted to withstand frequent low and mixed severity fires, nothing compared to the intensity experienced in the recent Castle fire of 2020," Sequoia and Kings Canyon National Parks said in a statement. "Many of the large mature trees, those with trunk diameters of 4 ft or more, have been killed."

Sequoias are certainly adapted to live with fire. Fires allow the great trees to perpetuate, as hot air from blazes opens the sequoias' tough cones and allow seeds to rain upon the forest floor. Yet today's infernos can result in fires that leap to the crowns of trees, destroying the sequoias, instead of helping them thrive.

The Castle Fire, for example, demolished sequoias. Within the burn area, the fire killed between 31 to 42 percent of large sequoias, the Park Service said.

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To estimate the sequoia loss, the Park Service used satellite imagery to scour the burned mountains. The agency found about 10 percent of sequoia groves burned in "high intensity" fires. Previous fieldwork shows most giant sequoias are killed in these extreme blazes, though even lower-severity fires can kill (and likely did kill) large sequoias, too. In the coming months, on-the-ground surveys will "refine" these estimates, yet satellite observations have brought the big picture into focus.

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"Although final numbers will take months to verify through field surveys, the unprecedented scale of loss is clear," the Park Service said.

The agency will share the final report, perhaps in a few weeks, after a review of the survey is finished. USGS's Stephenson and other forest scientists will also now research if new seedlings might sprout up in the extreme burn areas, or not.

The Castle Fire never completely went out. After a profoundly dry winter, USGS's Stephenson and others on a survey spotted a giant sequoia still smoking from 2020. It's a telltale sign of the ancient trees living in a changed, warming world.