that one fire alone. >> reporter: started by lightning in august 2020, the castle fire was part of the sequoia complex that burned more than 174,000 acres, scorching several sequoia groves. >> it was devastating, heartbreaking. everything had been incinerated. it was a field of the world's largest burned up toothpicks. >> reporter: after decades of suppressing forest fire, other trees and brush have grown rampantly around the sequoias. >> the fires that used to burn every five to ten years in the sierra would just keep down the competition and reduce the fuel naturally. >> reporter: on land owned by the save the redwoods league, we hiked out to see just how deadly castle fire was here. >> for you us to see 10 to 14% of the total of giant sequoias alive killed in one year in one