The use of small, controlled burns to clear out flammable underbrush has saved thousands of giant sequoias from devastating wildfires, new research finds. The use of small, controlled burns to clear out flammable underbrush has saved thousands of giant sequoias from devastating wildfires, new research finds. With their thick bark and high canopies, the trees can withstand small fires, but the more intense blazes seen in a warmer climate have proved deadly for thousands of trees. Together, the 2020 Castle Fire and 2021 KNP Complex Fire killed as many as 13,000 giant sequoias, or close to a fifth of all sequoias. According to the new study, the death count would have been considerably higher without the use of prescribed burns.