High in the evergreen canopy of General Sherman, the world’s largest tree, researchers searched for evidence of an emerging threat to giant sequoias: bark beetles.
The climbers descended the towering 2,200-year-old tree on Tuesday with good news.
“The General Sherman tree is doing great right now,” said Anthony Ambrose, executive director of the Ancient Forest Society, which led the expedition. “It appears to be a very healthy tree that can fend off any beetle attack.”
It was the first time climbers scaled the iconic 285-foot sequoia tree, which draws tourists from around the world to Sequoia National Park.
Giant sequoias, the largest living things on Earth, have survived for thousands of years in California’s western Sierra Nevada, the only place where the species is native.
But as the climate becomes warmer and drier, giant sequoias previously considered virtually indestructible are increasingly threatened by extreme heat, drought and wildfires.
According to park officials, record-breaking wildfires in 2020 and 2021 killed as many as 20 percent of the world’s 75,000 mature redwoods.
“The number one threat to giant sequoias is climate-induced wildfires,” said Ben Blom, director of stewardship and restoration at Save the Redwoods League. “But we certainly don’t want to be surprised by a new threat, which is why we are studying these beetles now.”
But researchers are increasingly concerned about bark beetles, which have not posed a serious threat in the past.
The beetles are native to California and have lived with redwoods for thousands of years. But only recently have they managed to kill the trees. Scientists say they recently discovered about 40 sequoia trees that have died from beetle infestations, mostly in national parks.
“We are documenting a number of trees that are actually dying from a combination of drought and fire, leaving them so weakened that they can no longer defend themselves against the beetle attack,” Ambrose said.
The beetles attack the trees from the canopy, boring into branches and working their way through the trunk. If left unchecked, the tiny beetles can kill a tree within six months.
That’s why park officials allowed Ambrose and his colleagues to climb General Sherman. They conducted the tree health inspection as journalists and visitors watched them pull themselves up on ropes dangling from the canopy. They examined the branches and trunk, looking for the small holes that indicate beetle activity.
But it is not possible to climb every redwood tree to directly inspect the canopy in person. That’s why they are also testing whether drones equipped with sensors and supported by satellite images can be used to monitor and detect beetle infestations on a larger scale in forests.
General Sherman’s health inspection Tuesday was organized by the Giant Sequoia Lands Coalition, a group of government agencies, indigenous tribes and environmental groups. They hope to establish a health monitoring program for the towering trees.
If they discover beetle infestations, officials say, they can try to control the attacks by spraying water, removing branches or using chemical treatments.
Bark beetles have devastated pine and pine forests in the western United States in recent years, but previously posed no threat to giant sequoias, which can live 3,000 years.
“They have withstood insect attacks for years. So why now? Why are we seeing this change?” said Clay Jordan, superintendent of Sequoia and Kings Canyon National Parks. “There is a lot we need to learn to ensure long-term good management of these trees.”
