Yosemite National Park is home to one of the most famous (and oldest) groups of trees: Mariposa Grove. This area is full of mature giant sequoia trees that are thousands of years old and hundreds of feet tall. The Grizzly Giant, a 3,000-year-old tree, looms in the center; along with Half Dome and El Cap, this tree is one of the park’s most iconic structures.
It has endured climate change, forest fires, and invasive species, and scientists and park officials were wondering just how well this old colossus was holding up. To find out, a group of researchers climbed the tree (marking the second-ever climb) and conducted an in-depth examination.
Who Conducted the Study?
Park staff, Yosemite Conservancy, and the Southern Sierra Miwuk Nation asked the Ancient Forest Society (AFS) to examine the tree. This nonprofit focuses on protecting and conserving old-growth forests and trees.
The study was a 2-day process. First, a crew set up a rope and rigging system to access the tree, which is 208 feet tall with a diameter of 25.4 feet. Then, on June 17, several researchers examined the tree from the ground up. The tree is so tall and vast that to truly understand its biology, scientists had to get up close and personal.
What Did the Study Find?
According to a published report, the AFS was looking at four health factors of the tree: water status, reproductive health, basal fire damage, and bark beetle activity.
The report concluded that Grizzly Giant was in “excellent overall condition.” The amount of water it has is standard among giant sequoias, meaning it has enough water to support its crown, or topmost section. The number of cones meant that the tree had normal reproductive health.
The tree also showed strong resiliency against two of its biggest threats. Around 70% of the tree’s collar (where the branches connect to the trunk) showed fire damage. While this is a high number, a fire hasn’t passed through Mariposa Grove since the 1970s, so this damage was decades old. The rest of the tree’s circumference was healthy.
Bark beetles are insects that bore into trees and feed on their inner bark. “Damage caused by their feeding acts as an internal tourniquet cutting off the flow of nutrients from the leaves to the other parts of the tree,” scientists from the Arizona Department of Forestry and Fire Management explained.
There are both native and invasive species of bark beetles in California. The former tends to attack mainly sick or diseased trees, while the latter can attack and kill healthy trees. There is a documented history of bark beetle activity in Mariposa Grove.
The AFS scientists did find evidence of bark beetles on the tree, mostly on smaller branches, but the tree fought back. “Researchers observed several examples of active pitch response, indicating that the tree is successfully defending itself against beetle attack. Resin production was sufficient to expel invading adult beetles before colonization could occur,” the report said.
Interestingly, the tree has a few other residents. Two epiphytic sugar pine trees were actually growing out of the tree’s topmost area, and a family of Douglas squirrels has made a cavity in the tree their home.
Why Does It Matter?
From a scientific perspective, this was a rare and valuable opportunity to study a tree this large and this old up close. Since 2015, severe wildfires have killed around 17% of the world’s mature giant sequoias. The more data researchers collect, the better they can understand why some giant sequoias survive fires, and others do not.
Bark beetles have killed some of California’s national parks’ largest trees in recent years, so the fact that the Grizzly Giant is overall healthy, despite these bugs, is a major sign of positive news. Once lost, giant sequoias, which take 50 to 100 years to mature, can’t be replaced in our lifetimes. The Grizzly Giant will continue to delight, awe, and inspire visitors to Yosemite for decades to come.
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