The scale of a Giant Sequoia is difficult to appreciate until you see it in person. One example: The General Sherman tree in Sequoia National Park has a base more than 36 feet across—wider than the average two-car garage. Its first large branch—yes, the first!—doesn't appear until 130 feet off the ground, and that branch is almost 7 feet in diameter. Average crown spread: 106 feet, wider than an NBA court.

And it's more than 2,000 years old.

It's one thing to read those statistics and say, "wow." In the canopy of these giants, those statistics become reality. That reality is what Anthony Ambrose, PhD, Wendy Baxter, and researchers with the nonprofit Ancient Forest Society (AFS) experience as part of their scientific work.

"Climbing a Giant Sequoia is a humbling experience," says Baxter. (In 2024, she and Ambrose became the first individuals to ever climb General Sherman.) "They're such large organisms, it can take a really long time just to get to the first branches. And their presence is so complex. The experience never gets old."

But they're not climbing just for the view. The trees are under threat, and AFS is climbing to understand why—and how to protect them.

After years of university work as plant physiologists and forest canopy ecologists, Baxter and Ambrose, along with tree enthusiast Steen Christensen, co-founded AFS five years ago. They started the organization to conduct research that would help land managers make smarter choices so these awe-inspiring giants could continue to exist.

"Right now, our research projects are focused on the different aspects of drought, fire, and beetle attack in the Giant Sequoias and the impacts of a changing climate," says Ambrose, who has done canopy science for more than 28 years. "What we're seeing: Climate and drought are stressing the trees out and increasing risks in expected and unexpected ways."

One example: Successful attacks by native phloem-feeding bark beetles, which are new in Giant Sequoias. Historically, the trees have been very pest resistant—they typically "pitch out" insect pests—but drought and severe fires are stressing the trees to the point that beetles can now do real damage. "It's only become a concern in recent years," Ambrose says. "We started noticing unusual tree deaths related to it in 2017."

To understand the impacts, AFS is working with scientists at Colorado State University on a two-year project examining bark beetle attack in Giant Sequoias throughout their range. The team collects samples of inner bark and sapwood that are analyzed for carbohydrate status, water content, and defense chemicals. They install sensors that measure trunk growth and water flow through the sapwood every 10 minutes. They inspect for beetle damage, both during climbs and using drones. During busy measurement periods, they climb the trees multiple times per day.

When asked why he continues to put in so much effort, Ambrose shrugs: "You gotta do what you can, right?"

The process is different than what most arborists might expect. First, there's the issue of getting into a tree whose first sizable branches are so far off the ground. "You'd spend a lot of time setting lines with something like a Big Shot," Baxter says. "We customized a crossbow to set lines instead." The crossbow fires a bolt with fishing line attached so ropes can be pulled into place.

Then there’s the rope itself. AFS uses 600-foot Sterling 9mm HTP ropes due to their low stretch and light weight. Depending on the load they’re carrying into the tree, the climbers might use a typical rope-walking system for the ascent. But for heavier loads, they choose the Texas system—since the load is attached to your foot loops, it lets you stand up to lift most of your body weight and then lift your feet plus the load, inchworm style. Ambrose also uses a DMM Kinisi Pro Harness. “It provides the comfort I need for long days in extremely tall trees,” he says.

Once in the canopy, cambium savers minimize friction and impact on the bark. Spikes are out. Every action is intentional—including leaving deadwood in place vs. removing it, as many arborists would typically do. (Much of the deadwood supports other parts of the ecosystem.) "We try to be as low-impact as possible,” Baxter says. “These are living cathedrals.” The researchers approach their work with a sense of awe. And respect.

The complexity can be humbling. Crowns are wide and uneven, with branches thicker than many other trees, and centuries of deadwood. The team uses custom 80-foot double-ended lanyards with two ART positioners to safely move through the canopy. The physical challenge is matched by the mental one: constant evaluation of rigging angles, anchor points, and crown movement. "These trees make everything I've done before feel like training," says Elsalim. " I can't imagine that there's anything else out there cooler than this."

It's hard to fathom that these trees are under threat. But they are, and it's why organizations like AFS exist. "My dream is for these forests and trees to persist well after I'm gone," Ambrose says. Interested in helping? Here are a few actions you can take.

• Volunteer. AFS relies on volunteers for their in-the-canopy research. In 2024, AFS had ninety-one unique volunteers from around the world. Learn more about volunteering for AFS.

• Donate. AFS is a small organization on a small budget. You can donate here.

• Get outside. "You could go to your local park," Baxter says. "The important thing is to reconnect with nature and want to protect it."

Explore the gear. Support the research. Protect the giants. Sherrilltree is a proud supporter of the Ancient Forest Society. Learn more at ancientforestsociety.org.