The tree that hits the moon
In a remote gorge near Taiwan's Da'an River, a millennium-old Taiwania fir named the Heaven Sword has been confirmed as East Asia's tallest known tree, standing 84.1 meters above the forest floor. A team of researchers spent twelve years combining satellite lidar, citizen science, and the oldest of tools — a tape measure dropped from the crown — to find it. The discovery is more than a record; it is a reminder that the most consequential things on Earth are often the ones most carefully hidden, and that understanding them may be essential to our survival.
- A tree estimated to be 1,000 years old had been quietly growing in one of Taiwan's most inaccessible valleys while researchers spent over a decade trying to prove it existed.
- Lidar technology — powerful enough to scan 950 million trees from the air — was systematically fooled by Taiwan's steep terrain, mismeasuring 93 percent of candidate trees and forcing the team to rebuild their methods from scratch.
- Reaching the Heaven Sword required swimming upstream, rock climbing, and two days of hiking through trailless wilderness — a physical commitment that separated rigorous science from remote-sensing guesswork.
- When a climber dropped a tape measure from the canopy and it read 84.1 meters, years of uncertainty collapsed into a single verified number, validating both the expedition and the hybrid methodology behind it.
- The find carries consequences beyond the record books: new biomass calculations suggest forest management models have been dramatically underestimating how much carbon giant trees store, reshaping what conservation policy should prioritize.
A team of Taiwanese researchers spent twelve years searching one of the world's most densely forested islands for a tree that locals had long called the one that hits the moon. What they found in a remote gorge near the Da'an River was a Taiwania fir named the Heaven Sword — 84.1 meters tall, roughly 1,000 years old, and now confirmed as the tallest known tree in East Asia.
The search began in 2014 among professional climbers, ecologists, and remote-sensing specialists who set out to systematically map Taiwan's giant trees. The real methodological leap came when researcher Dr. Rebecca Chia-Chun Hsu connected with lidar experts — specialists who scan forests from aircraft using pulses of light to build detailed 3D canopy maps. The technology seemed ideal for Taiwan's dense mountains, but the island's steep terrain kept deceiving the algorithm, making trees appear taller than they were. In 2020, the team invited citizen scientists to manually review and correct the lidar data. The results were sobering: 93 percent of trees had been mismeasured. By late 2022, the corrected Taiwan Giant Tree Map identified 941 trees exceeding 65 meters — and one that appeared to be the tallest of all.
Reaching it meant swimming and climbing upstream for over 20 kilometers, then hiking uphill for two days through terrain so remote the team had to forge their own paths. When they arrived in early 2023, the verification was refreshingly simple: a climber scaled the tree and dropped a tape measure from the crown. It read 84.1 meters. Michael Taylor, co-discoverer of the world's tallest tree in California, praised the team's insistence on manual confirmation — a discipline too often skipped when researchers trust automated software alone.
Taiwan's forests cover 60 percent of the island, shaped by steep terrain, heavy rainfall, and a stable climate that allowed ancient trees to grow undisturbed for centuries. Industrial logging between 1912 and 1991 destroyed many old-growth groves, but the most inaccessible stands survived, hidden by the same geography that made them so hard to find. Now the team is using lidar to model the biomass of these giants — work that has already revealed that standard forest management equations have significantly underestimated how much carbon they hold.
Giant trees are ecological anchors: carbon sinks, habitat creators, and living records of forest history. They are also among the most vulnerable to drought, typhoons, and the accelerating pressures of a changing climate. The Heaven Sword's discovery has opened a larger question — not just where the tallest trees are, but what it will take to protect them, and what we stand to lose if we don't.
A team of Taiwanese researchers spent a decade chasing a legend through one of the world's most densely forested islands. What they found—a towering fir tree named the Heaven Sword of the Da'an River—stands 84.1 meters tall in a remote valley near Taiwan's longest river, making it the tallest known tree in all of East Asia. The Taiwania fir, estimated to be roughly 1,000 years old, had been waiting in that secluded gorge the whole time, known to the Indigenous Rukai people of Taiwan's southern mountains by a more poetic name: the tree that hits the moon.
The search began in 2014 when a group of tree enthusiasts—professional climbers, ecologists, geologists, and remote-sensing specialists—decided to systematically map Taiwan's giant trees. They started with three massive Taiwania firs called The Three Sisters, already known to locals in the Cilan conservation area. The real breakthrough came when Dr. Rebecca Chia-Chun Hsu, an assistant researcher at Taiwan's Forestry Research Institute, met experts in lidar technology at a conference. Lidar works by transmitting pulses of light from aircraft and measuring how long it takes for the light to bounce back, creating detailed 3D maps of forest canopy heights. The technique seemed perfect for Taiwan's dense, mountainous terrain—except for one problem: the island's uneven landscape kept tricking the algorithm. Steep cliffs and tilted terrain made trees appear taller than they actually were.
So the team did something unconventional. In 2020, they invited citizen scientists to examine the lidar images and manually correct the algorithm's mistakes. The results were humbling: 93 percent of the trees had been mismeasured. By the end of 2022, after years of ground-truthing and careful analysis, the team released the Taiwan Giant Tree Map, identifying 941 trees exceeding 65 meters in height. One tree on that map stood out as the likely tallest. Reaching it meant swimming and rock climbing upstream for more than 20 kilometers, then hiking uphill for two days through terrain so remote and difficult that the team had to forge their own paths.
When they finally arrived at the Heaven Sword in early 2023, the verification process was decidedly low-tech. A climber scaled the massive tree and dropped a tape measure from the crown. When it read 84.1 meters—276 feet—Hsu felt immense relief. The grueling expedition had been worth it. Michael Taylor, the codiscoverer of California's Hyperion (the world's tallest tree at 116 meters) and a lidar specialist, praised the team's commitment to manual verification. Too many researchers, he noted, rely solely on automated software without confirming their measurements on the ground, especially when trees lean on hillsides as they reach for sunlight.
Taiwan's forests cover 60 percent of the island and contain an estimated 950 million trees. The island's steep terrain, abundant rainfall, and stable climate have created rare conditions for giant trees to grow undisturbed for centuries and millennia. Industrial logging between 1912 and 1991 devastated some ancient forests, but the most inaccessible groves survived in protected areas, hidden by the very geography that made them so difficult to find. Now, as the team moves forward, they're studying the specific bioclimates and terrains where Taiwan's tallest trees thrive. They're also using lidar to create 3D models that will calculate the biomass of giant tree species—work that has already revealed something significant: previous forest management equations have dramatically underestimated how much carbon these trees store.
Giant trees are ecological anchors. They absorb vast amounts of carbon dioxide, stabilize forest structure, and create habitat for countless other organisms. Taiwan's forests of giant trees may rank among the most carbon-dense environments on Earth. Yet they're also among the most vulnerable. Tall trees face greater sensitivity to drought and extreme weather—the typhoons and landslide-triggering rainstorms that regularly batter Taiwan. As the world loses tree species at an accelerating rate, with over 30 percent facing elevated extinction risk, the Heaven Sword and its companions serve as living records of forest history and indicators of where biodiversity thrives. Finding them, protecting them, and understanding their role in the climate system has become urgent work. The decade-long search for one tree has opened a window onto what conservation at scale might look like.
Notable Quotes
The common characteristics are probably that we are all tree lovers and like adventures— Dr. Rebecca Chia-Chun Hsu, lead researcher, Taiwan Forestry Research Institute
Giant trees have very long lifespans, and they have recorded and survived long-term climate changes on the planet. We shall feel humble when we know more about their secret life— Dr. Rebecca Chia-Chun Hsu
The Hearth Conversation Another angle on the story
Why spend ten years looking for a single tree when Taiwan has nearly a billion of them?
Because finding the tallest one tells you something about what's possible in that landscape. It's a marker. Once you know where the extreme trees grow, you can understand the conditions that allow them to exist—the rainfall patterns, the soil, the protection from logging. That knowledge scales.
The lidar technology sounds like it should have made this easier. Why did it fail so badly?
Terrain. Taiwan is mountainous and uneven. When light bounces off a cliff face next to a tree, the algorithm can't tell the difference. It measures the cliff as part of the tree. You need human eyes to sort out what's actually a tree and what's just the mountain playing tricks.
So citizen scientists corrected 93 percent of the measurements. That's a stunning failure rate for the technology.
It's not a failure of the technology—it's a failure of thinking the technology could work alone. The real discovery was that you need both. Lidar gives you the bird's-eye view of the whole forest. Humans give you the ground truth. Together, they work.
What does it feel like to finally reach a tree you've been searching for across a decade?
Hsu described it as relief. But I think it's more than that. You've hiked for days through terrain so remote you're making your own path. You're exhausted. Then you climb 276 feet into the air and drop a tape measure, and the number confirms what you suspected. The tree is real. It's been there the whole time, waiting.
Why does the carbon storage matter so much?
Because these old trees are carbon vaults. They've been absorbing CO2 for a thousand years. If we underestimate how much carbon they hold, we underestimate how important it is to protect them. And if Taiwan's giant tree forests are as carbon-dense as researchers think, they might be some of the most valuable carbon storage on the planet.