Taiwan, once known as Formosa, is home to one of Asia’s most remarkable natural wonders: ancient mountain forests filled with giant trees. Hidden within the island’s steep and rugged interior are Taiwania firs that rise more than 80 meters above the forest floor, making Taiwan one of the few places on Earth where truly enormous trees can thrive.
Since 2014, our group, the “Taiwan Tree Seekers,” has searched for, measured, and documented Taiwan’s largest trees. The team includes professional tree climbers, ecologists, geologists, and remote sensing specialists who work together to explore the island’s remote forests.
That long-term effort reached a major milestone in 2023, when we identified an 84.1-meter-tall (276-foot-tall) Taiwania fir (Taiwania cryptomerioides). Known as the “Heaven Sword of the Da’an River,” it is recognized as the tallest tree in Taiwan and throughout East Asia. The Indigenous Rukai people have a poetic name for these enormous firs: “the tree that hits the moon.”
Taiwan’s Mountainous Landscape
Taiwan’s geography helps explain why its forests can support such giant trees. The island covers approximately 36,000 square kilometers, an area similar to Switzerland. Much of Taiwan is mountainous, with 258 peaks higher than 3,000 meters. Its highest summit, Mt. Jade, rises to 3,952 meters.
This dramatic variation in elevation creates ideal conditions for an extraordinary diversity of plants. Approximately 5,000 plant species grow across Taiwan, occupying habitats that range from humid tropical rainforests near sea level to cold alpine tundra at the highest elevations.
Forests still cover about 60% of Taiwan, with an estimated 950 million trees spread across the island. Industrial logging between 1912 and 1991 destroyed much of the original primary forest. However, Taiwan’s steepest and most inaccessible mountains acted as a natural barrier, helping protect important areas of old-growth forest from logging.
The First Expeditions
Our organized search for Taiwan’s giant trees began in August 2014, when researchers from the Taiwan Forestry Research Institute (TFRI) entered the Cilan conservation area. The expedition focused on a famous group of giant Taiwania firs known as the “Chilan Three Sisters.”
Local communities had known about the three enormous trees for many years, but they had never been precisely measured or scientifically documented. Our survey found that the tallest tree reached 69.3 meters and had a trunk nearly three meters wide.
The Chilan Three Sisters gained international attention in 2017, when professional climbers from “The Tree Projects” in Australia traveled to Taiwan to photograph the trees in their entirety. Their work revealed the extraordinary scale of Taiwan’s ancient forests to audiences around the world.
A Difficult Search Near Great Ghost Lake
Inspired by the discovery, we shifted our focus to a more isolated area near Mt. Benya. Reports suggested that this region could contain one of Taiwan’s largest concentrations of Taiwania firs. It is located near Great Ghost Lake, a site considered sacred by Indigenous communities.
Reaching the area required four days of difficult hiking while carrying heavy scientific and climbing equipment. The expedition also exposed a major challenge in searching for giant trees from the ground: in old-growth forests with dense, multilayered canopies, visual estimates of tree height can be highly inaccurate.
During the expedition, we climbed a tree that measured 71.7 meters tall. However, the experience confirmed that traditional ground surveys alone could not cover enough of Taiwan’s remote forests. We needed a faster and more dependable way to identify potential giant trees across vast mountain landscapes.
Using LiDAR to Map Giant Trees
Searching through an estimated 950 million trees scattered across mountains, valleys, and remote wilderness areas was like looking for a needle in a haystack. To improve the search, we partnered with remote sensing specialists at National Cheng Kung University and began using LiDAR, or Light Detection and Ranging technology.
LiDAR is an advanced three-dimensional scanning method that sends laser pulses from an aircraft toward the landscape. By measuring how long each pulse takes to return, researchers can create detailed 3D models of the terrain and estimate the height of individual trees.
Citizen Scientists Join the Search
Taiwan’s steep, uneven terrain created another obstacle. Automated software frequently identified trees as being much taller than they actually were, particularly when the trees stood beside cliffs or abrupt changes in elevation.
Human observers were often better than algorithms at recognizing these geological “tricks.” In 2020, the project became a major citizen science initiative. Hundreds of Taiwanese volunteers began examining LiDAR profile images and helping researchers eliminate tens of thousands of false candidates.
The scale of the problem was significant. The automated system had incorrectly measured 93% of the trees it identified. Without citizen scientists reviewing the LiDAR data, researchers could have spent years traveling to trees that were far shorter than the maps suggested.
By the end of 2022, this collaboration had produced the “Taiwan Giant Tree Map,” documenting 941 individual trees taller than 65 meters.
Finding the “Heaven Sword”
In January 2023, during the Lunar New Year holiday, we used the Taiwan Giant Tree Map to investigate the strongest candidate for the title of Taiwan’s tallest tree. Reaching the tree required following a river for 20 kilometers and then completing two days of steep uphill hiking.
After climbers reached the crown, they lowered a measuring tape from the highest point of the tree to the ground. The final measurement was 84.1 meters.
The tree was named the “Heaven Sword of the Da’an River” and officially recognized as the tallest known tree in Taiwan and East Asia.
By early 2026, our continuing surveys had identified and climbed ten Taiwania firs taller than 70 meters. Two of these giant trees exceeded 80 meters in height.
Hidden “Temples of Giants”
The Taiwan Giant Tree Map also led researchers to exceptional concentrations of massive trees, which we call “temples of giants.” Near Mt. Benya, one hectare of forest contained 11 trees, each taller than 65 meters.
Ten years after our first expedition to the Great Ghost Lake region, we returned and encountered an even more remarkable landscape. Approximately 30 giant Taiwania firs were growing together in a dense, ancient “pure forest.” The immense cluster left the entire team speechless.
Giant Forests as Carbon Vaults
Taiwan’s giant forests are important for more than their beauty, rarity, and size. They may also play a significant role in storing carbon, preserving biodiversity, and supporting the health of the planet.
In 2024, we joined 15 citizen scientists to conduct a detailed study of the “Tao Tree” valley, home to Taiwan’s third-tallest tree. The goal was to measure how much carbon dioxide the forest removes from the atmosphere and stores in its wood.
The results were remarkable. Even without including the massive root systems, the forest’s total carbon density reached 1,384.5 Mg/ha.
This figure places Taiwan’s giant forests among the most carbon-dense ecosystems in the world, comparable to some of Earth’s best-known old-growth forests. The “trees that hit the moon” are more than towering natural monuments. They are also vital carbon stores and guardians of Taiwan’s mountain environment.
Source: www.sciencedaily.com