Some trees in Taiwan are so tall the Rukai people call them “The tree that hits the moon.”

Researchers say Taiwan’s steep, remote mountains have protected old-growth forests with hundreds of giant Taiwania firs, including an 84.1-metre tree now recognised as the tallest known in East Asia.

The finding comes from a long-running effort by the “Taiwan tree seekers”, a group formed in 2014 that includes professional tree climbers, ecologists, geologists and remote sensing specialists. In 2023, the team identified an 84.1-metre Taiwania fir, Taiwania cryptomerioides, which is now recognised as the tallest tree in Taiwan and East Asia.

Taiwan’s geography has helped these giant trees survive. The island covers about 36,000 square kilometres and has 258 peaks above 3,000 metres. Its highest mountain, Mt. Jade, reaches 3,952 metres. Researchers say this range in elevation supports about 5,000 plant species, from tropical rainforest near sea level to alpine tundra at the highest elevations.

About 60 percent of Taiwan remains forested, with an estimated 950 million trees across the island. Industrial logging from 1912 to 1991 removed much of the original primary forest, but steep and inaccessible terrain protected some old-growth areas.

The search began with an expedition in August 2014, when researchers from the Taiwan Forestry Research Institute entered the Cilan conservation area to investigate a famous group of giant Taiwania firs known as the “Chilan Three Sisters”. Local communities had known the trees for years, but they had not been carefully measured or scientifically documented.

The survey found the tallest of the three stood 69.3 metres high and had a trunk nearly 3 metres wide. In 2017, professional climbers from “The Tree Projects” in Australia photographed the Three Sisters in full, drawing wider attention to the scale of Taiwan’s forests.

Researchers then turned to a more isolated area near Mt. Benya, close to Great Ghost Lake, after reports suggested it could hold Taiwan’s largest concentration of Taiwania firs. Reaching the area took four days of hiking with heavy equipment.

That trip exposed a problem with ground searches in dense old-growth forest. Researchers climbed a 71.7-metre tree, but found visual estimates alone were unreliable in forests with multi-layered canopies.

To speed up the search, the team partnered with remote sensing specialists at National Cheng Kung University and started using LiDAR, a 3D scanning method that uses laser pulses from aircraft to model terrain and estimate tree height.

Even then, Taiwan’s steep terrain caused problems. The researchers said automated software often overestimated tree height near cliffs and sharp changes in elevation. In 2020, hundreds of Taiwanese citizens joined the project to review LiDAR profile images and help remove false candidates.

The researchers said the automated system had incorrectly measured 93 percent of the trees it identified. By the end of 2022, the work had produced the “Taiwan Giant Tree Map”, documenting 941 trees taller than 65 metres.

In January 2023, during the Lunar New Year holiday, the team used the map to check its strongest candidate for tallest tree. The route involved following a river for 20 kilometres and then two days of steep uphill hiking. Climbers dropped a measuring tape from the crown to the ground and confirmed the height at 84.1 metres.

The tree was named the “Heaven Sword of the Da’an River”. By early 2026, the researchers had identified and climbed 10 Taiwania trees taller than 70 metres, including two above 80 metres.

The map also led the team to dense pockets of giant trees they call “temples of giants”. Near Mt. Benya, one hectare of forest held 11 trees taller than 65 metres. Ten years after the team’s first trip to the Great Ghost Lake region, they returned and found about 30 giant Taiwania firs growing together in a dense and ancient “pure forest”.

The researchers also studied how much carbon these forests store. In 2024, they worked with 15 citizen scientists in the “Tao Tree” valley, home to Taiwan’s third-tallest tree, to measure how much carbon dioxide the forest removes from the atmosphere and stores in its wood.

They found the forest’s total carbon density, excluding the root systems, reached 1,384.5 Mg/ha. The researchers said that puts Taiwan’s giant forests among the most carbon-dense ecosystems in the world.

The findings were published in Frontiers in Forests and Global Change by Rebecca Chia-Chun Hsu, Chi-Kuei Wang and Chung-Cheng Lee.

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