The Tree Seekers (找樹的人), formed in August of 2014, searches for the tallest trees in Taiwan. The Tree Seekers are forest canopy scientists and tree climbers who use their climbing skills to search for tall trees in Taiwan. The group has grown through adding members who bring new expertise to further the mission.
Taiwan (formerly known as Formosa) is an island
in the southwest Pacific with an area of 36,000 km2. Active
orogenesis has built up an extensive mountain system on the island, including 258
peaks over 3000 m in elevation, with the highest reaching 3952 m. The dramatic
topography hosts a wide range of vegetation, from alpine tundra to tropical
rainforests. Approximately 60% of the island is forested with over 950 million
trees. Extensive logging from 1912 through 1991 significantly reduced the island’s
primary forests, but it is Taiwan’s rugged mountainous terrain which has preserved
significant tracts of old-growth forest.
Early Expeditions
Three Chilan Sisters (棲蘭三姊妹)
The Tree Seekers’
first expedition to find tall trees was inspired by information shared long ago
by a retired forester. The logging road leading to the area had been abandoned decades
previously. It took two expeditions, first in July then in August of 2014 to
locate the giant Taiwania (Taiwania
cryptomerioides). The team successfully climbed the second tallest tree,
and measured its height at 67 m. The tallest tree was later measured in 2017 at
69 m. These trees are named the Three Chilan Sisters. This expedition was featured
in the fall 2015 issue of What’s Up magazine.
Mt. Benya (本野山、平野山)
The second expedition was in March of
2016. The team went to a remote region known for having the largest population
of Taiwania firs. It took four days of hiking to reach the area, Mt. Benya (22.8882
N, 120.9013 E), located near a well-known aboriginal sacred site, Great Ghost
Lake (22.869 N, 120.8616 E). However, the expedition team could not identify
the tallest tree from the forest floor due to the great number of giant
Taiwanias, making it difficult to compare the height of the trees from below. The
team selected and climbed two trees based on experience. The second tree climbed
was 71.7 m high. The tree was named Twin Towers since the tree has two leading
trunks.
The Mysterious Great Ghost Lake
Danda (丹大)
In March of
2017, the team went to the Danda area in central Taiwan, a traditional
territory of the Bunun people. There, they discovered the tallest spruce tree found
on the island so far: a Taiwan spruce (“Songyunyun,” 62.4 m, Picea morrisonicola). The team also climbed
a nearby Taiwania (Ironman, 65.4 m) near the tallest spruce. Because there is
an abundant population of Taiwania in the Danda area, the team returned in January
of 2018 to search for giant trees, and climbed a 72 m high Taiwania (Danshi).
Danshi Giant 丹詩神木, 72m (23.798 N, 121.1799 E)
LiDAR Data Added
to the Search for Tall Trees
The Tree Seekers realized that it was not
possible to find the tallest tree on the island using the previous methods of interviews
and ground searches on foot. So, they consulted LiDAR data from the government.
However, they discovered LiDAR tends to overestimate tree heights in Taiwan’s
extremely mountainous terrain. In 2018, LiDAR experts from National Cheng Kung
University joined the team, and the team began using airborne LiDAR data to
search for tall trees on the island.
Qing Trail Giants Forest 清八巨木森林
In February of 2019, the Tree Seekers embarked
on a 9-day expedition to visit a legendary forest found by Bunun elders 11
years previously. The trip, over a decade earlier, had not left many clues to
follow. The team used LiDAR imagery to search for the giant tree forest rumored
to be near the abandoned historical Qing trail built in 1875. LiDAR data
successfully lead the team to the majestic forest, where they measured four
giant trees using a drone, including a tree that Bunun elders had found 11
years previously.
LiDAR image that lead the team to Qing Trail
Giants Forest
Nankeng Stream Giant (南坑溪巨木)
In September of 2019, the
Tree Seekers found another Taiwania that broke the previous height record. The
tree was located from a forester interview and LiDAR data. The tree is near
logging road No. 230, in the watershed of the major Daan River in central
Taiwan. The tree lies along the Xueshan Range and is 72.9 m tall, named after
nearby upstream Nankeng Stream.
The Tao Tree (桃山神木)
Building on their experience
with each successive giant tree search expedition, the Tree Seekers team found
that LiDAR measurement accuracy is related to the steepness of the slope where the
trees grow. The flatter the slope, the higher the accuracy of the tree height
predicted from LiDAR. Based on a preliminary report from the Taiwan Giant Tree Map,
the team focused on a tree with height measured by LiDAR of 76.38 m, growing on
a relatively flat 10% slope in a mountainous area.
It took three expeditions,
from March to June of 2020 to locate the
giant tree. The tree was finally climbed and measured in August of 2020. Tape
measurement of the tree height was 79.1 m. It remained the tallest tree on the
island until 2022. The tree was named after a nearby peak, Mount Tao.
Shihtzu Giant (西施神木)
Shitzu Giant was named
after an ancient beauty from Chinese history, as the forester who discovered
the tree was struck by its grace at first sight. The tree’s location is very close
to Nankeng Stream Giant. The team climbed this tree in August of 2021, measuring
the height with a tape at 73.7 m.
Kaalang Giant (卡阿郎巨木)
Kaalang Giant is located in the upstream reaches
of Taiwan’s longest river, the Zhuoshui River. The Tree Seekers found this tree
in March of 2022, in Bunun traditional territory. In the Bunun language “kaalang”
means “crabs.” The tree is located near sacred Qicaihu Lake (七彩湖) of the Bunun. Since
the top of the tree top includes a section of dead branches, the team measured
the final section using a 3 m fishing pole and drone photography.
Qicaihu Lake in snow
Behuy Giant (風之巨木)
Behuy Giant is also a Taiwania fir, like
other giant trees that exceed 70 m in height. The name “Behuy” comes from the language
of the Atayal people meaning “winds.” On the day the Tree Seekers followed the
river Tqzing (Atayal language) to its source, they enjoyed the winds in the
river valley. The tree is located in Atayal traditional territory and was measured
using the same method as Kaalang Giant.
The heaven Sword of Da'an river (大安溪倚天劍)
In 2023 January, during the Lunar new year,
the Tree Seekers set off an expedition to find the tallest tree candidate from the
Taiwan Giant Tree Map. The first day was a 20 km river trace along the Daan
river, followed by two days of hiking to reach the tree. LiDAR measurement was 79.9
m, while tape drop measurement from climbing the tree was 84.1 m. So far, The heaven sword remains the tallest tree in Taiwan.
LiDAR image of The heaven Sword
Tree Portraits
In 2017 and 2022, tree project members, Jennifer Sanger and Steven Pearce from Australia visited Taiwan to shoot giant tree portraits. Jen and Steve are from Tasmania, a place known for big trees and are highly experienced in climbing and photographing big trees. The first trip took them three weeks to complete the portrait of the Three Sisters, which became very popular after being published in Taiwan. In 2022 the team spent a week making a portrait of Tao tree including two days of tough hiking. Tao tree is the 11th tallest tree of the tree project’s collection of portraits.
 Three Sisters Portrait
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 The Tao Tree Portrait
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 The Heaven Sword
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The Tao Tree Portrait team in 2022
Taiwan Giant Tree Map
Since Taiwan is very mountainous, most tree height measurements using LiDAR are over estimated. This is because many trees grow on cliff edges, and their heights are estimated vertically to the cliff base by LiDAR. In January of 2021, the Tree Seekers uploaded 71,751 records of trees over 65 m high and engaged the public to help identify the locations of giant trees. Over 220 thousand crowd sourced tasks were completed within one month, resulting in the identification of 4,736 giant tree candidates. LiDAR experts then worked on these results, publishing data for 941 giant trees exceeding a height of 65 m at the end of 2022. Among these 941 giant trees, 202 trees over 70 m high and only 27 trees are over 75 m high.
Distribution of giant trees, red indicates trees
taller than 75 m
Other Projects
Removal of
Cables from Trees
Beginning in 2021, the Tree Seekers began removing
cables left on giant tree trunks during the logging era. The team uses an electric
grinder to cut off steel cables from the tree trunks. So far more than ten
trees have been released from theses potentially lethal logging cables.
The Tree Seekers hold a removed steel cable under the rescued tree
Cable scars on the tree
Quantifying
illegal logging using airborne LiDAR data
In 2000, there was a surge in
poaching medicinal mushrooms from cypress trees (Cunninghamia lanceolata var. konishii), as people
believe these mushrooms can cure cancer. The mushrooms grow inside
hollow trunks of giant cypresses, leading to the cutting down of many big trees
in remote mountain areas. The Tree Seekers inspected forests affected by illegal
logging over several expeditions. The team used LiDAR imagery along with field
observations to identify areas of illegal logging in mountain areas.
Mushroom hunters keep returning to poach mushrooms
Carbon Density
Inventory
To determine the carbon density of Taiwan’s
primary forests, the Tree Seekers along with 15 citizen scientists returned to the
Tao Tree valley for a 4-hectare forest inventory in August of 2024. During a one-week
workshop, volunteers measured the diameter of 180 giant trees, 80 fallen logs, surveyed
50 sample lines, and collected soil samples for analysis.
LiDAR image of the Tao tree valley
Extreme Weather
Events and Disappearing Giant Trees
By comparing LiDAR images of giant trees in Taiwan from 2010 and 2021, the Tree Seekers found that approximately 4% of the giant trees had disappeared. Considering that most giant trees are nearly one thousand years old, the recent mortality rate is surprisingly high. This may be due to an increase in extreme weather events. The research team is working to understand the reasons behind the disappearance of these giant trees.
 LiDAR image of a giant tree 2010
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 The tree disappearance by 2023
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See also
Taiwan giant tree map, https://no1tree.tw/
首留言，本野山的巨木林真的好壯觀。
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