Taiwan's giant trees are under threat: experts - Taipei Times

• By Wu Po-hsuan and Jonathan Chin / Staff reporter, with staff writer

Giant trees deep in the mountains of Taiwan proper are a vastly undervalued carbon sink, and could face extinction in the next two centuries, a team of Taiwanese forest surveyors who found the nation's tallest tree said on Friday.

Taiwan Champion Trees, a group consisting of arborists, spatial scientists, geologists and mountaineers, in 2023 discovered the 84.1m-tall Taiwan fir, or Taiwania cryptomerioides, near the source of the Daan River (大安溪) in Shei-Pa National Park (雪霸國家公園). It is currently the tallest known tree in Taiwan and the tallest recorded in East Asia.

In a news release published in Science Media Center Taiwan on Friday, the team said finding Taiwan's tallest tree required innovative approaches, including Light Detection and Ranging (LiDAR) and crowdsourced research.

Photo courtesy of Taiwan champion trees

Old-growth forests of giant trees are mostly found in the nation's most deep and forbidding mountain ranges, which cannot be easily surveyed, it added.

National Cheng Kung University geomatics professor Wang Chi-kuei (王驥魁), a principal team member, said the group used government LiDAR surveys and algorithms to identify 57,065 possible giant trees out of a total of 950 million trees in Taiwan proper.

The rough terrain made instrument readings and algorithms highly inaccurate, and the group had to recruit hundreds of citizen scientists on the Internet to double-check the data, he said.

They found that 93 percent of the algorithm-derived tree heights were incorrect, Wang said, adding that the process narrowed the candidates down to 941 trees.

Taiwan Forestry Research Institute assistant researcher Rebecca Hsu (徐嘉君), another co-founder, said an expedition spent two days scaling mountains of Shei-Pa National Park to find the tree, which was measured by tape.

This fir is the tallest tree known to exist in East Asia, she said.

In 2024, the group explored a four-hectare old-growth forest on Mount Tao (桃山), a mountain of the Syueshan Range (雪山山脈) spanning Taichung and Hsinchu County.

Volunteers estimated that this forest boasted a carbon storage of 1,324 tonnes of carbon per hectare — one of the densest in the world, she said.

In comparison, the giant trees of Tasmania in Australia store 1,867 tonnes per hectare, she added.

The figure likely grossly undercounted the Mount Tao forest's carbon density, as it was calculated utilizing the Forestry Research Institute's mathematical formula, which did not include the capacity represented in the trees' roots, she said.

Wang said the project found alarming signs regarding the survival of Taiwan's ancient trees.

Comparing the project's two sets of data, which were recorded about a decade apart, the team found that 5 percent of the 941 giant trees identified had died from typhoons, landslides and other causes, he said.

At this rate, ecologically important giant trees would die out in the next couple of centuries, he added.

The group's findings were published the same day in the online journal Frontiers in Forests and Global Change.