Seeing the Forest and the Trees—Taiwan’s Tree Researchers and Forestry Surveyors

Rebecca Hsu is fascinated by the epiphytic plants that grow in the forest canopy. (photo by Lin Min-hsuan)

Rebecca Hsu is fascinated by the epiphytic plants that grow in the forest canopy. (photo by Lin Min-hsuan)

How tall is a tree? How many leaves does it have? And how many trees are there in a forest? Almost all children ask such questions in their stage of inquisitive wonder.

After growing up, you aren’t likely to encounter these questions in daily life unless you’re a forestry professional. But when you do get a chance to go into a forest, do questions like these still prick at your curiosity: How do you go about measuring the forest? And what do the resulting figures really mean?


Forestry measurements can help to answer such questions, and they also offer a way of becoming acquainted with the forest. Researchers make use of all available means—including measuring tools, scientific instruments, mathematical formulas and statistical sampling—to under­stand the forest. Numbers are a language that can describe nature, and survey data provide basic information about a forest. People can draw from this well of knowledge both to manage forests and to learn how to coexist with nature.

Looking for the tallest tree

How does one know or describe how tall a tree is? For instance, Taiwania (Taiwania cryptomerioides) is the tallest tree species in East Asia, and Taiwan’s indigenous Rukai people describe it as the tree that “knocks the moon.” Rebecca C.C. Hsu of the Taiwan Forestry Research Institute takes a different approach, measuring the height of these trees by climbing them.

Hsu is a forest ecology researcher with a special interest in the epiphytic plants that grow in the forest canopy, so getting up into trees is essential for her work. At first, she adopted her predecessors’ methods of collecting plants and seeds, driving L-shaped spikes into trees to ascend them. Later she adapted rock-climbing techniques to climbing trees.

Apart from her work on epiphytes, Hsu also has an interest in finding giant trees. Since she was always hanging out in treetops, she began to wonder how tall the trees could grow, and what factors influenced their growth.

Early in her quest to find Taiwan’s tallest trees, she mostly worked on word of mouth from forestry professionals or used a clinometer and trigonometric calculations to make ­estimates. Nowadays she is using more advanced devices and techniques. She works with Wang Chi-kuei, a professor in the Department of Geomatics at National Cheng Kung University, and his team, applying an algorithm to data gathered by an islandwide airborne LiDAR (light detection and ranging) survey program commissioned by the Ministry of the Inter­ior following Typhoon Morakot in 2009. The technique takes advantage of the ability of laser beams to penetrate the forest canopy to chart out a model of the height of the treetops and the topography of the ground beneath. After using the ­LiDAR data to pinpoint areas with old trees, Hsu then goes with an exploration team to check out the sites in person. In 2019, they discovered the tallest Taiwania tree yet found in Taiwan. Measuring 72.9 meters, the tree is loc­ated on the upper reaches of Nankeng Creek on Mt. Daxue.

Hsu and her team also successfully scaled a 46.4-­meter giant camphor (Cinnamomum camphora) in Nantou ­County’s Shenmu Village, and got it listed on the Monumental Trees website as the world’s tallest known camphor tree.

Once you’ve measured the tallest trees, then what? “Actually, a lot of scientific research emerges from researchers’ curi­osity,” says Hsu. But curiosity can elicit great resonance. In 2017 she launched a project to make isometric photos of Taiwania specimens. She invited a photographic team from Tasmania-­based The Tree Projects to come to Taiwan and take isometric photos of three large trees known as the “Three Sisters,” located along Forest Route 170 in the Mt. Qilan Forest Area. The Three Sisters are at least 800 years old. One of them rises to 69.5 meters, about the height of a 23-story building. Seeing the trees fully revealed in photographs, many observers remarked on how few people even know that Taiwan has trees this beautiful, recalls Hsu. “It fosters a sense of pride and identity.” The project is spotlighting the beauty of Taiwan’s forests and raising awareness of forest conservation. It’s one more fruit of the search for big trees.

A tree creates its own ecosystem, and the scenes one can observe when climbing one are quite different from the view from the ground. (photo by Lin Min-hsuan)

A tree creates its own ecosystem, and the scenes one can observe when climbing one are quite different from the view from the ground. (photo by Lin Min-hsuan)

Forest resources survey

Cut to Hsinchu County, where we’re following the motor­cycles of Lee Shenming and Luo Shih-fan of the Forestry Bureau’s Zhudong Work Station as they wind their way through the mountains to the woodlands of Mt. Wuzhi. According to GPS data, we are approaching the sample plot, and Lee and Luo look everywhere for trail markers left by the previous surveyors. With much effort, they finally locate the center of the plot, where there is a planted stand of Taiwan fir (Cunninghamia konishii). Lee and Luo need to sample 50 trees for the survey. Using maps made by earlier teams, they find the sample trees and take new measurements of their dia­meters and heights. They then store the new information in the trees’ RFID tags. If any of the trees has fallen, this is recorded too.

Lee and Luo are taking follow-­­up measurements for Taiwan’s fourth national survey of forest resources. By documenting basic informa­tion such as the land area of existing forests, the stock of growing timber, and trees’ periodic growth increments, these surveys allow national forestry policy to be based on more reliable information.

There have been four islandwide surveys of forest resources, explains Huang Chyun-shiou, director of the Forestry Bureau’s Forest Planning Division. The goals of each survey have varied according to society’s needs. Forest resources were first surveyed in 1956, when postwar Taiwan desperately needed economic revival. With US assistance, an inventory was made of forest areas, wood volumes, and usable resources. The second survey was carried out in 1977, when Taiwan was transitioning from an agricultural to an industrial society. Its focus was on determining what land was still available for development. The third survey took place in 1993, when the island’s economy was already largely based on manufacturing and services. With universal edu­cation and rising incomes, an ethos of forest conservation was taking hold. Along with newly cataloging the forests’ animals and plants, that survey put more emphasis on the varied uses of forests, including their recreational value.

The fourth survey began in 2008, more than a decade after the previous one. By that time the available data no longer truly reflected Taiwan’s forest resources and land use. Also, growing international concern about shrinking forests and atmo­spheric warming—as expressed, for example, in the Kyoto Protocol, which affirms forests’ role in reducing greenhouse gases—highlighted the import­ance of both forest resource monitor­ing systems and the sharing of forestry data as a responsibility for every nation. Although Taiwan is not a member of the United Nations, it is still a part of the global community. Thus the Forestry Bureau launched its fourth survey of Taiwan’s forest resources, with a new focus on evalu­ating woodlands’ capacity as a carbon sink (their ability to absorb carbon dioxide) and establishing a long-term monitoring system for forest resources.

The need for forest management

Islandwide surveys of forest resources require enorm­ous inputs of time and money, and grueling effort by surveyors. But what can be done with the huge amount of data that such surveys yield? What do the numbers show?

The fourth survey found that forests covered 60.7% of Taiwan’s land, an increase of 2.2 percentage points over the 58.5% recorded in the previous survey. Landslides caused by Typhoon Morakot in 2009 destroyed large areas of forest, reducing the size of nationally owned forests, Huang explains, but total forest area still grew by more than 80,000 hectares thanks to reforestation in the foothills. As a consequence of Taiwan’s aging population and labor shortages, much farmland there has been abandoned to nature, becoming second-growth forest. What’s more, when Taiwan joined the World Trade Organization, govern­ment agri­cultural agencies promoted the reforest­ation of lowland areas. Both were important factors behind the increase in Taiwan’s forest coverage.

Globally, forests are disappearing at a rapid rate. And although the forest survey shows that Taiwan’s forest cover­age has grown and its forest resources have increased, that growth obscures some harsh realities. “As much as 60% of the island is covered by forests, but much of that wooded land can’t be managed productively,” Huang explains, breaking down some of the myths regarding forests in Taiwan. “For instance, the accessibility of forest land deep in the Central Mountain Range is low and the costs of logging there are high. Taiwan’s forest area per capita stands at only 0.092 hectares. The figure shows that Taiwan is far from self-sufficient in forest resources.”

Li Shengming uses a telescopic pole to measure the height of a tree. (photo by Lin Min-hsuan)

Li Shengming uses a telescopic pole to measure the height of a tree. (photo by Lin Min-hsuan)

Carbon sequestration

The forest coverage rate of each nation has different implications for action depending on the situation. “In Taiwan, the focus of forestry management should be on bolstering the health of existing forests and raising their capacity as carbon sinks,” says Huang Chyun-shiou.

Carbon sink capacity is a measure of how forest plants absorb carbon dioxide (CO2) through photosynthesis and fix it in vegetation and the soil, thus reducing the concentration of CO2 in the atmosphere. It may sound academic, but Huang quickly brings the subject down to earth: “It may be hard to connect life in Taiwan to carbon sinks, but globally 20% of growth in CO2 emissions comes not from the burning of fuel by factories and automobiles, but from the loss of forests.” In 2019, major forest fires in Australia and California put alarming amounts of CO2 into the atmosphere.

A more common misconception is that most people believe that cutting down trees is inevitably bad for the environment. “Wood from forests being used for furniture or other items is a form of carbon sequestration,” Huang explains. “Where the old tree grew, a new seedling will be planted that will continue to absorb CO2. It’s an example of sustainable use. That's why we advocate that people use more sustainable materials like wood.”

In terms of lumber production, Taiwan is far from self-sufficient, but that doesn’t mean we should simply rely on imports. “Taiwan’s forestry policies ought to put a greater focus on forestry management, including the proper management of lumber plantations,” says Huang. “To revive national natural resources, we need to make more efficient use of the land.”

Forests are among Taiwan’s most important natural resources, and an ethos of forest conservation is already widely established among the island’s people. Looking ahead, says Huang, “Taiwan must make better use of re­cyclable lumber to help reduce our carbon footprint.”