Researchers have identified Taiwan's tallest tree, a towering Taiwania cryptomerioides that reaches 84.1 metres, higher than a 20-storey building. Named Heaven Sword of the Da’an River, this ancient conifer is estimated to be 1,000 years old and serves as a critical carbon sink and habitat for diverse species.
Mapping Taiwan's forest giants
Dr Rebecca Hsu, assistant researcher at the Taiwan Forestry Research Institute, has led a team for over a decade to map and measure Taiwan's tallest trees. Using aerial scans and ground expeditions, they catalogued these giants. Her study, published in Frontiers in Forests and Global Change, revealed Heaven Sword as the tallest, surpassing previous records.
“In one tree, every species has their preferred location,” says Hsu. “Every metre the temperature, the wind, the sun, the light is different.” The tree hosts ferns, flying squirrels, owls, rhododendrons, lichens, and the rare orchid Bulbophyllum ciliisepalum at various heights.
Height as an engine for biodiversity
Height is not just a record; it fosters biodiversity, says Chris Swanston, director of science for Save the Redwoods League. “In a single 2,000-year-old tree you could have dozens of generations of species developing ecologically within the canopy,” he explains. “Their branches aren’t just branches like normal trees, they’re neighbourhoods.”
Older trees also combat the climate crisis by absorbing carbon. However, they face perils: wildfires, droughts, and extreme weather. In California, an estimated 17.6% of large giant sequoias have burned since 1984, mostly in 2020 and 2021. In Tasmania, 2019 fires killed at least 17 of the state's largest trees.
Threats from climate change
Climate change exacerbates droughts and pushes moisture-laden clouds higher, while typhoons in Taiwan have strengthened by 35% over four decades, threatening trees on steep slopes. Researchers found that tall trees in Taiwan had a death rate of about 4% to 5% over the past decade, a finding Hsu calls “beyond our imagination”.
Technology and challenges in measurement
Lidar technology, used in driverless cars, aids forest mapping but has limitations. In Hsu's study, 93% of lidar tree measurements reviewed by citizen scientists were inaccurate due to steep terrain. Matheus Henrique Nunes of the University of Maryland notes that accuracy varies with deployment method; airborne lidar is less precise than backpack-mounted systems.
Nunes believes more tall trees remain undiscovered in the Amazon. A 2019 airborne lidar survey identified an 88-metre tree but covered only 0.05% of the Amazon. “I would not be surprised if we had trees in the Amazon that are more similar in height to the dipterocarps of Borneo, reaching 100 metres,” he adds.
The old-fashioned climb
To reach Heaven Sword, researchers hiked for days and crossed a swollen river. They measured the tree by climbing it with ropes and ascenders. For the first 45 metres, the trunk is branchless. Steve Pearce, naturalist and photographer, describes the tree's evolution: “It probably grew up in an environment where there were other tall trees around it and really raced for the sky.”
The top of the tree, though sparse, is healthy and still growing. At over 80 metres, climbers hear a gentle “whirring or whooshing sound” as wind brushes through the leaves. Hsu attributes the tree's height to luck: “Nearby they have many fallen trees. So the surviving trees, they depend on their luck. I think they are lottery winners.”
Future research and conservation
Hsu's next project explores why Taiwania seedlings thrive after landslides. She hopes her work serves as a record: “I want to send these great trees’ images to the public. To let people know how lucky we are to have these beautiful trees.”
