The journey of finding the tallest tree in Formosa Taiwan

Introduction Giant trees are ecologically critical ancient organisms, and Taiwan is a key location for those exceeding 80 m in height. This study aimed to identify the tallest tree in Taiwan using a novel, multi-stage approach. Methods An island-wide Canopy Height Model (CHM) derived from Airborne Laser Scanning (ALS) initially identified 57,065 local maxima. To account for height overestimations caused by steep topography, tree profile images were evaluated by 372 crowdsourced volunteers, reducing the dataset to 4,736 candidates. These were further refined through expert 3D point cloud analysis, resulting in a verified map of 941 trees taller than 65 m. Final validation involved in-situ tape-drop measurements via tree climbing. Results Fieldwork in 2023 confirmed a Taiwania cryptomerioides in the Sheshan range as the tallest tree in Taiwan. With a verified height of 84.1 m, this specimen is recognized as the tallest known tree in East Asia. The study successfully cataloged 941 giant trees across the island. Discussion The integration of ALS data, crowdsourced visual inspection, and expert point cloud analysis effectively mitigates terrain-induced errors in tree height estimation. This comprehensive inventory provides a vital baseline for the monitoring and conservation of ancient forest ecosystems in topographically complex regions.