A novel method for cliff vegetation estimation based on the unmanned aerial vehicle 3D modeling

Abstract

The cliff ecosystem is one of the least human-disturbed ecosystems in nature, and its inaccessible and often extreme habitats are home to many ancient and unique plant species. Because of the harshness of cliff habitats, their high elevation, steepness of slopes, and inaccessibility to humans, surveying cliffs is incredibly challenging. Comprehensive and systematic information on cliff vegetation cover is not unavailable but obtaining such information on these cliffs is fundamentally important and of high priority for environmentalists. Traditional coverage survey methods—such as large-area normalized difference vegetation index (NDVI) statistics and small-area quadratic sampling surveys—are not suitable for cliffs that are close to vertical. This paper presents a semi-automatic systematic investigation and a three-dimensional reconstruction of karst cliffs for vegetation cover evaluation. High-resolution imagery with structure from motion (SFM) was captured by a smart unmanned aerial vehicle (UAV). Using approximately 13,000 records retrieved from high-resolution images of 16 cliffs in the karst region Guilin, China, 16 models of cliffs were reconstructed. The results show that this optimized UAV photogrammetry method greatly improves modeling efficiency and the vegetation cover from the bottom to the top of cliffs is high-low-high, and very few cliffs have high-low cover at the top. This study highlights the unique vegetation cover of karst cliffs, which warrants further research on the use of SFM to retrieve cliff vegetation cover at large and global scales.

The conservation impact of botanical drones: Documenting and collecting rare plants from vertical cliffs and other hard‐to‐reach areas

“…Many approaches have been developed to conduct UAS botanical surveys in hard‐to‐reach environments. For some researchers, a photogrammetry method has been used to create complete orthomosaics of the surface of interest to inventory specific species using a single pass (De Simone, 2020; Strumia et al., 2020) or double pass approach (Gao et al., 2024; Li et al., 2022). Others have conducted vertical transects to create checklists of floral components across elevational gradients (Zhou et al., 2021).…”

Use of the Drone for Cost-Effective Surveys In Natura 2000 Protected Areas: A Case Study on Monitoring Plant Diversity in Sicily (Italy)

“…They can also track changes in vegetation over time, providing essential data for assessing the impact of environmental changes and the effectiveness of conservation strategies [16]. The use of UAV photogrammetry has significantly enhanced the efficiency of 3D modeling and vegetation monitoring [17]. Furthermore, drone use contributes to democratizing science.…”