Monitoring of Plant Species and Communities on Coastal Cliffs: Is the Use of Unmanned Aerial Vehicles Suitable?

Abstract

Cliffs are reservoirs of biodiversity; therefore, many plant species and communities of inland and coastal cliffs are protected by Council Directive 92/43/EEC (European Economic Community), and their monitoring is mandatory in European Union countries. Surveying plants on coastal cliff by traditional methods is challenging and alternatives are needed. We tested the use of a small Unmanned Aerial Vehicle (UAV) as an alternative survey tool, gathering aerial images of cliffs at Palinuro Cape (Southern Italy). Four photo-interpreters analysed independently the derived orthomosaic and plotted data needed for the monitoring activity. Data showed to be not affected by photo-interpreters and reliable for the prescribed monitoring in the European Union (EU). Using the GIS analysis tools, we were able to: (a) recognise and map the plant species, (b) derive and measure the area of distribution on the cliff of habitat and species, and (c) count Eokochia saxicola individuals and gather quantitative data on their projected area. Quality of the images represented the main constraint, but incoming technological improvements of sensors and UAVs may overcome this problem. Overall results support the use of UAVs as an affordable and fast survey technique that can rapidly increase the number of studies on cliff habitats and improve ecological knowledge on their plant species and communities.

Impacts of rock climbing on cliff vegetation: A methods review and best practices

“…Advantages include alleviating safety concerns and reducing impact to cliffs while sampling. Strumia et al (2020) used an Unmanned Aerial Vehicle (UAV) and structure‐from‐motion photogrammetry to conduct a population census of four chasmophyte species on a coastal cliff in southern Italy. Botanists successfully identified and measured the distribution of the cliff‐dwelling species (Strumia et al, 2020).…”

“…Strumia et al (2020) used an Unmanned Aerial Vehicle (UAV) and structure‐from‐motion photogrammetry to conduct a population census of four chasmophyte species on a coastal cliff in southern Italy. Botanists successfully identified and measured the distribution of the cliff‐dwelling species (Strumia et al, 2020). Similarly, Harrison (2020) used structure‐from‐motion techniques to construct high‐resolution, full‐color 3D point clouds of cliff face survey quadrats in an effort to create a consistent method for quantifying surface heterogeneity.…”

The distribution of climbing chalk on climbed boulders and its impact on rock‐dwelling fern and moss species

“…Furthermore, it is worthwhile to continue with an experimental approach by applying climbing chalk on unclimbed rock and study its in situ impact on rock‐dwelling species (besides bryophytes and ferns, also including lichens and flowering plants) on different rock types. Finally, recent advances in drone and imaging technology may allow for mapping and analyzing visible climbing chalk traces and vegetation health along climbing routes with hyperspectral imaging by means of unmanned aerial vehicles (Peng et al., 2020; Strumia, Buonanno, Aronne, Santo, & Santangelo, 2020; Zhang, Zhang, Wei, Wang, & Huang, 2020).…”

Assessment of the Potential Risk of Rock-Climbing for Cliff Plant Species and Natural Protected Areas of Spain

“…Thus, rock-climbing poses a potential threat, not only for the diversity of cliff vegetation but also for unique and threatened plant species (Larson et al, 2000). However, only a few local small-scale field studies exist on the effect of rockclimbing on cliff plant species (e.g., Clark and Hessl, 2015;Lorite et al, 2017;March-Salas et al, 2018;Schmera et al, 2018;Strumia et al, 2020), and these have not always been properly conducted (Holzschuh, 2016). Moreover, these isolated case studies did not state the criteria used to select study sites, leading to an unknown relevance of the sites for conservation purposes.…”