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

Cliffs are reservoirs of biodiversity; therefore, many plant species and communities of inlandand 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 cliffby traditional methods is challenging and alternatives are needed. We tested the use of a smallUnmanned Aerial Vehicle (UAV) as an alternative survey tool, gathering aerial images of cliffsat Palinuro Cape (Southern Italy). Four photo-interpreters analysed independently the derivedorthomosaic and plotted data needed for the monitoring activity. Data showed to be not affected byphoto-interpreters and reliable for the prescribed monitoring in the European Union (EU). Using theGIS analysis tools, we were able to: (a) recognise and map the plant species, (b) derive and measurethe area of distribution on the cliff of habitat and species, and (c) count Eokochia saxicola individualsand gather quantitative data on their projected area. Quality of the images represented the mainconstraint, but incoming technological improvements of sensors and UAVs may overcome thisproblem. Overall results support the use of UAVs as an affordable and fast survey technique that canrapidly increase the number of studies on cliff habitats and improve ecological knowledge on theirplant species and communities.