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 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.