Mapping and monitoring water hyacinth (Eichhornia crassipes ) in Sardinia (Italy) based on color morphology features using Unmanned Aerial Vehicles

Invasive aquatic alien plants cause significant negative impacts in many inland waters worldwide. Importantly, Eichhornia crassipes can cause significant harm, including covering the water surface, obstruction of river channels, and depletion of oxygen. These effects can significantly impact native biodiversity, farmland irrigation and water transportation. Despite several control efforts, outbreaks of E. crassipes are common in rivers and irrigation or draining channels on the west coast of central Sardinia (Italy) with negative ecological and economic impacts. This study was conducted within the framework of a project funded by the Sardinian Regional Authority (i.e. POR FESR Sardegna 2014–2020 ‐ Asse 1‐ Azione 1.1.3, “MARS ‐ Multiple Airdrones Response System”). The objective of this study was to develop an efficient method, using Unmanned Aerial Vehicles (UAVs), to map and monitor the change in cover of Eichhornia crassipes in the invaded area in Sardinia (Italy) to a more refined quantification of the phytomass for planning control interventions. The species was monitored in the same site from late winter to spring (2018‐2019) using RGB, Red Edge and NIR cameras, installed on board of a UAV (Phantom 4 pro, DJI). The high‐resolution imagery, obtained from the different sensors, was evaluated in order to study the temporal variability, the covered area, and the distribution of the invasive plant. All images were analyzed using a pixelbased approach, for the classification of aquatic overlapping plants and partial obstruction in the water surface. As a preliminary result, we present the mapping of E. crassipes, highlighting the costeffectiveness and replicability of this approach to detect the presence of this invasive alien species in aquatic environments. This method could be applicable to other waterways and offers the potential for the early detection of infestations of floating aquatic species where the applicability other survey methods might be difficult.