From Source to Sea: UAV-Based Monitoring of Plastic Litter in Water and Coastal Environments

Plastic items are transported across interconnected freshwater, transitional, and marine environments. Tracking it across this continuum is essential for understanding its distribution and for designing effective mitigation strategies. The ADRIPLAST project addresses this need by developing a joint monitoring framework for plastic and microplastic pollution that combines in situ observations, laboratory analyses, and indirect monitoring approaches across aquatic systems. This study assesses unmanned aerial vehicles (UAVs) as a supplementary method for locating and mapping visible meso- and macroplastic debris in river, transitional, and coastal zones. High-resolution UAV images allow for identifying litter items, estimating their spatial density, and analyzing their distribution concerning land cover, vegetation, river shape, and coastal features. Multiple surveys also track temporal shifts in litter accumulation and redistribution, providing a dynamic perspective that a one-time sampling cannot provide. Beyond litter detection itself, UAV-derived products can guide field monitoring by flagging accumulation hotspots and priority sectors for ground surveys, sampling, and clean-up operations. Integrating UAV data with in situ observations improves spatial coverage, increases survey repeatability, and enables direct comparison across environments along the source-to-sea continuum—capabilities that are difficult to achieve through ground-based sampling alone. This approach supports the broader ADRIPLAST strategy, combining direct sampling and remote sensing to monitor meso- and macroplastics in freshwater, transitional, and coastal pilot zones. By integrating UAV-derived spatial data with field observations, it helps develop a more comprehensive and operational monitoring system—facilitating evidence-based management and pollution mitigation in the Adriatic–Ionian region.