Coastal and marine plastic litter monitoring using remote sensing: A review

Abstract

Plastic pollution in coastal and marine areas is an ongoing environmental concern in the world. Despite its growing concern worldwide, there is a knowledge gap in terms of its detection and quantification of spatial distribution patterns. In this review paper, we investigated the existing trends in monitoring marine and beached (macro and meso) plastic debris using remote sensing techniques. Marine plastic debris monitoring using remote sensing data is highly complex, partially due to the constraints in spatial and spectral resolutions as well as due to the differences in surface reflectance properties of different polymers. Modern remote sensing with high-quality data, including airborne, spaceborne, and data taken from an unmanned aerial vehicle (UAV), have revolutionized marine litter mapping. UAV platform offers a promising and cost-effective way for mapping both floating and beached marine plastic debris compared to data from other platforms. Automatic and manual delineation for mapping marine plastic litters can be applied depending on the objective of the study. For assisting beach clean-up processes, automatic detection of marine plastic debris is enough for locating the worksite. For detailed characterization of debris, including type, size and material, manual delineation of high resolution images is necessary. More accurate mapping of marine plastics can be achieved by developing detailed spectral libraries with material level details and launching dedicated sensors for marine litter mapping in the future. Challenges exist in mapping submerged marine plastics, plastic materials conglomerated with biomass and unaccounted for beached marine litter buried along the coasts due to accretion and erosion.