Use of Drone Remote Sensing to Identify Increased Marine Macro-Litter Contamination Following the Reopening of Salgar Beach (Colombian Caribbean) during Pandemic Restrictions

This study involves an integrated and innovative approach employing high-frequency monitoring, which is rare in studies focusing on solid waste on beaches. Eight drone flights were performed over a tourist beach in the Colombian Caribbean to achieve two main objectives: (i) to quantify the changes in marine macro-litter (>2.5 cm) density, focusing on the differences between the period when the beach was closed due to the COVID-19 pandemic and the subsequent reopening period; and (ii) to map changes in the abundance of marine macro-litter on the coast, with an emphasis on single-use waste. The number of items of litter on the beach increased 9-fold between the closed and reopening periods, and the main items found were crisp/sweet packets (n = 304, 13% of the total waste), plastic cups (n = 248, 11%), and expanded polystyrene (food containers) (n = 227, 10%). The factors contributing to the presence and distribution of the marine macro-litter were tourists, the use of the beach, and offshore wind direction. The results revealed that Salgar Beach can be considered a marine macro-litter exporter since waste is incorporated into the longshore current and redistributed either to nearby beaches or the ocean. This study emphasizes the potential for using drone images in an integrated approach to monitoring the presence of marine macro-litter as well as the efficiency of programs for combatting litter at sea.