Marine litter on remote islands: Case study of beaches in Ishigaki and Taketomi Islands, Japan

Marine litter pollution has become a global concern due to its adverse effects on biodiversity and general negative influence on marine ecosystem services. Marine litter pollution of remote islands is currently understudied due to accessibility challenges. This study evaluated marine litter abundance and distribution on 15 beaches around semi-remote islands of Ishigaki and Taketomi, Japan. A total of 2161 items weighing 206.01 kg with average density of 0.15 items/m² were collected from nine beaches around Ishigaki Island while 1098 items weighing 73.62 kg with average density of 0.10 items/m² were collected from six beaches around Taketomi Island. Shoreline activities, reflecting the variety of human activities on the islands, were the major litter sources at 68.26 % and 90.44 % for Ishigaki and Taketomi islands, respectively. Litter items were dominated by plastics at >80 % for both islands while single-use plastics (SUPs), dominated by PET bottles and caps, constituted 39 % of total litter items on both islands. Clean coast, plastic abundance and hazardous indices employed to assess the beach quality were all within low to moderate levels. This study draws attention to marine litter pollution of remote islands, particularly by plastic items, and recommends effective management of SUPs as the necessary first step towards marine litter reduction.