Abundance and characteristics of anthropogenic litter along the Tanzanian shores of the African Great Lakes: including volunteer involvement, outreach, and stakeholder engagement in a holistic approach.

Environmental pollution due to mismanaged anthropogenic litter is one of the most pressing issues facing the world today. To reduce existing environmental burdens of litter, clean-up events have increased in popularity. Here, we report on the results of the Clean Shores, Great Lakes project, in which we conducted 69 volunteer-based clean-ups along the Tanzanian shorelines of the African Great Lakes (Victoria, Tanganyika, and Nyasa (also known as Lake Malawi)). A total of 5483 volunteers engaged with the project across all clean-up sites, collecting 431,328 pieces (25,981 kg) of anthropogenic litter. Expressing the data as normalized to area (items m) or effort (items individual h) revealed that the interpretation of a polluted site varies with units, highlighting the need for consistency in the field. Litter density varied from 0.06 to 13.89 items m and 5.2-706 items individual h. Plastics were the major litter type constituting 75% of all litter (mean = 74.2 ± 12.5% across all sites), while clothing (10.9 ± 9.5%) and fishing gear (3.7 ± 5.2%) were also prevalent. Two items constituted > 40% of all collected litter, namely plastic beverage bottles (average 23.7 ± 17.1%, range 0-72.9%) and plastic bags (average 19.7 ± 13.2%, range 1-50.3%). Prioritizing intervention measures on these two items could reduce litter leakage significantly. Furthermore, a holistic approach was undertaken through voluntary engagement, citizen science involvement, stakeholder dissemination, and school visits to increase public awareness. Clean-up data when disseminated to relevant policymakers and stakeholders can motivate activity for the environmental management of anthropogenic litter and plastic pollution.