Quantifying Tourism-Derived Litter Accumulation on a Southern California Pocket Beach Using Citizen Science

Coastal plastic pollution monitoring efforts are frequently focused on riverine and offshore inputs and production. While these inputs are the majority of plastics to the coastal environment in many regions, Mediterranean regions with limited precipitation and relatively small, undisturbed watersheds may have limited fluvial inputs of plastics. However, the beaches of these regions are heavily utilized by the tourism industry, and littering due to beach visitation is an understudied, but potentially significant source of plastic pollution.In this study, we document a citizen-science led effort to quantify tourism-derived litter production on a pocket beach in a Mediterranean environment, Laguna Beach, California. This study trained community volunteers consisting of concerned citizens + local high school students in litter sampling and categorization. Field surveys from the summer of 2025 found over 1,300 items of trash, including 700 plastics, on a 100x20 meter pocket beach. We then tested the effectiveness of enhanced signage as an policy intervention for reducing tourism derived litter. Statistical analysis found no difference between trash loading pre vs post enhanced signage.Further analysis of the data found that a significant amount of trash production occurred during just a few holiday weekends. Future work will test a range of policy interventions from enhanced ranger patrols, to offering free parking to visitors who collect trash.