This dataset is synthesized coastline marine debris data from three existing sources and primary collected data. It covers the Central California region from Cambria to Naples for the years 2015-2023. This file contains 40 marine debris item type categories, 6 marine debris material type categories (plastic, glass, metal, cloth, paper and wood, mixed), and 7 marine debris source activity categories (personal hygiene, recreation, smoking, eating and drinking, fishing, dumping, and various). This data set is part of the broader research project conducted by students at the Bren School of Environmental Science & Management. See the research project's abstract for more information: 

California is both a major source of anthropogenic marine debris and an area particularly vulnerable to its damaging impacts. However, little is known about the quantities and impacts of marine debris in the proposed Chumash Heritage National Marine Sanctuary (CHNMS) along the central coast of California. This project, conducted by graduate students through the Bren School of Environmental Science & Management at the University of California, Santa Barbara, creates a baseline assessment of marine debris in the proposed CHNMS. It aims to inform the National Oceanic and Atmospheric Administration (NOAA) Sanctuaries West Coast Regional Office, along with sanctuary management partners and local communities, about local marine debris and potential management measures. Existing community science beach cleanup data and primary collected data were analyzed to understand spatial patterns in quantities and types of marine debris. We found that plastic debris is the most common material type; areas with the greatest debris densities are likely the Morro Bay, Avila Beach, Five Cities, and Gaviota Coast areas. Smoking, eating, and drinking are major activities that contribute to coastal debris in this region. Alongside this quantitative analysis, analyses of policies and interviews with agencies, local organizations, research institutes, and Indigenous communities revealed that current policies may not be effective at reducing marine debris, despite strong concern for marine debris and its impacts on the coastal environment in this region. Based on these findings, we recommend streamlining debris collection protocols with standardized debris categories and effort metrics, implementing innovative policies to reduce marine debris sources, ensuring co-stewardship of the CHNMS to include and prioritize Indigenous perspectives, and conducting additional research on marine and land-based sources of debris. These recommendations will enhance monitoring and mitigation of marine debris in the CHNMS.