Anthropogenic marine debris (AMD) is a widely researched topic, particularly for its impacts on marine wildlife. Terrestrial sources of AMD are substantial, increasing, and primarily considered a result of mismanaged waste. Yet, large-scale empirical research linking losses from waste management with pollution on beaches is sparse. This thesis undertook a national assessment of AMD densities across 41 beaches and evaluated correlated factors that might influence AMD densities, including beach characteristics (such as orientation, steepness), population density, catchment size, and waste management practices. The findings suggest a strong correlation between local waste management practices and variations in AMD densities across New Zealand’s beaches. Methods applied in this multidisciplinary project include a comprehensive systematic literature review complemented with quantitative and qualitative research. The results of empirical fieldwork across 41 beaches demonstrated a significant spatial variance, with the South Island showing a significantly higher mean debris density than the more populated North Island by count (P < .02) as well as by mass (P < .03). The majority (78%) of all AMD detected was plastic, and 72% arrived through the water. Analyses of local waste management practices showed that waste loss to the environment likely occurs due to uncoordinated planning, confusion resulting from discrepancies between local kerbside collection methods, and the inadequate management of (closed) landfills and farm dumps. Including waste management factors in generalized linear modelling resulted in a better fit. Models specified the following significant waste management predictors: 1) the presence of a regional coordinating waste management document (less AMD), 2) the presence of rubbish bins on the beach (more AMD), and 3) the manner in which waste management is financed locally. The type of waste receptacles (open crates or lidded bins) and the amount of the local waste budget were not significant. Environmental factors explaining variances in AMD detected included the orientation of the beach (NE significantly less than E and SE), type of backshore, steepness of beach, as well as the size and the relative location of the nearest catchment. The findings of this thesis contribute to the field of AMD research in the Southern Hemisphere and in New Zealand by establishing a national baseline whilst also refining the understanding of factors that may drive local and national waste loss to the environment. This study serves as a reference for follow-up studies, including in other locations (i.e., New Zealand’s West Coast) as well as accumulation studies, localized microplastic studies, invasive species transport, and global ocean modelling. Furthermore, this research is useful for waste prevention, policymakers, and local waste management planners in reviewing approaches to waste management at a local, regional and national level.