Spatial–Temporal Growth, Distribution, and Diffusion of Marine Microplastic Research and National Plastic Policies

Plastics account for 80% of material waste in the ocean. The field of marine microplastic (MP) research is relatively new and growing rapidly, in terms of published papers as well as institutions and countries conducting research. To combat plastic pollution, there is sufficient evidence that policies can lead to reduced plastic production and consumption both locally and globally. We aim to understand how marine MP research and national plastic policies have individually grown and spread. Specifically, we used scientometric and spatial diffusion methods to best explain how ideas (science and policy) clustered and spread geographically through time. We performed systematic literature searches to determine the spatial and temporal growth of marine MP publications and national plastic policies from 1900–2019. We found that more countries adopted national plastic policies than those that have conducted marine MP research. At each level of analysis (publication, institution, and country levels) within each field (research and policy), the temporal growth rate had a break point where doubling time changed significantly. Marine MP research grew exponentially, where doubling times ranged 1.1–3.7 years and the topics of inquiry increased steadily. National plastic policies also grew exponentially, where doubling times ranged 3.3–4.1 years. Different diffusion methods explain spatial growth, where marine MP research spread was best explained by a hybrid of expansion and relocation diffusion while national plastic policy spread was best explained by expansion diffusion. Both marine MP research and national plastic policies continue to spread, increasing global knowledge and mitigation efforts of plastic pollution.