Plastics in the Pacific: Assessing risk from ocean debris for marine birds in the California Current Large Marine Ecosystem

Understanding the impact of plastic debris on marine birds is important for conservation of some species, and assessing risk from this anthropogenic threat requires high-quality distribution data for both marine birds and plastic debris. We applied a risk assessment framework to explore the relative risk for 19 marine bird species posed by plastic debris in the California Current Large Marine Ecosystem. We estimated exposure for each species by combining scores from (1) spatial overlap of predicted marine bird densities from habitat-association models and predicted density of marine plastics from terrestrial input and ocean circulation models, (2) species' foraging behavior, and (3) species' residence time in the California Current Large Marine Ecosystem. We estimated sensitivity for each species by combining scores for (1) mortality/sub-lethal effects of ingested plastic debris, (2) off-loading of plastics via regurgitation, (3) fecundity, and (4) age of breeding maturity. Overall risk from marine debris was greatest for more pelagic species and lowest for nearshore coastal species and generally agreed with published plastic ingestion studies. Notably, marine plastic debris densities are greatest at the western edge and offshore of the study domain, which likely explains the greater risk we observed in more pelagic species. This study is the first to look specifically at plastic debris risk to marine birds in the California Current Large Marine Ecosystem, and our results suggest that any attempts to mitigate the impacts of plastic debris on marine birds will likely require assessment and actions beyond the California Current into the broader Pacific basin.