From the Cover: Threat of plastic pollution to seabirds is global,pervasive, and increasing

Plastic pollution in the ocean is a global concern; concentrations reach 580,000 pieces per km² and production is increasing exponentially. Although a large number of empirical studies provide emerging evidence of impacts to wildlife, there has been little systematic assessment of risk. We performed a spatial risk analysis using predicted debris distributions and ranges for 186 seabird species to model debris exposure. We adjusted the model using published data on plastic ingestion by seabirds. Eighty of 135 (59%) species with studies reported in the literature between 1962 and 2012 had ingested plastic, and, within those studies, on average 29% of individuals had plastic in their gut. Standardizing the data for time and species, we estimate the ingestion rate would reach 90% of individuals if these studies were conducted today. Using these results from the literature, we tuned our risk model and were able to capture 71% of the variation in plastic ingestion based on a model including exposure, time, study method, and body size. We used this tuned model to predict risk across seabird species at the global scale. The highest area of expected impact occurs at the Southern Ocean boundary in the Tasman Sea between Australia and New Zealand, which contrasts with previous work identifying this area as having low anthropogenic pressures and concentrations of marine debris. We predict that plastics ingestion is increasing in seabirds, that it will reach 99% of all species by 2050, and that effective waste management can reduce this threat.Introduction of plastic waste into the marine environment is a global concern. Plastic production is rapidly rising, with a doubling of production every 11 y since commercial production began in the 1950s (1). This growth in production has been accompanied by a corresponding increase in the concentration of plastics in the marine environment although it has been suggested that marine organisms may be a major sink reducing this increase (2–4). The durability of plastic implies that it is retained for years to centuries, in some cases failing to degrade at all if it is not exposed to bacterial activity or UV radiation (5).Plastic fragments can be found throughout the world’s oceans, with observed concentrations up to 580,000 plastic pieces per square kilometer (2, 3, 6). Modeling studies, validated by global sampling efforts, demonstrate that plastics are ubiquitous, with high concentrations in all five subtropical convergence zones and along the coastal margins near human population centers (3, 6, 7).In addition to the evidence of its prevalence, there is emerging evidence of the threats plastics pose to wildlife, and indirectly to human health. Plastic waste affects wildlife via two means: entanglement and ingestion (8). A recent review for the United Nations Convention on Biological Diversity documented over 600 species, ranging from microorganisms to whales, affected by marine plastic waste, largely through ingestion (9). Ingestion is known to have many effects, ranging from physical gut blockage (10) to organ damage from leaching toxins (11). Recent experimental studies have also demonstrated transmission and toxicological effects of plastics, or adsorbed chemicals, at environmentally relevant concentrations in higher vertebrates (11–13).The effect of plastic ingestion on seabirds in particular has been of concern. This concern is due to the frequency with which seabirds ingest plastic (12) and because of emerging evidence of both impacts on body condition and transmission of toxic chemicals, which could result in changes in mortality or reproduction (13–16). Understanding the contribution of this threat is particularly pressing because half of all seabird species are in decline, a higher fraction than other comparable taxa (17). Despite a recent extensive review of the threats to seabirds by a globally recognized authority (17), however, pollution has been identified only in a coastal context, and there is little mention of the impact of plastic ingestion, particularly on the high seas where the most threatened seabirds forage (17).We predict the extent of plastics exposure for 186 pelagic seabird species worldwide, excluding coastal taxa such as shorebirds, sea ducks, and gulls and species for which distribution data were not available (SI Appendix, Table S1). We compare our predictions with diet studies published over the last 40 y and incorporate additional factors such as foraging strategy, body size, and sampling method that may affect the relationship between exposure and ingestion. Based on this adjusted model of risk, we map the global distribution of plastic ingestion risk for seabirds and highlight global areas of concern.