Plastic pollution and conservation of imperilled seabird species

Anthropogenic impacts on the environment have caused a global biodiversity crisis. Contaminants expelled during human activities, including heavy metals, persistent organic pollutants, pharmaceuticals, and plastic debris, are a substantial part of anthropogenic impacts on biodiversity. Plastic pollution presents unique environmental challenges since plastic has both physical and chemical characteristics that affect organisms, and plastics can persist for hundreds of years. To date, over 331 marine species are known to ingest plastic debris, and the prevalence of plastic pollution across ecosystems makes it a threat to many taxa. Seabirds are a charismatic and ecologically important group of marine megafauna. Studies of plastic ingestion in seabirds can be used to detect, monitor and characterise environmental plastic in the broader environment.In this thesis, I contribute to (Chapters 2 and 3) and synthesise (Chapters 4 and 5) a growing body of literature on plastic ingestion in seabirds and present a straightforward approach for considering uncertainty in conservation decision-making contexts (Chapter 6). In Chapter 2, using standardised methods, I demonstrate how the Northern Fulmar (Fulmarus glacialis) can serve as a biological monitoring species for quantifying and characterising plastic pollution. In the remote, sub-arctic Labrador Sea, I discover that 34% (n= 70) of sampled birds exceeded the Ecological Quality Objective for marine litter, having ingested > 0.1 g of plastic, thus establishing a standardised baseline for future comparisons (Avery-Gomm et al., 2017). To more fully understand the occurrence of plastic ingestion and impacts on biodiversity, it is valuable to investigate plastic ingestion in novel species and regions using the same standardised approaches. In Chapter 3, I present plastic ingestion data for Dovekies (Alle alle), the most abundant seabird in the world. I find that 30% (n= 171) of beach wrecked Dovekies ingest plastic and that poor waste management practices are a likely source of plastic pollution. Importantly, comparisons between this study and another nearby study of plastic ingestion in Dovekies from the same wrecking event that did not use standardised methods were rendered incomparable. This demonstrates how a failure to follow standardised methods for quantifying plastic ingestion can undermine spatial and temporal comparisons (Avery-Gomm et al., 2016).In Chapter 4, I articulate how plastic ingestion research can be better linked to wildlife conservation by establishing a clearer understanding of how scientific discoveries can be integrated into conservation and policy actions. I review challenges associated with quantifying the impacts of plastic ingestion at the population level and consider how ingestion research could benefit wildlife conservation by prioritizing studies that: (i) identify causal relationships between plastic load and demographic parameters that impact populations, (ii) improve our understanding of the factors that influence a species or population’s susceptibility to ingesting plastic, and (iii) evaluate strategies for mitigating impacts (Avery-Gomm et al., 2018). In Chapter 5, I bridge the gap between individual baseline plastic ingestion studies and wildlife conservation using a phylogenetically informed analysis of a 57-year global dataset representing nearly 50,000 birds (Avery-Gomm et al., in review). I discover that diet, foraging method, age class and the decade of study partly explain observed patterns of plastic ingestion across the full phylogeny of seabirds. I develop predictions of plastic ingestion risk for all seabird species and conclude that plastic ingestion is already likely to be ubiquitous across all species. To guide future research on monitoring and mitigation, I highlight several highly vulnerable species that should be priorities for investigations of plastic ingestion including the Critically Endangered Magenta Petrel (Pterodroma magentae), Long-Tailed Jaeger (Stercorarius longicaudus), Endangered Newell’s Shearwater (Puffinus newelli), Little Shearwater (Puffinus assimilis), Vulnerable Hawaiian Petrel (Pterodroma sandwichensis) and Endangered Black-Capped Petrel (Pterodroma hasitata).Plastic pollution is one of many threats and environmental factors that affect marine organisms. Uncertainty about how the impacts from plastic ingestion will interact with other components of seabird ecology to affect population dynamics will be difficult to resolve fully. Thus, our understanding of plastic pollution as a threat to biodiversity is, and will likely remain, rife with uncertainty. Given the informational limits, straightforward approaches for dealing with uncertainty in a conservation decision-making context are critical. In Chapter 6, I present an approach that illustrates that data uncertainty does not always preclude cost-effective, transparent decision making using a decision-science problem involving the prioritisation of funding for threatened species recovery (Avery-Gomm et al., in prep).Plastic pollution pervades nearly all marine environments, from the deep sea to the poles. My results suggest that plastic has probably contaminated all seabird species, and highlight why urgent action at the international level is necessary. My thesis advances the field of wildlife plastic research and conservation of vulnerable species by contributing to our ability to detect, quantify and characterise plastics in the environment, improving our understanding of the exposure, impacts and occurrence of plastics in wildlife, and helping to explore uncertainty in the context of complex cost-effective, values-based conservation decisions.

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