Newswise — The thorough analysis examined the motions of 7,137 distinct avian creatures from 77 petrel species, a collection of migratory seabirds that encompass the Northern Fulmar and European Storm-petrel, as well as the highly endangered Newell's Shearwater.
This is the first time that tracking data for so many seabird species has been combined and overlaid onto global maps of plastic distribution in the oceans.
The findings reveal that the menace of plastic pollution endangers marine organisms on a magnitude that surpasses borders: a fourth of the entire peril of plastic exposure arises in the open ocean. This primarily correlates with gyres - expansive networks of swirling oceanic currents - where enormous collections of plastics amass, fueled by refuse entering the sea from vessels and numerous nations.
Avian creatures of the sea frequently confuse diminutive plastic fragments for nourishment or consume plastic that has already been ingested by their prey. This can result in harm, toxicity, and malnourishment, with petrels being especially susceptible due to their limited ability to regurgitate the plastic. During the breeding season, they unintentionally feed plastic to their offspring.
Plastics can also contain toxic chemicals that can be harmful to seabirds.
Petrels, an overlooked yet fragile assemblage of marine species, hold a pivotal position in the intricate food chains of the oceans. Their extensive presence throughout the entire expanse of the ocean renders them significant "sentinel species" in evaluating the perils associated with plastic pollution in the marine ecosystem.
"Oceanic currents generate substantial aggregations of plastic waste, swirling far away from coastal areas, concealed from view, and surpassing the authority of any single nation. Our research uncovered that numerous petrel species extensively forage in proximity to these mid-ocean gyres, rendering them highly susceptible to plastic ingestion," stated Lizzie Pearmain, a PhD student from both the University of Cambridge's Department of Zoology and the British Antarctic Survey. Pearmain is also a joint corresponding author of the study.
Pearmain further explained, "Upon consuming plastic, petrels encounter the risk of it becoming lodged in their stomachs and subsequently passing it on to their offspring. This results in reduced space for actual nourishment, leading to internal injuries or the release of toxins."
Petrels and other species are already imperiled by climate change, bycatch, fishery rivalry, and invasive species like mice and rats in their breeding colonies. The scientists argue that plastic exposure might diminish the birds' resistance to these concurrent perils.
The north-east Pacific, South Atlantic, and the south-west Indian oceans have mid-ocean gyres full of plastic waste, where many species of threatened seabird forage.
"Even species with minimal exposure risk have been observed consuming plastic. This demonstrates that oceanic plastic concentrations pose a global concern for seabirds, extending beyond regions of high exposure," stated Dr. Bethany Clark, BirdLife International's Seabird Science Officer and co-author of the study.
She further remarked, "Numerous petrel species face the peril of encountering plastic in the waters spanning multiple nations and the vast expanses of the high seas during their migratory journeys. Owing to oceanic currents, this plastic waste frequently drifts far from its initial origin. This underscores the imperative for international collaboration in addressing plastic pollution in the Earth's oceans."
Additionally, the study revealed that the Mediterranean Sea and the Black Sea collectively contribute to more than 50% of the global plastic exposure risk for petrels. Nevertheless, it is noteworthy that only four petrel species engage in foraging activities within these confined and bustling regions.
The research was spearheaded by a collaborative effort involving the University of Cambridge, BirdLife International, and the British Antarctic Survey. They worked in conjunction with Fauna & Flora International, the 5 Gyres Institute, as well as over 200 seabird researchers across 27 countries.
In order to obtain their findings, the researchers superimposed global location data obtained from tracking devices affixed to the birds onto pre-existing maps displaying the distribution of marine plastic. This enabled them to pinpoint the specific regions along the birds' migration and foraging routes where they are at the highest risk of encountering plastic pollution.
The researchers assigned each species an "exposure risk score" to quantify their likelihood of encountering plastic while at sea. Several species that are already facing threats received high scores, including the Critically Endangered Balearic Shearwater, which breeds in the Mediterranean, and the Newell's Shearwater, which is endemic to Hawaii.
The Hawaiian Petrel, an Endangered species, was also found to have a high plastic exposure risk, along with three species classified as Vulnerable by the IUCN: the Yelkouan Shearwater, which breeds in the Mediterranean; Cook's Petrel, which breeds in New Zealand; and the Spectacled Petrel, which exclusively breeds on Inaccessible Island, an extinct volcano in the Tristan da Cunha archipelago, designated as a UK Overseas Territory.
Professor Andrea Manica from the Department of Zoology at the University of Cambridge and co-author of the study commented, "Although the population-level consequences of plastic exposure remain largely unknown for the majority of species, numerous petrels and other marine species are already in a fragile state. The ongoing exposure to potentially harmful plastics only exacerbates the existing pressures they face."
He further added, "This study represents a significant advancement in comprehending the situation, and our findings will contribute to conservation efforts aimed at mitigating the threats faced by seabirds in their marine habitats."
The research was supported by funding from the Collaborative Fund for Conservation, which is part of the Cambridge Conservation Initiative, and is sponsored by the Prince Albert II of Monaco Foundation. Additionally, the Natural Environment Research Council also provided financial support for the study.
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