Seabird Species: Pollution's Impact And Threats

Seabirds are the most imperiled bird family, with nearly half of all seabird species in decline. The threats seabirds face are varied, but pollution is a significant factor, with marine debris and light pollution posing particular dangers. Marine debris, such as plastic pollution, is a growing issue, with 60% of seabird species found to have ingested plastics, and 40% getting entangled in debris. Light pollution from coastal buildings, boats, and oil platforms can disorientate and kill birds, with some evidence that it also affects nocturnal aerial courtship. Oil spills are another form of pollution that has decimated seabird populations, and with oil and gas companies drilling deeper in the oceans, this is likely to continue. Climate change, overfishing, and invasive species are also threatening seabird populations.

Plastic pollution

Seabirds are particularly vulnerable to plastic pollution due to their feeding habits. Many species in the petrel and storm-petrel families, for example, migrate over vast ocean areas, feeding on the water's surface where plastic accumulates. Unlike albatrosses and gulls, these birds cannot easily regurgitate plastic pieces, and the indigestible material piles up in their guts, leading to reduced stomach volume and starvation. Additionally, plastic fragments can concentrate organic pollutants up to 106 times that of the surrounding seawater, releasing toxic chemicals into the birds' bodies and causing health issues such as dangerous stomach scarring and altered blood chemistry.

Some of the seabird species most at risk of plastic exposure include the critically endangered Barau's Petrel, Balearic Shearwater, and Newell's Shearwater, as well as the endangered Hawaiian Petrel. These species are already facing multiple threats, including climate change, entanglement in fishing gear, competition with fisheries, and invasive species. Continued exposure to dangerous plastics further reduces their resilience and poses a significant conservation concern.

The impact of plastic pollution on seabirds highlights the need for international cooperation to address this global issue. It also emphasizes the importance of reducing plastic production and accumulation to protect the health and survival of these vulnerable species.

Invasive species

Seabirds are one of the most threatened groups of birds, with 31% of all seabird species facing global threats. Invasive alien species are the major threat to seabird species worldwide, affecting 165 species, 73 of which are threatened with extinction.

Seabirds that breed on isolated islands are particularly vulnerable to invasive species. Predation by introduced predators such as cats, rats, rabbits, and mice has decimated breeding colonies on islands worldwide, eradicating many seabird colonies. These introduced predators are an extra source of mortality, especially for eggs, chicks, and even adult seabirds. Invasive plants have also made many areas inhospitable to nesting. Fortunately, when these invasive predators and plants are removed, seabirds can quickly re-colonize abandoned breeding islands.

Other threats to seabirds include bycatch, overfishing, hunting/trapping, climate change, and habitat disturbance. Bycatch, or the accidental capture of seabirds in fisheries, is a significant cause of decline in many seabird populations. Overfishing is the main cause of decline for at least 24 species and is associated with other threats such as a decrease in prey abundance. Hunting/trapping has also decimated populations of many seabird species, such as the short-tailed albatross, whose numbers dropped from over one million to less than one hundred in a thirty-year span. Climate change is expected to affect seabirds in various ways, such as through habitat shifting and alteration. Finally, human habitation and use of coastal areas have removed seabird breeding, foraging, and resting habitats on islands and shorelines.

Climate change

Seabirds are under significant threat from climate change, particularly in the Northern Hemisphere. As birds that spend almost their entire lives on the ocean, they are important indicators of the health of marine ecosystems.

The rise in sea levels due to climate change has also resulted in the loss of safe and healthy coastal areas for nesting. Extreme high tides are already flooding nests in some areas, and low-lying islands that support nesting colonies of terns and Black Skimmers will soon be underwater. Ocean acidification further compounds these issues, as it will lead to the decline of phytoplankton and zooplankton, which are the foundation of the ocean food chain.

Human-induced threats, such as overfishing and fisheries bycatch, have also contributed significantly to seabird declines. The overfishing of prey fish, such as sardines and anchovies, directly impacts the ability of seabirds to find enough food to survive and feed their young. Additionally, commercial fishing operations often over-harvest forage fish to produce fertilizer, cosmetics, and fish meal, further reducing the food sources available to seabirds.

To protect seabirds from the threats posed by climate change, several actions can be taken. Updating fisheries policies to factor in the needs of seabirds and the effects of climate change is essential. Additionally, establishing marine preserves can help protect seabird feeding waters from overfishing, vessel traffic, pollution, and energy extraction. Protecting and restoring coastal ecosystems like wetlands, oyster reefs, seagrass beds, and barrier islands can also help address sea-level rise and provide nesting habitats for seabirds.

Oil spills

The impact of oil spills extends beyond direct exposure. Seabirds may ingest contaminated prey or struggle to find sufficient food in affected areas, leading to malnutrition and increased susceptibility to diseases. Oil spills during mating and nesting seasons can have even more severe consequences, as birds require additional energy for reproduction, and exposure to oil can hinder their reproductive abilities.

The 2007 Cosco Busan oil spill in San Francisco Bay, for instance, resulted in a Surf Scoter, a large sea duck, becoming covered in oil, showcasing the tangible impact of such incidents on seabirds.

The vulnerability of seabirds to oil spills highlights the importance of effective measures to prevent and mitigate the impacts of such incidents. Conservation organisations like BirdLife are actively working to address these threats and protect vulnerable seabird populations.

Light pollution

Petrels and shearwaters are among the most affected seabird species. Newell's Shearwater Puffinus newelli, an endangered species, is particularly vulnerable to light pollution, with up to 1,800 birds grounded in some years. Other impacted species include the Madeiran Storm-petrel Oceanodroma castro and the Vulnerable Hawaiian Petrel Pterodroma sandwichensis. Burrow-nesting petrel species, some of which are critically endangered, are also affected by light pollution during the fledging season, with thousands of fledglings grounded and exposed to injuries or death.

The effects of light pollution on seabirds have been recognised, and efforts are being made to mitigate its impact. Rescue campaigns by local governments and NGOs help to release grounded birds back into the ocean, although a significant proportion of these birds still perish. Additionally, modifications to buildings and lighting practices can reduce the impact of artificial light on seabirds. For example, shielding upward radiation, reducing light intensity, and eliminating unnecessary lighting can help minimise the negative consequences of light pollution on seabird populations.

Overall, light pollution poses a significant threat to seabirds, particularly nocturnal and migratory species, and concerted efforts are needed to minimise its impact and conserve vulnerable bird populations.

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