How Arctic terns may navigate the challenges of climate change

As climate change poses a far-reaching threat to wildlife, a compelling new study indicates that Arctic terns – known for undertaking the Earth’s longest migration journey – might have the adaptive capabilities to withstand the challenges brought about by our evolving climate.

Arctic terns lead lives in near-constant daylight, embarking on an astonishing bi-annual journey from their breeding grounds in the far north to Antarctica during the southern hemisphere’s summer season. 

Throughout their lifespan, these extraordinary birds cover distances so vast that they equate to traveling to the moon three times.

A collaborative research team led by the University of Exeter and the Met Office took on the challenge of investigating the potential impacts of climate change on these birds outside of their breeding season. 

Focus of the study

The study delved into factors such as shifts in prevailing winds, variations in primary productivity that influence food availability at critical sites frequented by the terns, and the conditions of Antarctic sea ice.

Despite the fact that a likely decrease in foraging success in the North Atlantic could pose a future threat to the Arctic terns, the research team concluded that the overall repercussions of climate change for migrating terns are expected to be minor. This resilience is attributed to the bird’s lifestyle, which plays out over expansive geographical areas.

However, the researchers underscore that even a combination of minor impacts may still pose a significant threat to this long-lived species, which can survive up to three decades. Other species that are less adaptable may not be as fortunate, and could struggle to escape the local and regional shifts induced by climate change.

Dr. Joanne Morten, from the University of Exeter, a key member of the research team, explained, “Arctic terns rely on productive oceans for food, sea ice for rest and foraging, and prevailing winds during flight.” 

All seabirds are at risk

Despite the Arctic tern being classified as a species of “least concern” on the IUCN Red List, Dr. Morten warns that breeding numbers are in decline and monitoring them can be a complex task.

“Climate change is a massive threat to all seabirds. Our study looked at specific aspects of this,” said Dr. Morten. “So, while our findings suggest this species may be resilient, this is only part of a bigger picture for Arctic terns and many other species. Meeting carbon emissions targets is vital to slow these projected end-of-century climatic changes and minimise extinction risk for all species.”

How the research was conducted 

The researchers utilized multiple climate and Earth System Models to predict alterations up to the year 2100, building on current observations of ongoing climate change. 

The team evaluated the impacts of two emissions scenarios: a “middle-of-the-road” scenario and a more severe “fossil-fuelled development” scenario.

What the researchers discovered 

Under the latter scenario, a notable decline in primary productivity, which is the foundational level of all food chains, was projected for the North Atlantic, an important feeding ground for a myriad of seabirds and marine animals. 

However, the study projected only minimal changes to primary productivity at three other pivotal sites for Arctic terns: the Benguela Upwelling, the Subantarctic Indian Ocean, and the Southern Ocean.

Implications of the study

While the consequences of an anticipated decline in Antarctic sea ice for terns remains uncertain, the study proposed that the projected minor changes to prevailing winds would have minimal impacts on tern migration – with the notable exception of the Southern Ocean, where strengthening winds could necessitate a shift in the birds’ flight routes.

Initiated with a virtual Climate Data Challenge “hackathon,” the interdisciplinary approach offered an opportunity for ecologists and climate scientists to converge. The research team encompassed members from multiple universities, including those in Liverpool, Bristol, Washington, Oxford and Iceland.

The study findings, which contribute significantly to our understanding of the interaction between climate change and wildlife, have been published in the journal Global Change Biology.

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