Cold Comfort: Arctic Seabirds Find Refugia from a Warming Climate in Sea Ice Margins and Cold Fjords

November 17, 2021

Two new studies in Ambio and Scientific Reports find that Arctic seabirds adapt to warmer climate by exploiting alternative cold habitats

Iceland is one of the few regions where Arctic (Brünnich’s guillemot) and temperate (Common guillemot) auks share ledges and feeding habitats.

Warming in parts of the Arctic is now at least 2.3°C above pre-industrial levels, causing unprecedented alterations to the ecosystems, biology and biogeochemistry of the Arctic Ocean. Loss of sea ice is one of the most striking manifestations of this warming, as the retreat of highly productive sea ice margins has profound influences on Arctic food webs. The consequences for cold-adapted species are particularly evident in near Arctic regions such as Iceland – an island that has been argued to represent the “Arctic in miniature.” An increased inflow of warm saline Atlantic waters combined with the rapid northward retreat of sea ice is causing a decline in true Arctic species in this region.

To understand how Arctic fauna respond to a warming climate, an international team of researchers from Iceland, the UK and Germany examined the population and foraging ecology of two Icelandic seabird species with similar feeding ecologies: the Arctic Brünnich’s guillemot and the temperate Common guillemot. In two recently published papers, the team found that the abundance of the Arctic species declined as sea surface temperatures rose. However, the decline was curbed by the accessibility of refugia in cold water currents or fjords. These refugia also helped the Arctic species to compete with temperate species for food sources.

Dr. Anne-Sophie Bonnet-Lebrun of the British Antarctic Survey, first author of both studies, says that “continued warming of the seas around Iceland is likely to reduce the seabirds’ accessibility to cold refugia, and lead to decline of both temperate and Arctic seabirds because of rapid and disruptive food web changes. Furthermore, our GPS and diving depth data revealed stronger differences in habitat use at sites with the most varied available habitats. But we were surprised to learn that the two guillemot species did not segregate their feeding habitats more in large than small colonies. We expected the competition to increase with colony size. “

Seabirds play a significant role in Arctic food webs in terms of prey consumption and nutrient transport. Besides delivering important ecosystem services, the loss of seabirds in an Icelandic context will have consequences for hunting and egging that are traditional aspects of national culture and identity.

“Another consideration is that spectacular seabird colonies are among the natural attractions that have stimulated the rapid growth of ecotourism in Iceland,” notes Dr. Norman Ratcliffe from BAS, senior author of both studies. “Also, declining populations will adversely affect income to remote coastal communities.”

Dr. Thomas Larsen, co-author of both studies from the Max Planck Institute for the Science of Human History says that “halting anthropogenic climate change is a global effort that unfortunately may take decades to achieve. In that light, it is important to implement measures that offset the effects of warming on Arctic seabirds such as lowering exploitation and pollution in both the breeding and wintering areas.”

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