Abstract
AbstractAimThe Arctic is warming rapidly, and sea ice is disappearing. This is expected to have profound effects on Arctic wildlife. However, empirical evidence that this decline in sea ice is associated with a decline in Arctic wildlife populations is lacking.LocationSvalbard Archipelago.MethodsUsing long‐term time series data (1988–2018) from two fjords in West Spitsbergen (Svalbard), we tested whether or not sea ice concentration was associated with the population size of two of the most common Arctic seabirds, the Brünnich's guillemot (Uria lomvia) and black‐legged kittiwake (Rissa tridactyla).ResultsWe found that the size of guillemot and kittiwake colonies has declined on Svalbard from the mid‐1990s onwards, though the shapes of these trajectories were not linear and kittiwake colony size has stabilized or even increased in recent years. sea ice concentration in West Spitsbergen also declined during the study period. Independent of these long‐term trends, sea ice concentration was positively and significantly associated with seabird colony size with a 2‐year lag, though variations in sea ice explained only a small proportion of the changes in colony size. One likely mechanism linking sea ice and seabird population size involves changes in the food chain, with poor sea ice conditions in a given year leading to low food availability 2 years later. This would affect breeding probability and hence colony size for kittiwakes and guillemots. This relationship between sea ice and colony size was the same in both fjords for guillemots. In the case of kittiwakes, it was not apparent in the fjord where productive glacier fronts, intensely used by kittiwakes to forage, may have buffered the effects of changes in sea ice.Main conclusionsOur study provides evidence that the ongoing decline in Arctic sea ice plays a role in Arctic seabird population trajectories. However, sea ice disappearance on the breeding grounds was likely not the main driver of changes in seabird populations.
Highlights
The Arctic is warming faster than any other region on Earth (Screen & Simmonds, 2010; Serreze & Barry, 2011), and temperature increases in the Arctic are more than twice the global average (AMAP, 2019)
Empirical evidence linking sea ice and Arctic wildlife population dynamics are relatively scarce, and there is a clear need for additional studies to provide further insights into how populations, species and communities are responding to sea ice retreat
We looked for potential mechanistic links between sea ice and seabird dynamics by testing for an effect of sea ice concentration on colony size
Summary
The Arctic is warming faster than any other region on Earth (Screen & Simmonds, 2010; Serreze & Barry, 2011), and temperature increases in the Arctic (observed and projected) are more than twice the global average (AMAP, 2019). We focused on six and five colonies of guillemots and kittiwakes, respectively, from Svalbard, a high Arctic archipelago located between the Greenland and Barents Seas This region has warmed much faster than the global rate and has shown some of the fastest rates of sea ice declines ever observed (Descamps, Aars, et al, 2017; Forland et al, 2011; Laidre et al, 2015). Concurrent sea ice conditions may affect seabirds’ reproductive success by shaping food availability and/or accessibility and the population size 4–5 years later when kittiwake and guillemot offspring start to recruit (kittiwakes and guillemots start breeding generally at 4 and 5 years of age, respectively, Coulson, 2011; Gaston & Jones, 1998) Such an effect between sea ice and colony size through bird breeding success, and. Considering the large-scale decline in sea ice and the inter-species differences in their association with sea ice, we predicted a similar effect of sea ice decline in both fjords but a stronger effect on guillemot than on kittiwakes
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