A scientific study of data from more than 500 colonies of black-legged kittiwakes distributed around the globe reveals that strong and sudden climatic changes over short time periods are what really cause problems for seabird population dynamics. A probable reason is that the character of the whole ecosystem can suddenly change, resulting from temperature-driven changes in primary production and predation pressure among the most important species in the food chain.

We may often think of global warming as a linear process – a slow and steady increase of temperature over time – but this is not at all the case. The temperature rises and falls, and from time to time we observe steep and stepwise warming over a relatively short timeframe. In order to understand how these sudden changes in the environment may affect species on top of the food chain, a group of scientists has assessed the relationship between population development in 556 colonies of black-legged kittiwakes between 1975 and 2010 and changes in sea surface temperature (SST) in the ocean areas surrounding each colony in the same period.

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The results from the study reveal that periods of moderate temperature increase at the sea surface had little effect on the kittiwake populations. On the other hand, a steep population decline clearly coincided with a swift and sudden increase in sea surface temperature in the 1990s. This sudden warming may have started large-scale circumpolar shifts in the marine ecosystem which led to strong deterioration of the food basis for kittiwakes. In other words, it seems that the kittiwake populations are more sensitive to the rate of ocean warming than to the warming itself.

This study is based on collaboration within the Circumpolar Seabird Group of CAFF and The Arctic Council.

Contact person: Sébastien Descamps, Norwegian Polar Institute

Sudden temperature changes in the ocean may reduce the food basis for black-legged kittiwakes substantially. This assembly of photos shows a kittiwake catching saithe.
Photo: Tycho Anker-Nilssen, NINA