14 April 2011

No "winning" penguin species when it comes to climate change

Adelie penguin colony on icebergs.
Photo: Sue and Wayne Trivelpiece
As global temperatures increase, ice-avoiding species like chinstrap penguins have often been considered one of the likely “winners” of changing conditions such as large-scale ice melting. A study published in the Proceedings of the National Academy of Sciences (PNAS), however, shows that the feisty Antarctic birds may actually end up as the most vulnerable to the impacts of climate change.

The research, which uses 30 years of field studies and recent surveys of chinstrap and ice-loving Adelie penguins, reveals that fluctuations in penguin populations in the Antarctic are linked more strongly to the availability of their primary food source - krill - than to changes in their habitats.

The populations of both Adelie and chinstrap penguins in the West Antarctic Peninsula and Scotia Sea have declined by respective averages of 2.9% and 4.3% per year for at least the last 10 years. Some colonies have decreased by more than 50%.

A previous assessment of krill in the Southern Ocean in Nature suggests that their abundance has declined as much as 80% since the 1970s.

“For penguins and other species, krill is the linchpin in the food web,” said Dr Wayne Trivelpiece, lead author and seabird researcher of the National Oceanic and Atmospheric Administration’s Antarctic Ecosystem Research Division.

“Regardless of their environmental preferences, we see a connection between climate change and penguin populations through the loss of habitat for their main food source. As warming continues, the loss of krill will have a profound effect throughout the Antarctic ecosystem.”

Lack of an abundant supply of krill has been particularly hard on fledgling penguins that must learn where to locate and how to catch the prey on their own, having never been at sea before. Data from the study suggest that fewer young penguins are surviving this transition to independence today than in previous years when these crustaceans were much more abundant.

Chinstrap penguins avoid feeding in icy habitats, but it is the sea ice that provides the necessary environment for krill to reproduce. Increasing temperatures and reductions in sea ice have made conditions unfavourable to sustain ample populations of this food source. The authors suggest that fishing for krill and increased competition among other predators also have made them less available to penguins.

Adélie penguins, which feed in icy habitats, are also declining due to food shortages and shrinking habitat. They differ from chinstrap penguins, however, in that they have breeding populations outside of the western Antarctic, which makes them comparatively less vulnerable to the rapid warming in the Antarctic Peninsula region.

“Penguins are excellent indicators of changes to the biological and environmental health of the broader ecosystem because they are easily accessible while breeding on land, yet they depend entirely on food resources from the sea,” said Dr Trivelpiece.

“In addition, unlike many other krill-eating top predators in the Antarctic, such as whales and fur seals, they were not hunted by humans. When we see steep declines in populations, as we have been documenting with both chinstrap and Adélie penguins, we know there’s a much larger ecological problem.”

Penguins that shun ice still lose big from a warming climate, 11 April 2011, Lenfest Ocean Program

PNAS citation
Variability in krill biomass links harvesting and climate warming to penguin population changes in Antarctica. Wayne Z. Trivelpiece, Jefferson T. Hinke, Aileen K. Miller, Christian S. Reiss, Susan G. Trivelpiece and
George M. Watters. Proceedings of the National Academy of Sciences. 11 April 2011.

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