Adélie penguin population on the rise

Adelie penguins
Photo credit: Michelle LaRue,
University of Minnesota

Adélie penguins have long been considered a key indicator species to monitor and understand the effects of climate change and fishing in the Southern Ocean. A first-ever global census of this penguin species shows that the population is 3.79 million breeding pairs – 53% larger than previously estimated.

By using high-resolution satellite imagery, researchers from Stony Brook University and University of Minnesota have applied a new method that lets them regularly monitor Adélie penguins across their entire breeding range – and by extension the health of the Southern Ocean ecosystem. Their findings were published on 9 July in leading scientific journal The Auk: Ornithological Advances.

Ecologists have been tracking Adélie penguin population declines on the Antarctic Peninsula for decades, but have found conflicting trends elsewhere in their breeding range. The new paper by Stony Brook University ecologist Heather Lynch and University of Minnesota College of Science and Engineering researcher Michelle LaRue finally puts all of these scattered pieces of information into a global perspective.

The study finds that Adélie populations at the global scale appear to be growing. Key to identifying the colonies was using satellite imagery to pinpoint the spectral characteristics of the penguins' guano, a way to clearly identify the species' breeding grounds.

Lynch and LaRue also used recent ground counts and other techniques to identify Adélie penguin colonies over the 5,500km Antarctic coastline in the lowest regions of the Antarctic Ocean, or Southern Ocean.

The 53% increase in known abundance is roughly equally divided between genuine growth of known colonies and the discovery of, or first population estimates at, previously unknown or unsurveyed colonies.

The researchers discovered 17 previously unknown Adélie colonies, but also did not find 13 previously known colonies, 8 of which were declared extirpated (extinct in that geographic area).

Stable or growing populations of Adélie penguins in Eastern Antarctica and the Ross Sea more than offset the rapid declines witnessed on the Antarctic Peninsula, where climate change has significantly changed the timing and decreased the extent of sea ice.

LaRue said, "We now have an important population baseline for Adélie penguins. Our methods also allow for annual, regional-scale comparisons of population trends that can more precisely inform us about ecosystem health and subsequent sustainability and conservation measures."

The research has implications to better inform policy makers and scientists about Marine Protected Areas and climate change.

Lynch said, "We believe this is a landmark study with data that provides not only information on the population dynamics of Adélie penguins but injects critically needed information into the ongoing negotiations regarding the implementation of Marine Protected Areas in the Southern Ocean."

Over the past several years, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) has discussed establishing a series of Marine Protected Areas surrounding Antarctica and the sub-Antarctic islands. Lynch explained that Adélie penguins are not only themselves a species of conservation concern, but their distribution and abundance globally also reflect the distribution of their marine prey – mainly krill and fish.

"Our finding of a 53% increase in Adélie penguin breeding abundance compared to 20 years ago suggests that estimates of krill consumption by this species may be seriously underestimated.

"Leaving enough prey for natural krill predators is an important element in ensuring fisheries proceed sustainably, and for the first time we have a global map of Adélie abundance that can be used by CCAMLR," she said.

Internationally, there has been an growing interest among scientists in using satellites to get near real-time information about populations and distribution of Antarctic species such as penguins, seals and whales.

The relative simplicity of the landscape makes satellite-based surveys an exciting way to look at Antarctic biology on a scale not previously thought possible, paving the way for Antarctica to become an unlikely hotbed of discovery for understanding the population dynamics of seabirds and marine mammals. 

Source
New study finds that Adelie penguin population is on the rise [media release], 9 July 2014, University of Minnesota

The Auk: Ornithological Advances citation
H. J. Lynch and M. A. LaRue (2014) First global census of the Adélie penguin. The Auk: October 2014, Vol. 131, No. 4, pp. 457-466.  doi: http://dx.doi.org/10.1642/AUK-14-31.1