What Are the Penguins Telling Us?

14 January 2014

Posted by: Steve Forrest |

     

Adelie penguins face numerous challenges from changing climate.

I recently returned from a trip to Antarctica, an annual migration of sorts, where I have been counting penguins for the past 20 years for the nonprofit research organization Oceanites. I had hoped to revisit a small island where I camped six years ago, studying the population and breeding biology of two species of penguins: the Gentoo and Adélie penguins, which tell two very different stories with respect to climate change.

Penguins need a relatively gentle terrain and access to the sea in order to establish a rookery. They also need ready access to abundant offshore food supplies, as they are tethered to this site for months while rearing chicks. Adélie penguins are habitat specialists: they need ice and eat mostly krill, which they are adept at hunting. Gentoos are more cosmopolitan in diet, eating both krill and fish when available, and seem to flourish in open water. In 2004, the small island named Petermann was the southernmost limit of the range of the Gentoo penguin, a distinction it had held since 1907 when the island was first visited by the French explorer Charcot. In Charcot’s time, Adélie penguins — the classic tuxedo-wearing icon of Antarctica — outnumbered the Gentoos by a margin of 20 to 1. At the time my studies began in 1994, the ratio had been reversed; Gentoos outnumbered the Adélies about 2 to 1, and were increasing as fast as the Adélies were going down. All of this had been happening over the course of just decades – the blink of an eye in ecological time.

On this year’s research trip, taking a precious break from my day job at Defenders of Wildlife, I’d hoped to see if the trends we had been observing at Petermann Island were holding. Unfortunately, as the recent headline-grabbing misfortunes of the Academik Shokalskiy (a Russian ship trapped in the ice on the other side of the Antarctic continent) made clear, almost any science project in Antarctica is at the mercy of the weather. Sadly, we were blocked from reaching Petermann due to ice. Regardless, our own ship, the Sergei Vavilov run by the tour company OneOcean expeditions, carried on to 13 other sites where we have been tracking penguin numbers on the Western Antarctic Peninsula, a region where the average temperature has risen several degrees centigrade in the past two decades alone. The result of this warming, its effect on sea surface temperature, the productivity of plankton, the retraction in annual sea ice formation, inshore ocean currents, and decline of krill – all of which are related and underpin the food chain for large predators such as penguins – plays out in the numbers: the ice-loving Adélies of Petermann now number fewer than 300 nesting pairs, while the gentoos have risen to 2,400.

Gentoo penguins at Petermann Island continue to grow in number. (© Steve Forrest)

This is a pattern we’ve seen repeated at hundreds of sites where Oceanites has continuously monitored for 20 years all across the northwestern peninsula. Adelies are disappearing from their rookeries while the open-water loving Gentoos prosper. And this season was no different, with larger nesting populations of Gentoos observed at places where our ship made calls. At places like Paradise Harbour, Gentoos now blanket exposed rocks left by the retreat of nearby calving glaciers. At Cierva Cove, at the head of formerly frozen bays, Gentoos now dot the moss and Antarctic hairgrass-covered hillsides above an Argentinian research station. There are many possible explanations for why the Gentoos – habitat generalists – are succeeding in the new environmental regime while the krill-dependent Adélie retreats in the face of these changes, but there is no doubt that global climate shifts are mediating these population trends. What is less clear is what happens to this finely tuned and exquisitely adapted system, in place for thousands of years, when the Adélie is gone?

Left: An Adelie penguin colony at Petermann Island during the Charcot expedition, 1908-1909.
Right: The same location during one of my recent trips to Petermann.

To be clear, we are talking about a very large area – thousands of square miles – but by no means all of the Adélies everywhere in Antarctica. Strongholds remain where the ice regime has not been disrupted to the extent that it has in the western peninsula. But will this change occur only on this portion of the continent, or will we see it affecting larger areas as the continent in its entirety warms? And what are the lessons for my work in the grasslands of the U.S., where similar habitat specialists, such as the black-footed ferret, which eats only prairie dogs, or the sage-grouse, which occurs only with the shrub after which it was named, already cling to precarious footholds in highly changed habitats? Will they, too, be driven out of the last of their habitats as the species on which they depend and the climatic regimes within which they thrive no longer meet their needs? And will that change be as fast and dramatic as what I have observed here in Antarctica over the past two decades? I try to remain objective about the prospects ahead, but the lesson of Petermann Island to me is that we likely have already tipped the balance, making the job of conservation all the more challenging, and demanding the most creative solutions we can muster to hold on to the most sensitive creatures among us.

Steve Forrest, Rockies & Plains Senior Representative

source