Has the last march of the emperor penguin begun?

Imagine the land you have built your home on disappearing right out from under your feet. 

The emperor penguins of "March of the Penguins" and "Happy Feet" fame are experiencing just that with their sea-ice habitat, researchers say.

The tuxedoed creatures who inspired these films are at risk as Antarctica's ice melts, shifts and changes with climate change, according to a new study published in Nature Climate Change Sunday. The study authors argue that the threat is so serious that emperor penguin should be listed as endangered species.

By 2100, the researchers estimate, the populations of two-thirds of the existing emperor penguin colonies will be cut in half if sea ice melts at the rates predicted by the Intergovernmental Panel on Climate Change (IPCC).

"The role of sea ice is complicated," said study lead author Stephanie Jenouvrier in a news release. As the popular 2005 documentary showed millions of viewers, the emperor penguin relies on the sea ice to raise young. Thick ice provides a secure location for breeding and parenting the baby penguins. 

But these researchers say changes in sea ice specifically impact the birds' access to food. In fact, both too much and too little ice causes problems for these royal penguins.

"Too much ice requires longer trips for penguin parents to travel to the ocean to hunt and bring back food for their chicks. But too little ice reduces the habitat for krill, a critical food source for emperor penguins," said Dr. Jenouvrier, a biologist at the Woods Hole Oceanographic Institution, in a news release.

Jenouvrier and colleagues gathered data from 45 colonies in the Terre Adélie region of Antarctica through direct and satellite observations. This is the northernmost reach of the emperor penguin's range. Terre Adélie begins along the coast south of Australia and extends deep into the frozen continent. The emperor penguins have been studied in this region for 50 years, so the researchers had no shortage of information about the bird's population patterns. 

With the varying ice changes, the researchers predict the emperor penguin population will actually expand slightly leading up to 2050. But don't be fooled by so many waddling birds. Come 2100, if the IPCC models are accurate, there will be no safe place for them. "None of the colonies, even the southern-most locations in the Ross Sea, will provide a viable refuge by the end of 21st century," said Jenouvrier.

The colonies that are in highest danger dwell between the Eastern Weddell Sea and the Western Indian Ocean. The researchers expect the birds in this region to experience the most dramatic population decline. In areas such as the Ross Sea, the penguins won't see as much of a sea ice decline, and will be secure from the threat of melt for longer. But, say these scientists, the melt will come. 

Thus the researchers advocate for the emperor penguin to be placed on the endangered species list. However, these birds do not meet the criteria set by the International Union for Conservation of Nature. A species must experience 50 percent decline over three generations to be officially endangered. For the emperor penguin, this would be only 16 years, still well before 2050. 

But by 2100 the population will be decreasing by 78 percent over three generations, the authors argued in their paper. This would certainly qualify the birds to be listed as endangered, they pointed out. 

The research team explained in the paper that long-term trends like climate change do not fit well in the accepted listing criteria. "We propose that the emperor penguin is fully deserving of endangered status due to climate change, and can act as an iconic example of a new global conservation paradigm for species threatened by future climate change," the authors stated. 

If the emperor penguin is listed as endangered, it may provide a platform for regulation that could help prevent habitat deterioration, say researchers. 

"Listing the emperor penguin will provide some tools to improve fishing practices of US vessels in the Southern Ocean, and gives a potential tool to help reduce CO2 emissions in the US under the Clear Air and Clean Water Acts," Jenouvrier elaborated in a news release.

Jenouvrier collaborated with colleagues at the Centre d'Etudes Biologiques de Chizé, the National Center for Atmospheric Research, the Cooperative Institute for Research in Environmental Sciences, and the University of Amsterdam.

Just last week researchers at the Polar Geospatial Center at the University of Minnesota in Minneapolis published a different study about the shifting habitat of emperor penguins. 

By studying fecal trails left behind at the penguin's breeding grounds, researchers noticed the habit-loving birds had changed something. Instead of returning to the same place they had gone year after year, the birds moved to new spots. Researchers believe this sudden change was a reaction to rising temperatures and shrinking ice sheets. 

Although the emperor penguins have begun this new march, Jenouvrier and colleagues doubt these birds will escape the shrinking of their icy habitat.