Unlike other species that migrate successfully to escape the wrath of climate change, a new study shows that dispersal may help sustain global Emperor penguin populations for a limited time, but, as sea ice conditions continue to deteriorate, the 54 colonies that exist today will face devastating declines by the end of this century.
If projections for melting Antarctic sea ice through 2100 are correct, the vanishing landscape will strip Emperor penguins of their breeding and feeding grounds and put populations at risk. But like other species that migrate to escape the wrath of climate change, can these iconic animals be spared simply by moving to new locations?
According to new research led by the Woods Hole Oceanographic Institution (WHOI), they cannot. Scientists report that dispersal may help sustain global Emperor penguin populations for a limited time, but, as sea ice conditions continue to deteriorate, the 54 colonies that exist today will face devastating declines by the end of this century. They say the Emperor penguin should be listed as an endangered species. The study was published in the June 6, 2017 edition of the journal Biological Conservation.
“We know from previous studies that sea ice is a key environmental driver of the life history of Emperor penguins, and that the fifty-percent declines we’ve seen in Pointe Géologie populations along the Antarctic coast since the 1950s coincide with warmer climate and sea ice decline,” said Stephanie Jenouvrier, WHOI biologist and lead author of the study. “But what we haven’t known is whether or not dispersal could prevent or even reverse future global populations. Based on this study, we conclude that the prospects look grim at the end of 2100, with a projected global population decline as low as 40 percent and up to 99 percent over three generations. Given this outlook, we argue that the Emperor penguin is deserving of protection under the Endangered Species Act.”
The relationship between Emperor penguins and sea ice is a fragile one: Too little sea ice reduces the availability of breeding sites and prey; too much sea ice means longer hunting trips for adults, which in turn means lower feeding rates for chicks. Only in the past few years have scientists become aware of the penguins’ ability to migrate to locations with potentially more optimal sea ice conditions.
“Before 2014, our studies of the impacts of climate change on these animals hadn’t factored in movement among populations,” said Jenouvrier. “But between then and now, a number of satellite imagery studies and genetic studies have confirmed their ability to disperse, so this was an important new variable to work into the equation.”
To determine whether migration will ultimately help Emperor penguins defend against population decline, Jenouvrier worked with mathematicians to develop a sophisticated demographic model of penguin colonies based on data collected at Pointe Géologie, one of the few places where long-term Emperor penguin studies have been conducted.
The model tracks the population connectivity between penguins as they take their chances moving to new habitats offering better sea ice conditions. “It’s like we’ve added roads between the cities the penguins live in and now get to see what happens when they travel between them,” she said.
A range of model inputs were used, including penguin dispersal distance, behavior and rate of migration. The model also factors in end-of-century sea ice forecasts from climate projection models to predict the fate of each colony.
According to Shaye Wolf, climate science director for the Center for Biological Diversity, the new modeling technique is key to informing policy around “much-needed protections” for the Emperor penguin.
“Dr. Jenouvrier’s research has been at the forefront of advancing our understanding of how climate change is impacting these animals now and into the future,” she said.