For emperor penguins, sea ice is essential to survival. The iconic birds, found only in Antarctica, breed, lay their eggs, and raise their chicks on fast sea ice (meaning it is attached to land). They arrive at their breeding sites in late March. In May and June, they lay their eggs, which hatch after 65 days during the brutal Antarctic winter. The chicks then remain on the ice until their fluffy down is replaced by waterproof feathers, finally fledging in the summer months of December and January.
Last year, sea ice levels in Antarctica were at an all-time low—a record first set in 2021. The Bellingshausen Sea region, to the west of the Antarctic Peninsula, saw the most extreme reduction of sea ice, with some areas experiencing a 100-percent loss.
Of the five known emperor penguin colonies in the Bellingshausen Sea region, all but one experienced what was most likely a total breeding failure due to the loss of sea ice, according to a paper published today in Nature Communications Earth & Environment. Satellite imagery clearly showed the sea ice had broken up before the chicks would have developed enough to survive on their own.
“We have never seen emperor penguins fail to breed at this scale in a single season,” the study’s lead author, Peter Fretwell of the British Antarctic Survey, said in a statement. “The loss of sea ice in this region during the Antarctic summer made it very unlikely that displaced chicks would survive.”
Since 2009, when satellite imagery monitoring began, there have been isolated cases of “catastrophic” breeding failure due to fast ice loss across Antarctica—but this is the first recorded incident of widespread regional breeding failures.
The study team also believe their findings support a projection that, if present warming rates continue, more than 80 percent of emperor penguin colonies will be quasi-extinct, meaning they have too few individuals to support a population, by 2100.
A snapshot of the future
Up until 2015, sea ice in Antarctica was increasing. But since then, the continent has experienced four years of the lowest sea ice extent in 45 years of satellite records. Between 2018 and 2022, 30 percent of the continent’s 62 known emperor penguin colonies were affected by partial or total sea ice loss.
This year doesn’t look likely to show improvement. Dana M. Bergstrom of the University of Wollongong has spent 40 years working in Antarctic and subantarctic research. Earlier this month, she wrote an article in the Conversation about the changes in Antarctica: “Much of this winter’s sea ice is missing. A crucial ocean current is slowing down, and glaciers and ice shelves are disintegrating.”
While it’s extremely difficult to determine if year-over-year changes in sea ice are predominantly the result of global climate change or seasonal wind and climate patterns such as La Niña, modeling does predict a long-term decline in Antarctic sea ice extent.
The recent breeding failures “could be a snapshot of what happens in a future Antarctica,” says Norman Ratcliffe of the British Antarctic Survey, a co-author of the new study.
Emperor penguins not only rely on stable sea ice for breeding and raising chicks, but also for molting and protection from predators.
“This kind of regional-scale event is likely to become more common, with devastating consequences for emperor penguins and other ice-dependent species,” says Annie Schmidt, the Antarctica program director at Point Blue Conservation Science and lead author of a 2020 study on early ice breakup that resulted in significant chick loss.
Researchers will now be watching to see if the Bellingshausen colonies return to their regular breeding sites or if they’ll explore different options, as seen with other colonies.
“Emperors are dealing with quite an ephemeral and unreliable breeding substrate, so they're adapted to move around to cope with these losses of habitat,” Ratcliffe says. “The problem is if it happens at a regional level. The Bellingshausen Sea is a huge area—we don't know what potential they have to relocate into a completely different part of Antarctica.”
Emperor penguins are important predators and prey in the Antarctic food chain. They’re also a charismatic species that many people are fondly familiar with through countless nature documentaries and films such as March of the Penguins and Happy Feet.
“I think everyone would think the world would be a poorer place and our stewardship of the Earth would have failed dismally if the species were to decline or disappear,” Ratcliffe says.
Specific suggestions to safeguard penguins in the immediate future include restricting access to colonies not yet or rarely visited by researchers and tourists to limit disturbance and pollution. And there are calls for emperor penguins to be reclassified from Near Threatened to Vulnerable.
The biggest threat to emperor penguins is undoubtedly climate change. As the world warms, sea ice will decline and emperor penguins—as well as other animals—will likely follow suit. Jeremy Wilkinson, a sea ice physicist at also at the British Antarctic Survey, stated that last year’s breeding failure “dramatically reveals the connection between sea ice loss and ecosystem annihilation.”
“The scientific community engaged in Antarctica-related research is generally very concerned,” says Schmidt, pointing to a call for immediate climate action following the recent Scientific Committee on Antarctic Research Biology symposium.
For species such as the emperor penguin, the crisis is already underway. “There is no time left,” Wilkinson says.