A scientific study published on Thursday points to a “grim” mortality of chicks in several Antarctic colonies of emperor penguins, following the record melting of the sea ice in recent months.
This has sparked fears that the birds may be the first polar species to disappear due to global warming.
Of five colonies monitored in the Bellingshausen Sea region of West Antarctica, all but one suffered a “catastrophic” 100% loss of chicks, which drowned or froze to death when the ice gave way beneath their tiny legs.
First across-the-board failure of emperor penguin reproduction
They were not mature enough to cope with such conditions, the researchers report in 'Communications: Earth & Environment,' a journal from the Springer Nature group.
“This is the first major failure of emperor penguin reproduction in several colonies at the same time due to melting sea ice, and is probably a sign of things to come,” lead author Peter Fretwell, a researcher at the British Antarctic Survey, told French news agency AFP.
“We’ve been predicting it for some time, but to actually see it happen is eerie,” he added.
Sea ice drops to its lowest level in 45 years
During last year’s southern hemisphere spring – from mid-September to mid-December – Antarctic sea ice, formed by the freezing of salt water from the ocean, reached record melting speeds, before dropping in February to its lowest level since satellite measurements began 45 years ago.
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This early melting came right in the middle of the emperor penguins’ breeding season, which is already complex and fragile.
These seabirds breed in the middle of the southern winter, when temperatures are at their harshest. The process that takes many months, between mating, brooding and the time when the chicks are self-sufficient, thanks in particular to the formation of waterproof feathers, generally around January-February.
Around 30% of emperor penguin colonies affected by the melt
Emperor penguins, aka Aptenodytes forsteri, number around 250,000 breeding pairs, all in Antarctica, according to a 2020 study.
Colonies in the Bellingshausen Sea account for less than 5% of this total. “But overall, around 30% of all colonies were affected by the melt last year, so there will be many more chicks that do not survive,” Fretwell explains.
Each year, from March onwards, the adults embark on a journey that can cover more than a hundred kilometres to reach their breeding sites on the pack ice, which are always the same.
The females lay a single egg and leave it in the care of the male while they go in search of food, sometimes several hundred kilometres away.
Record melting threatens penguins' ability to adapt
The male emperors keep the newly laid eggs warm, protecting them from the elements by balancing them on their feet and covering them with a fold of skin forming an incubator pouch, all without moving or eating, while waiting for the return of the mothers.
This unchanging ritual, recounted in the film 'March of the Emperor,' - a major public and critical success worldwide in 2005 - is now suffering the effects of climate change, which until recently had seemed to spare the Antarctic ice pack.
The emperor penguins are certainly capable of finding alternative sites, but the record melting since 2016 threatens to exceed their capacity to adapt, say the scientists.
“Such a strategy will not be possible if the breeding habitat becomes regionally unstable,” the study concludes.
Extinction warning
The emperor penguin was recently classified as an endangered species by the US wildlife authority.
In addition to the danger to its breeding grounds, it is also weakened by ocean acidification, another effect of global warming, which threatens certain crustaceans on which it feeds.
The British Antarctic Survey estimates that at the current rate of global warming, almost all emperor penguins could be extinct by the end of the century.
