Why emperor penguin chicks are the first victims of melting sea ice in Antarctica ?

Les manchots empereurs seront-ils la première espèce polaire à disparaître en raison du réchauffement climatique ? Mario_Hoppmann/Getty Images

Will emperor penguins be the first polar species to disappear due to global warming ? A scientific study published this Thursday, April 25, 2024 notes in any case a total and "sinister&quot mortality ; chicks in several Antarctic colonies, following the record melting of the sea ice in recent months.

Of five colonies monitored in the Bellingshausen Sea region of western Antarctica, all but one suffered a “catastrophic” of 100% chicks, which drowned or froze to death when the ice gave way under their tiny legs. They were not mature enough to cope with such conditions, the researchers report in Communications: Earth & Environment, a journal of the Springer Nature group.

"This is the first major breeding failure of emperor penguins in multiple colonies at the same time due to melting sea ice , and this is probably a sign of what awaits us in the future", the author told AFP Principal Peter Fretwell, researcher at the British Antarctic Survey. "We've been predicting this for some time, but seeing it actually happen is grim", he added.

Fragile

During last year's southern hemisphere spring – from mid-September to mid-December – the Antarctic sea ice, which forms by freezing salt water from the ;#39;ocean, had reached record melting speeds, before falling in February to its lowest level since satellite measurements began 45 years ago. However, this early melting occurred right in the middle of the emperor penguins' breeding period, which was already complex and fragile.

These seabirds reproduce in the middle of the austral winter, when temperatures are the harshest, a process which extends over long months, between mating, brooding and the moment when the chicks are independent, thanks in particular to the formation of waterproof feathers, generally around January-February.

Emperor penguins, aka Aptenodytes forsteri, number around 250,000 breeding pairs, all in Antarctica, according to a 2020 study. Colonies in the Bellingshausen Sea make up less than 5% of that total. "But overall, about 30% of all colonies were affected by melting last year, so there will be many more chicks that will not have survived", explains Mr. Fretwell.

Each year, starting in March, the adults embark on a journey of up to more than a hundred kilometers to reach their breeding sites on the ice floe, which are always the same. The females lay a single egg and leave it in the care of the male while they go looking for food, sometimes several hundred kilometers away.

Male emperors keep newly laid eggs warm, protecting them from the elements by balancing them on their legs and covering them with a fold of skin forming a brood pouch, all without moving or eating, while waiting the return of foster mothers.

Disappearance by 2100 ?

This immutable ritual, recounted in the film “The March of the Emperor”, a great public and critical success around the world in 2005, is now suffering the effects of climate change , which until recently seemed to spare the Antarctic ice pack.

Emperor penguins are certainly capable of finding alternative sites, but record melting since 2016 threatens to exceed their adaptive capacity, scientists estimate.

"Such a strategy will not be possible if breeding habitat becomes regionally unstable" , concludes the study. The emperor penguin was recently listed as a threatened species by the United States Wildlife Authority.

In addition to endangering its breeding grounds, it is also weakened by ocean acidification, another effect of global warming, which threatens certain crustaceans on which it feeds.< /p>

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.