Global warming robbed penguin colonies of all their chicks

Emperor penguin chicks hatch from their eggs on the coldest days of the Antarctic winter. For the first few months of their lives, the birds are defenseless gray balls of fluff, seeking warmth at the feet of their parents or in protective crowds in the center of their colony.

Unlike their parents, whose sleek black and white plumage protects their skin from the cold ocean, the chick’s downy plumage is not waterproof. They must stay on the ice and stay away from the sea until their waterproof feathers emerge, typically around four months after hatching.

It is now December and summer is coming to Antarctica. The ice is about to break for the season and the newest members of the colony can safely follow the adults into the sea to hunt.

The survival of each new generation of emperor penguins depends on the presence of ice beneath those tiny feet. As many biologists have feared, the unusually early disappearance of Antarctica’s winter sea ice last year proved catastrophic for the species.

Using satellite imagery, researchers found that four out of five observed emperor penguin colonies in the Bellingshausen Sea region of West Antarctica experienced a “catastrophic brood failure,” meaning none of the chicks born in 2022 are believed to have survived.

The complete demise of these four colonies is described in a piece of paper published today in Communications Earth & Environment magazine.

Upon completion of this research, lead author Peter Fretwell from the British Antarctic Survey said he had examined satellite imagery of the rest of the continent 66 known emperor penguin colonies.

In 19 of them – nearly 30% – most if not all of the chicks may have drowned or frozen to death when the ice that once supported them melted in the sea, he said.

Although individual colonies occasionally experience isolated breeding failures, “this is the first time an entire area has been lost to sea ice,” said Fretwell, a mapping specialist.

The chicks were victims of an unprecedented retreat in Antarctic sea ice. On February 21, NASA recorded 691,000 square miles of summer sea ice, an area 50,000 square miles smaller than the previous record set a year earlier.

It’s a record that’s likely to fall again this year. Antarctica’s winter sea ice extent is smaller than ever Area as big as Greenland is simply absent from the reporting expected by scientists. Since there is less ice at the beginning, it is very possible that there will also be less ice in the summer.

“It’s almost certain that this year will be even worse than 2022,” Fretwell said. “It’s a pretty depressing story for emperor penguins.”

Until recently, emperor penguins had a secure place in the Antarctic ecosystem.

An estimated 600,000 people live on the continent. Emperor penguins are the largest of the Antarctic penguin species, and in adulthood are distinguished by their sleek black back plumage, gold-striped beaks, and resting posture that gives the impression of a bird staring majestically at the sky.

Until the advent of satellite imagery strong enough to reveal remote patches of ice with the telltale smudges of penguin droppings, most of their colonies were completely unknown to humans. Almost half of the colonies identified today were discovered in the past 15 years by Fretwell, the pioneer of the science of satellite penguin counts.

Emperor penguins have made themselves comfortable on the ice, largely evading human efforts to hunt them down, overfish their prey, or invade their territories.

Still, scientists familiar with the species say it’s common in a colony to have an occasional bad breeding season.

“Colonial failures and early ice-breaking are not uncommon,” he said Michelle LaRue, a marine biologist at New Zealand’s University of Canterbury who was not involved in the research. It’s usually “a colony here and there every once in a while,” she said. “Not like what Peter just showed.”

For the study, Fretwell examined satellite imagery of five known colonies of emperor penguins in the Bellingshausen Sea region of Antarctica, which has seen a particularly sharp decline in sea ice over the past year.

The five colonies collectively host 7,000 to 10,000 breeding pairs of birds each year, Fretwell said. Beginning in September, about a month after the chicks hatched, his team began examining images of the area taken every few days to a few weeks.

In November, when the colonies’ chicks were still in their fluffy, vulnerable stage, Fretwell noticed that the sea ice, which normally persisted into January, was rapidly receding. Previous data showed that only one of the five colonies had lost its ice during the previous four breeding seasons.

It was different last year. By early December, the ice had completely disappeared in four of the five colonies, causing adult penguins to leave the nest site early and chicks to meet an untimely demise.

In the Rothschild Island colony, home to the smallest of the five populations, a serendipity in the geometry of the bay preserved the sea ice until the offspring of around 700 breeding pairs fledged.

It was “unprecedented,” Fretwell and his co-authors wrote, to see complete breeding failure in an entire region. And the future looks even darker.

“Our sea ice models and penguin population projections suggest that we will lose over 90% of the colonies and well over 90% of the population by the end of the century,” Fretwell said.

Few living beings at the poles are immune to the effects of climate change. But Antarctica’s largest penguin is critically endangered, biologists say, despite being a generally hardy bird.

“The Emperors are in deep trouble,” he said Steve Emsliean expert on Adelie penguins at the University of North Carolina Wilmington who was not involved in this research.

Without a significant adjustment, such. For example, moving to land to breed, emperor penguins “will continue to experience breeding season losses each year because the sea ice is melting and erupting too early, and the population will continue to decline,” Emslie said.

LaRue shared his concern.

“Emperor penguins tend to be quite resilient, but I don’t know how long that resilience can last given the extreme changes we’ve seen,” she said.

The colonies observed by Fretwell are not large enough for this missed season to have a lasting impact on the species’ overall population, LaRue said. The greater fear is that this collapse could prove to be the catalyst for repeated failures in other colonies.

“They are a window to the sea ice ecosystem,” Fretwell said of the emperor penguins. The future of birds is directly related to warming seas and retreating ice. Both are happening faster than scientists predicted.

But her fate is not yet sealed, he said. If humans can reduce greenhouse gas emissions and stop global warming from unabated, “we can change the fortunes of the emperor penguin and many other species,” he said, “including our own.”