Climate change and its consequences have been talked about since the beginning of the century. Thus, iconic images of a polar bear on a tiny piece of ice surrounded by the vast Arctic Ocean helped illustrate the magnitude of the drama to come. Now the tragedy has shifted south. Last year, four colonies of emperor penguins in Antarctica failed to raise their young. Their parents nested on icy water surfaces as usual, but in the southern summer of 2022, the Antarctic meltdown occurred before the chicks shed their down to access the hydrophobic feathers that would have allowed them to enter the frigid Antarctic waters to dive in
Adult couples were forced to abandon the colony, leaving their children to either drown or starve on tiny icebergs like those of polar bears in the north of the planet.
The emperor penguin (Aptenodytes forsteri) is the largest penguin and the largest warm-blooded animal living this far south. Discovered by Russian expeditionaries last century, it lives and nests only in Antarctica. It has not been hunted, hunted, or fished (except by accident) by humans. Its habitat, the Antarctic continent, has not been seriously changed either. It was therefore considered an iconic species without threat, and as a result became a sentinel of climate change.
More information
One essential aspect influences this: its life cycle corresponds to the ice cycle. The pairs of penguins reach the edges of the continent between late March and April, when it is autumn there. The eggs hatch in July, when this ice is at its maximum extent. And so it goes when the chicks grow up with their gray down that protects them from the cold. Under normal conditions and shaped by natural selection and climate, from mid-December the young lose this layer that protects them from the cold environment in favor of feathers rich in fat and highly waterproof. Especially in these weeks, the sea ice that has been crumbling since October is partially disappearing completely. This facilitates the transition of the chicks from land life to sea life. But in 2022 everything collapsed.
“When the ice supporting the ramp crumbled, the parents would not have been able to reach their colony. Here the chicks would have starved or frozen to death.”
Norman Ratcliffe, British Antarctic Survey
Only three of the more than 60 discovered colonies nest on the continental ice, i.e. inland. The rest happens on the so-called fast ice (land ice, in the technical jargon of Anglophone glaciologists). It’s not continental ice, but it’s not sea ice either, that is, the part that rests on seawater. This is the frozen portion that is still in contact with the submerged continental shelf. Researchers from the British Antarctic Survey (BAS), a scientific organization that has worked continuously on the Antarctic continent since 1962, observed an anomalous melt at the westernmost edge of the Antarctic continent. On the shores of the Bellingshausen Sea (named after the aristocrat who led the expedition that first saw emperor penguins) the ice was gone by November, leaving only water underfoot for unprepared, non-flying birds to swim .
“There is evidence that in one of the colonies the chicks used a stranded iceberg as a kind of lifeboat, but the satellite data suggests they did not survive there until it was time to fledge,” says Norman Ratcliffe, a BAS researcher. researcher. . Ratcliffe and his colleagues used data from the Sentinel2 satellite to observe two processes in parallel: ice shrinkage and plumage change. Ice extent reached a record low in early December 2022. There is no direct evidence, based on observations by scientists on the ground, of what happened to the chicks but, as Ratcliffe says, “whether the sea ice beneath the colony is breaking up.” Before the chicks have waterproof feathers in early December, they fall into the water and drown or float away on ice floes and lose their parents.”
The image shows the ice situation in October 2022 on Smyley Island, where 6,500 pairs nested (the dark spot in the middle). On the right, on December 10, where the colony was located, there was only water.BAS
The scientists analyzed images taken throughout the penguin breeding cycle from this area of Antarctica. There are five imperial colonies in the central and western part of the Bellingshausen Sea. From the sky they can be seen as dark spots in the snow, the gray-brown of the young animals is accompanied by the brown color of the guano, their excrement. Melting marked historic lows across the Antarctic Peninsula in December 2022, but by November 100% of the sea ice in the Bellingshausen Sea had disappeared.
The consequences are detailed by scientists in a study just published in the journal Communications Earth & Environment. Of the five colonies in the area, three were abandoned in early December and a fourth, at Ensenada Verdi, with about 3,000 pairs, was abandoned even earlier, in November, two months before the young shed their down. There were no on-site controls. The five colonies were discovered in the last decade and there are no bases in this region of Antarctica. Everything that is known about them is thanks to satellites. And satellite images show that where ice should be, there was water long before the chicks had their hydrophobic feathers.
Emperor penguin chicks in Antarctica on January 21, 2005. Zhang Zongtang (AP)
The most dramatic case was probably that of the Punta Pfrogner colony. Discovered in 2019, it consists of about 1,200 pairs and is one of the few colonies nesting on continental ice. Satellite images show the brownish patch through October. But there was no black ice in the November 8 image, and there was no sea ice on November 12. Here it seems unlikely that the hatchlings fell into the water, but the alternative that Ratcliffe explains is worse: “Ice shelves often have a sheer cliff at the edge leading to the sea, which penguins cannot normally scale. At Prfogner, a snow ramp had formed on the sea ice below the cliff, allowing access. When the ice supporting the ramp crumbled, the parents would have been unable to reach their colony. Here the chicks would have starved or frozen to death.”
So far, 62 imperial colonies have been discovered in Antarctica. In the Bellingshausen Sea there are only a few and small specimens with a few thousand pairs. There are groups of up to 20,000 pairs in southern and northern Antarctica. In addition, the effects of climate change on the Antarctic continent are more complex and less clear than in the Arctic. The eastern part has been growing in the ice for decades, while in the west, West Antarctica, melting is accelerating. But if greenhouse gas emissions continue at current rates, most of Antarctica will sooner and longer lose most of its sea and fixed ice. Based on these models, a study published in 2020 estimated that 90% of colonies could disappear by the end of the century.
Lead author of the study, Peter Fretwell, also of BAS, said: “We know that emperor penguins are at great risk in an increasingly warming climate, and current scientific evidence suggests that extreme sea ice losses like this will be more frequent and more widespread. ” . Although only four colonies collapsed last year, 30% of the 62 known emperor penguin colonies were affected by partial or total sea ice loss between 2018 and 2022. From previous local collapses, scientists know that emperor penguins crowd out their nesting sites. In a BAS release, climate scientist Caroline Holmes said of what could happen this season: “At this point, in August 2023, sea ice extent in Antarctica is still well below any previous record for this time of year.” of the freezing of the oceans, we see areas that are surprisingly still largely ice-free.” Where will the emperors then go to raise their children?
you can follow THEME on Facebook, Twitter and Instagram, or sign up here to receive our weekly newsletter.