2023-08-24 17:00:51
What happens to penguins when the ice melts? Researchers led by Peter Fretwell from the British Antarctic Survey present the sad answer to this question in the journal Communications Earth & Environment. They monitored five colonies of emperor penguins using data from the Copernicus Sentinel-2 satellite mission from 2018 to 2022. The colonies were located in the Bellingshausen Sea on the west coast of the Antarctic Peninsula.
The Entire Life of Emperor Penguins (Aptenodytes forsteri) takes place on and near the sea ice of Antarctica. This is where they retreat to sleep, molt, breed on the ice and raise their young here. They are protected from large predators such as leopard seals, as these usually do not venture far onto the kilometers of ice. They are the southernmost living penguin species and also the tallest at one meter in height. According to the information, about 630 (Rothschild Island) to 3500 pairs (Smyley Island) breed in the five colonies considered. Altogether there are dozens of colonies with hundreds of thousands of animals in the west of the Antarctic Peninsula. However, climate change is causing the sea ice to melt earlier in the year and more and more – this reduces the retreat area for the emperor penguins.
Drastic sea ice retreat
In 2022, the melting of the sea ice was particularly drastic – and meant that in four of the five penguin colonies observed, not a single young bird survived. Emperor penguins usually form their colonies between March and April, they lay their eggs in May and June. After 65 days, the chicks hatch and by the end of December have replaced their downy clothing with real feathers, which they can use to swim in the icy water. So between April and December the ice on which the colony is located must be firm and stable.
As sea ice has melted faster and further over the past few decades, scientists have already made grim forecasts for the survival of emperor penguins. If global warming continues unchecked, 90 percent of their colonies will be gone by the end of the century. The species would then be almost extinct.
The past year has shown what this extinction could look like. Sea ice has crumbled and thawed away under four of the five observed colonies. Since the chicks were not yet in their feathers and could not swim, they probably drowned. One must assume that no young bird survived, write the scientists. The fact that four out of five breeding colonies have experienced a total failure at the same time has never happened before, writes Fretwell’s team.
The warming fluff of the chicks is not waterproof. If they fall into the water, they drown or freeze to death. : Image: picture alliance / Westend61
Of course, such total failures of an entire generation do not immediately lead to the extinction of the species. But if they accumulate and there is no offspring, the populations will quickly decline.
Unlike many mammals such as whales, walruses or polar bears, penguins have never been hunted on a massive scale. Nor are they directly affected by severe local overfishing. In the remote Arctic, there is no direct habitat destruction by humans, as is the case in rainforests, for example. Thus, the survival of emperor penguins depends almost entirely on climatic conditions, which the authors point out is unusual for a vertebrate species.
However, the scientists are not surprised that emperor penguins will be severely affected by the loss of sea ice. In their publication, however, they recall that the most recent efforts to provide additional protection for the birds at the meeting of the Antarctic States Parties in 2022 failed.
Since more than 45 years of satellite monitoring of the sea ice in Antarctica, the ice surface has repeatedly been shrinking. However, the four years with the lowest volume fall in the past seven years, with the lowest values being achieved in the 2021/22 and 2022/23 seasons. “As of August 2023, sea ice extent in Antarctica is still well below any previous record for this time of year,” said Caroline Holmes, a polar climate researcher with the British Antarctic Survey.
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“Whether these continent-wide conditions are symptomatic of an ongoing trend or a more episodic phenomenon is not yet known,” write Fretwell’s team. The long-lasting weather phenomenon La Niña would probably have had a part in it. “Nevertheless, our results show a clear connection between negative sea ice anomalies and breeding failures in emperor penguins.” Such events could become more frequent in the future. And since the birds cannot establish their colonies in regions where there is more sea ice in all regions of the Antarctic, many breeding failures must be expected in the future.
#Loss #sea #ice #wipes #colonies