Emperor penguins (Aptenodytes forsteri) are highly dependent on stable sea ice for their entire life cycle, using it for breeding, molting, and foraging. Almost all emperor penguin colonies rely on land-fast sea ice, which needs to remain stable from April to January to ensure successful breeding. Climate change, leading to sea ice loss, is a major threat to emperor penguins, with studies showing links between sea ice decline and breeding success, colony site loss, and population decline. Predictions suggest that, with continued warming, many colonies could face quasi-extinction by the end of the century. Unlike many other species, emperor penguins have not faced significant threats from hunting or other anthropogenic factors, making climate change the primary driver of their population changes. While conservation efforts are underway, they haven't adequately addressed the critical breeding habitat needed for chick survival. This study investigates the impact of the record low 2022 sea ice extent on emperor penguin breeding success.

Numerous studies have documented the negative impacts of climate change-driven sea ice loss on emperor penguin populations. Early research focused on the effects of sea ice loss on breeding success. Later studies examined the loss of colony sites due to long-term sea ice decline and regime shifts. Recent predictive modeling efforts, using forecasts of sea ice loss, have painted a grim picture, projecting significant population declines and potential quasi-extinction by the end of the century if current warming trends persist. These studies consistently highlight the critical role of stable sea ice for emperor penguin survival and emphasize the need for effective conservation strategies.

The researchers used satellite imagery from two platforms to monitor emperor penguin colonies: ESA's Sentinel-2, providing continuous monitoring since 2015 with a revisit time of 3 to several times per month, and high-resolution WorldView-3 data from MAXAR. Sentinel-2 imagery, accessed through the Copernicus Open Access Hub and Sentinel Hub browser, was analyzed to detect the presence or absence of penguin colonies based on the presence of brown pixels indicative of guano staining. WorldView-3 imagery, with a spatial resolution of 0.31 m, was used to obtain population estimates and confirm observations from Sentinel-2. The researchers manually assessed each image, focusing on the presence or absence of brown pixels within the colony area. The analysis covered imagery from August to December of each year to monitor the colonies throughout their breeding season. High-resolution imagery was used to confirm colony presence and provide population estimates for certain colonies. Data from other sources, such as helicopter surveys, was used to corroborate some findings. Data availability is provided in the article.

In late 2022, four of the five studied emperor penguin colonies in the central and eastern Bellingshausen Sea experienced catastrophic breeding failure due to early sea ice loss. These colonies, previously visible in October and November, were abandoned before the start of the fledging period in December. This widespread failure is unprecedented in the records using satellite imagery since 2009. The sea ice anomaly was most intense in the Bellingshausen Sea region, showing almost complete sea ice loss in some areas. Each of the five colonies (Verdi Inlet, Smyley Island, Bryant Coast, Pfrogner Point, and Rothschild Island) showed varying degrees of impact. Verdi Inlet, Bryant Coast, and Pfrogner Point colonies experienced complete breeding failure due to sea ice break-up before chicks could fledge. Smyley Island colony split into two groups, with at least one group moving to a grounded iceberg. Only the Rothschild Island colony, located in a sheltered bay, maintained stable sea ice and experienced some successful fledging. The timing of sea ice break-up and colony abandonment was analyzed, showing a clear correlation between early sea ice loss and breeding failure.

The findings demonstrate a strong link between extreme sea ice loss and catastrophic emperor penguin breeding failure at a regional scale. This unprecedented event highlights the vulnerability of these colonies to rapid changes in sea ice conditions. While emperor penguins can sometimes adapt to localized sea ice loss by relocating to alternative sites, this strategy is unlikely to be effective in the face of widespread regional habitat loss. The study's findings suggest that similar catastrophic events may become more frequent and widespread in a warming Antarctic, potentially having devastating consequences for emperor penguin populations. While the specific extreme weather conditions cannot be directly linked to climate change, the long-term trend of declining sea ice extent, as predicted by climate models, makes such events increasingly likely. Understanding how sea ice, especially land-fast sea ice, will respond to future climate change is crucial for effective conservation strategies.

This study provides compelling evidence of the catastrophic impact of record low Antarctic sea ice extent on emperor penguin breeding success. The widespread breeding failure observed in the Bellingshausen Sea highlights the urgent need for comprehensive conservation strategies to mitigate the effects of climate change on these vulnerable populations. Future research should focus on refining predictive models of sea ice loss and its impact on emperor penguins, exploring the adaptive capacity of these birds, and developing effective mitigation and adaptation strategies.

The study focuses on a specific region and a single year. While this provides strong evidence of a link between sea ice loss and breeding failure, it may not represent the variability in response across all emperor penguin colonies in Antarctica. The resolution of the satellite imagery might limit the precise assessment of chick survival rates in some cases. Future research should expand the geographic scope and time scale of the study to provide a broader understanding of the impacts of sea ice changes on emperor penguins.