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Emperor penguin colonies abandoned after ‘unprecedented’ loss of sea ice
The breeding failure of four emperor penguin colonies is a sign of things to come, researchers have warned.
This follows previous research which suggests the world’s largest penguin could be on the verge of extinction by 2100.
Over 9,000 emperor penguin chicks are thought to have perished following record low levels of sea ice in 2022.
Analysis of satellite imagery suggests that no chicks from four out of five colonies in the Bellinghausen Sea appear to have survived in 2022. What little ice there was melted before the young birds had developed their waterproof feathers, leaving them to perish.
The unseasonal temperatures in western Antarctica are believed to be linked to climate change, with levels of sea ice set to be lower than ever in 2023.
Dr Peter Fretwell, the study’s lead author, says, ‘We have never seen emperor penguins fail to breed, at this scale, in a single season. The loss of sea ice in this region during the Antarctic summer made it very unlikely that displaced chicks would survive.’
‘We know that emperor penguins are highly vulnerable in a warming climate - and current scientific evidence suggests that extreme sea ice loss events like this will become more frequent and widespread.’
The findings of the study were published in the journal Communications Earth & Environment.
From left to right, these satellite photos show the condition of the Smyley Island colony on 10 October, 28 October and 10 December 2022. Image © European Commission, Copernicus SENTINEL-2.
Penguins in western Antarctica
Penguins are heavily dependent on sea ice as part of their life cycle. In particular, they need land-fast sea ice, which is connected to nearby coastline, to rest, moult and hunt from. Many penguin prey species also depend on the ice for their own life cycles.
Penguins breed on the ice and raise their chicks there too. As well as providing a place to incubate their eggs, the ice also provides a platform for the chicks to stay until they have developed their waterproof feathers in a process known as fledging.
As the largest living species of its kind, emperor penguins need the ice to remain stable for a long period of time so that their chicks can fully develop. After arriving at their breeding sites in April each year, the ice must stay intact until the chicks have fledged by January.
In recent years, however, the sea ice has become increasingly unstable. The West Antarctic Peninsula is warming at around twice the rate of the rest of the continent, putting penguin colonies in this area at particular risk of breeding failure.
Even some of the largest are not immune to these losses. Between 2016 and 2019, no chicks from the Halley Bay colony, at one point the second largest in the world, are thought to have survived after the ice broke up early.
The pattern now appears to be repeating itself in the Bellingshausen Sea, located on the other side of the peninsula. Researchers looked at satellite imagery to investigate the health of the penguin colonies, with the extent of sea ice and faeces marks being used to work out how the colonies were faring.
The imagery revealed that while the colonies appeared to be occupied until the end of October, the early break up of sea ice in November 2022 led to three of the colonies being abandoned during the next month. A fourth colony, Pfrogner Point, was also abandoned, though the reasons are unclear.
Only the Rothschild Island colony, where the ice is protected by the shape of the bay, is known to have bred successfully, with 820 chicks counted from helicopter surveys of the site. While it’s possible that a few chicks may have fledged from the other colonies, this hasn’t been confirmed.
As emperor penguin colonies breed all around the Antarctic coastline, the breeding failure in one region isn’t an immediate threat to the species. However, researchers have described the collapse of four previously stable colonies as ‘very concerning.’
‘The consensus view is that sea ice will not recover to its previous levels and that what we are now seeing is evidence of a continuing decline,’ Peter says. ‘This will mean that these breeding failures are an indication of what is to come for the emperor penguin.’
While specific events are difficult to link to climate change, climate models predicts that Antarctic sea ice will decline significantly by 2100. Image © Kaspars Grinvalds/Shutterstock.
The uncertain future of emperor penguins
While seabirds are renowned for their ability to bounce back from population declines, the penguins’ breeding failures put pressure on a species which is already under a great deal of stress.
This pressure does not appear to be letting up in 2023. The extent of sea ice around Antarctica is approximately 2.2 million square kilometres less than it should be at this time of year, which is an area about the size of Greenland.
This is already much less than at the same point in 2022, suggesting this year will also be a bad one for penguin breeding.
‘While it’s possible for penguins to recover from breeding failure in one year, 2022 came on top of an already bad year in 2021,’ Peter says. ‘Looking at the extremely low winter sea ice we currently have around Antarctica, 2023 is almost certain to be worse than 2022.’
‘Though breeding failure is not happening everywhere, it’s starting to look like some areas such as the Bellingshausen Sea may become untenable in the long run for successful breeding sites.’
Because of the complexities of modelling the atmosphere, it’s not completely certain that climate change is responsible for the recent temperature extremes in Antarctica. However, as temperatures rise, levels of sea ice are expected to decline towards the end of the century.
Dr Caroline Holmes, a polar climate scientist at the British Antarctic Survey, says, ‘Year-to-year changes in sea ice extent are linked to natural atmospheric patterns such as El Niño-Southern Oscillation, the strength of the southern hemisphere jet stream, and regional low-pressure systems.’
‘We’ll need years of targeted observations and modelling to know precisely how much the current conditions are being influenced by these phenomena and by natural ocean variability. However, the recent years of tumbling sea ice records and warming of the subsurface Southern Ocean point strongly to human-induced global warming exacerbating these extremes.’
By the end of the century, melting ice may mean that 90% of emperor penguin colonies may be on the verge of extinction. While penguins can move to more stable regions to set up new colonies, they will be left with fewer and fewer options.
Ultimately, the main way to protect these animals is by taking urgent action to reduce greenhouse gas emissions. There are also calls to upgrade their conservation status at a regional and global level, which will allow plans to be put in place to protect these iconic birds.
