Melting of Antarctica threatens the existence of penguins – 01/02/2024 – Environment

The rapid decrease in sea ice areas in Antarctica, mainly in the western portion of the continent, puts at least two species of penguins at risk, whose life cycle depends on the region’s frozen shelves.

A series of recent studies shows that the situation is not at all auspicious for the largest and most famous bird in the group, the emperor penguin (Aptenodytes forsteri), and also brings worrying signs for the Adelie penguin (Pygoscelis adeliae). The first species usually raises its young on Antarctic sea ice. The second uses the frozen sections for the annual phase of shedding feathers, essential to maintain its ability to withstand the worst winter months.

Despite the almost immediate association between Antarctica and penguins in people’s imagination, the fact is that the majority of the approximately 20 species in the group do not live in Antarctic territory. In addition to the emperor penguin and the Adelie penguin, which are present in the continental region of Antarctica proper, three more species have colonies on the northern tip of the Antarctic peninsula, the spit of land that extends towards South America. Penguins on the peninsula usually nest on the ground rather than on the ice.

In the case of emperor penguins, a study coordinated by Peter Fretwell, from the British Antarctic Service, revealed that 2022 was catastrophic for colonies of the species that live in the Bellingshausen Sea region, on the western side of the peninsula. Based on high-resolution satellite images that show brownish stains (basically penguin feces) contrasting with the whiteness of the ice and snow, Fretwell and his colleagues estimate that, of the five colonies in the area, four have lost all their their young due to the accelerated decrease in sea ice.

The risk is so great because the baby penguins’ breeding phase takes place on sea ice that is “anchored” on dry land (in theory, they are not pieces of ice that float freely in the ocean, therefore). According to the study, published in the specialized journal Communications Earth & Environment, pairs of the species usually occupy these stretches of ice from April to January. Females lay their eggs between May and June and the chicks are born after 65 days of incubation.

The problem is that babies only gain their adult feathers, which are waterproof and essential for them to avoid sinking in the water, between December and January. However, in 2022, in the colonies that disappeared, the stretches of sea ice where the nests were located had already melted in November – most likely, therefore, the chicks ended up sinking and their parents had to abandon the area.

“We have never seen emperor penguins lose their breeding season on this scale in a single year. The loss of sea ice in this region during the Antarctic summer has made the survival of chicks that have lost their nests very unlikely,” said Fretwell. “Current evidence suggests that extreme sea ice loss events like this will become more frequent and affect wider areas in the future.”

In fact, according to a statement from the British Antarctic Service, the region has been the site, since 2016, of the four smallest extensions of sea ice over the last 45 years of satellite records.

In another study, coordinated by Annie Schmidt, from the American NGO Point Blue Conservation Science, scientists monitored around 200 Adélie penguins living in the Ross Sea region of continental Antarctica, in addition to using satellite data on sea ice. in the region.

The results, published in the specialized journal PNAS, indicate that the areas of sea ice used by birds to shed their feathers have been decreasing in the Ross Sea since the 1980s, with this process accelerating in the last five years.

Furthermore, there is a clear correlation between ice concentration and the ability of birds to return to their colonies after moulting their feathers. For every 10% reduction in sea ice areas, there is a drop of between 2.4% and 4.8% in the number of penguins that are able to return to breeding colonies.

As if these threats were not enough, there are also indirect effects linked to krill, a small crustacean similar to a shrimp that is one of the main dishes on the penguins’ menu. Krill also use sea ice for food and protection, which means melting could make the penguins’ diet much less plentiful. Impacts on the crustacean can even affect species on the Antarctic peninsula that do not directly depend on sea ice for their reproduction or shedding of feathers.