ANTARCTICA’S SEA-ICE CRISIS: CLIMATE CHANGE THREATENS ANTARCTIC WILDLIFE AS SEA-ICE LEVELS DROP

By: Emily Grilly, WWF Antarctic Conservation Manager

Antarctica is the coldest region on the planet. It is also experiencing some of the world’s most intense heatwaves.

The warming climate caused sea-ice around Antarctica to shrink to the smallest area on record in February 2023¹, followed by additional record-breaking low levels during Antarctica’s winter from June to September, continuing a decade-long decline. This is a stark indicator of the rapidly changing environment, with consequences for Antarctic wildlife.

Antarctic sea-ice provides refuge for a range of species, from tiny crustaceans like Antarctic krill, to the largest penguin species – the emperor penguin, who rely on sea-ice habitats for their survival.

As the Antarctic environment experiences rapid environmental change, many Antarctic species are feeling the heat.

Emperor Penguins are navigating an uncertain future

Emperor penguins are the only penguin species that breed during the Antarctic winter. During this time, they rely on stable sea-ice to lay their eggs and raise their young. As regional temperatures rise, the break-up of sea-ice during the spring season is happening earlier. This can be fatal for chicks that have not yet developed their adult waterproof feathers or learned to swim.

This is exactly what happened in late 2022 – a significant reduction in sea-ice in the Bellingshausen Sea was the cause of catastrophic breeding failure across four colonies, resulting in the death of thousands of chicks².

The fate of emperor penguins is closely tied to sea-ice. Research has found that 98% of emperor penguin colonies may be pushed to the brink of extinction by 2100 if no changes are made to the current rates of carbon emissions and climate change³.

Krill population declines will have far-reaching consequences for a range of wildlife

At the heart of the Antarctic food web lies a tiny, yet mighty, organism known as krill. These shrimp-like creatures are the primary food source for countless species, including penguins, seals, and whales. Antarctic krill also provide important an ecosystem function for our planet – each year, they capture millions of tonnes of carbon and transport it for safe storage in the ocean, which helps to maintain stable climatic conditions.

Krill rely on under sea-ice habits during key phases of its life cycle, especially during the larval stages for food and refuge from predators.

Krill populations have already been found to be declining in some regions around the Antarctic Peninsula⁴, and projections indicate that krill abundance could decline by over 40% by the end of the century in areas such as the North Scotia Sea⁵.

Krill are also the target of a large-scale industrial fishery that operates around the Antarctic Peninsula. Current management of this fishery is considered outdated as it does not take into consideration climate change impacts on Antarctic krill, and allows for concentrated fishing effort, meaning fishing vessels target the same small-scale locations repeatedly each year. Evidence has indicated that climate change, coupled with krill fishing, is impacting Antarctic krill and krill predator populations⁶.

Declines in krill abundance and changes in their distribution will continue to have significant consequences for whales, penguins, fish and seabirds that all rely on krill as their primary food source. Evidence is already emerging that indicates chinstrap and Adelie penguins, as well as humpback whales, are suffering the consequences.

Research has revealed a 30% decline in chinstrap penguin numbers around the Antarctic Peninsula, which represents a substantial portion of the population⁷. This decline is likely linked to reduced krill abundance during years of low sea-ice⁸ - when there is less krill, penguins must spend more time foraging, which can increase the risk of breeding failure.

Projections for chinstrap and Adelie penguin populations indicate significant population declines by the end of the century⁹.

Humpback whales undertake epic migrations to Antarctic waters each year to feast on krill. They rely on the predictable timing of krill blooms, which are closely tied to the formation and melting of sea-ice.

Less sea-ice means krill abundance is changing, making it challenging for humpback whales to locate their primary food source. As a result, these majestic creatures may be facing longer journeys with more energy devoted to foraging. Research has found that humpback whales in the Western Antarctic Peninsula have reduced pregnancy rates in years following poor krill availability¹⁰.

Urgent solutions needed: Marine Protected Areas provide a safe refuge

The record low levels of Antarctic sea-ice in 2023 are a stark reminder of the urgent need to address climate change. The impacts on species like krill, humpback whales, and penguins are not isolated incidents; they are symptomatic of a continent in crisis.

There are tools available and ready for implementation that will provide the support urgently needed by Antarctic wildlife to develop resiliency to their changing environment. Marine protected areas (MPAs) are a nature-based solution supported by sound science. MPAs can protect wildlife by reducing human pressures, such as industrial fishing, and providing a safe refuge for wildlife to adapt.

The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) is the international organisation responsible for the conservation of Antarctic wildlife. At their upcoming annual meeting in Hobart, Tasmania (October 16^th – 27^th), decision-makers from 27 countries will have the opportunity to establish three large-scale MPAs around Antarctica – in the Antarctic Peninsula, Weddell Sea and East Antarctica.

As we witness these iconic species struggling to survive, it becomes abundantly clear that we must take swift and decisive action to protect the fragile Antarctic ecosystem. We call on CCAMLR to prioritise conservation in their decision-making and urgently establish these three MPAs.

References

1. Siegert, M. J. et al. Antarctic extreme events. Frontiers in Environmental Science. 11 (2023).
2. Fretwell, P. T., Boutet, A. & Ratcliffe, N. Record low 2022 Antarctic sea-ice led to catastrophic breeding failure of emperor penguins. Commun. Earth Environ. 4, 1–6 (2023).
3. Jenouvrier, S. et al. The call of the emperor penguin: Legal responses to species threatened by climate change. Glob. Chang. Biol. 27, 5008–5029 (2021).
4. Kasyan, V. et al. Composition and Distribution of Plankton Communities in the Atlantic Sector of the Southern Ocean. Diversity 11, 923 (2022).
5. Klein, E., Hill, S., Hinke, J., Phillips, T. & Watters, G. Impacts of rising sea temperature on krill increase risks for predators in the Scotia Sea. PLoS One 13, e0191011 (2018).
6. Watters, G. M., Hinke, J. T. & Reiss, C. S. Long-term observations from Antarctica demonstrate that mismatched scales of fisheries management and predator-prey interaction lead to erroneous conclusions about precaution. Sci. Rep. 10, 1–9 (2020).
7. Krüger, L. Decreasing Trends of Chinstrap Penguin Breeding Colonies in a Region of Major and Ongoing Rapid Environmental Changes Suggest Population Level Vulnerability. Diversity 15, (2023).
8. Salmeron, N. et al. Contrasting Environmental Conditions Precluded Lower Availability of Antarctic Krill Affecting Breeding Chinstrap Penguins in the Antarctic Peninsula. Sci. Rep. 13, (2023).
9. Cimino, M. A., Lynch, H. J., Saba, W. V. & Oliver, M. J. Projected asymmetric response of Adelie penguins to Antarctic climate change. Sci. Rep. 6, (2016).
10. Pallin, L. J. et al. A surplus no more? Variation in krill availability impacts reproductive rates of Antarctic baleen whales. Glob. Chang. Biol. 29, 2108–2121 (2023).