In The News: Only 2 chicks survive from a colony of 18,000 pairs in Antarctica

This week we were met with the terrible news that only 2 Adélie penguin chicks had survived the breeding season, from a colony of 18,000 pairs, in Antarctica earlier this year.  But is this an indicator of climate change or just part of the natural variability in breeding cycles?

Adélie penguins in Antarctica (Image: National Geographic) 

For 45,000 years, populations of Adélie penguins have survived and adapted to the melting and expansion of ice in Antarctica. Today, the penguin colonies' success varies across the southern continent: on the East Antarctic Ice Sheet, numbers have been growing steadily but rapid warming in other areas, particularly across the Antarctic Peninsula, is threatening breeding sites. 

This year, it is believed that the low survival rate of chicks was caused by unusually high amounts of ice which meant adult penguins had to travel much further for their food and leave their chicks for longer. This late sea ice has been attributed to the breakup of the Mertz Glacier in 2010; this glacier had previously helped to keep the nearby ocean ice free. Ice-free areas are known as polynyas. 

Polyn-huh?

Ice-free areas, or coastal polynyas, are maintained by the presence of a topographic or glacial feature (in this case the Mertz Glacier Tongue) and a persistent wind in a singular direction. Simply, this wind drives newly formed sea ice away from the barrier, leaving open water behind it (for a more detailed explanation please follow this link). As Campagne et al., 2015 highlight, the break up of the Mertz Glacier in 2010 disrupted this process: the once ice free area was filled with ice as the important barrier was removed. 

An ice berg (right) collides with the Mertz Glacier tongue in 2010 (Image: Neal Young)

The Future for Adélie Penguins

This catastrophic breeding season may not be linked directly to climate change. However a paper by Cimino et al, 2016 has projected that by 2060 a third of the current colonies will be diminishing. Fishing and tourism, combined with the threats that climate change places on the availability and quality of food, are likely to threaten populations further. Yan Robert-Coudert, who leads the penguin research programme at Durmont D'Urville, recently told The Guardian:

"there may still be years when the breeding will be OK, or even good for this colony, but the scene is set for massive impacts to hit on a more or less regular basis"

Predicted changes in the suitability of breeding sites for Adélie penguins (Image: NASA)

Although this specific event cannot be attributed directly to climate change it highlights the sensitivity of Antarctic species to changing environments. The frequency of such dramatic events is likely to increase with a changing climate and this could threaten the balance of delicate Antarctic ecosystems.