In 2019, researchers used Sentinel-2 satellite images to find eight unreported emperor-penguin breeding colonies, lifting the known total to 61

Antarctica might have just got a bit more crowded, at least on paper. Eight previously unknown emperor penguin colonies have been identified by a team from the British Antarctic Survey, using images from the European Space Agency’s Sentinel-2, a satellite mission run for the European Commission’s Copernicus program. The study, published in Remote Sensing in Ecology and Conservation in August 2020, also confirmed three other colonies that scientists had long suspected but never been able to prove. Together, these findings brought the number of currently active emperor-penguin colonies to 61, a rise of nearly 20 percent, even though 65 sites have been recorded across the species' history, since a handful of older ones are no longer occupied.

How penguin droppings gave the colonies away

Observing emperor penguins is difficult because they live in some of the remotest and harshest locations on Earth, where the temperature falls to minus 50 degrees Celsius. Satellite photos are too small to clearly show the birds themselves. Their droppings, however, are a different story. The guano stains are large reddish-brown patches on the sea ice, which are easily visible at the 10-meter resolution that Sentinel-2 offers. The BAS scientists had been searching for a similar stain along the Antarctic coast for about a decade now. Clearer Sentinel-2 images captured between 2016 and 2019 helped them identify colonies missed by earlier satellites.

More birds than anyone realized


The project’s lead scientist and geographer at the BAS, Peter Fretwell, referred to this discovery as "an exciting find" in an official BAS statement. These new colonies are, however, quite small. According to BAS figures, the newly identified colonies increased the estimated emperor penguin population by 5 to 10 percent, to more than 500,000 birds, or 265,500 to 278,500 breeding pairs. The figures come directly from the research team and are consistent with the satellite data in the study.

A discovery with climate implications

Most of the newly identified colonies are in areas at the outer edge of the species' breeding range that climate models predict will be among the first to lose their sea ice. The birds are the "canaries in the coal mine" for the wider region, as they are likely to feel the effects of a warming Antarctic before other colonies, said Phil Trathan, head of conservation biology at BAS and co-author of the study. The study also reported something unexpected. A number of colonies were found far from shore, some as much as 180 kilometers out, nesting on sea ice that had formed around icebergs stuck in shallow water. The researchers called it a surprising new finding in the behavior of an already well-studied species.

A bigger climate warning in the numbers

Another study, headed by Stéphanie Jenouvrier of Woods Hole Oceanographic Institution and published in 2019 in Global Change Biology, made projections about the effect of the melting of sea ice on Antarctica on the changes in the population numbers of emperor penguins. The paper's abstract projects that if global emissions keep rising at current rates, total abundance will decline by at least 81 percent by 2100, regardless of how much the birds disperse to new sites. If countries hold warming to the Paris Agreement's stricter target of 1.5 degrees Celsius, the projected decline falls sharply, to at least 31 percent.

Sea ice is not a side note to these birds. Emperor penguins feed on it, breed on it and molt on it, and both too little and too much ice can be detrimental to their chances of raising healthy chicks, the study's authors said. Most of the newly discovered colonies are located in the zones expected to lose ice first, so the discovery brings no comfort, but a sense of urgency.

Why this matters

A higher colony count might sound like reassuring news. It will be easier to track how the population is being affected by the changing environment because researchers know where the penguins live now. An updated map, however, might not be a fix. The new colonies are small, highly vulnerable to melting ice, and in areas where climate models predict the fastest changes. For now, the story of the emperor penguin is a familiar one in climate science: a species turning out to be a little more resilient than expected, while the conditions it depends on keep slipping away.