New emperor penguin colonies discovered from space | Polarjournal
Emperor penguins breed at the beginning of the Antarctic winter on the fast ice around Antarctica. The colonies are usually a few hundred to thousands of breeding pairs large and disband around the end of December. Photo: Michael Wenger

Emperor penguins are the icons of Antarctica and the object of desire for most visitors, whether tourists or researchers. But the largest penguin species in the world is also the most difficult to observe. Because the animals breed in the middle of winter and the colonies often lie in very difficult places to reach. That is why it is not surprising that researchers keep resorting to satellite imagery. Now, two British researchers from the British Antarctic Survey have discovered 11 additional colonies on new images from the Sentinel2 satellites.

“This is an exciting discovery. The new satellite images of Antarctica’s coastline have enabled us to find these new colonies.”

Dr Peter Fretwell, British Antarctic Survey

In the discovered colonies around the Antarctic continent, eight places were previously unknown and three places that were formerly known as colony sites, but have only now been rediscovered and confirmed. This brings the number of known breeding sites of emperor penguins to 61 around the entire continent. The discovery was made possible thanks to the latest high-resolution images from the Sentinel2 mission of the European Copernicus program. SCAR, the Scientific Committee on Antarctic Research for the Antarctic Treaty states, has been receiving data from Antarctica for research purposes since the start of the mission. Dr Peter Fretwell, one of the two scientists, says: “This is an exciting discovery. The new satellite images of Antarctica’s coastline have enabled us to find these new colonies.”

The satellite images show the brown spots on the ice created by the penguins’ guano. Through accurate image analysis, the researchers were able to determine whether the spots were actually penguin colonies or not. Images of: From Fretwell & Trathane (2020) Rem Sens Ecol Cons

The satellite images show that the newly discovered colonies are all located on the fast ice around Antarctica. Most colonies are probably not very large, according to the researchers, usually only a few hundred to a thousand breeding pairs. The largest of the new colonies is probably located at Cape Gates, where several thousand pairs of emperor penguins should be located. “The colonies are small and so only take the overall population count up by 5-10% to just over half a million penguins or around 265,500 – 278,500 breeding pairs,” explains Dr Fretwell. With the new colonies, 30 of the 61 existing colonies have been discovered with the help of satellite images, which emphasizes the importance of this tool.

The map shows where the 8 additional colonies are (red circles). The rediscovered colonies (yellow rectangles) could be precisely located thanks to the high-resolution images. In addition to the 61 colonies (green triangles), there are four other places that were formerly known as colonies and are now abandoned (blue triangles). Picture: From Fretwell & Trathan (2020) Rem Sens Ecol Cons The rediscovered colonies (yellow rectangles) could be precisely located thanks to the high-resolution images.

In addition to the size of the colonies, the two researchers also examined the location of the colonies, which could be more precisely determined thanks to the high resolution of the satellite images. Thus it turned out that the rediscovered colonies were up to 50 kilometers away from the previously known position. In addition, the two researchers were able to show that the colonies lie at regular intervals along the coast and that no emperor penguins breed in front of the large ice shelf regions. But in terms of the distance to the coast, the results were a big surprise.

“We need to watch these sites carefully as climate change will affect this region.”

Dr Phil Trathan, British Antarctic Survey

Because some of the new colonies are located on the outermost edge of the known distribution area of the emperor penguins, partly up to 180 kilometers away from the actual coast and the fast ice. This puts penguins at risk from the effects of global warming. “Whilst it’s good news that we’ve found these new colonies, the breeding sites are all in locations where recent model projections suggest emperors will decline.,” said Dr. Phil Trathan, the study’s second author. “Birds in these sites are therefore probably the ‘canaries in the coalmine’ – we need to watch these sites carefully as climate change will affect this region.” According to a study published last year, most colonies will decline due to climate change and progressive warming around the continent. How much depends on the further global emissions trend.

The images used by the two researchers were taken by the two Sentinel2 satellites A and B. They have been in space since 2015 and 2017 and are part of ESA’s Earth Observation Programme. In the visible range, the cameras can reach up to 10 meters resolution. Photo: ESA

The results were achieved thanks to the high-resolution cameras of the two Sentinel2 satellites A and B, whose resolutions range from 10 to 60 meters. These two satellites, which collect data on the climate and its effects on the earth’s surface as part of the European Union’s Copernicus programme, fly around the globe at an altitude of around 800 kilometres. Since 2016, the Scientific Committee on Antarctic Research (SCAR) has been receiving data from ESA to study the impact of climate change on Antarctica. The two satellites weighing just under 1,200 kilograms are expected to continue to orbit at least until 2022 and 2024 respectively, helping to further unravel the mysteries of Antarctica.

Dr Michael Wenger, PolarJournal

Link to the study:
Peter T. Fretwell, Philip N. Trathan. Discovery of new colonies by Sentinel2 reveals good and bad news for emperor penguins. Remote Sensing in Ecology and Conservation, 2020

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