Every day, Landsat satellites orbit the planet, capturing images of things like changing cities, massive fires, and melting glaciers. Among the more curious photos they snap are those of Adélie penguin populations in Antartica. This strange task is the work of NASA scientist Mathew Schwaller, who reasoned in 1984 that because penguins pooped a lot, scientists could estimate the size of penguin populations from space by examining the sheer number of guano stains on photos of the ice. On Friday, scientists used this data to announce some very good news.

In an open-access paper in Scientific Reports, scientists announced the discovery of a mega-colony of 1.5 million Adélie penguins at the northernmost tip of the Antarctic Peninsula, an archipelago of nine islands known as the Dangers Islands. An examination of the guano stains scattered across the jagged landscape suggested to the scientists that there could be nearly 200,000 penguin nests below. This identified the Dangers Islands as an unrecognized Adélie penguin hotspot.

Adélie penguin
An Adélie penguin and quadcopter on Brash Island, Danger Islands.

“The sheer size of what we were looking at took our breath away,” co-author Heather Lynch, Ph.D., told the BBC. “We thought, ‘Wow! If what we’re seeing is true, these are going to be some of the largest Adélie penguin colonies in the world, and it’s going to be well worth our while sending in an expedition to count them properly.”

The scientists combined the satellite images with photographic surveys taken by drones and direct on-the-ground counts by the expedition team to conduct the first comprehensive seabird survey of the Dangers Islands. They discovered that the islands host 751,527 pairs of Adélie penguins, indicating that this site is either the third- or fourth-largest Adélie penguin colony in the world.

Three minute intervals, showing how often penguin partners swap over their nest care duties.

A comparison of the images they took via drone with the historical record of satellite images shows that these colonies have been stable, with signs of small increases, for the last 60 years. This is notable because Adélie penguin populations in other areas have seen dramatic shifts in abundance, with sharp declines in the Western Antarctic Peninsula and sharp increases in the Ross Sea and Eastern Antartica. While the scientists don’t know exactly why these changes are happening, they write that “several studies have linked Adélie penguin population trends to changes in sea ice extent and concentration as well as changes in air temperature and precipitation patterns and their population effects on prey availability.”

The primary reason the massive populations on the Dangers Islands haven’t been discovered before is because the islands are so difficult to access. Located in the Weddell Sea, pack ice surrounds the islands, prohibiting access to them for most of the year. Heroína Island, the most frequently visited of the nine islands, has a median visitation rate of only one ship landing per year. While Adélie penguins were photographed by a passing ship in 2008, no one had any idea how many of them were spread throughout the islands. The population estimate in the new study is three times larger than the one proposed by a different survey of scientists in 1996 because “several colonies, not known to exist at the time, were missed entirely.”

Penguins, Antartica
Adélie penguins jumping off an iceberg in Danger Islands, Antartica.

The scientists are hopeful this discovery will lead to two major changes. One is that they will be able to gain a better understanding of how climate change is affecting the region by examining an ecosystem and population that hasn’t been studied.

The second is that this region will quickly be protected. Now that we know these penguin populations are here, it provides further evidence that they must be conserved. In January, UN delegates from Germany proposed the creation of the Weddell Sea Marine Protected Area, which at 1.8 million square kilometers would be the world’s largest marine protected area. Several countries have announced support for the proposal, which will go to a vote at the UN in October.

“The size of these colonies makes them regionally important and makes the case for expanding the proposed Weddell Sea Marine Protected Area to include the Danger Islands,” co-author Michael Polito, Ph.D., told The Guardian. “More than that, I think it highlights the need for better protection of the West Antarctic Peninsula, where are seeing declines.”

Two-year monitoring of Adélie penguins.