The population of emperor penguins in one part of Antarctica appears to be declining faster than previously thought, according to a new analysis of satellite imagery released Tuesday.

The estimated population of 16 penguin colonies — visible in satellite photos taken between 2009 and 2024 – had declined 22% during that period mainly because of climate change that’s shrinking the amount of available sea ice. It’s unclear whether this drop is seen across the continent, scientists said.

Scientists previously estimated that the total emperor penguin population declined about 10% across all of Antarctica over the past decade and a half. The latest survey included a region covering the Antarctic Peninsula, Weddell Sea and Bellingshausen Sea.

“It’s absolutely alarming that the numbers are so much worse than predicted,” said Daniel Zitterbart, a penguin researcher at the Woods Hole Oceanographic Institution, who was not involved in the study.