Adélie Penguin

Without Adélie penguins, some of the krill they would have eaten — several million birds across the continent — would remain available to crabeater seals, whales and other penguin species feeding on the same shoals, which would benefit from it as early as the first season.

Over about a decade, that krill surplus would likely spread thin across many species rather than mainly benefiting one: baleen whales, still recovering from decades of historical hunting, would probably absorb a good share of it without any single population showing dramatic growth.

On the western Antarctic Peninsula, where colonies have already declined 65% over 25 years, a century of continued decline would likely empty that stretch of coastline of one of its main visible krill consumers — a gap that seals and whales in the same region would probably fill in gradually, without dramatic knock-on change to the rest of the local food web.

Over a thousand years, even a continent-wide disappearance of the Adélie penguin would likely leave few lasting, species-specific traces in the Antarctic food web: other major krill consumers would take up the vacated space, and the ecosystem would mostly bear the mark of krill decline and warming themselves — not the absence of any one species.