New Research Shows Shifting Fortunes of 2 Southern Ocean Penguin Species

Elephant Island, where British explorer Ernest Shackleton and his crew were marooned for several months in 1916, is today inhabited only by wildlife and sits at an ecological crossroads between Antarctica and the Southern Ocean.

In early 2020, funded by a grant from The Pew Charitable Trusts, scientists from Stony Brook and Northeastern universities spent 12 days surveying the island, a feat that had been accomplished only once before, by a British Joint Services expedition in 1970-71.

That survey 50 years ago counted more than 120,000 penguin nests on Elephant Island, and researchers last year sought to learn whether that number had changed.

The answer, published in November in the journal Polar Biology: Yes, it has, and drastically.

Elephant Island is a traditional stronghold for chinstrap penguins, a species that prefers cold, exposed Antarctic coasts. But the 2020 census, conducted using drones and on-the-ground counts, documented a more than 50% decline in active chinstrap penguin nests on the island compared with 1970-71, a significant drop for the area’s most abundant bird.

“It’s unclear what caused the decline; however, we have several hypotheses,” says Heather Lynch, a professor of ecology and evolution at Stony Brook University and an author of the study. One theory is that the chinstraps must compete harder for krill—a main food source—which are under pressure from an increasingly concentrated commercial fishery and resurgent whale populations, Lynch says. “And climate change, which has disproportionately warmed the West Antarctic Peninsula, affects the marine ecosystem in ways we are only beginning to understand.”

Additionally, separate studies show that several smaller chinstrap colonies on nearby islands have recently declined; because adult penguins rarely emigrate to other colonies, it’s unlikely that the Elephant Island decline can be explained by individuals moving elsewhere.

@wethington_mj

But other penguins on Elephant Island appear to be doing well. The 2020 expedition discovered that the number of gentoo penguins there more than doubled since 1970, to at least 3,600 nests, and researchers even found a couple of king penguins—a sub-Antarctic species rarely seen so far south—incubating eggs on the island. Gentoos and kings thrive on sandy, ice-free beaches in the Falkland Islands and South Georgia Island and seem to be spreading south as the Antarctic Peninsula warms, the authors wrote.

A second study, published in the journal Scientific Reports in November, establishes the first rigorous global population assessment of chinstrap penguins, examining data from all 375 colonies going back to the 1970s.

A few of those colonies, known mostly from satellite imagery, do not have enough historical information to determine a trend. Of the rest, some appear to be stable, 18% have increased, and 45%—including most of the breeding chinstrap penguins on the West Antarctic Peninsula—have significantly declined.

This is a worrying tally, but other data may give additional context to this decline for chinstraps. Reports from the mid-20th century indicate that their numbers had been increasing up to the 1970s, perhaps because heavy whaling earlier in the century decimated a major competitor for krill. So chinstrap populations may have been at a high point 50 years ago. And several mega-colonies of chinstraps in the South Sandwich Islands, along the largely submerged ridge connecting Antarctica with South America, appear to be more stable than colonies farther south.

The most striking finding of both studies is how fast things are changing.

Penguin numbers naturally fluctuate, but when breeding populations rapidly halve or double in size—or drop by more than 70%, as one of the largest chinstrap penguin colonies on Elephant Island did—it suggests major, ecosystem-level changes are underway.

“Sentinel Antarctic species like the chinstrap penguin may not be able to adapt as quickly as behaviorally flexible, more northern species like the gentoo penguin,” says Noah Strycker, a master’s student in Lynch’s lab at Stony Brook and the lead author on both papers. “If conditions keep shifting, then the Antarctic Peninsula’s seabird community will look quite different in the future than it does today, with a greater dominance of subantarctic species that thrive under these warmer, less icy conditions, and a reduction of true Antarctic specialists.”

A key way to help penguins and much of the peninsula’s wildlife adapt to the myriad stresses is designation of a marine protected area (MPA) in the region. The benefits of this tool were underscored in October by a trio of studies showing that marine protections would help many of the species found on the Antarctic Peninsula, including resident penguins. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), the governing body responsible for protecting Southern Ocean wildlife, passed on this chance in October, when it failed to approve an MPA proposal for the Antarctic Peninsula. That proposal, submitted by CCAMLR member countries Argentina and Chile in 2018, calls for protections throughout the region, including Elephant Island.

This new research is more evidence that conservation measures are critical to offset climate change impacts to Southern Ocean ecosystems. Additional stresses, such as tourism and pollution, are only increasing. The two studies published in November provide more evidence that conservation measures—namely, establishment of MPAs—are vital to conserving the rich biodiversity of Antarctica far into the future.

The two studies described in this article were funded by The Pew Charitable Trusts with field work supported by Greenpeace International.

Andrea Kavanagh directs and Anne Christianson is a principal associate with The Pew Charitable Trusts’ protecting Antarctica’s Southern Ocean project