Across the Bellingshausen Sea at least seven thousand chicks fell into the sea too soon for them to survive. The overall death toll was lower than at Halley Bay, but the catastrophic breeding failure in 2022 was on a scale never seen before, with the four out of the five colonies abandoned. And unlike at Halley Bay, there are no other colonies nearby for any surviving adult emperor penguins to easily relocate to.
The collapse of colonies in the Bellingshausen Sea was precisely the kind of disaster predicted in the most detailed study to date of what could happen to emperor penguins as the climate heats and sea ice vanishes. Analysis conducted in 2019 by Stéphanie Jenouvrier from Woods Hole Oceanographic Institution in Massachusetts and her colleagues showed that if humanity blunders on regardless and allows greenhouse gas emissions to continue unabated, Antarctica’s frozen fringe of sea ice will shrink by around half, and many more emperor colonies would see their sea ice vanish entirely during the critical times when females should be laying and males should be caring for eggs balanced on their feet. In this ice-starved, stressed state, emperor penguin numbers would crash in 80 per cent of colonies, and the entire species would be shrinking year by year. It would effectively spell the end of the emperor penguin.
Jenouvrier’s analysis offers little hope that the situation would improve if emperors in the future do as the Halley Bay penguins did and swim off to join other colonies that aren’t faring so badly. Nobody knows for sure how well emperor penguins disperse. Jenouvrier tested out various possibilities, including penguins that disperse either short or long distances and either seek out areas of good habitat where other birds are already breeding well or simply swim about searching at random. The models suggest that regardless of how well penguins disperse and find their way to other colonies, it won’t be enough to counteract the declines in the population caused by shrinking sea ice.
We also can’t assume emperor penguins will start using other types of ice that will last longer in warming seas. Their legs are not long or strong enough to let them easily climb onto the tall, longer-lasting ice shelves; they can’t easily scale the steep edges of icebergs, nor have they any hope of leaping their big bodies that far, even with the added push of bubbles. Occasionally emperors come across a ramp of snow to clamber up onto a high ice shelf, as happened in 2017 in Atka Bay to the east of the Weddell Sea. However, with no easy access to the sea to gather food, the penguins were left stranded and had no other choice but to jump fifteen to thirty feet into the water. For those that hadn’t fully molted this was a lethal leap. Moving onto land may not be a good option either, because the penguins would likely be too far from oceanic foraging grounds to feed themselves and their growing chicks. It seems likely that emperor penguins simply don’t have it within their biology to save themselves as a species while the Anthropocene changes their world. Their main hope comes from the possibility that human-made carbon emissions won’t continue to relentlessly rise.
As sea ice retreats, the precarious future of emperor penguins is tied closely with that of millions of people around the world. Melting sea ice doesn’t directly contribute to rising sea levels, just as melting ice cubes don’t cause a gin and tonic to spill over the side of the glass. Seawater itself freezes each year, and when it melts, no additional water is added to the ocean. However, sea ice plays a part in protecting coastlines where other forms of ice are attached to the land, helping to buffer ice shelves from waves and storms. When there’s less sea ice around, these towering ice platforms flex and bend, and it becomes more likely for icebergs to calve off and the ice sheets to break apart.
Melting glaciers and ice shelves are already causing global sea levels to rise. In Antarctica’s Amundsen Sea, Thwaites Glacier (nicknamed the Doomsday Glacier) is melting and retreating because of the warming sea around it. Part of this slab of ice, roughly the size of Great Britain, is braced by a floating ice sheet that is pushed up against an underwater seamount and acts as a giant plug. Recent studies sending autonomous robots under the ice shelf have found deep cracks and crevasses in its underside that are melting fast as warm water flows into them.
If the Thwaites Glacier collapses, scientists predict it could cause more than two feet of sea level rise. And if it drags other glaciers and ice sheets with it, the rise could be as much as ten feet. This catastrophic rise, compared to six inches in the twentieth century, would unfold over the centuries to come and impact the lives of coastal communities all around the world.
Scientists are working hard to predict how Thwaites and other ice forms in Antarctica will behave as the planet continues to heat. A major question is whether the whole ice sheet covering West Antarctica could collapse. Evidence suggesting this happened in the not-so-distant past, and hence could happen again, has come from an unusual source. Turquet’s octopuses have lived in waters all the way around Antarctica for the past four million years. A 2023 study of their genetics showed that their seabed-dwelling populations on opposite sides of the continent intermixed with each other roughly 125,000 years ago. This was the most recent time the earth was in a warm phase between ice ages, when global temperatures were between 0.5 and 1.5 degrees Celsius warmer than today. The only likely route to allow those octopuses to mingle would have been a seaway right across Antarctica, between the Weddell Sea and the Ross Sea, which could have happened only if the ice sheet had completely collapsed.
This doesn’t mean Antarctica’s ice sheet definitely is doomed, but it warns that, the way climate change is going, it could happen. The more swiftly and deeply carbon emissions are reduced, the greater the chance Thwaites Glacier and other critical parts of Antarctica’s vast icy landscape will stay intact.
It took a little over a century for emperor penguins to transform in human minds. What was once a kind of near-fabled, otherworldly animal that few people knew about, and explorers risked their lives to find, has become a species imperilled by the changing world. The penguins’ future depends on the decisions and actions of people thousands of miles away, leading lives entirely removed from theirs. If climate change is allowed to continue unchecked, and the emperor penguin walks along a pathway towards extinction, as predicted by Jenouvrier’s study, it will become a sorrowful symbol of the destructive forces humanity is unleashing on the planet. The potential loss of this beloved animal is a rallying cry to take the climate crisis seriously, and urgently curb emissions—otherwise the emperor penguin could easily go the way of the dodo, and how will people think of them then?
These two oversize, flightless birds have a fair amount in common. Dodos were the biggest members of the pigeon and dove family, the Columbidae, that people ever saw; emperor penguins are the biggest living members of the penguin family, the Spheniscidae. But in other ways the two species will be very differently remembered. Far more is known about the lives of emperor penguins than we will ever know about dodos. No keen-eyed scientists trailed after dodos through the forests of Mauritius noting down the details of their lives, and the species was allowed to disappear without any reliable descriptions or well-preserved specimens. Drawings of dodos from the time when the species was last seen alive, sometime towards the end of the seventeenth century, were often based on overfed captive birds or dead birds badly preserved by taxidermy. What living dodos actually looked like is not clear.
In contrast, emperor penguins are one of the most famous and easily recognisable birds. They are the adored stars of documentaries and animated movies; we can fall asleep in emperor penguin pyjamas while cuddling emperor penguin soft toys that bear more than a passing resemblance to the real thing. My favourite chocolate bar as a kid had an emperor penguin (and a joke) on the wrapper. Real emperor penguins could come to an end, but they would surely live on as avatars in the human world; only their meaning would have to change. People could no longer watch documentary footage and imagine all those birds are somewhere out there, devoted parents surviving in extreme conditions. Instead, the emperors would become memories from a past that is no more accessible than the time of the trilobites, ichthyosaurs, or giant aquatic sloths.
Like dodos, emperor penguins would not be a lone extinction. Through stories and poetry, such as Lewis Carroll’s Alice’s Adventures in Wonderland, dodos have become legendarily extinct, but they shared the tropical forests of Mauritius with many other endemic species that also vanished at a similar time and for similar reasons—those other animals, however, have largely been forgotten about. There were Mauritius blue pigeons, with red face, green beak, and feathers of indigo and shining metallic blue; at the water’s edge were Mauritius shelducks with black-and-white wings; stalking through the forests were flightless rails that looked like red-tinted versions of Aotearoa (New Zealand) kiwis; there were broad-billed parrots, Mascarene grey parakeets, Mascarene coots, Mauritius night herons, Mauritian giant skinks, small flying foxes, and two species of giant tortoise. All of them went extinct when people cut down the island’s forests, let pigs and cats run wild, and found the native animals gleefully easy to hunt, as none had instincts to fear humans. A few species lasted a while longer, like the Mauritius scops owl, but in the mid-nineteenth century it lost its final fragments of forest to sugarcane plantations.
Just as dodos joined a parade of animals that disappeared along with the Mauritian forests, so emperor penguins are among a rich mix of species that could be lost to the warming waters of the Southern Ocean. A lot of Antarctic animals face an uncertain future because they share with emperor penguins a diet that depends on the icy seas: they all eat a lot of krill.
A single adult Antarctic krill is finger-size, beady-eyed, and mostly transparent except for spots of pigment that give penguin guano its rosy tint. Aptly named Euphausia superba, krill sparkle in the dark as bioluminescent patches along their body pulse with blue-green light, perhaps to communicate with mates or help organise themselves in shoals.
Female and male krill meet up in the deep sea, hundreds of yards underwater, where they perform an elaborate mating ritual. A male chases after a female and touches her body with his long antennae. The couple embrace in a clinch of flickering legs, then the male wraps himself around his partner’s body in a sideways loop, and for a few seconds they spin together in circles. While all that is going on, the male transfers sperm to the female.
Sometime later, she releases into the sea thousands of fertilised eggs, which drift off and hatch into larvae. At first, the young krill look like fat spiders with only six legs; then, for several months, they keep reinventing themselves, casting off a dozen versions of their exoskeletons and reshaping their bodies, gradually taking on their shrimplike adult form.
By the time the Antarctic winter arrives, the adolescent krill have made their way to the surface to seek shelter and food on the underside of floating sea ice. In channels and cracks, they hide from predators while raking over the ice with the bristly ends of their legs to feed on a layer of microscopic algae.b During the rest of the year, krill eat planktonic algae floating in the water column, using their forelegs as a filtering device. But their overwintering grounds contain little plankton, and they get most of their food from ice algae. Here, the more sea ice there is and the longer it lasts, the more krill there are. And when Antarctic krill are doing well, they can be fantastically abundant.
Drop a bucket over the side of a ship in the Southern Ocean, and if you’re in the middle of a squirming pink shoal, you could easily catch a hundred krill in a single scoop. Typically, a shoal is the length of a football field, extends thirty feet deep, and contains more than one hundred million krill. They inhabit the entire circular loop of the Southern Ocean, all the way around the Antarctic continent. Collectively, the biomass of these little crustaceans adds up to an estimated half gigaton, making them the most abundant species on the planet that you don’t need a microscope to see.
In their colossal abundance, krill lie at the heart of Southern Ocean ecosystems. They harness energy from plankton and ice algae and create a vast pool of biological energy on which most other large animals in Antarctica depend.
Krill are food for elephant seals and fur seals, squid, and silverfish. Krill are plucked from above by a great many seabirds, including Wilson’s storm petrels, southern fulmars, and snow and Antarctic petrels, which in turn get their food stolen in midair by scavenging skuas. Many penguin species, not just emperors, hunt for krill as they dive through the Southern Ocean.
Whales are another major group of krill consumers. Southern right whales and humpbacks, sei and fin whales all come to Antarctica to eat krill and replenish their energy stores. Minke whales skim along just under the sea ice, lunging dozens of times on each dive, swallowing down great mouthfuls of krill. A single blue whale, the species with the biggest mouth of all, can gulp 3.6 million krill every day.
Curiously misnamed, crabeater seals don’t in fact consume crabs but have the whale-like habit of straining krill from the sea. To do so, they evolved the most specialised teeth of any carnivore, with multiple curved cusps that interlock to act as a sieve. A crabeater seal swims through a shoal of krill, mouth open, then snaps its jaws shut and pushes out the seawater through its teeth, holding back the krill and then swallowing them.
No other ecosystem on earth relies so much on a single species. Even apex predators, such as orcas and leopard seals, are no more than one step away from krill when they chase after fish, squid, and penguins.
How all this will change as the climate crisis bears down is not an easy matter to get a handle on, especially as krill populations naturally fluctuate year by year. Even so, plenty of studies cast grim predictions for the future of krill because of their reliance on sea ice and their need for cold, productive waters. Female krill need to eat a lot during the summer to build up their body reserves and store enough energy to successfully spawn the following year. The way ecosystems are changing, female krill could soon struggle to get the food they need to see them through the year. It’s likely that individual krill will grow to less than half the size they are now. The total population of krill could shrink by a third by the end of the century. Add in the impacts of the ocean absorbing more carbon dioxide and becoming increasingly acidic, and Euphausia superba could collapse altogether in three hundred years or so.
Currently, enough krill swarm around Antarctica that there are no pressing concerns for their extinction. But as certain parts of Antarctica are showing, what matters is where exactly krill are at their most plentiful.
The term global warming can give the misleading impression that the whole planet is heating gradually by the same amount everywhere. Changes already taking place in the global climate are by no means uniform. The Antarctic Peninsula is one of the fastest-warming places on the planet. This thousand-mile finger of icy land and islands—which points towards Tierra del Fuego, South America’s southern tip—is the spinal column on the brain map of Antarctica. Since the 1950s, the air temperature here has risen by three degrees Celsius, and the surface seas by one degree. During a heatwave in February 2020, a new record for the Antarctic continent was set at the peninsula’s northern tip, where the air temperature reached 64.94 degrees Fahrenheit (normally, summer temperatures don’t rise more than a few degrees above freezing). It’s no great surprise that the sea ice here is rapidly melting, and krill populations are retreating polewards, tracking their icy habitat to the south. At the same time, two krill-eating penguin species that used to live all along the peninsula are now in drastic decline.
Adélie penguins are small and sleek, their whole heads black, as if dipped in paint, leaving a white-ringed eye. They’re easy to tell apart from their close relatives the chinstrap penguins, whose black cap appears to be held in place by a dark band secured neatly under the chin. Colonies of both species, which used to be noisy with thousands of nesting birds, are growing increasingly sparse and quiet. On several subantarctic islands north of the peninsula, chinstrap numbers are less than half what they were in the 1970s. Adélie colonies are similarly collapsing. The number coming to nest near the American Palmer research base has dropped by around 80 per cent.
Chinstrap and Adélie penguins are not at imminent risk of going extinct. Across the whole of Antarctica, there are between six and seven million birds of each species living in hundreds of colonies. In the more stable parts of Antarctica, including the Ross Sea, numbers of Adélies are still healthy; chinstrap colonies in parts of the South Orkney Islands are increasing in size. Even so, their dire status along the peninsula is worrying enough, in and of itself, and it’s an ominous sign of what could lie ahead.
Penguin experts don’t yet understand precisely what is going wrong with the peninsula’s chinstraps and Adélies. It must have something to do with the shifting ice and krill populations, particularly during the nesting season, when penguins rely on a nearby supply of krill to feed their chicks. If there aren’t enough krill in the neighbourhood, then foraging adults are forced to set off on longer journeys to search for food, and they risk leaving their chicks to go hungry for too long.
Further complicating matters is the fact that whales, seabirds, seals, squid, and penguins aren’t the only ones hunting for krill. Now humans are too. The immense biomass of krill around Antarctica has proven too tempting for industrialists to resist. Factory ships, notably from Norway and China, head south to scoop up Antarctica’s krill. Specially designed trawl nets are lowered into the water and continuously scoop up krill shoals for weeks at a time, sending them straight to onboard processing plants. These krill will end up being eaten by domesticated animals. Most are mashed and turned into feed for salmon farms or into pet food.
Of all the krill shoaling around Antarctica, fisheries currently capture less than 1 per cent. People in favour of the industry consider this amount to be far too small to be of any ecological concern. The devil is in the granular details. If fishing vessels were to spread themselves out and gather their catches from across the entire range of krill, then these fisheries would likely have little impact. But that’s not what they do. Factory ships focus their attention on the peninsula, a krill hot spot that is the easiest and most profitable place to operate. Since 2000, the krill catch around the peninsula has tripled from 88,800 to 289,500 metric tons. By concentrating their effort, the ships may be competing with local wildlife trying to fill their bellies. For now, it’s difficult to disentangle the combined impacts of climate change and krill fishing because they’re happening in the same time and space. Indeed, as the ice is retreating south, the factory ships are also motoring farther south to access newly exposed regions of previously untouched sea.
Rather than industrial fisheries exploiting those waters, another option is to leave them alone. The organisation that regulates fishing around Antarctica, the Commission for the Conservation of Antarctic Marine Living Resources, has pledged to set up marine reserves to protect key parts of the Southern Ocean. At the time of writing, two such reserves exist. One is around the South Orkney Islands, which lie hundreds of miles north of the peninsula, and a second is on the other side of the continent, in the Ross Sea, where Apsley Cherry-Garrard went to find emperor penguin eggs. Since 2018, experts from Argentina and Chile have been leading a proposal to set up a third protected zone in the seas along the western coast of the Antarctic Peninsula. The safeguarding of these waters from exploitation would give krill and all the wildlife that depend on them as good a chance as possible of weathering the climate crisis. It would prioritise the Southern Ocean’s biodiversity over directing profits to the pet-food and fishmeal industries. So far, through several rounds of negotiations at the commission, plans to protect the peninsula’s waters have been rejected.
Even as sea ice and krill populations continue to rapidly decline, not all Antarctic species will suffer right away or to the same extent. Some will cope more easily than others. Gentoo penguins are already doing much better than their close relatives the Adélies and chinstraps. Similar in appearance to their sister species, except with a red beak, black head, and white band between the eyes, gentoo penguins live on the Antarctic Peninsula and on offshore islands, although not around the perimeter of the Antarctic continent. Their entire population is increasing, especially along the peninsula, where they’re moving south and claiming new territories as the ice retreats. The gentoos’ success most likely comes down to their flexible diet—they don’t rely solely on krill—and they seem to prefer it when there is not so much ice around. Thanks to the gentoos’ more resilient and, one might say, less refined nature, Antarctica in a warming world should still be home to large numbers of at least one species of penguin.
Drawing up lists of the likely winners and losers is perhaps a pragmatic way of dealing with the climate crisis. Some people argue that conservation efforts should be focused on the likely winners, leaving us to search for ways to grieve for the species that won’t make it through the Anthropocene. It may come as some comfort to know that survivors will exist even in the most imperilled places, including in Antarctica and the Arctic, where other species depend, to differing extents, on the swiftly shrinking ice. Among the survivors will be plenty of generalists, the species best equipped to make do and carry on. They will take the place of the specialists that carve out exquisite niches, that depend on predictable seasonal timings or rely exclusively on another species that may also soon be gone. The Anthropocene will have less and less room for great evolutionary phenomena, the likes of crabeater seals with their unique, krill-straining teeth and emperor penguins with their bubble-making feather suits.
But still, it is too soon to consign those sensitive, more specialised species to the loser list. As the planet rushes past one degree of anthropogenic heating, there are locked-in changes that we can do very little to stop. But we do still have a chance to decide how much we will continue to heat the planet, and that very much matters. From this point forwards, every half degree of heating that can be avoided will make a critical difference for the future of all sorts of species and their endangered habitats.
If corporations and governments do nothing to decelerate the climate crisis, emperor penguins will dwindle within the lifetime of human babies now being born. Not long after 2100, the species will most likely be extinct—if not sooner. But this is not an unstoppable fate for these giant, ice-walking birds. There is still a chance to prevent them from becoming little more than memories of a species that people knowingly allowed to disappear.
Simulations of the future of Antarctica run by Stéphanie Jenouvrier and colleagues explore two alternative possible climate scenarios. If emissions can be reduced enough to keep global temperature rise this century to two degrees Celsius above preindustrial levels, then the outlook for emperor penguins will be distinctly improved. Instead of losing 80 per cent of emperor colonies, as would likely happen if humans carry on with business as usual, we can expect only around 31 per cent to collapse. Limit temperature rise to 1.5 degrees Celsius, and the number of lost colonies is even smaller, around 19 per cent. In that scenario, by century’s end the entire population would stabilise at a new, lower level. Emperor penguins would be a great deal rarer than they are today, and they would persist in only a few climate refuges in Antarctica where enough sea ice remains, but the species would still exist.
There is also a more nuanced story that emperor penguins will tell. They will become a visible, incremental barometer of the climate crisis. A lot of the world’s most endangered species will fade out without anyone tracking their decline or watching for the point in time when they are gone for good. Like the dodo, those ones will slip away before anyone realises they are no longer around. Extinctions in the ocean will be especially hard to prove and easy to overlook—given the vast nature of this liquid habitat, which contains plenty of places to hide—so that people can continue to wonder if certain species might still be out there, somewhere. Emperor penguins would be different because of their habit of hauling out onto the ice to rear their young. The entire breeding population leaves the sea at the same time and stands on the white ice, making it possible to count them year on year. The more that humans successfully limit carbon emissions and minimise future global heating, the more intact sea ice will remain, and the more emperor penguins there will still be. Scientists will be keeping an eye on them via spaceborne satellites and hoping to see that when another winter ends and the sun illuminates Antarctica once again, the emperors will still be there with their new chicks, waiting until they grow new feathers and can return to the sea and slip back out of sight.
a The magnetic south pole wanders about as the earth’s molten iron core swirls.
