How is climate change affecting biodiversity at the poles?

At the planet’s polar extremes, life has evolved under trying conditions, including year-round cold and six-month stints without sunlight. This has made Arctic and Antarctic biodiversity some of the planet’s richest and most unusual, extending far beyond its poster penguins and polar bears.

Yet as climate change warms oceans, melts ice and alters weather patterns, many polar species are being forced to adapt or perish. This is leaving scientists and communities scrambling to locate, understand and learn from the poles’ unique casts of characters and their various efforts to survive.

A penguin’s-eye view of Antarctica

To get a better sense of Antarctic biodiversity, Steven Chown, a professor at Monash University in Melbourne, suggests imagining you’re an Adélie penguin (Pygoscelis adeliae) swimming along on the ocean’s surface, snug in your well-insulated feather-and-blubber suit. 

If you look up, you’ll see a variety of seabirds in the skies above you, such as albatross and skuas. In the waters around are whales, seals, fish and krill. 

And if you dive down to the sea floor, you’ll see an ecosystem flourishing with rare forms of life: sponges, sea spiders, aquatic invertebrate filter-feeders called bryozoans, corals, and deep-sea hydrothermal vents with Yeti crabs living on their edges. Microbes help keep everything alive, such as by munching methane from a recently-discovered, naturally-occurring sea-floor gas leak.   

“The Antarctic sea floor is as diverse as some tropical areas,” says Chown. 

Back on land, in contrast, there isn’t much to see. As you cast around for a nice and cold area in which to nest, there are no terrestrial birds, land mammals, reptiles or amphibians, and no trees or shrubs either. However, you might come across green or pink snow, colored as such by snow algae (Chlamydomonas nivalis), or the two species of flowering plants that live here – the diminutive, rock-hugging Antarctic hair grass (Deschampsia antarctica) and the yellow-flowered, moss-like Antarctic pearlwort (Colobanthus quitensis). 

“There is this incredible diversity – still quite low, but incredible because it’s so strange – of mosses and lichens and small invertebrates,” says Chown.

There’s unusual microbial diversity on land as well. “And people might think, ‘oh, so what?’,” he says. “But these microbes have among them groups that are very weird, in the sense that they can scavenge trace gases such as hydrogen and carbon monoxide out of the air, which is really rare. They can even couple hydrogen with oxygen and make water for themselves.”

As the ocean warms, many of Antarctica’s species are already changing their habits. Adélie penguins, seals and krill are all moving south to colder parts of the continent, and the two flowering plant species have become increasingly commonplace. 

Chown is also worried by the increase of foreign species establishing themselves in Antarctica, such as grasses from other parts of the world, likely introduced during research and activities. 

“We’re starting to make Antarctica look more like other places and less like its unusual self,” he says.

Arctic invaders

At the other end of the Earth, Arctic communities and scientists have similar concerns. The Arctic is warming at least twice as fast as the rest of the planet, with record-high temperatures recorded during the Northern summer’s heatwave. As its icy world gets warmer, temperate species are moving farther and farther north. 

“What’s happening now, and what we are expecting to see more of in the future, is a loss of that biodiversity that’s very specific to the Arctic,” says Jen Lento, a researcher at the University of New Brunswick, who played a lead role in compiling the first-ever circumpolar assessment of Arctic freshwater biodiversity. “It’s going to start to look more like temperate regions, and we’re losing those unique ecosystems that we currently have.”

Arctic char (Salvelinus alpinus) – a relative of salmon and trout with a bright pink-red underbelly, and a critical food resource for many Indigenous peoples – are declining in some areas due to rising temperatures. 

“Other species that aren’t as sensitive, or don’t require the cold temperatures, are starting to come in,” says Lento. “So you’re starting to see a higher abundance of trout and other fish that will compete with Arctic char. And you could potentially end up with higher biodiversity of fish, but it’s a loss of those fish that are so vital for Indigenous communities.” 

Fishing practices are changing as well: Lento recalls visiting one Arctic village where a community member told her that in the past, they could set their fishing nets and then leave them for a few days because any fish they caught would be preserved by the cold waters. “And now they have to go back the same day, because the water is so warm that the fish aren’t being preserved so well,” says Lento. “So there’s a lifestyle change happening, too.” 

Thawing permafrost (soil, rocks and sand bound together by ice that remains frozen year-round) is also impacting Arctic biodiversity and communities. Water has less volume than ice, so when permafrost melts, it creates a depression known as a slump, or thermokarst. “The impacts of these on freshwater and in lakes is huge,” says Lento. “You get all this mud slurry that runs out from the thaw slumps, and these streams that were previously clear now they look like chocolate milk. They’re thick with all the mud that’s coming through them.” This can quickly wipe out invertebrate and fish communities.

The Arctic has also experienced record-breaking wildfires over the past two summers, a natural occurrence that is now happening at unprecedented scales. “We’ve seen fish mortality,” Edward Alexander, who co-chairs the Indigenous representative group Gwich’in Council International, told Climate Home News after the 2019 fires. “Some of the rivers got so warm that the fish died before they spawned. We’re seeing new insects. We’re seeing a prevalence of unusual species.” Over time, scientists believe these outsized burns could precipitate a shift from the coniferous forests that are prevalent in the Arctic toward the kinds of deciduous forests found further south.

As has been seen in landscapes across the globe, when elements of an ecosystem are transformed, “the system functioning changes in ways we can’t predict,” says Chown. Losing species matters in and of itself, too. “Some of our most iconic animals are starting to become very stretched in their capability to deal with the change,” he says. 

“Emperor penguins are predicted to be extinct by the end of the century if we don’t do something. Imagine a world with no emperor penguins.” 

Charismatic megafauna aside, Chown remains inspired by the example of Antarctica’s peculiar, water-creating microbes. “In the darkest, coldest, weirdest times, they actually make a go of it,” he says. “And that’s probably a very good analogy for what life elsewhere might have to do in the future.”