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Seven Worlds, One Planet

What a dramatic chase shows us about climate change

Antarctica is a haven, but life there is changing

Listen to Andrew Stewart describe the creatures that live in the seas around Antarctica and you will be transported into a world of fantastic shapes and colours.

“Banks and beds of these bright red starfish,” he says. “Butter-yellow crinoid sea lilies. Sponges, hard corals, soft corals, Nemertine worms – just absolutely mind-blowing the beauty and diversity of what lives underwater in Antarctica.”

If you thought Antarctica was just a big block of ice in the middle of a desolate sea, think again.

Stewart, at the Museum of New Zealand, principally studies fish from Antarctic waters. Many of his specimens come in as bycatch from commercial fishing trips. Anything of scientific value ends up on his desk – or rather, in the tanks and storage facilities in his museum.

Stewart has countless stories that reveal not just that life in Antarctica is rich, but that there is so much of it still waiting for us to discover. In 2008, for example, he and his colleagues documented a previously undescribed species of skate, a type of ray, that had been found living in Antarctic waters.

Stewart also mentions a book published 30 years ago, Fishes of the Southern Ocean, which described known species at the time. “Since then I think there’s been over 300 species added to that,” he notes.

The krill that southern right whale sometimes feed on are declining in numbers. © BBC Studios
The krill that southern right whale sometimes feed on are declining in numbers. © BBC Studios

A paper published in January this year discussed wildlife of the Southern Ocean, the expanse that cradles the ice and land of Antarctica itself. The authors made this point: the Southern Ocean is “the only place on Earth left where all the established fauna are native”.

But this chilly paradise is, like so many places, threatened. Threatened by warmth that melts ice and stresses sea creatures and by pollution that disturbs ecosystems. Antarctica is a haven at the end of the world – but for how much longer?

The lead author of the paper mentioned above, Simon Morley at the British Antarctic Survey, thinks the outlook is mixed.

Perhaps surprisingly, there are quite a few species that stand to do well as the Antarctic warms. Clams that feed on phytoplankton, for example, will probably only have more food to eat as sea ice melts away and more light reaches into the depths – phytoplankton use photosynthesis to obtain energy. Jellyfish and sea urchins will likely also benefit from increased phytoplankton stocks.

And king penguins, which feed on lanternfish, will probably also have an increased abundance of food at their disposal. But there is a battle of royal penguins afoot. Emperor penguins, conversely, are facing a dire situation. Not so much because their food supplies will decrease, but because the ice on which they breed is disappearing.

In 2016, thousands of emperor penguin chicks drowned when the ice shelf they were huddled on collapsed into the sea. It was a catastrophic loss.

“The chance of those reproductive failures will be increasing,” says Morley.

As warming impacts species north of Antarctica too, the cool waters of the Southern Ocean may draw certain species closer to the continent.

“Potentially, species will be able to invade from the tips of the big land masses that are just on the edge of the Antarctic,” Morley adds.

Gentoo penguins are migrating south to ice-free areas © BBC Studios
Gentoo penguins are migrating south to ice-free areas © BBC Studios

One example is the gentoo penguin. Its main colonies are mostly on islands off the tip of South America, but it is now migrating south to areas that are increasingly ice-free.

For some gentoo penguins, melting glaciers are putting their population at risk. As this scene from Seven Worlds, One Planet shows, brash ice (small blocks of slushy ice) is filling bays, making it harder for gentoos to get to the open ocean to hunt for food without getting crushed and makes avoiding predators like this leopard seal even harder.

Leopard seal vs penguin

When it comes to whales, the future is very hard to predict. Morley thinks there is a chance that the southern right whale will do well, if their primary food source of copepods – small crustaceans – increases thanks to more open waters.

However, Vivitskaia Tulloch at the University of Queensland noted in a paper published in February that krill populations, which the southern right whales also sometimes eat, are likely to decline. It’s possible that these whales and fin whales could go extinct by the year 2100, according to a model developed by Tulloch and her colleagues.

Minke and blue whales, in contrast, which spend much of their time in the coldest waters, may hold out for longer, since the effects of warming may reach them later.

Competition with smaller marine mammals may also come to bear.

“Seals are probably the other key species that might actually affect whale survival or prey availability for whales – that’s just because there are so many of them,” says Tulloch.

With krill populations falling and seals gobbling up whatever is left, whales might simply find it hard to compete.

In truth, it’s hard to know for sure how Antarctic marine species will fare in a world affected by climate change. But we can be certain about some things: climate change is already happening, it is affecting ecosystems in the Southern Ocean – and those ecosystems are, for now, wonderfully diverse. They are full of surprises representing a treasure trove that we may soon squander, should we fail to save it.

“We’re racing to discover these things,” says Stewart. “It seems that every year when I get bycatch back from the observers, I get something new.

“This is what we must bend every part of our will to protecting because when it’s gone, we’re going to be so much poorer for it.”

By Chris Baraniuk

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