Ozone hole: Why Antarctic wildlife gets 'sunburn'

For Antarctic wildlife, exposure to the sun's harmful rays has increased in recent years, scientists say.

The hole in the ozone layer – the protective barrier of gas in the upper atmosphere – has been present above the frozen continent for more than a year.

One of the main causes of ozone loss is believed to be the amount of smoke generated by the unprecedented Australian bushfires, which have been fueled by climate change.

Professor Sharon Robinson, a climate change biologist, told BBC News: “When I tell people I'm working on the ozone hole, they say: 'Oh, isn't this better now?'

Scientists working in Antarctica discovered the hole in the ozone layer in 1985 – by measuring the amount of solar radiation reaching Earth.

A large group of ozone-depleting chemicals were responsible – primarily chlorofluorocarbons or CFCs – that were used as refrigerants. All countries agreed in 1987 to phase out a group of ozone-depleting chemicals. It was an agreement known as the Montreal Protocol and is considered the most successful environmental treaty in history.

The ozone layer is now recovering. “But there is a hole – an area where the ozone layer is extremely depleted – that appears every spring over Antarctica,” Professor Robinson explained.

This ozone loss is specific to Antarctica, due to chemical reactions that occur at very low temperatures and high atmospheric clouds. These reactions cause ozone to decompose, creating a hole in the layer.

The annual appearance of this crater usually peaks in September and October, when most terrestrial plants and animals are safely hidden under the snow cover and marine animals are protected by expansive sea ice.

It now continues until December, i.e. summer in Antarctica. “This is the time when things become more exposed and vulnerable,” Professor Robinson said.

Certain types of ultraviolet radiation from the sun, called UVB, increase the risk of skin cancer and cataracts in humans, but researchers don't yet know if the same is true for Antarctic mammals and birds.

Professor Robinson explained that anything covered in fur and feathers, such as seals and penguins, would likely be protected.

“But perhaps the biggest risk to Antarctic animals is eye damage.”

In their research, Professor Robinson and her colleagues sifted through all the studies they could find on the effect of ultraviolet radiation on Antarctic plants and animals.

They found evidence that Antarctic algae make their own “sunscreen compounds.”

“And if they're investing energy in sunscreen, they're investing less energy in growth,” Professor Robinson said. “There is always a cost to sun protection.”

There is also evidence that krill – the small but abundant marine organisms that form the basis of the Antarctic food chain – move deeper into the ocean to avoid ultraviolet radiation, which can affect the whales, seals, penguins and other seabirds that feed on them. .

Professor Robinson said: “We also know that the phytoplankton that krill feed on must make sunscreens to avoid damage.

One of the main reasons for the longevity of the ozone hole is the large scale and extent of the 2019 and 2020 Australian bushfires.

Jim Haywood, professor of atmospheric sciences at the University of Exeter, told BBC News that the record duration of the Antarctic ozone hole in recent years was a “wake-up call”.

“Society cannot be satisfied with our achievements in addressing it,” he said.

But there are still a number of factors delaying ozone's recovery, including wildfires and major volcanic eruptions — particles that fuel the ozone-eating reactions that have already caused so much damage.

Professor Robinson explained that some proposed climate cooling experiments – so-called geoengineering – suggest “cloud formation” by releasing particles into the upper atmosphere.

“It will also lead to ozone depletion, so it's a bad idea,” she said.

“The biggest thing we can do to help Antarctica is to act on climate change – reducing carbon emissions as quickly as possible so that we have fewer forest fires and do not put additional pressure on the recovery of the ozone layer.”