Ozone hole: Why Antarctic wildlife is being 'sunburnt’
For Antarctic wildlife, exposure to the Sun's damaging rays has increased in recent years, scientists say.
A hole in the ozone layer - the protective barrier of gas in the upper atmosphere - now lingers over the frozen continent for more of the year.
A major cause of ozone loss is believed to be the amount of smoke from unprecedented Australian wildfires, which were fuelled by climate change.
The study is published in the journal Global Change Biology.
Climate change biologist Prof Sharon Robinson told BBC News: "When I tell people I work on the ozone hole, they go: 'oh, isn't that 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 CFCs or chlorofluorocarbons - that were used as refrigerants. Every country agreed, in 1987, to phase out a group of ozone-depleting chemicals. It was an agreement known as the Montreal Protocol and is considered to be the most successful environmental treaty in history.
The ozone layer is now healing. "But there's a hole - an area where the ozone layer is very depleted - that appears every spring over Antarctica," Prof Robinson explained.
That ozone loss is particular to the polar continent, because of chemical reactions that occur in very low temperature, high atmospheric clouds. Those reactions break down ozone - eating a hole in the layer.
The annual appearance of this hole usually peaks in September and October, when most land-based plants and animals are safely tucked away under snow cover and marine animals are protected by extensive sea ice.
It is now lasting through to December - well in to the Antarctic summer. "That's when things will be exposed and most vulnerable," said Prof Robinson.
Certain types of ultraviolet radiation from the Sun, called UV-B rays, increase the risk of skin cancer and cataracts in humans, but researchers do not yet know if the same is true for Antarctic mammals and birds.
It's likely that anything covered by fur and feathers - seals and penguins - would be protected, explained Prof Robinson.
"But probably the biggest risk to the Antarctic animals is eye damage."
In their paper, Prof Robinson and her colleagues combed through all the studies they could find about the effect of UV on Antarctic plants and animals.
They found evidence of Antarctic mosses synthesising their own protective "sunscreen compounds".
"And if they're putting energy into sunscreen, they're putting less energy into growing," said Prof Robinson. "There's always a cost to sun protection."
There is also evidence that krill - the small and hugely abundant marine creatures that are the foundation of the Antarctic food chain - move deeper into the ocean to avoid UV rays, which could affect the whales, seals, penguins and other seabirds that feed on them.
"We also know that the phytoplankton that the krill feed on will have to make sunscreens in order to avoid damage, said Prof Robinson.
One major reason for the longevity of the ozone hole is the vast scale and extent of Australian bushfires in 2019 and 2020.
Jim Haywood, who is Professor of Atmospheric Science at the University of Exeter, told BBC News that the record duration of the Antarctic ozone hole over recent years was "a wake-up call".
"Society cannot be complacent about our achievements in tackling it," he said.
But there are still a number of factors that are delaying ozone recovery, including wildfires and major volcanic eruptions - these release particles that fuel the ozone-eating reactions that have already done so much damage.
Prof Robinson explained that some proposed climate-cooling experiments - so-called geoengineering - propose "making clouds" by releasing particles into the upper atmosphere.
"That would also deplete ozone, so it's a bad idea," she said.
"The biggest thing we can do to help Antarctica is to act on climate change - reduce carbon emissions as quickly as possible so we have fewer bushfires and don't put additional pressure on ozone layer recovery."
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