Despite the Montreal Protocol, the ozone layer, vital for obstructing UV radiation from the sun, isn’t fully repaired. This spells danger to Antarctic plant and animal species.
The warning comes from 4 members of the UN’s Environmental Effects Assessment Panel, who Global Change Biology that the annual ‘hole’ that widens in the ozone layer each year now remains open into Antarctica’s summer.
This risks exposing species to harmful UV-B radiation at a time where plants and animals emerge periods of dormancy. The typically peaked in September and October.
“That’s very different to what’s been happening for the last four years where the depletion has been extending right through to December,” says Sharon Robinson, a climate change biologist based at Australia’s University of Wollongong.
“Once we get to December, in the southern hemisphere the sun is much higher in the sky and the radiation coming down to earth is higher. We’re seeing a UV index of 14 in Antarctica in December, up from pre-ozone hole levels of 6. A UV index of 14 is extreme – what we’d experience during summer in Sydney or San Diego.”
The result is more the double the exposure to harmful UV-B radiation in Antarctica than the 1970s .
Unknown risk to marine ecosystems
Robinson and her colleagues highlight the unknown risk to juvenile emperor penguins and seals, noting the potential for UV-related disease in humans like skin cancer and cataracts to occur in other vertebrate species.
Though land-based vertebrates like birds and mammals have UV-resistant fur and feathers, which is absent in marine species like fish and microscopic organisms which form the base of marine food webs.
Robinson highlights the energy cost required for plants and animals to protect themselves against UV exposure.
“For most organisms, increased UV exposure means they have to invest more into sun protection and repair of any damage,” Robinson says.
“Plants do that by making their own sunscreen compounds. But if they’re putting energy into sunscreen, they’re putting less energy into growing – there is a cost to making your own sunscreens. There’s always a cost to sun protection.”
That cost could also play out in the way larger consumers are able to access and feed on ‘producers’ like krill and phytoplankton.
“If krill are exposed to high UV radiation they tend to move down deeper into the ocean, we also know that the phytoplankton they feed on will have to make sunscreens in order to avoid damage from the UV,” Robinson says.
“If the phytoplankton need to make sunscreens, then there may be less plankton, or they may be less palatable. This then changes the behavior of the animals that feed on them.
“The extended UV radiation may not kill things, but we know that there’s a cost to creating sun protection and that takes away from the other things the animals and plants are able to do.”
Climate cost compounds UV risk
While UV exposure may now persist into the southern hemisphere summer, the threat it could pose to Antarctic species is compounded by shifts in ice and ocean behaviour due to climate change.
With increasing global temperatures driving annual sea ice formation to in recent years, Robinson notes the potential dual hazard to life on the frozen continent.
Reports from the British Antarctic Survey in 2022 noted, for instance, mass penguin deaths due to rapid sea ice loss.
The consequences of a warming climate also play into the delayed repair of the ozone hole, with Robinson noting the increased risk of bushfires due to warmer temperatures release ozone-depleting chemicals.
The result is a handbrake on the gains made by the Montreal Protocol of 1987, where nations agreed to end the release of ozone-depleting substances, mainly occurring in manufacturing and industrial processes.
In 2023, bushfire smoke particles carrying chlorine from burnt plant material can break down atmospheric ozone.
“The ozone is recovering. It’s just taking time for all the ozone-damaging compounds humans have put into the stratosphere to dissipate,” Robinson says.
“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.
“The best way to protect animals in the Southern Ocean is to keep global heating as low as possible so that we keep as much sea ice as possible. The best thing that we can do for the environment is to take action on climate change by reducing carbon emissions.”