Climate change means unpredictable hay fever seasons

People with allergies will enjoy some relief as the weather cools down, but experts say climate change may extend hay fever season. Amanda Diaz reports.

If hay fever had you sniffling your way through the spring and summer months, there's good news and bad news.  

On the bright side, people with allergies to pollen can expect some relief as we move further into autumn. 

The bad news is that climate change is impacting the seasonal cycle, making it increasingly difficult to predict when to crack out the antihistamines. 
 
Dr Simon Haberle from The Australian National University (ANU) is the Director of the ANU School of Culture, History and Language, and Canberra Pollen, a service that forecasts the level of pollen in the air. He says the most recent hay fever season reached record-breaking extremes early on due to the rainy conditions of the preceding winter.  
 
The arrival of La Nina also played a part; the weather phenomenon led to increased rainfall across most of Australia. 

"We are beginning to see these really interesting patterns around what wet weather can produce," Haberle says. "La Nina provides the ideal conditions for plant growth and pollination, and that's what we've seen in this last season." 

Though research is yet to confirm a definitive link between La Nina and high pollen levels, Haberle says the data suggests a broad correlation. 

Grass pollen had a particularly strong spring season in 2021 and Canberra recorded its highest level of pollen in a decade at the end of October. The nation's capital is a hot spot for hay fever, with one in three people coping with allergic rhinitis - the highest rate in the country.  

Though Haberle anticipated a sneezy January and February due to subtropical grasses, the spike in pollen was not as high as forecast. The most recent flowering season, which finished mid-March, was due to trees including Chinese elms and casuarinas. 

"The good news is there is probably relief on the horizon," Haberle says.  

Canberra's mix of native and introduced plant species means people can experience varying levels of discomfort between late June to March.  

But climate change may extend the hay fever season even further, as unpredictable weather patterns and temperature changes cause stress to plants, warns Dr Janette Lindesay, from the ANU Fenner School of Environment and Society. 

"We can't rely on past experience of what we know of the allergy season. There's no guarantee it'll be true in the future because all of that is shifting." 

As the planet heats up, spring is starting earlier and summer is lasting longer. Plants are sensitive to the rising temperatures and are flowering outside of their usual patterns, which may lead to unseasonal spikes in pollen.  

"Heating is exponentially faster and natural systems can't adjust," Lindesay says. 

The trend towards unpredictable and unseasonal rainfall is also having an effect. Australia used to receive most of its rainfall through light showers paired with cold fronts in winter, but summer storms have become the norm in recent times. The stress of these events can lead plants to switch from a state of vegetative growth to reproduction - the process that produces pollen.  

Lindesay says it's hard to know precisely what the 'new normal' will look like, and that even if Australia can achieve an emissions target of net zero by 2050, it will take at least another half a century for the environment to begin to adapt. In the meantime, we should expect warmer temperatures, sudden cold snaps and punishing thunderstorms. And, most likely, more pollen in the air. 

So, what's a hay fever sufferer to do?  

Haberle recommends checking the Canberra Pollen and AirRater apps - both initiatives in which ANU is involved - and limiting time outdoors when pollen levels are high.

Lindesay notes mask wearing was commonplace in parts of Asia long before the pandemic for people battling colds or allergies and this strategy could be taken up in Australia too.  

"We have to be adaptable if we want to get on with our lives while the environment is changing around us."