Pollen season could start nearly six week earlier, and last almost three weeks longer by the end of the century, according to a study out of the University of Michigan.
In findings published in the scientific journal Nature Communications, researchers reported that, thanks to rising temperatures and CO2 levels, the amount of pollen in the air each year could increase by 200 per cent.
“Pollen-induced respiratory allergies are getting worse with climate change,” Yingxiao Zhang, first author of the study, said in a release. “Our findings can be a starting point for further investigations into the consequence of climate change on pollen and corresponding health effects.”
As of 2017, 27.3 per cent of Canadians aged 12 and older, about 8.4 million people, reported having allergies, according to Statistics Canada. Allergies vary from person to person, with some only experiencing a stuffy nose, while others can have difficulty breathing or anaphylaxis, a potentially deadly reaction in the body that can occur within seconds.
Researchers developed a model that examined the 15 most common pollen types, and projected how each will react to changes in temperature and weather. By studying the pollen data from 1995 to 2014, scientists were able to determine how a changing environment is impacting plants’ pollen production.
“Current data is very limited, and it’s not enough for us to understand the effect that increased carbon dioxide has on pollen,” Zhang told NBC News. “But we do currently know that temperature increases pollen, and we’re already seeing that now.”
Researchers collected data from 100 sites all over North America, and used their findings with historical figures to estimate what the amount of pollen will be in the future. By running tests multiple ways, and accounting for factors such as temperature and weather, the team was able to determine a worst-case scenario.
A rise of four degrees would extend pollen season by 10 days
If the temperature is to rise about six degrees Celsius by the end of the century, allergy season would extend by about a month — an increase of four degrees would extend pollen season by about 10 days.
“Land cover change can either increase or decrease the future pollen emission maxima, but the regional impacts are smaller (−32 to six per cent) than other factors and we conclude that the land cover change influence on pollen emission is likely to have less of an impact than the influence of meteorological factors or CO2,” the study authors wrote.
The predicted trends match up well with the data from the last three decades, during which allergy seasons began 20 days earlier and ended eight days later than what was once the standard.
Still, the study authors acknowledge some potential limitations to the research, such as the uncertainty of future plant communities, how land will be used in the future, and that the study mostly focused on urban areas.
“More measurements across space and time could improve our understanding of pollen production and better constrain the model simulations,” they wrote.
Chris Arnold is a Toronto-based writer.