The results of a study released on Monday, February 8, show that the pollen season in North America has lengthened considerably in thirty years. Pollen concentration has also changed, in part due to a warmer climate.
Pollens represent the male reproductive elements of plants, released to allow fertilization. There are two types. On the one hand, there is the so-called “entomophilic” pollen, carried from flower to flower by insects. And on the other hand, there are the so-called “anemophilia” pollens which are the main culprits of allergic reactions.
The latter are indeed emitted in large quantities by vegetation and can be dispersed by the wind over tens of kilometers. Their small size also allows them to easily enter the airways. It is estimated that pollen allergy affects about one in four French people. The real causes of these allergies are not really known. However, genetic makeup would be a fairly important factor.
Typically, the pollen season begins in early spring and runs through summer and ends in early fall. However, many people with allergies feel that things get worse over time. There is indeed an increasing sensitivity with age. However, Dr. William Anderegg, of the University of Utah, thought there might be another factor at play: climate change.
More pollen and a longer season
As part of a study, he and his team examined data from pollen counting stations across the United States and Canada, ranging from 1990 to 2018. The researchers then found several things. Already, the pollen concentration had increased by 21% during this period. This concentration has also changed more where temperatures have increased the fastest.
In addition, the authors found that the pollen season now seems to start about twenty days earlier on average compared to the early 1990s and end about ten days earlier. In other words, it lasts an average of ten days longer than thirty years ago.
While these changes were seen everywhere, areas like Texas and the US Midwest experienced the greatest increases in total pollen in those years. “A number of smaller-scale studies, usually in greenhouses on small plants, had indicated strong links between temperature and pollen,” Anderegg said in a statement. “This study reveals this connection on a continental scale.”
For the authors, climate change may not be the only factor explaining these observations. However, according to their model, it is likely that climate change is still responsible for about half of the extra days observed during this period, as well as 8% of the extra pollen concentration. Finally, they also found that climate change had a greater influence on the pollen season over the years.
In other words, “it is likely that climate change will have an even greater impact on pollen seasons and respiratory health in the near future,” concludes William Anderegg.