Pollen allergies will get worse as the weather warms

Millions upon millions of people suffer from seasonal allergies. They are forced to endure recurrent bouts of watering eyes, runny noses, constant sneezing and other symptoms of hay fever.

Here’s some bad news: climate change is expected to make such allergies worse in coming years.

The Union of Concerned Scientists warns that the amounts of airborne allergens released by flowering plants will likely increase as the climate warms. For starters, higher levels of carbon dioxide in the air will boost plant growth, including the pollen content of plants like daffodil and ragweed that cause hay fever (as the condition allergic rhinitis is popularly known).

In addition, as temperatures increase, springs will come sooner and last longer, which will mean longer allergy seasons too. Longer springs will also change the nature of blooms and fungal spores, which could make symptoms worse, especially for people with more severe forms of pollen allergy.

“Spring appears to be coming earlier, and this is affecting the tree pollen, which is a main source of spring hay fever,” says Lewis Ziska, a weed ecologist at the Agriculture Research Service division of the U.S. Department of Agriculture.

In his research Ziska has examined plant traits under various conditions in both urban and rural areas, including different growth rates, bloom times and pollen production levels. He’s also looked at environmental factors such as varying levels in the air of carbon dioxide and moisture.

The scientist has found that certain species of plants that grow in cities where the urban heat-island effect prevails can outgrow their counterparts in the countryside. That is thanks to the increased levels of heat and CO2 in urban areas. Weeds like ragweed can grow two or even three times as tall in cities as they do in the countryside. They also flower earlier and produce more pollen.

If CO2 emissions remain at current levels, ragweed could boost its production of pollen by 60% or even double it within 65 years. Meanwhile, the plant’s pollen could turn even more allergenic. Allergy sufferers will be much the worse for it. In more severe cases these people experience swelling in their eyelids or red, itchy eyes as well as constantly congested noses. Such cases may become more common.

“The influence of climate change on plant behavior exacerbates or adds an additional factor to the number of people suffering from allergy and asthma,” Ziska notes.