The arrival of spring brings with it allergy season for millions of people around the world as flowering trees and plants release allergy-inducing pollens. Now, thanks to climate change, allergy season is about to get worse: The warming planet is extending the growing season, and along with it allergy-caused risks to human health.

By 2100, the amount of pollen produced during the flowering season could rise by 40 percent, according to research published in March 2022 in Nature Communications–raising an urgent need to better understand the factors driving that increase. Even as drought and heat damage forests and grasslands, some grasses, weeds, and trees that produce allergy-inducing pollens thrive on rising temperatures and higher carbon dioxide concentrations,