Common allergen, ragweed, will shift northward under climate change

Common ragweed, Ambrosia artemisiifolia, is common in North America and is spreading in Europe. The plant releases a fine pollen in late summer and fall that causes allergy symptoms in people with hay fever.Andreas Rockstein/Flickr

New research from the University of Washington and the University of Massachusetts – Amherst looks at how the most common cause of sneezing and sniffling in North America is likely to shift under climate change.

A recent study published in the open-access journal PLOS ONE finds that common ragweed will expand its range northward as the climate warms, reaching places including New York, Vermont, New Hampshire, and Maine, while retreating from some current hot spots.

“It was surprising that nobody had looked at ragweed distributions in the U.S.: As climate conditions are changing, where will it spread to in the future?” said corresponding author Michael Case, who did the work as a postdoctoral researcher in the UW School of Environmental and Forest Sciences.

Ragweed is a native North American plant that thrives in open areas, moving quickly into disturbed areas. It produces copious fine-powder pollen from August to November, causing sneezing, runny noses, irritated eyes, itchy throats and headaches for people with hay fever.

Several studies of ragweed’s future geographic distribution have been done in Europe, where people are concerned because this invasive species is expanding its range. This is the first study to consider future ragweed distribution in the United States.

Case’s previous research looks at how climate change may influence the distribution of various species, mainly native trees in the Pacific Northwest. Co-lead author Kristina Stinson, an assistant professor of plant ecology at UMass Amherst, is an expert on ragweed, including mapping allergy hot spots in New England.

“One reason we chose to study ragweed is because of its human health implications. Ragweed pollen is the primary allergen culprit for hay fever symptoms in summer and fall in North America, so it affects a lot of people,” Stinson said.

For the new study, the two authors built a machine learning model using Maxent software that takes some 726 observations of common ragweed in the eastern U.S., drawn from an international biodiversity database, then combines those with climate information to identify conditions that allow the plant to thrive. Researchers next ran the model into the future using temperature and precipitation output from 13 global climate models under two different pathways for future greenhouse gas emissions.

Read the rest of the story at UW News.