Allergy season will start much earlier than normal and be far more intense because of climate crisis, study suggests

By Rachel Ramirez, CNN

Future allergy seasons will start more than a month earlier and be far more intense because of the climate crisis, new research shows.

The study, published Tuesday in the journal Nature Communications, found by the end of the century, pollen season could begin as much as 40 days earlier than it has in recent decades in the US because of global warming. Researchers also found annual pollen counts could climb by up to 250%.

“Pollen is something that is on people’s radar because it influences their daily lives if you are allergic,” Allison Steiner, author of the study and professor at the University of Michigan, told CNN. “A huge component of the population is affected by these allergies, and people are really interested in understanding how [their allergies] might change so they can manage their symptoms better.”

While there have been studies in the past pointing out how allergy season is getting longer and pollen concentrations are getting higher, Steiner — who has two children suffering from allergies — said their research is unique because it breaks down the individual types of pollens and tree sources by region, specifically analyzing a variety of plant sources including oak, cedar or ragweed.

The timing of tree pollen is released — especially in regions where there are a number of deciduous trees — varies. For instance, in Michigan — where Steiner lives — birch trees typically pollinate first, then oak or pine, followed by other species over the course of a few months.

In the future, though, the study found different tree pollen varieties that once varied in timing will eventually overlap with each other, leading to overall higher concentrations that threaten public health.

“Some people are allergic to certain pollen; some are not; and some have more allergenic proteins that can drive more allergies. If you’re an allergy sufferer, you may or may not know what you’re allergic to, depending on what kind of testing you’ve done,” Steiner said. “The [projected] higher concentrations of pollen is in addition to what you might be allergic to individually.”

Lewis Ziska, a plant physiologist and associate professor at Columbia University, suffers from allergies himself and carries a rescue inhaler at all times. He said the study extends the work that’s already been done and makes clear the climate crisis will, at some point, exacerbate allergies, asthma and other public health problems.

“It’s a very solid piece of science,” Ziska, who is not involved with the report, told CNN. “Looking at forecasting, particularly for both the high and low projections, it’s a very good indication of the kind of impact that climate change can directly have with respect to people’s health.

“I was impressed by the granularity of the study that it was looking at more on a very specific regional basis and also looking in regard to specific plant species,” he added.

Wind-driven pollen, which plays an important role in plant fertilization, is closely tied to temperature and precipitation changes. So as spring seasons get warmer earlier due to climate change, plants could pollinate much earlier and for a longer period of time than they currently do.

Climate change also impacts the number of winter chill hours and spring frost-free days, which then affects the timing and duration of pollen season.

As temperatures get warmer in the South and drought plagues the Southwest, pollen from plants like ragweed or poaceae — a plant that typically grows on grassland or salt-marshes — is projected to be higher across those regions than in the North.

A longer and earlier start to pollen season could trigger a public health emergency, researchers say. More than 24 million people in the US experience pollen-induced respiratory allergies or hay fever, according to the Centers for Disease Control and Prevention.

While more research is needed in determining larger socioeconomic implications, Steiner said this could result in a large economic loss due to missed work, school days, medical expenses, and early deaths.

A recent UN climate report emphasized greenhouse gas could be removed from the atmosphere by planting more trees and plants in green spaces, which could lead to an increase in pollen in those areas. But not all plants produce pollen. Steiner said as long as planners are careful of what trees to plant, people shouldn’t worry about more trees intensifying pollen concentration.

As the window to adapt to the climate crisis rapidly closes, Steiner said the projections could still be avoidable if the world reduces greenhouse gas emissions at a large scale, while simultaneously getting carbon dioxide already in the atmosphere to a manageable point.

“What happens between 2050 and 2100 really depends on human choices,” she said. “We’re really hoping that’s going to change. A lot [of us] in the climate community want to see those cuts, this concentration start to level off and hopefully start to have temperatures plateau, but a lot of work has to happen to make that change.”

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