A new USDA-led study finds a warming planet makes for more pollen and a longer, more intense allergy season in many parts of the United States.
Given the millions of allergy sufferers held hostage by the drippy noses, burning, watery eyes, and continuous sneezing sessions it induces, ragweed may be one of the most hated plants on the planet. And a new the U.S. Department of Agriculture (USDA)-led study published in the Proceedings of the National Academy of Sciences confirms what many allergy sufferers and allergists have already been noticing--hay fever season and the ragweed allergies it brings seems to be getting more intense and lasting longer.
The study is the latest to make the connection between climate change and human health. (Allergy-related issues cost the United States about $21 billion a year, so a warming planet affects economics, too.) "The main takeaway is that we are already seeing a significant increase in the season length of ragweed; and that this increase in season length is associated with a greater warming at northern latitudes, consistent with the Intergovernmental Panel on Climate Change projections regarding climate change," explains lead study author Lewis Ziska, PhD, research plant physiologist with USDA's Crop Systems and Global Change Lab.
Researchers used ragweed pollen and temperature data
recorded between the late 1990s and 2005 in 10 different locations in the U.S.
and Canada and found that in all but two of the areas analyzed, the ragweed
season increased—in some cases by nearly a month. The lengthening of the
allergy season coincides with an increase in warmer, frost-free days.
Researchers noticed a general trend—the ragweed allergy season grew longest in
the higher latitudes of the northern United States and Canada. Winnipeg,
Ontario, allergy sufferers endured a 27-day-longer ragweed pollen season in
2005 compared to just 16 years earlier. In the U.S., Fargo, ND, and
Minneapolis, MN, experienced a more than two-week increase in ragweed allergy
season, with LaCrosse and Madison, WI, not far behind.
Climate change threatens human health in a
number of ways, but allergies may be the most immediate, easy-to-recognize
ailment thus far, says Linda Marsa, investigative journalist and author of Fevered: Why a Hotter Planet Will Hurt Our Health—And How We
Can Save Ourselves. And our increasingly chaotic climate's
allergy-accelerating properties are already afflicting millions of people.
Ragweed is one of the most common weed allergens, affecting about 10 percent of
the population. Among allergy sufferers, nearly a third endure hay fever misery
brought on by ragweed pollen. Under normal circumstances, a single ragweed
plant creates 1 million pollen grains; but a climate change–charged, more
CO2-rich environment boosts that number to upwards of 3 to 4 million pollen
grains per plant, according to Clifford Bassett, MD, medical director of
Allergy and Asthma Care of New York and a member of the public-education
committee at the American College of Allergy, Asthma and Immunology.
Furthermore, Marsa points out, the CO2 in the atmosphere acts like plant food
to weeds, changing weeds' chemical makeup and causing them to produce pollen
that contains more allergenic proteins than normal. (Don't your eyes water just
thinking of it?)
And scientists are also suspect of other potentially climate
change–infused weed species. Ziska says there are concerns that other specific
plant allergens are worsening due to climate change. His research group is
working with Rutgers University in New Jersey and the Environmental Protection
Agency to begin assessing pollen production and season length for other annual
weeds like lambsquarters, mugwort, and plaintain, in addition to ragweed.