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Whether it’s the season’s cool, crisp air or leaf-peeping adventures calling you outdoors during autumn, you can be sure of one thing when you step out into nature: Ragweed will be waiting.
What is ragweed?
The ragweed plant is also known scientifically as Ambrosia artemisiifoliaLate summer and fall allergies are common. They can cause sniffles and sneezes. 15% to 20% of Americans. And it’s no wonder – not only is ragweed found in every U.S. state except for Alaska, it has a knack for survival. It thrives in poor soils. Its seeds can be kept alive for many years. It can take root in dirt almost anywhere, from roadsides to your rose-garden.
Ragweed is an evergreen, meaning it can only be grown for one growing season. A single plant can produce as many as 1 billion pollen grains. What’s more, those grains are so featherlight that they can travel for hundreds of miles on a breeze. According to the Asthma and Allergy Foundation of America, they’ve been detected as far as 400 miles out to sea and as high as two miles, the equivalent of eight Empire State Buildings, above ground.
How climate change impacts ragweed pollen levels
As if ragweed isn’t hardy enough, the warming climate is fortifying these nuisance plants in a number of ways.
One, warmer air temperatures are making the ragweed season last longer. Since 1970, the average temperature of autumns in the contiguous U.S. has been 2.5 degrees Fahrenheit (1.4° Celsius) warmer. Average delay of 11 days for first fall frosts. It takes temperatures of 25 to 28 F, or what’s known as a moderate freeze, to kill ragweed. But as global warming keeps temperatures balmier later in the calendar year, the August-through-September ragweed season that traditionally occurred across much of the U.S. now lingers well into November in some states.
With temperatures rising faster at higher latitudesThe northern U.S. experiences the longest ragweed seasons. Minneapolis, Minnesota is an example of this. The average autumn temperature has risen by approximately 5% in Minneapolis. Nearly twice the U.S. rateThe length of the ragweed pollen season has increased by more than 2.5 weeks.
What’s more, the longer air temperatures remain pleasantly mild, the later into the year people will flock outdoors to enjoy them, all the while increasing their exposure to airborne allergens.
As the world gets warmer, ragweed will likely expand northward. Although the nuisance plant is already found in New York and New Hampshire’s northeastern states, its documented distribution is restricted to their southern parts. One 2018 study found that the nuisance weed was not widespread in the southern part of the country. ProjekteIn the worst case scenario of high-emissions global climate change, where neither carbon dioxide concentrations nor average temperatures stabilize before 2100 is it likely that ragweed will expand north of Albany, New York, Montpelier, Vermont, Concord, New Hampshire, and Augusta, Maine within the next 30 year.
In addition to rising temperatures, climate change’s Droughts more frequent and more severeEncourage the already lightweight ragweed spores to spread more easily in wind. Moisture can clump pollen and weigh it down, so dry conditions keep it loose, airy, and away from the sinus passages.
Rising carbon dioxide concentrations supercharge ragweed
Climate change isn’t just enabling ragweed to push farther north, it’s also changing the species’ biological life cycle. Higher levels of carbon dioxide encourage ragweed plants grow larger, flower faster, and produce more seeds. According to researchPublished in the American Journal of Botany
In another Study, researchers observed carbon dioxide’s ability to heighten ragweed’s “allergenicity” – that is, its potential to trigger an allergic response in humans. They exposed ragweed plants both to ambient (700 ppm), and elevated (700ppm) carbon dioxide levels. The pollen was then extracted and given to the test subjects. The researchers found that the pollen grown under elevated carbon dioxide conditions increased the amount of the plant’s major allergen protein, Amb a 1.This increased the severity of allergic lung inflammation. This suggests that recent increases of carbon dioxide have already contributed to an increase in the severity of fall allergy season, and will continue to do so in the future.
How to reduce ragweed allergy symptoms
This research paints a bleak future for allergy sufferers, but there’s no need to panic-buy your favorite over-the-counter antihistamine just yet. You can also take extra precautions while outdoors.
First, limit outdoor activity if you have ragweed sensitivity. Ragweed pollen count peak in the mornings and around midday.
What if your job requires you to be outside during the day? In that case, KN95 or N95 respirators (familiar sights during the COVID crisis) will largely filter out any ragweed pollen you’d otherwise inhale. You can cover your hair with a baseball cap, or bandana. Check your local pollen forecastGood habits to practice before you leave the house are also important.
Track pollen indoors and take precautions when returning home. Simple steps like removing your shoes outside, storing “contaminated” items in a mudroom, immediately changing into indoor-only clothes, and showering before bed, can help keep pollen at bay.
Good news: Ragweed season usually ends in mid-to-late October. After that, you’ll be able to breathe easier – that is, until indoor mold and dust make you sneeze. True to the old saying, you can breathe easier if there is indoor mold and dust. It isNo rest for the (allergens) weary.
