If you or your kids already suffer from hay fever, be prepared: the more the climate changes, the worse those runny noses and itchy eyes are going to get.
The impact of all this pollen on people is being noticed nation-wide. The Kansas City Star said studies show that,
“In 1970, about 10 percent of the U.S. population suffered from hay fever. By 2000, the number had risen to 30 percent.”
The links between climate change and poison ivy have already been documented. But Lewis Ziska, a plant physiologist with the U.S. Department of Agriculture’s Crop Systems and Global Change Research Unit, wanted to look into whether higher temperatures and carbon dioxide build-up could also be affecting a disease like hay fever. To do so, he pulled together a scientific team that examined at least 15 years’ worth of pollen data collected at ten locations ranging from Saskatoon, Canada to Austin, Texas. The scientists found that from 1995 to 2009, as the number of frost-free days increased, so did the length of the ragweed pollen season. In fact, the pollen season lasted from 13 to 27 days longer in 2009 than in 1995. They also found that a longer ragweed pollen season was strongly correlated with a delay in the onset of the first fall frost.
Children’s Mercy Hospital in St. Louis, which is monitoring pollen levels in that community, is reporting that the amounts of ragweed pollen are two to three times higher now than they were in the late 1990s. The ragweed pollen season used to end by mid-October. Now, it is extending into late October or even mid-November.
Other plants that emit pollen are being affected by climate change, as well. As the Kansas City Star reports, scientists worldwide have found the amount of pollen being emitted by birch and oak trees also on the rise.
How does climate change factor into all of this? Plants grow in response to warmer temperatures and the presence of carbon dioxide (CO2). As cars, factories, and power plants put more CO2 into the atmosphere, the gas creates a vaporous greenhouse that traps CO2 and heat on earth, forming ideal conditions that enable noxious plants like ragweed to thrive.
This is not just a theory. The USDA’s Ziska put beds seeded with ragweed in various urban, rural, and suburban settings. Beds in urban areas where traffic is high were exposed to more CO2 from vehicle exhaust. Temperatures in urban areas were also higher, thanks to heat-absorbing buildings in the area. Ziska reported that the urban ragweed flowered earlier and grew to six to 10 times the size of the rural plants.
Hospitals are noticing the consequences of this longer, more potent hay fever season, too. Said Jay Portnoy, an allergist at Kansas City’s Children’s Mercy Hospital, hay fever patients are getting sicker than they used to and over a longer period of time.
In the short term, people who suffer from hay fever will have to be extra vigilant over a longer period of time. This is especially true for parents whose children are at risk from severe hay fever reactions when they play outside. But staying indoors is not the solution to this problem. Reducing CO2 emissions is essential if we are going to dial back climate change and protect our health and that of the planet.