People who sneeze and suffer from pollen may be in for a more extended pollen season due to the effects of light pollution lengthening the growing season in cities.
Artificial nighttime lighting has disturbed plants’ natural growth cycle where they are leafing-out earlier. There is so much artificial lighting across the United States that it blankets half of the country. In turn, it has led to leaf budding about nine days earlier than average compared to sites completely in the dark.
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Leaves stay greener longer as well pushing back the fall color change on average by nearly six days across the lower 48 states.
Researcher Yuyu Zhou at Iowa State University looked at nearly 3,000 sites in across the U.S. to see how they responded under different lighting conditions over a five-year period.
In general, he found that the more intense the light was, the greater the difference from normal.
The longer growing season can exacerbate asthma and other breathing problems. A study in Maryland found a 17% increase in hospitalizations for asthma in years when plants bloomed very early.
According to the Centers for Disease Control and Prevention (CDC), more than 25 million Americans have seasonal pollen allergies. Millions of people are suffering every year, and climate change is only making it worse.
In addition to light pollution boost on the growing season, human-induced climate change is also having a similar effect on extending the plant cycle.
Spring-like temperatures are arriving earlier in the year, and fall-like temperatures linger later, therefore, the growing season (the time between the last spring freeze and first fall freeze) and pollen season are getting longer.
The climate Central study suggests that pollen concentrations in the U.S. could increase 200% with high future rates of carbon dioxide emissions.
The scientists say cities should pursue developing lighting strategies that minimize artificial lighting on ecosystems.