Nighttime Lights May Prolong Allergies and Researchers Explain How

A study published in April shows how nighttime lights are prolonging the growing season in cities, which can impact everything from allergies to local economies.

City lights blazing all night are profoundly disrupting the phenology of urban plants, shifting when their buds open during spring, and then their leaves are changing colors and dropping during fall, a Fast Company report specified.

In a study, Associate Professor of Environmental Science Yuyu Zhou, from Iowa State University and his colleagues analyzed trees and shrubs at approximately 3,000 sites in several cities in the United States to find out how they responded under different lighting conditions over a five-year period.

Plants are using the natural day-night cycle as an indication of seasonal change along with temperatures. As a result, the team discovered that artificial light alone advanced the date that buds broke in the spring by approximately nine days on average, to sites minus nighttime lights.

Nighttime Lights

The timing of the fall color change in leaves was more complicated, although the change in leaves was still delayed on average by almost six days throughout the 48 states.

In general, the study authors discovered that the stronger the light was, the greater the discrepancy. The team also projected the future impact of nighttime lights for the five cities in the US.

These cities include Minneapolis, Chicago, Washington DC, Houston, and Atlanta, "based on different scenarios for future global warming," and up to a one-percent yearly increase in nighttime light intensity.

In their research published in the PNAS Nexus, the researchers discovered that increasing nighttime light would likely continue shifting the beginning of the season earlier, although its impact on the fall color-change timing was more complicated.

Season Changes Essential for Climate and Health, Among Others

This kind of shift in the biological clocks of plants is essential for the climate, health, economic, and ecological services urban plants provide.

On the favorable side, longer growing seasons could enable urban farms to be active over longer periods. More so, periods could provide shade as well, to cool neighborhoods earlier in spring, and later in the fall as worldwide temperatures increase.

However, changes to the growing season could increase the vulnerability of the pants, as well as to spring frost damage.

More so, it can develop a mismatch in terms of the timing of other organisms like pollinators that some urban plants are depending on.

Pollen Season Linked to Asthma, Other Breathing Problems

An active season for urban plants that's longer suggests an earlier, not to mention pollen season, which can also worsen asthma and other breathing problems.

Furthermore, a Maryland study showed a 17 percent rise in hospitalizations for asthma in years "when plants bloomed very early," the researchers reported

The manner of fall-color timing will change moving forward as night lighting strengthens and temperatures increase less clearly.

Temperature and artificial light together, are impacting the fall color in a complex manner, and the researchers' projections suggested that the delay of coloring dated because of climate change might stop midcentury and plausibly reverse due to artificial light. This though will require more research, as indicated in The Conversation, where this report first came out.

Related information about worsening allergies is shown on CBS Los Angeles's YouTube video below:

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