Research led by Iowa State University has established that artificial lighting at night (ALAN) affects natural seasons for urban plants and consequently impacts human life in the United States. The findings now underpin the impacts of urbanization on the natural world on both humans and plants.
According to Associate Professor Yuyu Zhou of geological and atmospheric sciences at Iowa State University and co-author of the study, night lighting alters the rhythm of plants. For instance, the professor notes that night lighting may lengthen the pollen season for many plants in urban areas. As a result, city dwellers who suffer from pollen allergies are more likely to endure longer periods of allergic reactions than non-city dwellers.
“From this study, we found urban nighttime light has significant impact on urban plant phenology,” Zhou said. “We found artificial light significantly advanced spring phenology and delayed autumn phenology in the United States.”
The research involved observation of satellite images in over 3,000 urban sites. For the observations made between 2012 and 2016, researchers noted that where there was increased artificial lighting, there was also an advanced date of breaking leaf bud in spring by about nine days. This is a significant period of time for plants to show differences based on artificial lighting. The researchers also observed that there were delays in the coloring of leaves by up to six days in the fall. This means that there is a longer active season for the plants in urban areas compared to non-urban locations.
Professor Zhou argues that urban environments can be used as natural laboratories and are ideal to help humans understand the impact of their actions. Further, he says that since urban areas are microclimate, they can be used to study the carbon and water cycles of the earth systems for a better understanding of human impacts.
“Urban environments can serve as natural laboratories to study responses of plants to changing climate. Urban research can be used as a lens to give us clues on how carbon and water cycles of the Earth system will evolve under a changing climate,” Zhou concluded.
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