Some people think cities and nature don’t mix, but a new NASA-funded study finds that concrete jungles create warmer conditions that cause plants to stay green longer each year, compared to surrounding rural areas.

Urban areas with high concentrations of buildings, roads and other artificial surfaces retain heat, creating urban heat islands. Satellite data reveal that urban heat islands increase surface temperatures compared to rural surroundings.



Using information from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the Terra satellite, Boston University, Boston, researchers discovered that city climates have a noticeable influence on plant growing seasons up to10 kilometers (6 miles) away from a city’s edges. Growing seasons in 70 cities in eastern North America were about 15 days longer in urban areas compared to rural areas outside of a city’s influence.



“If you live in a rural area and drive regularly into the city, and if you pay attention to vegetation, you will see a difference in the growing seasons in early spring and late autumn,” said Xiaoyang Zhang, the study’s lead author and a researcher at Boston University. The study appeared in a recent issue of the American Geophysical Union’s Geophysical Research Letters journal.



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