Artificial light extends urban plant growing seasons: study

BEIJING, June 23 (Xinhua) -- A group of Chinese researchers and their international counterparts has found that artificial light at night exerted stronger influence than high temperature in extending the urban plant growing season, bringing new inspiration to urban ecosystem conservation and sustainable development.

Light and temperature largely regulate the plant growing seasons. For example, compared with the surrounding rural areas, the increase in light and temperature in cities leads to earlier budding and flowering in spring and later coloring in autumn for urban trees. However, the scientists have not fully investigated the extent of the impact of these factors.

The researchers from China's Wuhan University, the United States' Vanderbilt University, and other international institutes used multiple satellite observations of 428 cities in the Northern Hemisphere, including Beijing, New York, Paris and Toronto, from 2014 to 2020 with data of artificial light at night and surface air temperature to carry out the study.

The study, recently published in the journal Nature Cities, found that artificial light at night increases exponentially from rural to urban centers, which has a greater impact on the start and end of the urban growing season than the temperature increase.

It revealed that the impact of artificial light is more pronounced at the end of the growing season than at the beginning. In the cities analyzed, the start of the urban growing season is 12.6 days earlier than in the surrounding countryside, while the end is 11.2 days later.

The study also found mixed influence brought by extended urban plant growing seasons, which may reduce the Urban Heat Island effect and enhance carbon sequestration. However, it may disrupt interactions between plants and pollinators, and lead to an earlier occurrence of pollen allergy symptoms.  ■