Satellite image of light pollution on 27 February 2019 in north-west Europe. Photo: NASA / VIIRS / SUOMI NPP
Artificial light extends the growing season in urban environments by up to three weeks compared with rural areas, according to analyses of satellite data.
He wattage of artificial light increases exponentially from rural areas towards urban centres, and artificial light – even more than rising temperatures – extends the growing season there by over three weeks. This is the finding of analyses of seven years of satellite data from 428 urban centres in the Northern Hemisphere, published on 17 June by environmental scientists in the journal Nature Cities, which launched last year. Urban ecologist Lin Meng of Vanderbilt University in Nashville and colleagues found that artificial light both advances the start of the growing season and delays its end. For the cities studied – including New York, Beijing, Paris, and numerous other (European) cities – the growing season begins on average 12.6 days earlier and ends 11.2 days later than in the surrounding rural areas.
Although the general patterns are consistent, particularly for the effects on the end of the growing season, the authors also found differences between continents. The season starts earliest in European cities, followed by those in Asia and then North America, even though cities in North America are the most brightly lit. Furthermore, it remains unclear what the precise consequences are for the growing season of the relatively recent and widespread switch from sodium lamps to LED lighting – which is more plant-friendly – in cities.