Scientists are discovering that light pollution finds its harmful way into all aspects of life, some with unexpected consequences and some, strangely associated with global climate change. In this Dark Sky segment of Western Slope Skies, I’ll cover one that surprised this old atmospheric scientist experienced in land-atmosphere interaction but it made sense. You just had to look.
An article in the international journal Nature Cities by Lvlv Wang and co-authors document the effect of light pollution on the growing season in 428 Northern Hemisphere cities between 2014 and 2022. They note that the typical growing season is controlled by heat and light. While cities are getting warmer due to climate change, they are also getting brighter due to excessive lighting. After controlling for the warming effect, they found that the excessive light was extending the growing season.
Now you would think that would be beneficial. Longer growing season, more ecosystem growth, which should be a good thing. Maybe if you tend a patio, balcony, or community urban garden but they found that the overall the ecosystem suffers because of something well known in the world of climate change research; ecosystem timing, especially when plants spring into action and when they die or go dormant.
As an ecosystem develops, sometimes over centuries to epochs, the interweaving of plant, land and aquatic animal life, and insects results in an overall healthy, sustainable landscape. In this complex world, timing is everything. If a flower blooms early or waits an extra week to die, the insects that normally pollinate it, responding to centuries of training, are either too late for the early bloom or late for senescence, the dying phase of plant life. That plant’s survival potential is reduced as a result. If a migrating bird is dependent on a plant’s fruit or seeds and those seeds are not available before the bird bulks up for a migration flight, that bird’s survival during the flight is reduced. These are only two examples, there were several others. So, the overall effect of light pollution is to cause change in the ecosystem resulting in a period of reduced viability during the change.
This is very similar to the impact of climate change on ecosystem timing. As the planet warms ecosystems are thrown into confusion as plants move, growth patterns change and the mutual dependence on air, water, and land life is corrupted. The overall result a decrease in what ecosystem scientists call “ecosystem services” to humanity such as clean air and water.
Since light pollution is a relative newcomer to the urban scene like climate change, there is the possibility that light pollution could be reduced, and the ecosystem would recover to near the earlier state but that, like climate change, is not guaranteed.
DarkSky International, an international organization dedicated to reducing light pollution, is promoting a new Dark Place, the DarkSky City for those cites, like Tucson, Arizona, that voluntarily reduce their exterior lighting according to DarkSky International guidelines. One can only hope that other cities, like Grand Junction and Montrose in the KVNF listening area would investigate that DarkSky International designation. Their ecosystems and the services they provide, currently under stress from heat and light, would be more supportive.