There was a time when street lighting means someone had to go light the lamps. Electricity changed that, but street and outdoor lighting has been quietly going through a new revolution: LEDs. The problem, though, is that LEDs provide what scientists call “broad white” light and there are concerns about the impact the unnatural lighting will have on ecosystems, including people and animals.
Of course, the first step in worrying about something is to measure it. You would think that satellites would have a bird’s-eye view of the nighttime lighting landscape, and, of course, they do. But most of the imagery isn’t suitable for looking at the spectrum of wavelength data scientists need to quantify what they call ALAN — Artificial Light at Night.
The ISS imaging is, however, sufficient. Using special data techniques, they were able to track the adoption of LEDs over sodium lights and other technologies between 2012-2013 and 2014-2020 across Europe. For example, in the title image, you can see Belgium with an orange tint indicating low-pressure sodium lights. The Netherlands, France, and the UK have a more yellow hue, indicating high-pressure sodium lamps. Germany is more of a blue color due to fluorescent and mercury vapor bulbs.
The data shows that LED adoption is happening at different rates in different countries and the paper discusses the potential biological impacts ranging from melatonin production to impacting the lives of insects and bats. Besides that, the sensors used to measure the intensity of artificial light from space now respond to the wrong wavelengths, and are thought to underreport readings as more and more LED lighting appears. The real gem, though, is the Materials and Methods section discussing how they processed and calibrated the data.
This is one of those unintended consequences where making any change seems to impact a lot of non-obvious things. For example, reducing sulfur emissions isn’t always as good as you think it is. Then there is the problem of running “endless” wells dry.