The natural world

Artificial light at night is now identified as ‘one of the most pressing and imminent threats to global biodiversity’. Every aspect of the natural world is currently being profoundly disrupted by light pollution. This is not just around cities – skyglow can be detected far away from the light source, and hundreds of meters deep into the ocean.

The use of artificial light has grown exponentially over the last century and surged in the past decade. There has been a big change in the quality as well as the quantity of artificial light. The rapid rise in LED (or ‘solid state’ technology) has meant more light – because it is perceived as cheaper and greener – and has resulted in more ‘blue’ light in the night-time environment.

Light is time

This matters, because light is time in the natural world. Life on Earth has evolved to a steady, cyclical rhythm of dark nights, light days and the phases of the moon. These changes in colour and intensity of light are the cues that living creatures respond to throughout their lives. It’s the clock and the calendar of the living world. Light controls the systems within each being and affects the interactions between species.

A growing body of science is revealing the harm that light pollution is causing, to individuals, to populations and to ecosystems. It disrupts plant and animal reproduction, migration and communication. It can even influence how species evolve, weaken the immune system and alter the relationship between predator and prey.

Light pollution and climate change

Light pollution is exacerbating the effects of climate change in terms of the disruption of the natural world. The ‘blue colour’ of much LED outdoor lighting is precisely the frequency that’s most disruptive. Advances in technology are now bringing orange and red-coloured outdoor lighting, and in some places this is installed as ‘bat friendly’ or ‘eco-friendly’ lighting.

Yet scientists caution that we cannot know that any artificial light at night is ‘eco-friendly’ – what is beneficial for one species can be problematic for another. The relationship between light and life is extraordinarily complex. What we call ‘light’ is itself a human perspective, based on the sliver of the electromagnetic spectrum that can be perceived by human vision. But there are millions of other types of eyes, and light-detecting mechanisms in mammals, insects, fish, plants and more. LED light has certain qualities that make it different from previous artificial lighting, the light behaves in different ways, and the effects of this are not yet understood.

All in all it calls for humility and caution, when making decisions about light. Current legislation and regulations are based on measures that only reference human vision. We need to take into account the different responses of other creatures to light. All artificial light at night is pollution, and minimising light pollution is an urgent requirement for the natural world.

References

This summary is drawn from the following papers:

Artificial Light at Night: State of the Science, 2022
International Dark-Sky Association
https://darksky.org/app/uploads/2022/06/IDA-State-of-the-Science-2022-EN.pdf

Leading ALAN researcher, Professor Travis Longcore, technical report for the State of California: Effects of LED Lighting on Terrestrial Wildlife.
Download Professor Travis Longcore’s latest paper

Resources

The ALAN (Artificial Light at Night) database provides references to scientific literature on all aspects of research on light pollution. No login is needed, to access the ALAN database.

For the latest findings on specific species or subjects (eg seabird, coral, tree) key the word into the search window on the top right.
Access the ALAN Database

More information on light pollution and wildlife is available from DarkSky (formerly the International Dark-Sky Association):
https://www.darksky.org/light-pollution/wildlife/