Light pollution is defined as the inappropriate or excessive use of artificial light at night, and it is the fastest growing pollutant on the planet. Whilst astronomers lament the loss of stars, preventing over 80% of the world’s population from access to a natural sky, light pollution’s impacts are far more reaching. At the same time, it is also the easiest pollutant to address.
Light pollution negatively impacts on wildlife, which, much like humans, rely on the cycle of night and day to determine the timing of their biological activity. Studies have shown these impacts to include everything from wide-ranging effects on species physiology; seasonal disruptions; rate and timing of reproduction; alteration of daily activity patterns; and changes to species populations. These impacts are occurring under a range of lighting intensities, including very low lighting levels below 1 lux, and the consequences can be long-term and, in some cases, irreversible.
Light pollution by its very nature is also wasted energy, adding significant amounts of greenhouse gas emissions to our planet. There are also associated implications in the disruption of the human circadian system and our health. Without question, the outdoor lighting that once defined human progress has now become a serious human and environmental problem.
Light hasn’t historically been considered as a pollutant, but the weight of scientific evidence in recent years is now overwhelming. Indeed, there is sufficient demonstrated risk to both people and the environment that we must now adopt the ‘precautionary principle’, which places the burden of proof on those supplying, designing, installing and managing lighting to demonstrate that their products and lighting installations are not harmful. The importance of committing to environmentally sensitive design has never been more important.
To be clear, this is not just a story about street lighting. There are many other forms of public lighting that are contributing to the global light pollution problem. These include lighting from sports fields, advertising signage, media screens, facade lighting, public space lighting, not to mention the vast amounts of spill light that escapes from practically unoccupied commercial buildings on a nightly basis. It is little wonder that light pollution is increasing at a global rate of over 2% per annum.