Light Pollution in London
Did you know?
Artificial light at night is a harmful form of environmental pollution.
High amounts of light pollution increase the risk of birds crashing into tall buildings.
Light pollution causes a variety of effects on animals, plants and ecosystems.
Reducing light pollution involves simple steps that can save money and energy.
A Forest City without darkness
Light pollution in the City of London is significantly more intense than in the surrounding area. Artificial light at night in London can be seen from space!
We can see from satellite imagery that although light pollution is diffuse across the entire city, there are areas where light pollution is more intense.
Light pollution in London comes from a variety of sources including buildings and outdoor lighting infrastructure.
Light pollution in 2020 shown in London and surrounding area. Source: Light Pollution Map
Closeup view of light pollution in London in 2020. Bright spots indicate higher light intensity. Source: Light Pollution Map
Light pollution and bird collisions
Birds are most likely to collide with building windows during the day. Learn more
However, during bird migrations in spring and fall, a significant number of birds may collide with windows at night, especially on tall buildings. This is thought to happen because of light pollution.
Birds use subtle celestial cues in the night sky to navigate during migration. In cities with a lot of light pollution, these cues are interrupted by skyglow and birds cannot see them.
As birds fly over the City of London, the glow in the night sky produced by artificial lights may draw birds in and towards light sources. Birds may become disoriented and crash into building windows. It is believed the risk for bird collisions is especially high in the early morning hours as birds descend into the city to stop over between their long-distance travels at night.
Light pollution and ecosystems
When artificial light at night spills into natural areas, it can disrupt everything from insects to fish to trees. Many organisms depend on darkness conditions to fulfill their natural day/night bodily rhythms, to reproduce, to forage and to move around.
The ecology of light pollution is a topic of ongoing research. There are many things we still don't know about how light pollution impacts the environment. While some effects of leaving lights on at night may be positive for human society, light pollution seems to mostly harm animals and plants at individual and system levels.
What can be done?
The simplest thing that
anyone can do to reduce
light pollution in London
is to turn off unnecessary
artificial lights at night.
Homeowners and renters, businesses and building managers all have important roles to play in reducing light pollution. In general, light pollution can be addressed through changing behaviour and upgrading infrastructure including light switches and sources.
It is important that properties adjacent to natural areas minimize light spillage from buildings and outdoor light fixtures. Some suggestions are offered below.
To reduce light pollution...
Learn about Outdoor Lighting Basics from the International Dark Sky Association.
Use only downward-directed light fixtures outdoors with full cutoff.
Install light timers or occupancy sensors for fixtures inside buildings.
Install motion sensors for lights outside buildings. Make sure to calibrate sensors to appropriate sensitivity for lights to be triggered by pedestrians.
Use warmer-coloured lighting outdoors and avoid cool or white light.
Reduce the number and brightness of lights outdoors within an acceptable limit.
Keep track of reductions in light pollution by monitoring changes over time and targeting remaining sources of excessive light at night.
For more information about reducing light pollution, check out these resources:
Take Action with the International Dark Sky Association