Why is darkness at night important?

Many animals rely on darkness at nights to live a healthy life. The majority of organisms, including humans also rely on dark nights to keep circadian rhythms (natural sleep and wakefulness patterns). Diurnal (active during the day) organisms rely on darkness for restful sleep while nocturnal (active at night) organisms rely on dark nights for hunting, feeding, mating and much more. For example creatures such as moths, birds and frogs rely on the stars for navigation!

The issue: illuminating the night sky

Artificial light can be disturbing to organisms because it disrupts their circadian rhythm, quality of sleep, mating success, and/or forging which can result in death, sub-optimal health or species evacuating from an area. In particular, full spectrum (includes UV light) and blue lights are the most detrimental, especially when they are intense (bright). This light is especially harmful because it is only found during daylight hours and thus disturbs both nocturnal and diurnal organisms alike. Artificial outdoor lighting can also cause many organisms to become disoriented because it blocks out the natural light of the moon and stars which are used for navigation in some species (as mentioned above). This disorientation causes many species of moths to fly straight into lights in a confused daze and other flying creatures to change their orientation to aim below lights (this is because natural light is always above them in the sky). The negative effects that lights have on insect abundance, for example on large moth species (they are more likely to die when they come into contact with artificial lighting), has been shown to have negative effects on the bird populations whose diets depend on these moths.

Outdoor lighting can also encourage the presence of organisms that you do not want. For example outdoor lighting at night can also increase algae growth because they are able to photosynthesize and grow all night (on top of all day)! Night lighting has also been shown to increase mosquito presence and the active season of mosquitos - meaning more time to bite us!

Artificial lights cause light pollution (the presence of non-natural light outside at night) which not only effects the immediate area (luring organisms for many meters), but can also cause skyglow - a blanket haze of illumination in the sky which blocks out the stars. This phenomenon occurs when there are many lights in an area or when lights are pointed into the sky. Currently, more than 80% of the world's population lives under light polluted skies. When you stop and think about this it is not hard to believe. Consider your own neighbourhood. Are their street lights? Do you or your neighbour keep patio lights on all night? That is light pollution.

Many people travel to cottage country to go stargazing, however as more cottages are established more night lighting occurs. In order to keep our view of constellations and celestial bodies, we must strive to limit light pollution on our properties.

The Land Between is one of the last places in Southern Ontario where you can still see the Milky Way.

Is night lighting effective against crime?

Night lighting can be an ineffective method of preventing crime and in come cases can even increase the instance of crime. In addition, bright lighting results in the "darker darkness" phenomenon. When lights are bright it is much more difficult for humans to see into dark areas, versus when lighting is dim because our eyes need time to adjust to see in darkness. Therefore, when there is a dark area beside a brightly lit area it is extremely difficult to see into the darkness. Instead of constant lighting for security consider installing motion sensor lighting. If lighting must be installed, consider the guidelines mentioned below.

What can you do to help?

1. Turn off lights when you are not using them: Avoid keeping lights on when they are not directly in use and consider replacing traditional light with motion lights. This will not only help the wildlife in your area, but will also help out your wallet!

2. Replace full spectrum and white lights: Replace your outdoor lighting with warm coloured bulbs (orange, red, yellow). You can also cover your existing bulbs with warm coloured or UV filter films

3. Use low wattage or dimmable bulbs: The moon is only 50 lumens, but often provides enough light for us to see at night. In comparison, a 45 watt bulb is 400+lumens! That’s at least 4 times greater than the moon! Install low wattage or dimmable bulbs to reduce the lumens (brightness) of your outdoor lights. These lights are still able to provide ample visibility while also disturbing all species (including us).

4. Angle lights downwards <70° and install lights with caps: By angling lights downward and capping the (similar to a lampshade) you help to reduce the negative effects of light pollution by limiting how far the light travels.

5. Learn your local bylaws: Many municipalities have night lighting guidelines. Click here for a wonderful example (thanks to Highlands East)!

Where can I find more nature friendly lights?

Click the links below to find examples (we are not affiliated with these stores in anyway):

• Motion lights
• Dimmable red bulb, orange bulb, yellow bulb

Want more information? Click the links below to find out more:

• Videos
  • Issues of Blue Lights
  • Can Night Lights Deplete Sleep and Health
  • Animals Navigating the Night
• Dark-Sky Preserves
  • First Night Sky Preserve in Canada: The Torrance Barrens Conservation Area and Dark Sky Reserve in Muskoka,ON.
  • North Frontenac Dark-Sky Preserve
  • Dark-Sky Preserves in Canada
• Effects of light pollution
  • Health effects of light pollution
  • Artificial light at night in freshwater habitats and its potential ecological effects
  • Dark Skies for Health
• Policy and law
  • Night lighting for policy makers
  • Switch On the Night: Policies for Smarter Lighting
  • City of Toronto-Best Practices for Effective Lighting
• Additional learning resources
  • Extra learning materials by the International Dark-Sky Association
  • Light pollution around the world
  • See a story map of changing night skies in the world
  • Street lights affecting insect populations and therefore bird declines and other cascades

Works cited

Groenendijk, D., & Ellis, W. N. (2011). The state of the Dutch larger moth fauna. Journal of insect conservation, 15(1), 95-101.