The Birds and the Bees: Lighting Up the Night

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Light at night not only causes human health problems, but it also messes with the birds and the bees. Along with pretty much all the other critters…

While you and I can put up some blackout shades or sleep with an eye mask, the outdoor critters have little escape from the ever-increasing lighting at night.

Earlier this year, I was reminded of this impact on the animal world by our human propensity to light up the night. I was catching an early flight out of our local airport, and the parking garage was very well lit. The outside of the parking garage was also illuminated with pretty, bright blue lights. At 4:30 am, when the rest of the bird world was sleeping, the birds around the well-lit airport were noisily chirping away — active when they should have been sleeping.

Let me give a little context as to how much artificial light is illuminating the night:
A full moon under clear skies produces 0.1 – 0.3 lux. Residential street lights average about 5 lux, and lights for major roads usually produce 15 lux.  The urban sky glow on a clear night is around 0.15 lux (similar to a constant full moon), and it increases when it is cloudy. [ref]

Prior to cities and towns lighting up the night, there would be the warm, yellow glow from fire or candles as the only illumination.  Nocturnal critters would scurry around in the darkness — and it would truly be dark without a full moon.

Throughout the 20th century, municipalities have increasingly lit up the streets. Initially, this was only in major areas, on nights without moonlight, and only until midnight.  Yes, the streetlights used to shut down at midnight.

Lighting has switched in the past twenty years from the yellowish sodium streetlights to bright white (blue-enriched) LED streetlights.

What is all of this light doing to animals?  There have been a number of studies showing various effects.

First, the pollination of plants at night by insects is reduced by 62% in areas with artificial light at night. That is huge! About 88% of plant species rely on insect pollinators. Researchers have also found that there is a cascading effect from light at night on daytime pollinators, such as bees. Overall, fruit-set (a measure of plant reproduction) decreased by 13%. [ref]

While insect pollination at night isn’t going to be a fascinating topic or rallying-event for environmentalist, it is vital for food security.

How is artificial light affecting animals? It suppresses melatonin production, it alters the circadian clock, it disrupts the seasonal timing (reproduction, etc), and it changes nocturnal behavior. These are fundamental ecological activities of animal species.  And we are messing with it by light at night. [ref]

Here are a couple of specific examples:

  • Wallabies that are exposed to artificial light at night are more likely to forage more and spend less time on ‘antipredator vigilance’. [ref]
  • Bat behavior is changed by bright white streetlights. They are three times more likely to forage near the streetlights, due to the attraction of insects. This seemed to be either a neutral or beneficial thing for some species of bats, but it negatively affected bat species that fly more slowly.[ref] [ref]
  • Mating behavior is changed by artificial light at night. It has affected amphibian mating and substantially changed the timing of when birds lay their eggs.[ref][ref]

People who live near the southern beaches in the US are well aware of one aspect of light at night — it messes up the hatching sea turtles, causing the babies to head the wrong direction.  Communities have rallied, homeowners have shut off their outdoor lights, and whole cities have lowered their nighttime illumination. Save the Sea Turtles.

We now need to save the rest of the animal kingdom, including us humans.

What can you do?

Start at home…  Shut off your own bright outdoor lights. Switch to small, low impact lighting just at the places that it is needed, such as next to walkways.

Talk with your local city council about decreasing municipal lighting.

Send an email to local businesses asking them to decrease their light at night.

Spread the word! So many people are unaware of the impact of light at night both on human health and on our environment. You may be surprised at how much of a difference we can make just by letting people know that this problem is important.



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