The Russellville City Council has recently taken a look at providing lighting for the four interstate interchanges. Studies show that the incidence of nighttime accidents can be reduced by better lighting. A study in Minneapolis showed that the ratio of nighttime to daytime automobile accidents at intersections is reduced by twelve percent by providing intersection lighting.
The Council approved half a million dollars for the project. To illuminate the entire interstate corridor through Russellville would cost on the order of two million dollars. Reducing accidents is a good thing but it comes at the cost of dark skies.
NASA has published numerous composite photos showing just how illuminated the planet really is. The eastern half of the United States, the west coast, western Europe, Japan, even India are clearly outlined by lighting. In one photo from over a decade ago, Russellville shows its own little speck on the nighttime.
With the exception of the extremes of the polar regions and the abyssal plains in the ocean, all life is adapted to regular day-night cycles. Disruption of the circadian rhythm enforced by day-night cycling can have effects on everything from plants to humans, especially humans.
Franz Halberg in 1959 coined the term circadian, from the Latin words “circa” (about) and “dies” (day). The rhythm is provided by the day-night environmental cue, called “zeitgebers, ” German for time givers. Time rhythms in animals are entangled with biochemistry through the production of the hormone melatonin produced by the pituitary gland.
Although sales of melatonin as a sleep aid is a multi-million dollar business, there is scant evidence of any effect. At least when properly controlled studies are considered. What there is strong evidence of is the untoward effects disruption of the circadian rhythm on humans.
Disrupted circadian rhythms due to shift work have long been known to have negative consequences. Elevated health threats include cardiovascular disease, diabetes, obesity, ulcers, and depression. Most obvious is the increase of work-related accidents from shift work schedules.
Light pollution is not a new phenomenon, records from the 1800s describe birds flying into lighthouses. A current problem is bird kills from illuminated buildings and especially cell towers.
Among insects, two effects have been observed. Nocturnal pollinators are less effective as artificial lighting confuses the pollinators and makes finding the flowers more difficult. Additionally, predators such as bats find easy pickings among the confused nocturnal insects.
The advent of Light Emitting Diodes (LEDs) has made the problem of light pollution worse for two reasons. Because LEDs produce light more cheaply, their use is expanding. Also, the wavelength of light produced by LEDs seems to cause greater behavioral changes in animals compared to the Sodium Vapor lights used for street lighting until recently.
The city council should think long and hard about just how much light is needed and what type of lighting is employed to minimize negative environmental effects.