Even on the darkest and clearest of nights, nearly 70 percent of Americans cannot see the Milky Way in the night sky. A person standing on the observation deck of the World Trade Center would only be able to see only one percent of the stars someone from the 1700’s would able to view on any given night. True dark skies – Class 1 on the Bortle Dark Sky Scale – are nearly eradicated from North America, thriving only in the remotest of locations around the globe.
This is not simply something to romantically lament, as if our nostalgia for the heavens were some quaint artifact of generations past – light pollution is real, and has serious repercussions on human health and the environment. It is the most pervasive and fastest growing of environmental concerns, and ironically one of the most simple to reverse.
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Light pollution takes many forms, but its most obvious are over-illumination and sky glow. Over-illumination comes from inefficient, poorly designed exterior and interior lighting that throw light into unwanted areas, wasting electricity and having measurable environmental consequences. Sky glow is the orange hue that results from highly dense urban areas, where over-illumination from stadiums, street lights, billboards and the like inundate the horizons with wasted light.
One of the most obvious problems with light pollution is its economic ramifications – in the U.S. alone, over 2 million barrels of oil are wasted daily because of unnecessary lighting, resulting in upwards of $4 billion annually of economic strain. The energy needed to power this unused lighting contributes to global warming effects and pumps more pollutants into the air that only magnify the problem of sky glow. The toll on the environment is large, and poorly understood. Anywhere from 98 million to 1 billion bird deaths each year are caused by light pollution, while newly hatched turtles, bats, frogs, and other nocturnal animals are harmed by its effects as well.
The human cost, though, is more jarring. Over-illumination causes stress, headaches, and eyestrain in the office, and has even been linked to higher breast cancer rates in women due to inhibition of melatonin. Women living in urban areas have a 73 percent higher risk of cancer than their rural counterparts for this reason. Many observatories and astronomy centers have had to be decommissioned because of low-quality skies from encroaching city lights, and billions of people around the world live without access to a fundamental natural resource that has formed human culture and thought for millennia.
The problem is vast and its repercussions serious, but reclaiming our dark skies requires only smart policy and minimal changes to current construction and lighting practices. Most lighting fixtures, especially exterior lighting, are poorly designed and throw much of their light uselessly into the atmosphere or where it is not needed. Properly shielded lighting, along with high-efficiency and low-luminosity emitters, are the first step towards reigning in the creep of urban light pollution. Motion sensors that activate outdoor lighting only when needed is another step in the right direction – but what is needed most is a fundamental shift in mindset to help preserve a precious resource that has been spoiled over the course of just a few short decades. It’s time to darken the skies once more.