The Value of a Dark Night Sky

This is one in a continuing series of educational columns about fostering environmental stewardship and leadership coordinated by ACES — the Alliance of Climate and Environmental Stewards.

by Madelyn Kaplin

If you were to travel back in time 200 years, you would probably notice quite a few differences compared with our modern world. Sure, there would be no cars on the roads, and the people walking on the street would dress and speak rather peculiarly- but look up: the night sky you would see is vastly different from the one you see today.

The reason? Light pollution.

The advent of the electric light bulb in the 19th century revolutionized the way people were able to live, travel, and work. But the ability to artificially light our world at night has had unintended consequences on our health, our perception of the world around us, and the ecosystems we depend on.That view of the night sky from 200 years ago would have been unobscured- truly dark and bursting with stars on a clear night.

Today, 80% of the world’s population lives under light polluted skies, unable to see the Milky Way.

Over the past decade the night sky has grown brighter by nearly 10% annually. Light pollution- the human alteration of outdoor light levels from those occurring naturally- obscures our view of the universe. We rarely think of light as a ‘pollutant’ in the same way we consider plastic or carbon dioxide- but when lighting is used in excess, and light ends up in places where it is not needed or intended, it, too, can become an environmental pollutant with negative effects.

Exposure to high levels of artificial light at night suppresses melatonin production and disrupts our natural circadian rhythm, increasing our risk for a host of negative health outcomes such as sleep disorders, depression, diabetes, and heart disease. Outdoor lighting that shines when or where it is not needed also wastes energy and money- nearly $3.3 billion annually, according to some estimates.

Humans are not the only ones affected. Every species alive today has evolved with the daily cycle of light and dark. Light pollution prevents fireflies from finding each other to mate, reduces the efficiency of nighttime pollinators like moths and bats, and can even impact when trees bud out and drop their leaves.

Every spring, 3.5 billion birds return to the U.S. from wintering grounds in Central and South America to make nests, lay eggs, and raise their chicks.

80% of migratory species are nocturnal migrants, taking flight at night to avoid predators and stay cool.

These birds cross vast distances (anywhere from a few hundred to many thousands of miles) and use the position of the stars to help guide them.

Not only can a bright night sky make it harder for birds to navigate, but the glow cast upwards from cities and developed areas attracts birds in from miles away, luring them off their course and into dangerous, unsuitable habitat. Disoriented, they may become entrapped, circling lighting sources until they become exhausted, depleting themselves of the energy they need to migrate. Collisions with buildings are perhaps the biggest risk- more than 500 million birds die from flying into buildings every year.

Light doesn’t endure the way plastic or other pollutants do.

If we change how we choose to light our outdoor spaces, we can quickly undo some of the harm caused by light pollution.

Now, as spring migration reaches its peak, is the perfect time to act. Turning off outdoor lights at night, especially between 10pm-6am, using automatic light controls such as timers, dimmers, or motion sensors, switching to warmer color lights (3000 or less on the Kelvin scale), and using down-shielded outdoor lights that prevent light from escaping upward are excellent steps toward helping protect a dark night sky for both wildlife and people.

Madelyn Kaplin is a member of Biology and Visitor Services teams at Parker River National Wildlife Refuge. She can be reached at madelyn_kaplin@fws.gov.

ACES and its Youth Corps invite you to stay updated on environmental matters by subscribing to our monthly newsletter via the “Subscribe to Updates” link on  Please consider joining our community of stewards committed to Mak Every Day Earth Day by contacting acesnewburyport@gmail.com We can make a big difference together.

This educational column first appeared in The Daily News of Newburyport on May 24, 2024.