Article

By Eric Johnson

January 7, 2025—At a recent meeting of the Santa Cruz chapter of DarkSky International, the conversation touched on the impact of light pollution on stargazing, but covered many other topics.

Responding to a reporter’s questions, several participants shared their favorite places to view the night sky in and around Santa Cruz. But there was also discussion of the impact of artificial light on salmon in the San Lorenzo River. There was talk of street lights near bluffs on the West Side that negatively affect life beneath the waves. One member told of the ways artificial light hurts birds. And there was a conversation about the city of Santa Cruz’s efforts to implement lighting policies suggested by the DarkSky people themselves.

The International Dark-Sky Association, now DarkSky International, was founded by two astronomers—one an amateur who bought a piece of property outside Phoenix, Arizona, and built his own telescope, and the other the director of the Kitt Peak National Observatory—one of the largest arrays of optical and radio telescopes in the world.

DarkSky’s mission, which has launched a successful global movement, was to decrease the effects of light pollution and darken the sky so that astromoners—and the rest of us— could better see the stars. As the organization has grown, its mission has expanded.

Andy Kreyche, the local DarkSky chapter’s de facto communications guy, says artificial light is damaging to nature in myriad ways, and hurts people much more than we realize. He points out that for millennia, our hominid ancestors lived in a world where every day was followed by a dark night, and that this pattern was in fact imprinted in our genes from eons before that.

“Life absolutely evolved with cycles of light and dark as a natural state of things,“ Kreyche says, “and when we disrupt that, it does damage that we are just beginning to understand.”

Two DarkSky Santa Cruz members were interviewed by Saratoga High School students for this short film:

Studies have shown that too much light exposure at night disturbs circadian rhythms and suppresses the production of melatonin, thereby disrupting sleep. Other studies have linked bright light at night with risks for hypertension, depression, and even cardiovascular disease and cancer. In recent years these health problems have become acute across the globe.

After Thomas Edison created the first commercially viable incandescent light, the cycle of darkness for many people began to get shorter. The invention of streetlights exacerbated that situation. And as lighting has become cheaper and brighter, Kreych says, light pollution has become something of an ecological and public health catastrophe. And that’s a difficult problem to solve—again on account of our genetic programming.

“As diurnal creatures, we have it in our DNA to fear the dark,” Kreyche says. “Darkness is unsafe—there could be a sabertooth tiger out there ready to kill me. I understand where the fear is coming from, and the DarkSky movement needs to overcome that fear.”

Kreyche and his allies have developed a rather simple, if not easy, solution to the problem they’re trying to solve.

Five Principles for Responsible Outdoor Lighting

1. USEFUL - Use light only if it’s needed.
All light should have a clear purpose. Consider how the use of light will impact the area, including wildlife and their habitats.

2. TARGETED - Direct light so it falls only where it’s needed.
Use shielding and careful aiming to target the direction of the light beam so that it points downward and does not spill beyond where it’s needed.

3. LOW LEVEL - Light should be no brighter than necessary.
Use the lowest light level required. Be mindful of surface conditions, as some surfaces may reflect more light into the night sky than intended.

4. CONTROLLED - Use light only when it’s needed.
Use controls such as timers or motion detectors to ensure that light is available when it’s needed, dimmed when possible, and turned off when not needed.

5. COLOR - Use warmer colored lights where possible.
Limit the amount of shorter wavelength (blue violet) light to the least amount needed.

The Santa Cruz Chapter of DarkSky International contains a number of resources, including ways to get a free light-shield if a nearby streetlight is throwing unwanted light into your home.