As night falls on University Avenue, the illumination of streetlights and storefronts casts a cozy glow onto the sidewalk. But beyond the inviting atmosphere, a hidden issue arises as the excess light floods into the sky: light pollution.
On April 7, the Palo Alto City Council announced a new ordinance to reduce light pollution throughout the city. The proposed regulations discussed during the meeting are unofficially known as a “dark sky ordinance.” If passed, the regulations would establish an outdoor lighting curfew, curb the use of warmer light bulbs and require shielded fixtures to prevent light from polluting the sky.
Councilmember and former Mayor Greer Stone has been a major proponent of the ordinance.
“I was inspired to pursue a dark sky ordinance because protecting our natural environment — including our night sky — is part of protecting the well-being of both our community and our local ecosystems,” Stone stated in an email to Verde. “In a city like Palo Alto, where we value innovation, environmental stewardship and quality of life, I believe we should lead by example and be proactive in addressing this issue.”
According to Stone, the proposed ordinance requires outdoor lighting to be shut off by 10 p.m., and has many expected benefits for both residents and the environment.
“For residents, reducing light pollution directly benefits sleep health and mental well-being,” Stone stated. “Environmentally, minimizing unnecessary nighttime lighting helps protect species like birds, bats and pollinators that rely on natural light cues for migration, feeding and breeding patterns. Restoring more natural darkness also strengthens the biodiversity that makes Palo Alto special.”
However, with these benefits also come possible challenges that the City Council must consider. According to Stone, balancing legitimate concerns around safety and visibility with the ordinance’s goals is the main challenge.
“Some residents and businesses understandably worry about ensuring that streets, parks and downtown areas remain well-lit for public safety,” Stone stated. “The goal is not to make downtown or other commercial areas less inviting or less safe. The ordinance would allow for necessary lighting, but would encourage features like shielded fixtures, warm light temperatures and lighting only where and when it’s truly needed.”
One concern regarding this ordinance comes from business owners who worry that reducing nighttime lighting could compromise the number of customers.
Dashiell Leeds, conservation organizer at the Sierra Club, said that the ordinance was designed with flexibility in mind.
“Palo Alto’s proposed ordinance will not force any business to turn their lights off when they are operational,” Leeds stated in an email. “The lighting curfew states that lights must be turned off or motion-sensor -operated at 10 p.m., two hours after close of business, or when people are no longer present in exterior areas, whichever is later. This language is incredibly flexible and will ensure that when people are outside or at a business, they will have the light that they need.”
Leeds supported this ordinance with a growing body of scientific research on Artificial Lights at Night, or ALAN. He referenced the 2024 State of Science Report by DarkSky International, which collects studies on how exposure to artificial light can negatively affect human health.
“While exposure to blue light during the day is important for healthy circadian functioning, exposure to this light at night can disrupt the human circadian rhythm,” Leeds stated. “This can affect everything from the timing of hormone release in the body, to the duration and quality of our sleep.”
The effect of artificial light on the environment is also substantial. Leeds noted that in the Baylands, the endangered and nocturnal salt marsh harvest mouse could be put at a greater risk due to excess light being spread into its habitat.
Leeds said that this ordinance is meant to strike a balance between helping people and the environment without putting safety or local businesses at risk.
“The species I think that has the most to benefit from this ordinance is humans,” Leeds stated. “With this ordinance, we’ll save energy and have less disturbances to our sleep and health without compromising safety or business operations.”