A new study, published in the journal Lighting Research & Technology, has revealed that much of light pollution, which negatively impacts human health and animal migrations and wastes energy, is not coming from streetlights. Researchers conducted an experiment in Tucson, Arizona, where all 14,000 streetlights in the city were dimmed at 1:30 a.m. for 10 days. Satellite images recorded during this period revealed that even with the lights dimmed, there was still sufficient light polluting the natural look of the sky.

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“We used a satellite to measure what fraction of the total light emissions are due to the streetlights,” said Christopher Kyba, physicist at the German Research Centre for Geoscience in Postdam. “And late at night, when people are sleeping — that is exactly when we can save a lot of energy.”

Related: Switching to outdoor LEDs has made light pollution worse — without saving energy

The study indicates that much of the light and energy used at night to illuminate streets and buildings is wasted. Consequently, the wasted light ends up in the sky and disrupts wildlife. Among the sources that cause most light pollution include stadium floodlights, advertisements, facade lighting and parking lots.

According to Kyba, controlling light pollution will require concerted efforts from different industry players, including light users and policymakers.

According to the International Dark-Sky Association, about 35% of artificial lighting at night is poorly aimed. In other words, the light does not serve the intended purpose and ends up as wasted light. This equates to about $3 billion per year in wasted energy in the U.S. alone.

“A lot of people talk about climate emergency but never talk about light pollution,” Kyba said. “But it’s an important part. And at night, when most of us are asleep, all that electricity could be going to do other things — charging electric vehicles, for example.”

Although lighting at night is acceptable, light pollution results in a glow in the sky, which interrupts the migration of birds, insects and other animals. Further, the constant lighting denies those who are born in this age the chance of seeing a clear, dark sky with stars.

+ Lighting Research & Technology


Image via Hikarinoshita Hikari