It is International Dark Sky Week, an annual event when stargazers around the world raise awareness of our diminishing night sky. In many bustling cities and towns, bright lights from towering high-rise buildings, houses and street lamps obscure views of the cosmos and contribute to an environmental problem called “light pollution.”

“Light pollution is any unintended consequence of our use of artificial light at night,” said John Barentine , an astronomer and program manager at the International Dark-Sky Association, the nonprofit group that helps to promote this week’s events and year-round awareness. Although measuring light pollution can be tricky, Dr. Barentine said it occurs when light is wasted either because no one is using it or because it’s superfluous.

But unlike many environmental issues, light pollution is a problem researchers say could disappear with the flick of a switch. Solutions include turning off unnecessary lights and putting shields on streetlights to direct beams downward.

Researchers want to mitigate urban illumination not just because it creates an annoyance for amateur astronomers but also because it can adversely affect wildlife and human health.

“Start thinking of a photon as a potential pollutant,” said Michael Justice, a behavioral ecologist who studies how artificial light affects insects. “Much like a chemical spill or gas leak, the photons being used to light your porch and street can unintentionally leak into surrounding areas and affect the local ecology at every level from plants to apex predators.”

Christopher Kyba, a physicist who studies skyglow, the hazy yellowish illumination of the night sky by artificial light, at the German Research Center for Geosciences in Potsdam, Germany, traced the history: For billions of years, biology evolved in a world where light and dark was controlled by the length of the day. When the sun went down, celestial sources like the moon, stars, planets and Milky Way lit the sky. Life learned to operate under their glow. Only in the last 100 years or so — with the spread of artificial light — has that cycle largely gone away.

Here are ways researchers say that light pollution influences the world around us.