Stargazing is best on the cold, dry nights of winter, when the haze and smog that veil the heavens much of the year give way to crystal-clear skies. Yet in much of the U.S., it’s increasingly difficult to make out any but the brightest stars thanks to the prevalence of outdoor lighting. That’s why scientists are trying to keep some of our most pristine locales in the dark.

The National Park Service (NPS) now considers protecting the night sky part of its mission to preserve scenery. The agency’s Night Sky Team is working to reduce light pollution at more than 50 parks. A four-person team of scientists measures the parks’ nighttime brightness, helps rangers switch to dimmer lights, and develops education programs for visitors. New government funding will allow the team to collect data from more parks to better understand the threats of light pollution. Chad Moore, an earth scientist who formed the team in 1999, says these efforts allow visitors to get something they can’t get anywhere else: “an inspirational view of the cosmos.”

But that view is in danger of being lost. Light pollution can travel 200 miles and mask easily recognizable constellations like the Big Dipper; in fact, two-thirds of Americans can’t see the Milky Way from their homes. Development around parks has been tainting previously unpolluted night skies. According to one 2006 analysis, since 1990, more than 1.3 million people had moved into counties surrounding six popular parks, including Everglades and Yellowstone. Some fear the problem will only get worse. A 2001 study found that by 2025, even deserts and other remote places will be bright — meaning folks throughout the U.S. will see at most 100 stars from their yards. And the glare disrupts more than stargazing: It can distract turtle hatchlings from finding the ocean, divert birds from migratory paths, and alter amphibians’ hormone production.

Moore, however, says the situation isn’t so dire. Some cities and states are already switching their outdoor fixtures to low-intensity and shielded lighting, dimming the glow and saving money. And when national park visitors view the constellation-filled heavens, “they go home unsatisfied with what they can see in their backyards,” which could entice people to think twice before adding outdoor lights.

“This is a special resource, so we need to do all we can to educate the public,” says Bryan Faehner of the National Parks Conservation Association. “Then future generations can experience it and be inspired.”

This article originally appeared in Plenty in February 2008.

Copyright Environ Press 2008.