GREAT SAND DUNES NATIONAL PARK – People escaping light pollution where they live have forded an icy creek and are rediscovering the night, wandering around on mystical moist sand in the near-total darkness of this wilderness.

They covet silence and stars — splayed across a moonless sky revealing the Milky Way Galaxy — increasingly popular assets at national parks nationwide.

Some sit for hours. Some lie on their backs. Some use headlamps to navigate, softening the glare using the red filters favored on nocturnal military missions.

“Light pollution is terrible. It disrupts your natural sleep system. This is just so gorgeous,” said Jonathan Rhoton, 36, joined by his spouse, Brooke, their daughter Olivia, 4, and friends from Oklahoma City.

“Words cannot say why you go out here,” he said.

Darkness is increasingly rare. And land managers here and at other U.S. national parks — joined by more and more towns — are trying to set themselves up as preserves by obtaining official “dark sky” designations. They’re hoping these will serve as protection against an onslaught of light pollution.

How bad is it? The latest ground measurements and satellite data, showing widespread washout from oil and gas industry flares and floodlights, have established that more than half of Americans no longer can see the main features of Earth’s celestial neighborhood, such as the horseshoe-shaped Milky Way, from their home communities.

The primary culprit in cities such as Denver is street lights, which lack hoods that direct light downward and shoot out white light that scatters. And developers increasingly install ultra-bright light-emitting diode signs and digital billboards, luring consumers like moths to malls, fast food and car lots but further diminishing night skies.

Light pollution has been surging since World War II. Defined as the spread of artificial light from manmade sources, such as car lights, into nature, light pollution can obliterate stars. Air pollution compounds the problem as particles help scatter light in the atmosphere. Doctors blame light pollution for widening disruptions of circadian systems, making it harder for people to fall asleep, and as a factor in aging and cancer.

“For the United States, the situation is getting steadily worse,” International Dark-Sky Association program director John Barentine said, citing data showing that 99 percent of Americans live under night skies where pollution from electric lights has reduced darkness by at least 10 percent.

“It is getting worse, even in places where people have light ordinances, because the enforcement is terrible,” Barentine said. “Cities generally don’t have the properly trained employees to substantiate violations of the ordinance.

“We now have second and third generations of people who may think not seeing the Milky Way is just a consequence of living in a city. Does it have to be the case that cities will not have dark night skies? We need an act of Congress. What we really need is a Clean Night Skies Act.”

But big, bright light has steady backing from the lighting industry, big-box retailers, advertisers and others. Police tout light as the enemy of criminals. The latest energy-efficient light-emitting diodes, or LEDs, let communities illuminate more at a lower cost.

Yet light pollution, including the addictive blue-white glow from smartphones and computers, increasingly hurts children, keeping kids from settling into healthy sleep patterns. Turtles and other wildlife also are disturbed. The blue columns shooting up from the absent twin towers in New York, an art project memorializing those lost on 9/11, disrupts coastal migration for birds.

There’s evidence urban residents may be noticing.

Karen Treviño, chief of National Park Service’s Natural Sounds and Night Skies Division, pointed to Apple and other smartphone makers who increasingly offer apps or operating-system features that dim light or shift hues to softer reds and yellows. This suggests market recognition of a growing concern, she said.

The intensifying light pollution in cities puts parks in a complex position as last bastions of true night, where dark skies can be observed in their fullness with stars.

“On one hand, it would be an honor to be able to provide the American public with an experience they are seeking, particularly if they cannot get that anyplace else. That’s partly why national parks were established,” Treviño said. “On the other, it’s kind of sad to think we might get to a point one day where national parks are the only places where Americans could have that type of experience.

“I think, as awareness of this problem grows, because of health reasons or otherwise, we likely will see more cities becoming more sensitive.”

Scientific understanding of light pollution’s health impacts — research boosted this month with a Nobel Prize for three Americans exploring how molecular mechanisms control circadian rhythms — may be driving people to see a more traditional balance of daytime and darkness.

At the Great Sand Dunes, visitation increased to nearly 400,000 last year from 320,000 in 2015, with more people coming primarily to savor stars. The park’s most popular interpretive programs with rangers revolve around the night skies.

“You want solitude? You want quiet? You want to get out of Denver? Don’t want to merge into traffic any more? Come out here,” said Fred Bunch, the park’s chief resource manager, who first arrived riding a bicycle in 1968 and for a decade has led efforts to protect night skies.

“Half the park is after dark,” Bunch said, suggesting that people, due to evolutionary history that included celestial inspiration, may have “a right to starlight.”

The park’s application for the International Dark-Sky Association, or IDA, designation is in the works.

A couple years ago, town leaders in Westcliffe and Silver Cliff, on the eastern side of the Sangre de Cristo Mountains, achieved the designation, for mostly economic reasons, hoping to attract star-gazing tourists. The southwestern Colorado towns of Nucla and Norwood now are seeking dark-skies community designations.

An official IDA designation “would add another layer of protection” for the ecologically fragile dunes, Bunch said. “The key is to keep things that are pristine pristine.”

How that would work is unclear. The 1964 Wilderness Act requires maintaining untrammeled natural conditions but does not specifically mention stars. The Environmental Protection Agency does not regulate light pollution, although Obama-era EPA Administrator Gina McCarthy called it a problem and said officials were “thinking about it.”

Around Colorado, Black Canyon of the Gunnison National Park received the IDA Dark-Sky Park designation in September 2015, after a 2014 designation for Hovenweep National Monument that straddles Colorado and Utah. Federal land managers at Mesa Verde National Park and Dinosaur, Chimney Rock and Canyon of the Ancients national monuments are preparing applications.

And Rocky Mountain National Park officials, just west of Colorado’s booming Front Range, have contacted IDA experts to discuss seeking a designation in the future.

Protection of dark skies and stars in parks “is gaining huge traction,” said Park Service dark-skies coordinator Randy Stanley, who helps guide individual parks in measuring light levels and retrofitting facilities with minimalist lighting.

The IDA designation requires land managers first to “clean up your own backyard.” At the Great Sand Dunes, that meant persuading a commercial compound south of the park’s gates to remove a white neon-gas station sign. Park managers then must demonstrate a commitment to educating people about night skies and light pollution. Interpretive talks have drawn up to 200 visitors at a time, and rangers now lead nighttime walks across sand to see stars.

The dunes are mostly wilderness. Park boundaries soon will expand to encompass 12,000 acres on an adjacent ranch, bringing the total area to 148,951 acres. Bunch recently hired an electrician to install more timers, softer lights and downward shading wherever appropriate to reduce glare.

It is cold now, temps dropping below freezing at night. The Medano Creek waters that flow around the base of the dunes are rising. Bears are devouring as much food as possible as they head into winter hibernation. Dry orange leaves rattle, barely clinging to tree branches. A yearling deer, seeking warm milk, nudges her nose under her mother’s belly.

But the people trekking into the dunes to see stars are determined, bobbing as they stagger in the darkness up and down steep slopes, one step back for every few steps forward.

Relying on a handheld global-positioning device to find their way, Avery and Angie Peechatka, who quit their jobs in Washington, D.C., for a cross-country trip, had been perched atop the 750-foot-high dunes for three hours, since before sunset.

“Helps teach you patience. You have to appreciate the slow transformation from day to night,” said Avery, 30, noting they saw plenty of comets. Angie regards starry night skies as “one of our natural resources — worth conserving.”

The other night, Bunch went out, too, after waking at midnight. He has been taking star-visibility measurements using a sky-quality meter. The highest score on this instrument’s logarithmic scale is 23. Great Sand Dunes readings consistently exceed 21. Bunch said he recently recorded a 21.9 — about as close to natural darkness as at any national park.

But he sees the glow from Alamosa 40 miles to the south, confident that by working with community leaders and electricians, the degree of darkness will rise.

“I want more. I want it to be higher,” he said. “We can do better than this.”