(C) Google Earth, Fabio Falchi et al (2016)
By Robert Gay

Light pollution, which has joined air, water, and soil pollution as a major environmental concern, occurs by direct transmission of light which we experience as “skyglow.” 

It can be caused by many sources including homes, businesses, signs parks, roadway lighting, sports events, vehicles, construction, airports and military bases. In Santa Cruz County, added sources include mining exploration and border illumination. Dr. Emilio Falco, astronomer at the Fred L Whipple Observatory, has found that “huge, barely shielded lights at the Border Patrol checkpoints add to our local light pollution at the Observatory, especially the I-19 one near Amado.” 

The skyglow from Las Vegas can now be seen from the South rim of the Grand Canyon, about 250 miles away. In Southern Arizona, skyglow from Phoenix troubles astronomers at Mt. Graham, Mt. Lemmon, Kitt Peak and Mt. Hopkins, and sky-watchers from Patagonia, Sonoita and Elgin can see skyglow from Tucson, Nogales or Sierra Vista. Light pollution is slowly eroding access to the skies. 

Even if there are local decreases in light pollution there has been significant development-related increases, reports NASA-funded astronomer Michael Schwartz, who recently closed his home observatory near Patagonia Lake. “One of the factors in the closing of Tenagra Observatories is the lack of enforcement for residences,” he said. “When I set up the observatories in 2000, Rio Rico was a hamlet. Its immense growth has caused severe sky glow of the worst kind. Additionally, unenforced commercial and residential lighting in Nogales, Tucson and Phoenix make the stars inaccessible. I don’t expect this to ever improve.” 

Dark Skies in Arizona 

From a regional map of light pollution, it’s easy to see that Southern Arizona skies are troubled. Still, one of Arizona’s 14 designated “Dark Sky Places” is the Tumacacori National Historic Park. Communities can become designated dark-sky places also, as did Flagstaff in 2001. In 2016, the town of Patagonia had some interest in becoming a dark-sky community, but the idea did not get enough momentum. With enough citizen interest, notes Harold Meckler, an amateur Patagonia astronomer, “Patagonia may yet become a recognized dark-sky village.” 

If Patagonia obtains dark-sky designation in the future, it would join a worldwide movement now including over a hundred dark sky locations and communities in the U.S. alone. 

The designation program originated with the International Dark Skies Association (IDSA), formed 30 years ago in Tucson. IDSA’s Director or Public Policy, John Barentine, explained in an interview that the group is rooted in the growing awareness that darkness is a vital diminishing resource. 

Astronomers Without Borders (AWB) does related work internationally, under the banner “One people, one sky.” Dark-sky activists encourage us to see that light pollution is much more reversible than other kinds of pollution – often with just the flick of a switch or the change of a fixture. 

Dark-sky enhancement benefits humans and many other species. The Center for Biological Diversity elaborates: “Species known to be impacted [by excess artificial light] include mammals, birds, reptiles, amphibians, invertebrates, fishes and plants.” Migratory birds, for instance, navigate by stars and have been known to become disoriented and crash into illuminated structures. An estimated 100 million to 1 billion birds die each year in North America in these collisions, according to the Cornell Lab of Ornithology. 

Excessive artificial light can cause sleep disorders, disrupted circadian rhythms, eyesight difficulties for the elderly, melatonin deficiency, and potentially increased cancer risk in humans. In 2009, the American Medical Association (AMA) adopted a resolution urging reduction of light pollution and use of shielded light fixtures. 

Saving the Night 

Voluntary reduction of excess light by individuals and communities has become a first route to helping “save the night,” by selecting shielded fixtures and minimizing lighting. The IDSA helps cut over-illumination via a light-fixture-certification program that extends to Home Depot, where consumers seeking outdoor light fixtures can look for the DARK SKY APPROVED labeling. Another key light-reduction strategy is the use of LED bulbs – except for the low-wavelength blue ones, which are harmful. 

Light pollution regulations are in place in some jurisdictions. At the Federal level, IDSA’s Berentine suggests that Environmental Impact Statements should include assessment of a proposed project’s light emissions, and that, in parallel with the Clean Air and Clean Water Acts, EPA regulation should include a Dark Sky Preservation Act. This will require new legislation. 

At the State level, the Arizona Revised Statutes Title 49, “The Environment,” devotes Chapter 7 to “Light Pollution,” a brief regulation of light emissions. And at the county level, Pima and Santa Cruz Counties have both adopted Light Pollution Ordinances. Pima County’s ordinance creates its most restrictive zone, emission-wise, in a 25-mile radius around Mt. Hopkins, home to the Fred L. Whipple Observatory.

Santa Cruz’s ordinance, however, describes the whole county as a unified “County Lighting Area,” without defining regions of special concern, even though approximately 60% of the Mt. Hopkins light regulation zone lies within Santa Cruz County. This 50-mile diameter critical light circle skims a part of Nogales and northern Sonora at the border, then swings east to include the Patagonia and Santa Rita Mountains, as well as Canelo Hills and Empire Mountain Ranges.

This critical zone includes the Fairborn Observatory and the entire sites of the Hermosa and Rosemont mining projects. Hudbay was made to negotiate light pollution limitations in its permitting process for Rosemont mine construction, but compliance has not yet been required of the Hermosa Project in the Patagonia Mountains. 

The loss of the experience of the night sky is a cultural and personal loss as well. “80 % of Americans Can’t See the Milky Way Any More” was the title of a June 2016 National Geographic article. The over-bright sky is a barrier to the nourishing sense of wonder and cosmic curiosity, which has always marked the human relationship to the darkness that endlessly chases the light around the planet in 24-hour laps. 

Clearly, light pollution and nightsky consciousness is spreading. Will it spread quickly enough to rein in the excess lumens and give us back the night? If the skies can be darkened again – even in small corners – we stand to get reconnected with that dynamic and fascinating profundity that lives and swirls overhead every night.