Light pollution is threatening the night sky, a phenomenon that has left the Milky Way invisible to one-third of the world’s population. It’s a problem affecting 80% of Earth’s population, and satellite imagery reveals the problem is only getting worse, according to Nazim Aksaker, of the Turkish Astronomical Society. “If we do not take precautions, next generations will see the Milky Way from books,” he said. The society is hosting activities and workshops as part of International Day of Light. Light pollution is a theme for events scheduled on May 16 in Turkey, Argentina, Columbia, and Italy. Ricardo J. Tohmé, executive director of the Fundación Cielo Sustentable in Argentina, will present “Light Pollution: The Dark Side of Light,” which will address the physical causes of light pollution and its consequences for biodiversity, energy expenditure, human health, and scientific and cultural knowledge. Artificial light production has increased rapidly through the last two centuries, Tohmé said, and the pace of those changes has been accelerating in the last decades. The disappearance of the night sky is an unprecedented situation in the course of human history. “Light pollution began to be recognized as a pressing problem about 45 years ago by astronomers who witnessed a progressive deterioration of the night sky quality at some of the leading astronomical observatories of the time,” he said. The problem, Tohmé said, will only get worse if proactive measures are not taken. Recent studies suggest that light pollution has increased worldwide by roughly 2% a year between 2012 and now. “I believe those are actually conservative estimates, so the problem is already becoming bigger every day,” he said. Environmental effects of light pollution Because light pollution disrupts the cycle of light and darkness produced by the rotation of the planet, plants and animals whose DNA is encoded with the natural rhythm of day and night are at risk, Tohmé said. “Light pollution affects a wide variety of living organisms, including mammals, birds, reptiles, fishes, insects, and even microorganisms in unanticipated ways, causing adverse effects on the environment and the ecosystem,” he said. Tohmé also said that several recent scientific studies show that light pollution, “a severely underestimated problem,” interferes particularly in the behavior of migration and reproduction of various types of creatures, which will eventually threaten biodiversity. The effect called “skyglow,” or radiance of the sky, is the result of the reflection and dispersion of artificial light by clouds, aerosols, and particles suspended in the atmosphere. The dispersion propagates the effects of light pollution at distances beyond the position of the original source of light, illuminating the night sky in its entirety and forming a kind of luminous dome or “dome of light” when observed from a certain distance, Tohmé said. “The skyglow can also affect the habitats of wetlands that harbor amphibians such as frogs and toads, whose nocturnal croaking is part of their mating ritual,” he said. “In addition, the decrease in populations of some insects attracted by excessive lighting negatively affects all the species that depend on them for food or pollination.” Finding solutions Tohmé and officials of the International Dark-Sky Association said the problem can be tackled on large and small levels beginning with individuals making smart lighting choices. “Individuals can take action with simple measures that go a long way to mitigate light pollution such as using warmer LED and compact fluorescent lamps with a color temperature under 3000 K,” Tohmé said. “It's important to install outdoor lighting fixtures that shield the light source to minimize glare and light trespass, directing their light onto the ground. Also, unnecessary outdoor lighting should be reduced by using dimmers, motion sensors, or timers.” On the larger scale, state and local governments need to get involved to be part of the solution, Tohmé said. “We as a society need to decide if light pollution is something we care about. That’s the only way to effectively address the problem, by passing and enforcing local and regional lighting ordinances to protect the night sky in our communities.” Today’s youth and future generations are not the solution, Tohmé said, because “unlike other forms of environmental pollution, it’s not a technically difficult problem. In the end, we just need cultural change. The solutions are already at hand.” It is the responsibility of the current generation to make the necessary changes that will counter the trend. “The light pollution problem is continually getting worse,” he said. “In my opinion, just as with any other environmental problem, waiting for future generations to take care of it would be incredibly lazy and reckless on our part. As a matter of fact, I think it’s the other way around. We owe our descendants dark skies without light pollution.”