Light pollution is a reference to the photons created by artificial sources which are "wasted" or otherwise have lost their direct use and instead escape into the night. Gazing across any nighttime cityscape, millions of point sources of light can be identified, each contributing to the regional light pollution, photon-by-photon. Is something as benign as flipping on the lights at night really a source of pollution on par with the myriad of chemical pollutants we face on a daily (or nightly) basis?

In a word: yes. Light pollution can be broken down into three topics worthy of blogging about. The first, and always on any sustainably minded individual's plate, is energy waste. For the same reason your father harped on you for leaving the lights on in an unattended room, any light lost to the night sky costs somebody, somewhere another tick on the electricity bill. Accounting for this wasted light is a daunting challenge, but the economists over at Starrynightlights attribute light pollution to a significant portion of the $130 billion Americans waste on electricity every year. Not only does this waste cost us money, but the carbon emissions which come along with any large-scale energy production will also end up biting us humans in the collective rear-end. The impacts of carbon-driven climate change are vast, but recently the world watched as unprecedented droughts drove unthinkably huge wildfires across the Russian landscape. While energy efficiency and waste reduction may be a no brainer to those of you who frequent EcoHomeResource, this is only the tip of this well-lit iceberg.

Second to energy waste, the other commonly recognized implication of light pollution is the loss of our star-studded night sky. For those who've grown up under the artificial city lights of any large city, the Milky Way may only refer to a candy bar or a conceptualize location of our planet in the universe, but for those who have escaped the polluted skies of the city and partaken in the art of star-gazing, the Milky Way, or Via Lactea as it was known to Latin astronomers, is truly breathtaking. Outshined by the perpetual light of technology, our eyes simply cannot see the night sky in all its grandeur without a field trip to the boondocks. The drowning out these spectacular views has become a serious issue for modern astronomers: the Mt. Wilson observatory has experienced an 89% drop in efficiency since opening as the lights in the surrounding Los Angeles sprawl grew. The loss of starlit vistas also includes most of the universe's awe-inspiring events. As I compose this article (ironically by artificial light), the Perseid meteor shower looms overhead as a missed opportunity to witness a rain of 200 fiery particles per hour. The lights of Southern California flat out prevent me from seeing anything except a handful of the brightest meteors. While this may represent a superficial trade-off for well lit hallways and streets, the loss of the night sky will almost certainly push me to invest in some secluded property in the Mohave in the far future. In the meantime, for my stargazing readers, this simple Google maps tool will help you in your quest for that galaxy-piercing darkness.

As I've mentioned previously, artificial lighting can have drastic effects on the human diurnal cycle, contributing to added stress, retinal damage, and many a poor night's sleep. By tricking our brains into treating a late night study-session as daytime, the chemical pathways which have developed over our evolution as a species to allow sleep during the dark hours of night, we short circuit our sleep cycles. The flood of neurotransmitters which keep us awake over the course of the day continue to bathe our brains as long as the lights remain on - preventing the sleep so many of us desperately need. 

But the damage to diurnal cycles is not limited to humans. The ecological effects of light pollution are widespread, but relatively ignored by academia except for a handful of influential papers. I've had the privilege of studying for my undergrad with the mentorship of a leading figure in the field of urban and natural interfaces, Dr. Travis Longcore. Of his admirably extensive list of authored papers, one aptly named article Ecological Light Pollution, discusses the effects of artificial lighting on the numerous taxa in contact with the urban landscape. 

The ecological damage is widespread, in many cases attributed to ancient dependencies on delicately predictable seasonal day-length or moonlight to signal mating behavior. This attraction to moonlight leads to the deaths of thousands of moths and mayflies at the hand of a single streetlight and mass predation on prey species which gather at the tantalizing lights of offshore drilling rigs. Endangered sea turtles and amphibian species face confusion under the "perpetual full moon" of artificial lighting. Newly hatched sea turtles typically follow the path of moonlight to the roiling waves and can be diverted by an ill placed beach house while frogs will halt their mating croaks and calls when their sheltering veil of darkness is interrupted by a stadium's spotlights. These are merely a sample of the copious light-dependent behaviors exhibited in nature which are irreversibly disrupted by artificial lighting. <image: Longcore, "Ecological Light Pollution">

Can anything be done? Aside from prudent light discipline from homeowners, it seems that light pollution is as crucially intertwined with human civilization as carbon emissions or chemical waste for now. While some states have light pollution statutes on the books (5 to be exact), there is very little civic outcry against light. Unfortunately, until 5 million barrels of crude photons pour into the Gulf of Mexico, light pollution will remain a topic without public illumination.