- Approximately 83% of the world’s population lives under light-polluted skies. In the United States and Europe, about 99% of the population cannot experience a natural night sky.
- Birds are one of the biggest victims of light pollution as city lights can disorient them and cause them to collide with brightly lit buildings.
- Some solutions to curb light pollution include using timers or motion sensors for outdoor lights, using lower temperature LEDs, turning off unnecessary indoor lights in empty rooms or buildings.
What Is Light Pollution?
According to the IYA2009 Cornerstone Project, billions of dollars each year are spent on unnecessary lighting in the US alone, with approximately $1.7 billion of energy wasted each night through unshielded outdoor lights. Wasted lighting also releases about 38 million tons of carbon dioxide into the air each year, and unshielded outdoor lights account for approximately 1.2 million tons of carbon dioxide waste.
Causes of Light Pollution
Artificial exterior and interior lights, advertisements, streetlights, and illuminated sporting venues are among the many causes of light pollution. Light pollution has been exacerbated by the invention of new types of energy-saving bulbs, such as LEDs. Due to its low energy consumption and cheaper price tag, LEDs have become a popular light source for many homeowners. However, these lights are much brighter, and cast wasted light across greater distances, contributing to light pollution.
There are four types of light pollution:
- Light trespass
People who live in cities with high sky glow levels cannot see many stars and the Milky Way. Skyglow also affects astronomers’ ability to observe objects in space. Approximately 80% of the world’s population and 99% of Europeans and Americans live under a sky glow. However, more rural and densely populated areas such as small towns or forests have less sky glow, and the Milky Way is visible.
Glare occurs when an unshielded light source hits reflective surfaces, causing excessive brightness to become a public-health hazard. There are four subcategories of glare: distracting, disabling, discomforting, and blinding. Distracting glare can usually be seen at night when it forms a halo around streetlights or headlights. Disabling glare is when reflected light reduces visibility, generally due to light reflected through a fog. Discomforting glare can cause eye fatigue after lengthy exposure to bright conditions, and blinding glare can cause loss of vision if the reflected light is from the sun.
Glare is hazardous while driving, as it can temporarily blind you and create unsafe driving conditions. People with poor vision are also negatively affected by glare due it reducing visibility and contrast.
Light trespass is when light falls in an area it is not intended, wanted, or needed. An example is when a street light shines into someone’s personal property. This type of light pollution can disrupt sleeping patterns, especially when it spills into someone’s bedroom.
Negative Impacts of Light Pollution
There is growing evidence that links the brightening of the night sky to ecosystem disruptions, health and environmental issues, and increased energy consumption. Lights account for at least a quarter of all electricity consumption worldwide. Poorly directed and over illuminated lights result in energy wastage and can expand carbon footprint.
Light pollution is one of the main drivers of the insect population decline. According to researchers, artificial light affects every aspect of an insect’s life. Artificial lights interfere with insects’ mating rituals, development, and search for food. For example, outdoor lights lure moths to their deaths. A recent study in the UK found that moth population decline was more prevalent in light-polluted areas than darker sites.
Artificial lights also interfere with the mating signals of fireflies and affect field crickets’ development as it can alter the perceived length of day and night. Some insects may hover around light sources for extended periods, making them more vulnerable to predators. Night pollinators may also miss the opening of flowers as artificial lights can make them think dusk is much later. Vehicle headlights attract insects and act as deadly moving hazards, and they have been linked to almost 100 billion insect deaths per summer in Germany.
Animals depend on the planet’s natural light and dark cycle to govern their behavioral patterns such as reproduction, sleep, and nourishment. When light pollution disrupts this natural rhythm, it can pose severe threats to many creatures. This issue is particularly harmful to nocturnal animals as light pollution alters their nighttime environments. For example, artificial light can disrupt the nighttime breeding rituals of frogs and toads.
Light pollution also changes predator-prey relations. Prey relies on darkness as cover from predators. However, with light pollution illuminating the night sky and shadowy areas, the prey is more vulnerable to predation. Underwater animals also may be affected by artificial lighting. A study documented how brightly lit panels submerged in water altered specific marine animals’ behaviors. It found that fewer filter-feeding animals, such as sea squirts, set up homes near the lighted panels, suggesting that artificial lights from oil rigs or harbors can alter marine ecosystems and behaviors.
Birds are one of the biggest victims of light pollution. Light pollution confuses their migratory patterns. Many migratory birds fly at night as the light from stars and the moon help guide them to their destination. As birds fly over large cities, the glare from artificial lights disorients them and causes them to veer off course and head towards dangerous areas of the city. Experts have estimated that more than four million migratory birds die each year in the US alone only through collisions with brightly lit buildings and towers.
Also, migratory birds depend on seasonal cues for their migration. Artificial lights can disrupt these signs and cause them to migrate too early or late and miss ideal climate conditions for nesting and other behaviors. Light pollution has been one factor in the drastic decline of specific migratory songbird populations over the past decades. In response to this problem, many cities have adopted a “Lights Out” program to turn off building lights during bird migration.