When an otherwise natural area is contaminated with something that is harmful to
it, it becomes polluted. The item introduced may be certain substances or
factors. For example, most often when people think of pollution they think of
the pollution in the air or water by chemicals. There are other types of
pollution, however, such as pollution caused by light. Light pollution, also
known as luminous pollution, is defined as the excessive introduction of
artificial lighting to the outdoor environment. People who are unfamiliar with
this problem often do not fully understand how light can become a pollutant.
Around the world, street lights, stadium, park, and other lighting are
illuminating the sky to such a magnitude that it creates a number of problems
that are detrimental in terms of energy use, the environment and even to people.
While light serves an undeniably important purpose, understanding light
pollution can help people reduce its negative impact.
Types of Light Pollution
Light pollution falls into several different categories, or types. Each of these
types illustrates a different way in which light spreads and, as a result,
affects the surrounding environment. The different types of light pollution are
sky glow, glare, light trespass, and clutter. Sky glow, which is frequently
referred to as urban sky glow, occurs when artificial light projects upward and
brightens the sky over an area. The glow seen over a city at night is an example
of sky glow. Light trespass is when light from one area spills, or trespasses,
onto another area where it was not intended to be. Glare is excessive brightness
that comes from a light that is visually uncomfortable. In some cases, glare may
also be disabling in that it reduces visibility. Clutter, in terms of light
pollution, means large groupings, or clutters, of bright lighting. Light clutter
can be distracting and confusing, and as a result it may prove dangerous to both
aircraft pilots and drivers. Over illumination is yet another type of light
pollution. This is the use of lighting beyond what is necessary. Empty parking
lots with lights on are an example of over illumination.
Energy Usage Impact
Light pollution not only affects the sky, but it also wastes a significant
amount of energy. According to the U.S. Energy Information Administration, 13%
of the electricity use in the U.S. goes toward lighting in residential and
commercial areas alone. Some studies show that one-third of the light that is
used is wasted light. As a result, the energy that is used is also wasted. This
comes at an estimated cost of approximately $2 billion a year.
Consequences
The excess of artificial lighting comes with many negative side effects for both
human beings and nature. Blocking the view to the stars is one of the more
apparent negative aspects of light pollution. When the light from cities shines
upward, it is reflected back by airborne dust, air molecules, and droplets of
water vapor. This makes it increasingly difficult to see the stars and their
constellations. This is most noticeable by astronomers and amateur star-gazer.
The behavior of certain animals is greatly affected by light pollution. Insects,
for example, often fly toward light. At night, the position of the stars helps
migrating birds to find their way. If the stars are not visible, the birds may
become confused. Bright lights may also confuse birds, causing them to fly
towards the light. This can result in unnecessary impact with other birds or
buildings. When insects gravitate towards light, they become prey to animals,
such as bats. Plant life may also be affected by excess illumination. Certain
plants may require pollination from nocturnal insects, but light pollution may
give off enough light that it interferes with the act. Some trees are sensitive
to the length of the day and may be affected by night lighting, as well.
Additionally, it affects the ecosystem and the life cycle of organisms within
it.
Light pollution is also thought to affect human health. For instance, light
pollution is known to disrupt circadian rhythms. This is a person's internal
clock, which regulates 24 hour biological functions in the body. Interference
with the circadian rhythm can hinder things such as the production of melatonin,
which is believed to help prevent cancer. Metabolism is also affected and can
cause problems such as obesity and diabetes.
Reduction
Reducing light pollution requires the effort of both residents and city
officials. Everyone must make efforts to reduce the amount and type of
artificial light that is used at night. Motion-sensing lighting can help reduce
over-illumination by only turning on lights when they are needed. Less lighting
can be used to illuminate an area, and the intensity of lights may also be
reduced. Using shielded lighting helps in several key ways, such as controlling
light from traveling upward and reducing light trespass and glare. Current city
lighting plans should also be reevaluated and updated more efficiently.
Image courtesy of NASA's Astronomy Picture of the Day from November 27,
2000.
Written by
Chris Johnson