Each night almost of a third of the light used out-of-doors escapes
into the night sky where, instead of providing useful illumination, it
causes glare, sky glow and other types of light pollution. About 2.500
individual stars should be visible to the human eye in an unpolluted
night sky; but in a typical suburb only 200 to 300 stars are visible,
and in a city, fewer than a dozen stars may shine through the
artifically lit sky.
In addition to compromising the
quality of the environment, light pollution amounts to an enormous
amount of wasted energy. The International Dark-Sky Association
estimates that each year in the United States, over $1 billion dollars
is spent to generate this wasted light.
The most
common causes of light pollution are streetlights that fail to deliver
all of their light downward, outdoor security lights around buildings,
billboards lit from below, landscape illumination directed upward, and
businesses like convenience stores and gas stations that operate under
extremely high levels of illumination.
Many of
municipalities, counties and states have adopted, or are considering
adopting, ordinances designed to limit light pollution. We have listed
a few of the strategies that stand out. The
International Dark-Sky Association is the primary on-line resource for light pollution information.
In the heart of downtown Tucson, Arizona, a city of nearly 500,000, one
can view the Milky Way with the naked eye. Tucson and Pima County first
adopted outdoor lighting ordinances in 1972 in an effort to provide
standards so that night lighting did not interfere with nearby
astronomical observatories. The lighting control ordinance of
Tucson/Pima County has been revised many times over the years. The 2006
Code is still quite strong and it is copied below.
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Through the implementation of light pollution reduction design and
technologies and an off-site mitigation plan, Springfield, Vermont will
be home to a new state prison, but will keep its dark night skies.
When
Stellafane, a local astronomy organization with observatories just four
miles from the proposed site of the Southern State Correctional
Facility, raised opposition to the construction of the prison, the
state hired Clanton and Associates, a lighting engineering firm, to
design an outdoor lighting plan that would minimize light pollution.
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Initially outdoor light ordinances were adopted by communities with
research observatories at the urging of astronomers. But star-gazing is
not the only reason for regulating night lighting. Many of Florida's
oceanfront communities have adopted lighting codes to protect the
nesting sea turtles along beaches. Sea turtle hatchlings instinctively
head toward light. Before electric lighting, bioluminescence and the
reflection of the moon on the water made the ocean brighter than the
land. But due to light pollution, hatchlings often head inland. The
strict limits on street lighting on Sanibel Island aim to remedy the
imbalance between the unnatural brightness of the shoreline and the
natural bioluminescence of the sea.
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