Artificial lighting on marine turtle nesting beaches disrupts the
ability of hatchlings to find the sea from their nest, an effect
termed "hatchling disorientation."
Disorientation from artificial lighting
causes thousands of hatchling deaths each year in Florida and is a
significant marine turtle conservation problem. Long-term
monitoring of this threat involves an annual statewide effort to
gather information from disorientation reports, to use this
information in facilitating light management on nesting beaches and
to research into additional remedies for the threats caused by
lighting.
In a technical report written by FWRI scientist Blair E.
Witherington and R. Erik Martin of Ecological Associates Inc., the
problem is looked at in depth. The report, "Understanding,
Assessing, and Resolving Light-Pollution Problems on Sea Turtle
Nesting Beaches," also includes diagrams of common lighting
fixtures and mounting positions as well as a model lighting
ordinance for marine turtle protection. The following questions and
responses are from Appendix J. The complete report can be
downloaded in PDF form at the bottom of the page.
COMMONLY ASKED QUESTIONS
When do hatchling sea turtles emerge from their
nests?
The first hatchlings of the season emerge from nests approximately
eight weeks after the first nesting of the season, and this
activity continues for up to eight weeks after the final nesting of
the season. Outside the tropics, hatchlings generally emerge
throughout the summer and early fall. In the southeastern USA,
hatchlings emerge throughout the months of June, July, August,
September, and October. It is a myth that hatchlings emerge only
around the time of the full moon. Hatchlings ready to emerge wait
just beneath the sand surface until conditions become cool. This
temperature cue prompts them to emerge primarily at night, although
some late-afternoon and early-morning emergences have been
documented.
How do hatchling sea turtles
know where the ocean is when they emerge from their
nests?
Sea turtle hatchlings have an inborn tendency to move in the
brightest direction. On a natural beach, the brightest direction is
most often the open view of the night sky over, and reflected by,
the ocean. Hatchlings also tend to move away from darkly
silhouetted objects associated with the dune profile and
vegetation. This sea-finding behavior can take place during any
phase and position of the moon, which indicates that hatchlings do
not depend on lunar light to lead them seaward.
Why do artificial light sources attract hatchling sea
turtles?
Hatchlings that crawl toward artificial light sources are
following the same instinctive response that leads them seaward on
naturally lighted beaches. The apparent brightness and glare of
artificial lighting is what often leads hatchlings astray. To a
hatchling on a beach, an artificial light source appears bright
because it is relatively close by, yet it is not intense enough to
brighten the sky and landscape. The resulting glare makes the
direction of the artificial source appear overwhelmingly bright-so
much brighter than the other directions that hatchlings will ignore
other visual cues and move toward the artificial light no matter
where it is relative to the sea.
There are other lights near my beachfront
property that are visible from the beach. Why should I modify my
lights?
Any reduction in the amount of artificial light reaching the
nesting beach helps sea turtles. As lighting is reduced, hatchlings
emerging on moonlit nights and at locations far from the lighted
property will have a better chance of finding the sea.
Can hatchlings be protected by increasing the number of
lights on a nesting beach in order to prevent turtles from
nesting?
Although artificial lighting tends to deter sea turtles from
nesting, many do nest on lighted beaches. Apparently, the level of
artificial lighting necessary to misdirect hatchlings is well below
the level necessary to deter nesting. But even if beaches were
lighted to the extent that no nesting occurred, hatchlings on
adjacent beaches would be harmed. Regardless, chasing sea turtles
away from nesting beaches means that important habitat is lost to
them; therefore, it is not a beneficial conservation strategy.
How bright can a light be without affecting hatchlings
or adult sea turtles on the beach?
Unfortunately, no simple measure of light intensity can reveal
whether a light source will be a problem. The effects of artificial
lighting on sea turtles may actually increase as ambient
light-levels decrease on darker, moonless nights. Because any
visible light from an artificial source can cause problems, the
most reliable "instruments" to use when making judgments about
problem lighting may be the eyes of a human observer on the nesting
beach. Any light source producing light that is visible from the
beach is likely to cause problems for nesting sea turtles and their
hatchlings.
What should be done with misdirected hatchlings found on
the beach?
Hatchling sea turtles found wandering away from the ocean should
be taken to a darkened portion of beach and allowed to walk into
the surf on their own. Those that do not crawl vigorously can be
placed in the water and allowed to swim away. In all cases, local
natural resource or environmental protection agencies should be
notified. (Call 1-888-404-FWCC)
Whom should I notify about a light that is visible from
a sea turtle nesting beach?
The owner or resident of the property where the light source is
located should be contacted. In most cases, people are simply
unaware rather than uncaring. Local government conservation
agencies should also be notified. A growing number of coastal
communities have adopted ordinances that prohibit lighting on the
beach during the nesting season. Code enforcement offices often
oversee the enforcement of these ordinances. If there is inadequate
regulation of beach lighting in your area or if lighting problems
persist, private conservation organizations may be able to help.
Consult Appendix I for a list of governmental and non-governmental
conservation organizations.
I do not have the ability to turn off a problem light
that is located on my property. What can be done?
Luminaires that do not have convenient on-off switches are most
often controlled by the utility company. Property owners should
contact the entity to whom electricity bills are paid or to whom
lighting lease payments are made.
Will lighting on a pier affect sea turtles on the
adjacent beach?
Yes. Lighting on piers is very difficult to shield from the beach.
Hatchlings on adjacent stretches of beach may crawl for great
distances in the direction of the lighted pier. Hatchlings that
enter the water near the pier may linger in the glow beneath the
lighted structure and fall prey to fish, also attracted to the
light, rather than disperse offshore.
Will placing bright lights on platforms offshore guide
hatchlings into the water off lighted beaches?
Apart from being an overly expensive and complicated solution,
lighting the ocean to draw hatchlings offshore would probably
create additional problems. Lighting on the water can interfere
with hatchling dispersal and increase mortality from fish
predation.
There is not
enough sea turtle nesting on this beach to justify beach-darkening
efforts. Why is light-management legislation needed?
Beaches where small numbers of turtles nest can be very important.
The entire nesting range of a population may be made up of sparsely
nested beaches. Hawksbill turtles, for instance, one of the most
endangered sea turtles, do not nest in great numbers anywhere.
Moreover, any group of nesting turtles may constitute a genetically
unique and vulnerable unit. Losing even small populations may mean
the permanent loss of diversity. The irony in disregarding lighting
problems at sparsely nested beaches is that artificial lighting may
have caused the nesting to be so low. Many lighted beaches with
little nesting may again attract more nesting turtles once they are
darkened.
Crime will increase if the beach is not
lighted.
Generally, beaches are not areas where there is a great need for
crime prevention. Very little valuable property is stored on
beaches and there is seldom much nighttime human activity to
require security. Fortunately, areas adjacent to nesting beaches
where people reside, work, recreate, and store valuables can be
lighted for protection without affecting turtles on the nesting
beach. Where this type of light management was legislated in
Florida coastal communities, the Florida State Attorney's Office
has found no subsequent increase in crime.
Implementing a beach-darkening program will be
prohibitively expensive.
Darkening nesting beaches for sea turtles is one of the least
expensive ways we can benefit the environment. The simplest
solution to the problem-turning off lights visible from the beach
during the nesting season-costs little or nothing and may actually
save money in electricity costs. Most of the essential lighting
that remains can easily be shielded so that the light performs its
intended function without reaching the beach. Proper shields can be
fashioned from inexpensive metal flashing and fastened with screws.
Replacing fixtures is more expensive but is necessary only when an
owner decides that greater lighting efficiency or aesthetics are a
concern. Choosing well-designed fixtures and incorporating
light-management techniques into the plans for coastal development
are the most effective ways to fulfill lighting needs while
protecting sea turtles.
There are too many disadvantages to using low-pressure
sodium-vapor lighting to protect sea turtles.
As is true for any light source, there are both advantages and
disadvantages to using low-pressure sodium-vapor (LPS) lighting.
The following is a list of issues specific to LPS.
- Expense-The initial costs of LPS are substantially higher than
for incandescent and fluorescent sources but are only slightly
higher than costs for high-intensity discharge lighting (e.g.,
HPS). Operating costs, however, are generally much lower for LPS
than for any other commercial source.
- Color-Because LPS sources are monochromatic, they give poor
color rendition. For safety and security applications, however,
full-spectrum color is seldom needed. At U.S. Air Force
installations near nesting beaches in Florida (areas certain to
have rigorous security requirements), most outside security areas
are lighted by LPS sources.
- Disposal-The lamps within LPS luminaires contain elemental
sodium, a substance that can cause fires if not disposed of
carefully. However, unlike the mercury-containing high-intensity
discharge lamps (e.g., mercury-vapor, high-pressure sodium vapor),
the contents of LPS lamps are not toxic.
- Availability-Although LPS luminaires are not as readily
available in retail stores as other light sources are, a wide
variety of LPS fixtures are available from a number of
manufacturers.
Sea turtle nests on our beach are moved to darker areas
to protect hatchlings from lighting. Are our lights still a
problem?
Yes. Although it may seem that moving nests out of harm's way will
solve the problem, doing so only partially solves the problem and
may create new ones. In moving nests, nothing is done to prevent
lighting from deterring nesting turtles and interfering with their
orientation on the beach. Moving nests also has its own negative
consequences that stem from the limitations of this technique:
- In nearly every effort to find nests, some are missed.
Hatchlings from missed nests will suffer the effects of beach
lighting.
- Moved clutches of eggs often have poorer hatching rates. Moving
eggs kills at least some of them, and often many die, depending
upon how skillfully the moving is done.
- Putting eggs in places other than those chosen by the nesting
turtle can be detrimental. A specific nest environment is critical,
both for the survivorship of eggs and for the determination of the
hatch-lings' sex ratio.
How can the sacrifice of human safety and security to
save a few sea turtles be justified? Thankfully, no such
choice is necessary. The safety and security of humans can be
preserved without jeopardizing sea turtles. The goal of any program
to reduce sea turtle harassment and mortality caused by lighting is
to manage light so that it performs the necessary function without
reaching the nesting beach. Still, some may contend that any
inconvenience at all is too much and that the concerns of humans
should always outweigh those for turtles. People insistent on this
generalization should not ignore the large and resolute
constituency that values sea turtles. Sea turtles are valuable to
people both ecologically and for pure enjoyment. In many ways, the
protection of sea turtles is in our own best interests.
What good are sea turtles?
Measuring the true worth of anything is difficult, but it is
especially difficult to make this measurement of a common resource.
Although some may appreciate sea turtles more than others, sea
turtles are of value to all. Short of a thorough discussion on the
ecological place of sea turtles, suffice it to say that the world
would be a poorer place to live without them. We just don't know
how much poorer. With regard to sacrificing the diversity of life,
Aldo Leopold wrote in his Sand County Almanac: 
"The last word in ignorance is the man who says of an animal
or plant: 'What good is it?'... If the biota, in the course of
aeons, has built something we like but do not understand, then who
but a fool would discard seemingly useless parts? To keep every cog
and wheel is the first precaution of intelligent
tinkering."
More information or solutions are
available:
Visit the sea
turtle management site.
Understanding, Assessing, and Resolving
Light-Pollution Problems on Sea Turtle Nesting Beaches
Understanding, Assessing, and Resolving Light-Pollution Problems on
Sea Turtle Nesting Beaches (Spanish Version)
"Coastal
Roadway Lighting Manual" (PDF)
To view the PDF file, you will need Adobe Reader. To download
Adobe Reader, visit http://get.adobe.com/reader
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