Many of you have heard this before – artificial lighting on the beach is bad for sea turtles – so this article is nothing new. However, this article will expand to discuss the problem with night lighting in general.
Yes, it is true – sea turtles struggle with evening lighting. They prefer to conduct their nesting and hatching activities under the cover of darkness. This makes sense… I would. I am sure you have experienced the sensation of “night vision”, where your eyes adjust and you actually can see okay with little or no light. It takes a few minutes for this to happen but it does happen. Then there are nights when the moon is so bright that it appears that lights are on somewhere. You appreciate those evenings when you are trying to find your way in the dark.
Sea turtles nesting or hatching experience the same. They intentionally do this at night to reduce predation. Some of it is physical as well. Sea turtles are reptiles and therefore cold blooded. Their bodies are adapted to living in cooler ocean water and can quickly over heat on land during the day – so they avoid it.
Nonetheless, dark beaches are needed and they are not alone – many other creatures need darkness. Actually we do. Studies have shown physiological problems associated with increase illumination at night. One study showed exposure to 39 minutes of artificial illumination at night could reduce melatonin by 50%. Melatonin is a hormone that manages certain physiological cycles in our body as well as the cycles other hormones. There has even been a link between sleep deprivation with obesity, heart disease, and even some cancers. It is known that psychological problems occur with people living at high latitudes where the sun does not set for weeks, or shift workers whose circadian rhythm is thrown off by changes between daylight and night.
Other animals are known to adjust their feeding and reproductive cycles when evening illumination occurs. This can be caused by changes in the lunar cycle but evidence suggests artificial lighting as well can cause it. With the artificial lighting issue occurring every night, changes in these behavioral rhythms can have negative ecological impacts, such as reduction of natural reproductive cycles. Artificial lighting adds another twist. Natural lighting is general from above down towards the ground. Artificial lighting is directed from a variety of angles, including upwards. One study showed that 30% of our outdoor artificial lighting is directed towards illuminating the atmosphere, and nothing more; wasting energy and money, as well disorienting wildlife. These angled lighting sources disorient the movements of flying insects and other nocturnal moving animals.
The response to this problem… move towards darker skies. Studies have shown that sea turtles nest more frequently when outdoor lighting is of a longer wavelength, yellow, orange, or red. Directing the light downward by using shields is more natural and nocturnal moving animals will reduce disorientation. Dark skies significantly increases sea turtle nesting. Even condominiums with all lights out have helped block light coming from town across the bridge. Beach lighting should therefore be as low to the ground as possible to be blocked by dunes and other structures, but off ground enough to illuminate walkways and parking lots.
This is certainly different from what we are used to. However, the benefits of darker skies is evident for both humans and wildlife and we can adjust to this.
To deal with this problem, Escambia County passed an exterior lighting ordinance for Pensacola Beach. To view a “cliff note” of this ordinance visit http://escambia.ifas.ufl.edu/marine/2017/01/03/escambia-county-fl-turtle-lighting-ordinance/. There is link at the bottom of this document to view the ordinance in its entirety. If you have questions about this issue, or would like a list of local companies that provide turtle friendly lighting products, contact me at the Escambia County Extension Office. (850) 475-5230 or email@example.com.
Navarre, K.J., R.J. Nelson. 2007. The Dark Side of Light at Night; Physiological, Epidemiological, and Ecological Consequences. The Journal of Pineal Research. Vol 43(3). Pp. 215-224.
Mills, J.N. 1967. Circadian Rhythms and Shift Workers, Occupational Medicine. Vol 17(1). https://academic.oup.com/occmed/article-abstract/17/1/5/1355034.
Salmon, M. 2003. Artificial Night Lighting and Sea Turtles. Biologist. Vol 50(4). Pp. 163-168. https://www.researchgate.net/profile/Michael_Salmon3/publication/283857765_Artificial_night_lighting_and_sea_turtles/links/56e95cb008ae47bc651c6da3/Artificial-night-lighting-and-sea-turtles.pdf.