I admit that I had not thought about this matter in a while and wasn’t planning to discuss it here on the seed. But when it came to my attention lately I recalled the problems we have had here in Florida with the sea turtles on the beach. It was a horrible thing that happened when people were leaving their lights on along the beach during the turtle hatches. The poor baby turtles were running backwards, up onto the sea oats, towards city lights instead of the light of the moon on the water, and getting lost in the sand rather than running towards the ocean. Since that time, years ago, it has been a common practice here to leave lights out along the beach during the hatches. I am not sure if it is a law, however I do know that everybody just does it.

Lately came this study from a group of ecologists, biologists and biophysicists that has since been published in the journal, “Frontiers in Ecology and the Environment”. In this study they came to the conclusion that manmade light sources alter the natural light cycle and can cause animals that rely on light cues to make dangerous mistakes when moving through their environment. Although I don’t think they really needed this study, seeing that we had come to this conclusion years back on the beaches as I just noted, but I am glad I saw it because it brought it back to my attention.

Also currently discovered is that, in addition to direct light sources, this same problem occurs with polarized light. In fact, polarized light can trigger animal behaviors that lead to injury and often death. What is commonly called “light pollution” is artificial light from whatever source that occurs at unnatural times or places. This can attract or repel animals, resulting in animals migrating in the wrong direction, choosing poorly placed nests, choosing the wrong mates, increasing predatory activity out of fear or disorientation. Also possible are collisions with structures as a result of light blindness and stopping the search for food in the belief that morning has come when it hasn’t. All of this confusion is deleterious to animal security and safety, making them vulnerable in places and under conditions where they normally would be safe.

In the study I mentioned, lead author Gabor Horvath, Bruce Robertson – an ecologist at Michigan State- and their colleagues explain that many animals are also thrown off course by light reflecting from man-made structures. The darker and smoother a surface is, the more highly polarized its reflected light. In most cases, artificial polarized light symbolizes one thing to animals. They mistake it for water.

“Environmental cues, such as the intensity of light, that animals use to make decisions occur at different levels of severity in the natural world,” explains ecologist Robertson, a participant in the study. “When cues become unnaturally intense, animals can respond unnaturally strongly to them.” That heightened response, he says, happens because of the way humans have changed the environment. “For example, the primary source of horizontally polarized light in nature is water. Biologists discovered in the 1980s that such polarized light is an amazingly reliable cue for finding bodies of water.”

This makes total sense to me. Having grown up around large bodies of water, with the reflective moonlight always on the horizon and the surface, I can’t tell you how many times I thought a lighted parking lot or roadway was a part of the river. It is almost impossible to tell, under these conditions, where the water ends. And even without bodies of water like the ocean or the river, I have also confused lighted asphalt for small ponds or lakes. Consider this dilemma in the case of dragonflies and other insects, which often lay their eggs and spend their first phase of life in ponds, streams and lakes. Mistaking manmade objects like mirrored buildings, cars or asphalt surfaces for water can be deadly. These surfaces reflect horizontally polarized light that is more strongly polarized than any other light, including moonlight, that is reflected by real water.

In general, light pollution, polarized or direct, can disrupt the entire food chain in any ecosystem. When insects mistake the sheen of an oil slick for water, they, and the predators who follow them, can end up trapped in the oil and drowning. Even in the absence of a sticky trap like oil, the attraction of light can be so strong that animals become paralyzed by it and cannot move. A prime example would be a dragonfly that lays its eggs on a shiny black asphalt highway dooms itself and its offspring to certain death. This is a form of “eco trap” that occurs when environmental changes happen more quickly than animals can evolve to adapt. If large numbers of animals fall victim to these false cues, says ecologist Robertson, it could cause populations to decline or to even become extinct.

Now, you are asking yourself, what can be done about this? I mean, humans can’t see at night so lights are desperately needed. If not just to navigate ourselves but also for safety. However, there are efforts that can be made to mitigate the overall impact of light pollution. Studies have shown that simple white hatch marks on roadways prevent insects from mistaking them for bodies of water. Another good idea would be to hang white curtains on the windows in dark, shiny structures to keep birds, bats and larger insects from collisions with death. I have found here in Florida, where water is hard to distinguish from black tar asphalt under moonlight, that the use of yellow, dimmer streetlights and building lights make the surface more granular and stark and less shiny and reflective. And like we have come to do on a regular basis, turning out unnecessary outdoor lighting at night can go a long way in saving animals and birds. Our sea turtles have made somewhat of a comeback here, thanks to the efforts of our coastal residents.

“It’s yet another case where we’re faced with a choice between what’s more expensive or what’s better for biodiversity,” Robertson says. “Aquatic insects are the foundation of the food web, and what’s harmful to them is harmful to entire ecosystems and the services they provide.”

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