Human light pollution is wreaking havoc and confusion in the natural world, scientists have warned in a new research study.
Some birds and insects are migrating in the wrong direction. Baby turtles are chasing after car headlights instead of swimming into the ocean. And dragonflies are laying their eggs on busy tar roads which they mistake for water ponds.
These are the findings of a group of American and Hungarian researchers who published a study last week in the Ecological Society of America journal Frontiers in Ecology and the Environment.
Lead author Gabor Horvath said a high concentration of artificial lighting in built-up areas was altering the natural light cycles that many animals, birds and insects relied on to navigate their way through unfamiliar environments.
It was not just street lights, floodlights or car headlights which caused the chaos. In many cases, more subtle effects from polarised light sources were leading animals into injury or death.
For example, the light reflecting off big glass buildings and other man-made structures could be confounding birds and insects, which often depended on natural sources of polarised light.
Researcher Bruce Robertson, an ecologist at Michigan State University, said the main source of horizontally polarised light in the natural world came from reflections off water bodies.
"Biologists discovered in the 1980s that this polarised light is an amazingly reliable cue for finding bodies of water," he said.
Now, however, dragonflies were mistaking human-made structures for ponds, streams or lakes where they normally laid their eggs.
In a statement, the researchers said shiny, dark surfaces - including glass buildings, black tar roads, black plastic sheeting or dark-coloured cars - reflected horizontally polarised light more strongly than polarised light from water.
In some cases, these shiny black structures acted as powerful magnets.
"For example, a dragonfly laying eggs on a shiny black highway may become paralysed by attraction to the road pavement after laying its eggs, effectively dooming its fate and that of its offspring."
Closer to home, ecologists at Ezemvelo KZN Wildlife have known for decades about the hazards of light pollution for baby leatherback and loggerhead turtles, which breed along the northern coastline of KwaZulu-Natal.
When they emerge from their nesting sites on the beach on dark nights, hatched turtles are guided towards their new home in the ocean by the reflection of the moon and stars on the surface of the ocean.
However, Ezemvelo scientists have noticed that the hatchlings get confused by torches, cottage lights and other artificial light sources. There have often been cases of day-old turtles scrambling madly inland in pursuit of car headlights.
The authors of the latest study voiced concern that if large numbers of animals fell victim to the increasing number of light sources, it could lead to serious population declines, and possibly extinction.
Robertson suggested that some of the damage could be ameliorated by putting up white curtains on shiny black buildings, or painting hatch marks on black tar roads to prevent insects mistaking them for water bodies.