Hydrochara caraboides, a species of diving beetle that is attracted to lay its egg on cars, especially red ones. Vehicles are very strong polarizers of light. The coating of the eggs is acidic and eats away the surface of the car's paint. This occurs worldwide. Credit: Gyorgy Kriska

Smooth, dark buildings, vehicles and even roads can be mistaken by insects and other creatures for water, according to a Michigan State University researcher, creating "ecological traps" that jeopardize animal populations and fragile ecosystems.

It's the polarized light reflected from asphalt roads, windows -- even plastic sheets and oil spills -- that to some species mimics the surface of the water they use to breed and feed. The resulting confusion could drastically disrupt mating and feeding routines and lead insects and animals into contact with vehicles and other dangers, Bruce Robertson said.An ecologist studying at the W.K. Kellogg Biological Station in Hickory Corners, north of Kalamazoo, Robertson said polarized light reflected from man-made structures can overwhelm natural cues to animal behavior. Dragonflies can be prompted to lay eggs on roads or parking lots instead of water, for example, and such aquatic insects are at the center of the food web. Insect population crashes can impact higher levels of the food chain.

"Any kind of shiny, black object -- oil, solar cells, asphalt -- the closer they are to wetlands, the bigger the problem," he said.

A stonefly is laying eggs on asphalt, thinking it is water. That year's eggs won't hatch, and the fly itself could be killed by a passing car. Credit: Gyorgy Kriska

Predators following misdirected insect prey then also can find themselves in danger. The importance of natural light to creatures' ability to navigate -- and the impacts of visible light pollution from man-made sources -- are well understood. Those include the tendency of newly hatched sea turtles to move from their beach nests toward landward light sources instead of following moonlight to the safety of open water. Horizontally polarized light has been found to be a reliable cue for creatures to locate water, Robertson said, and now he and fellow researchers are discovering the effects of light reflected from man-made structures.Robertson worked with Gabor Horvath from the biooptics laboratory at Lorand Eotvos University in Budapest, Hungary, and other researchers. Their findings were reported in Frontiers in Ecology and the Environment Jan. 7. That journal is published by the Ecological Society of America (www.esa.org).

Although the research highlights new concerns about human impact on native species and ecological communities, it suggests the importance of building with alternative materials and, when necessary, employing mitigation strategies. Those might include adding white curtains to dark windows or adding white hatching marks to asphalt.

There also might be potential for turning it to an advantage, Robertson said. In locations where trees are being destroyed by insect infestations, for example, "you may be able to create massive polarized light traps to crash bark beetle populations," if such species are found to be responsive to polarized light cues.