They often check off consequences to the animal life of luminous pollution procreated by human activities. As the turtles whom, once laid, do not find the way of the sea. But they recall that more seldom the impact of the human buildings on the quality of light which rocks nature. According to a study appeared in the magazine Frontiers in Ecology and the Environment, the polarisation of the light caused by the reflexion of the wave on human facilities unsettles gravely life and reproduction of many animals and insects. (1)

Natural light is a wave which vibrates aléatoirement in all directions. But when she interacts with material, some directions are favoured. It is for example the case of the molecules of air which, when the weather is fine, polarise light and tend to blur the contrasts of a sky of cumulus. The photographers know it, who use a filter to polariseur who allows to get nicer pictures. Or the sailors and skiers, who carry polarisantes glasses to reduce the reflexion of the sun on the water and the snow and to attenuate the phenomena of dazzle.

Many animals, mainly insects, use the polarisation of light to get bearings. It is for example the case of the honeybees who use it to determine the position of the sun and to turn. Others use it for their migrations, or to find the best place where to reproduce. Provided that nothing comes to corrupt environment. Because buildings, roads, cars, swimming pools and even tablecloths of pollution change the polarisation of light and unsettle fauna, explain Gabor Horvath, György Kriska and Péter Malik (University of Eötvös, Hungary) and Bruce Robertson (State university of Michigan, the United States).

The more surfaces are smooth, and the more light focuses when it is reflected over. In the point, according to the researchers, to create true ecological traps. They relate so that some insects lay their eggs on the asphalt of roads, without any chance to see them a day hatching. Others rush to the fact that they believe they are a pond, to find a puddle of toxic hydrocarbon for their eggs.

This disturbance of the life of insects splashes back on other animal kinds. Deprived of their first source of feeding, fish and batrachian could suffer from it. Among offered solutions: use less reflective materials for the building, and cover the communications of more harsh coatings. But there, it is the residents-humains-that would complain about another pollution, sound this time.

(1) Last November, Israeli researchers showed that an insect suspected of transporting the cholera when it lays chooses its pools by setting the course by the polarisation of light.

Picture: A simple swimming pool can unsettle the reproduction of insects © Denis Delbecq - on 2007