When a Building Is Like a Pond

The problem, as Robertson and colleagues report online today in Frontiers in Ecology and the Environment, is that as people and their structures have taken over more and more of the planet's land area, they have created "ecological traps" by generating artificial sources of polarized light. In a series of optical studies, the researchers compared the light polarization caused by artificial surfaces with the same effect caused naturally by water. They found that any smooth, dark surface returns an even stronger polarized light signature than water does, and the effect is particularly pronounced with shiny dark surfaces. Humans are building "structures that look more like water to animals than water," says Robertson.