Planet earth runs on light energy. Light energy from th […]
Planet earth runs on light energy. Light energy from the sun powers photosynthetic processes in plants and different wavelengths of light cue these plants to flower, move their leaves, and grow taller. These same cues influence animals as well. Insects are attracted to narrow range UV lights, based on the evolved sensitivities to UV light in their eyes. Some birds are adapted to only sing mating calls at night based on the light quality from a full moon. High light levels can increase the mating behaviors of some frogs and changes in the quality of light can affect bird nesting behaviors. With so much of the natural world dictated by fine-tuned associations with light quantity and quality, how does the constant light pollution of cities affect the behavior of these organisms? Can different types of light pollution (street lights, billboards, or cars) affect ecological interactions in different ways? And can we design cities to interfere less with these naturally evolved relationships?
Work published this week in PLoS One explores the differences between different types of light bulbs (newer LED vs. older low-pressure sodium) on the behavior of suburban bat populations.
Many cities worldwide have begun to shift towards LED light bulbs in streetlights due to improved color rendering (broader spectrum light quality) and increased energy efficiency over time. In fact, the United States Department of Energy reports that residential LED's can reduce energy use by 75 percent and last 25 times longer than traditional incandescent lighting. In places like New York City, these changes are projected to result in up to $14 million annually (energy savings and maintenance) and are a huge step towards to city's goal of reducing carbon emissions 30 percent by 2030.
However, changes in light quality and quantity resulting from widespread changes in streetlight bulbs will almost certainly affect urban populations of plants and animals as well – but maybe not the bats?
This week, Rowse et al. (2015) demonstrated that bat populations in suburban areas of the UK were unaffected by a switch from low-pressure sodium (LPS) bulbs to higher efficiency LED bulbs.