Light Pollution Harms Wildlife

Ben Harder writes in Science News that Dr. Kenneth D. Frank and a handful of other scientists are trying to understand the impact of artificial light on a multitude of living creatures. We can see evidence of this ourselves, when we notice how moths tend to fly into lamps and flames. The researchers suspect that artificial night lighting disrupts the physiology and behavior of many other nocturnal animals, as well.

Some of the best data on light pollution comes from Florida, where sea turtles are struggling to survive urban development on their nesting sites. When turtle hatchlings emerge at night from their eggs and head for the ocean, lights from hotels and other sources lead them off course. Sometimes the hatchlings get killed when they attempt to cross roads. If they don?t make it to the ocean by daylight, the turtles often die of exposure or are eaten by hungry predators. Installing low-pressure sodium lamps, which produce light only at a specific yellow wavelength, could help these creatures, since the turtles don?t see light at that frequency.

Even when animals aren’t exposed directly to artificial lights, the illumination from urban areas that reflects off clouds can produce unnaturally bright conditions at night?an effect known as sky glow?that may have biological or behavioral effects on them. Sky glow is already a recognized problem for astronomers, who have trouble identifying celestial objects against the background light near urban centers. Astronomers have created a movement, led by the International Dark-Sky Association in Tucson, that advocates limiting light pollution to improve sky-viewing.

Dark-Sky supporters favor the broader use of low-pressure sodium lights. “Astronomers would like [ecologists] to conclude that sodium lights are the most ecologically sound light sources,” says Frank, whose work suggests that low-pressure sodium lamps are less harmful to moths than traditional streetlights are.

But sodium lights don?t always help. Some animals, it turns out, cope no better with narrow-spectrum, yellow light than with any more traditional artificial lights. Some, such as frogs and salamanders, even seem to do worse. Sharon Wise of Utica College in Utica, N.Y. and Bryant W. Buchanan, another frog researcher at Utica, have found that sudden exposure to artificial light can cause nocturnal frogs to suspend normal feeding and reproductive behavior and sit motionless long after the light has been turned off.

Under yellow and red lights, salamanders can’t navigate from one pond to the next. While they wander, they may fall prey to hungry nocturnal animals or die of exposure. Wetlands?home to many frogs and salamanders?could be one of the first types of habitat to benefit from measures controlling light pollution. “Because wetlands are already afforded some protections, it would be relatively straightforward to add [artificial light] to the list of things they should be protected from,” says Travis Longcore of the Urban Wildlands Group.

Animals that live entirely in water are also hurt by artificial lighting. Marianne V. Moore and Susan J. Kohler of Wellesley College examined how artificial light affects small aquatic invertebrates in New England lakes and ponds. Their data show that the nighttime activity of these animals near the surface drops off in proportion to the amount of light reaching them. That could reduce the amount of surface algae they eat, leading to algae blooms and poor water quality. This is already a big problem in U.S. rivers, lakes and coastal areas.

River ecosystems can also be affected by artificial light at night. Barbara Nightingale of the University of Washington in Seattle says several river-navigating fish species, including salmon, herring, and sand lance, gather under the artificial lights that illuminate portions of their waterways. The unnatural concentration of fish, along with the illumination the lights provide, may facilitate hunting by bears and other predators and negatively affect vulnerable fish populations.

For more than a century, observers have reported that birds are attracted to towers with lights and often collide fatally with the structures or with each other. A single lighted tower kill can end the lives of thousands of birds in a single night during peak migration periods.

Sidney A. Gauthreaux, a bird researcher at Clemson (S.C.) University, has studied the factors that contribute to tower kill. He found that towers with red lights, that are meant to warn airplanes, may be particularly dangerous for birds.

Gauthreaux and Carroll G. Belser monitored the number and behavior of birds at three different sites on 14 evenings during a fall migration season. Birds more often departed from direct flight paths near the two sites that featured artificially lit television towers than they did at the site without a tower. One of the two towers had a white strobe light; the other had an array of steady red lights. Of the three sites, the red-lit tower attracted the greatest concentration of birds and caused the greatest bird collision risk. “Birds’ magnetic compasses seem to break down in red light,” Gauthreaux says. Due to cell phones, there are more of these towers now than there have been in the past.

Richard Podolsky has been studying birds known as Newell’s shearwaters on the Hawaiian island of Kauai. Shearwaters nest on land, and fledglings leave on an autumn evening to make their first, critical flight to the sea. Urban development presents obstacles to these maiden flights, however, and many young birds crash into lit bridges and buildings, sometimes fatally.

A local citizens’ group called Save Our Shearwaters, or SOS, has been rescuing these birds for more than a decade. Using data collected by SOS, Podolsky and his colleagues estimate that 10 percent of Newell’s shearwater fledglings die each year and an additional 15 percent are injured from crashes. Restrictions on light pollution might help reverse the this reduction, and such restrictions are already in effect on the nearby island of Hawaii.

Newell’s shearwater deaths have been lower in years when the October full moon falls near the fledglings’ midmonth flight than in years when the young birds take off on nights with little moonlight. Natural light’s domination over urban lights helps the shearwaters navigate, Podolsky says.

In addition to their noted tendency to fly perilously close to street lamps, moths and insects may respond to artificial light. Moths go into erratic dives when they sense that they have been detected by nearby bats. Jens Rydell of the University of G

NOTE: This news story, previously published on our old site, will have any links removed.