By Russel Barsh and Madrona Murphy

As descendants of sun loving, fruit-eating primates whose worst enemies were the large cats, humans have long feared the night. And ever since humans first discovered how to make and manage fire, hundreds of thousands of years ago, we have pushed back the darkness. Today our city lights can be seen from space, and even here on Lopez, our nighttime skies have a soft red glow punctuated by glare from cars, yellow outdoor bulbs and the flickering of television screens.

The benefits of artificial lighting seem obvious to most people, but what does it cost? A great deal of electricity, for one thing, which in most states means burning fossil fuels. Most electricity in Washington is hydroelectric, although that also has impacts on our environment (think dams and salmon). As our population grows, moreover, we must either reduce per capita energy consumption, or increase production – which in the short term means using fossil fuels.

There is an aesthetic and some would say spiritual dimension, insofar as lighting obscures the stars and planets, and with them, unmistakable evidence of the immensity of the universe. The proportion of our species that can see the Milky Way from their homes continues to diminish.

But darkness is also an important factor in human health. Our bodies’ molecular Circadian (literally: “daily”) clock is set by the light falling on our eyes, in particular the shorter blue wavelengths. We can become disoriented if actual day length is a lot longer or shorter than our internal clock says it should be: jet lag, for example, or the effects of working long hours in artificial light. Even low levels of artificial light at night interrupt sleep as well, and loss of sleep in turn can cause depression and even learning disorders.

Artificial light also appears to disrupt the body’s Circadian-regulated DNA repair cycle, resulting in higher mutation rates and greater cancer risk. During the day, humans and other animals metabolize food, producing free radicals that damage molecules within cells. Cells repair the damage at night. Darkness activates the repair function.

Plants also experience this repair problem and they cannot shut the blinds at night. Furthermore, plants use day length or night length to decide when to grow, flower, or die back and go into dormancy. The pupae of moths and butterflies use day length to decide when to metamorphose and emerge as adults. Many birds use day length to decide when to migrate. Indeed, many birds, fish, and sea turtles also navigate by the moon or stars. Artificial lighting can disrupt life cycles and migrations throughout the food web.

Nocturnal animals are losing the darkness they use to cloak themselves as hunters, or to avoid being detected and hunted. Bats have eyes but use sonar to find insects and navigate around barriers. Bright lights confuse bats, causing crash landings and missed meals! Moths attracted to lights are more likely to be eaten by visual predators such as amphibians and small mammals. Here, too, artificial lighting alters food webs.

In the islands, these impacts are easy to mitigate. Nighttime lights can be shielded or focused to minimize glare; filtered or masked to reduce blue wavelengths; attached to a timer or motion sensor rather than left on all night; and simply replaced by lower power bulbs or hand-held personal lighting: flashlights and headlamps. Curtains and blinds can make a big difference in light leaks from inside homes. And think twice about Christmas lights after the time when most primates have retired to their beds!

Kwiáht scientists are planning to measure light levels around Fisherman Bay and learn more about sources of nighttime glow and glare. For tips on softer outdoor lighting visit the website of the International Dark Sky Organization, www.darksky.org.