In late fall and winter days not only get colder but shorter as well , making it more likely that our outdoor lights remain on for many hours. What effect does this artificial light, now and throughout the year, have on the natural environment?
When unneeded or unwanted light causes adverse effects, it is termed "light pollution." Scientists are just now beginning to understand the long-term harmful consequences light pollution can have on plants, animals and even humans. The continual twilight from artificial lights can affect the mating habits, feeding patterns, and navigational ability of a number of animal species. Besides disrupting the migration patterns of some birds, it leads to the death of millions each year as the result of collisions when birds are drawn to lighted buildings. But other nocturnal creatures also suffer negative effects, including frogs, bats, sea turtles, fish, moths and fireflies, whose females only flash their lights to attract mating partners at a certain level of darkness. And it's not just animals that are at risk. Trees , shrubs, and other plants can be affected by nocturnal lighting. The photoperiod, or hours of darkness, a plant is exposed to governs a number of developmental processes. For example, artificial light may keep a plant growing actively when it should be preparing to shut down for the winter, making it more susceptible to winter injury.
To help decrease the hazards associated with light pollution to your landscape plants and the environment in general, start by keeping outdoor lights on only when you need them. Using motion sensors and timers can be very helpful. Close your blinds or curtains at night so indoor light remains inside and turn off lights when you leave the room. Choose properly designed light fixtures that are shielded to direct light downward where it's needed, and don't use more wattage than necessary. The International Dark-Sky Association (IDA), a non-profit organization whose mission is to preserve and protect the night-time environment through environmentally responsible outdoor lighting, suggests checking for their "IDA Approved Dark-Sky Friendly Fixture" label when you shop for outdoor lighting.