Artificial Light Is Now Harming Rain Forests

Most people know leaving the lights on at night is bad for the environment because it wastes electricity, which produces pollutants, which melt icebergs and cause cancer and generally lead us inextricably toward our doom. But now scientists have discovered that the light itself could be harming the environment.

In a new study from Berlin’s Leibniz Institute for Zoo and Wildlife Research, researchers found that ever-increasing light pollution in tropical habitats may be hampering the regeneration of rain forests because of its impact on “nocturnal seed-dispersers." (That's a science-y way to say “bats.”) When bats were presented with a dark compartment and one illuminated by a sodium street lamp — the world's most common kind of street lighting — the bats chose the dark compartment more than twice as much. Each compartment contained the same kinds of fruit; the bats harvested 100 percent of it in the dark, but only about three-quarters of it in the light.

“Without the pollination services provided by the world’s nectar-feeding bats and the seed-dispersal services provided by fruit-eating bats, we would not have many important human food crops such as mangos, bananas, avocados, tequila, peaches, dates, cashews, figs — the list goes on and on,” Cindy Myers, the leader of Project Wildlife’s bat rehabilitation program, told VICE News. “Brightly lit areas discourage fruit-eating bats from foraging, and that is no doubt because they know it makes them too visible to predators.”

Tropical rain forests around the world rely on bats to pollinate plants and spread seeds, especially seeds of species that are the first to recolonize land cleared by deforestation or fire. Bats do so by producing copious amounts of “seed rain.” (That’s a science-y way to describe bats shitting out the seeds they eat while they fly around.) When those seeds land on the ground, some germinate and become plants.

Light pollution is a well-known issue in well-developed parts of the world, but it's a relatively new issue in much of the tropics, where most of the world's rain forests are. As populations and economies grow, access to electricity and technology improves. That means more and more artificial light closer and closer to rain forests.

According to the World Wildlife Fund, between 30 million and 37 million acres of forest are lost each year. Deforestation reduces biodiversity, releases greenhouse gasses, disrupts water cycles, increases soil erosion, and poses a major problem to the millions of people who rely on the forests for food. The scientists conducting the study called for changes in lighting design and "dark refuges connected by dark corridors" for light-sensitive animals. There is no indication their recommendations will be followed.

Photo via Flickr