Nightlights for Stream Dwellers? No, Thanks

Artificial light at night isn’t just a health problem for those of us sitting in bed scrolling through Instagram instead of hitting the sack — it hurts entire outdoor ecosystems.Light pollution is having impacts on the surrounding environment.

When the critters that live in and around streams and wetlands are settling into their nighttime routines, streetlights and other sources of illumination filter down through the trees and into their habitat, monkeying with the normal state of affairs, according to new research from The Ohio State University.

“This is among the first studies to show that light at night has detrimental effects not just on individual organisms in the environment, but also on communities and ecosystems,” said Mažeika Sullivan, lead author of the study, which appears today (Dec. 19, 2018) in the journal Ecological Applications.

“Nighttime light is having profound impacts that extend to the entire ecosystem,” said Sullivan, director of Ohio State’s Schiermeier Olentangy River Wetland Research Park and associate professor of environment and natural resources.

Though many people might not consider it, artificial light is a pollutant, changing the natural course of life for people, animals and plants, he said, adding that urbanization is rapidly increasing both in the United States and around the globe.

The new study explored the role of light on streams and wetlands in and around Columbus.

They also discovered that the food chain length of the invertebrate communities – a measure that tells researchers about the complexity of a food web – shortened with more light.

“Decreases in food chain length are a pretty big deal, as it reflects not just changes in the architecture of an ecosystem – the numbers of various species – but also shifts in ecosystem stability and nutrient flows,” Sullivan said.

The researchers also saw detrimental changes in energy flow – how nutrients are cycled between aquatic and nearby ecosystems. In particular, invertebrates became less reliant on food sources that originate in the water when they were exposed to moderate light levels.

The reasons for the changes are complex however, previous studies have clearly shown that individual species are impacted by artificial light.

“The classic example is hatchling sea turtles that became disoriented and instead of going toward the moonlit ocean at night, they were headed inland, toward coastal lighting,” Sullivan said. “In that case, light-management tactics have helped address the problem.”

But until now, scientists haven’t fully detailed the broader implications – how light might affect species interactions, communities and important ecosystem functions.

“I think we’re going to start to find that that light has cascading consequences that are linked to other environmental problems we’re seeing, possibly including harmful algal blooms."

Learn more about how light pollution is affecting the environment and the solutions proposed for reducing that impact.