Impact of light pollution on wildlife

Measuring and mitigating the impacts of artificial light on wildlife

Indianapolis at night. Photo by Jimmy Baikovicius

The Problem

Many animals rely on Earth’s daily light cycle as a cue for when to wake, when to migrate, and even when to breed. Human development and the proliferation of artificial light, however, threatens to disrupt those cycles, potentially throwing wildlife, such as birds, out of step with nature’s rhythms.

Consequently, understanding how birds respond to artificial light can help guide efforts to minimize harm to wildlife.

The Project

To better understand the effects of artificial light on birds, Indiana University researchers with the Ketterson Lab captured two subspecies of dark-eyed juncos, one migratory and one non-migratory, that share wintering grounds in Virginia. They transported the birds to Kent Farm Research Station in Bloomington, Ind. and subjected them to different light regimes in a lab setting.

In one experiment, the research team subjected the birds to a light regime that mimicked what they would experience in the wild. Some of the birds, however, were exposed to low levels of white light during periods that would normally be marked by the pitch black of night. Researchers observed that the latter regime contributed to the reactivation of dormant infections, such as malaria. The finding potentially has implications for public health as birds serve as a reservoir for human diseases, such as Lyme disease and West Nile virus.

During the study period, the researchers measured the male birds’ reproductive organs, which enlarge during the breeding season, to determine when the birds were starting and ending their breeding cycle. On average, birds subjected to artificial light at night started their reproductive cycle approximately two weeks earlier than birds subjected to darkness, a response that risks placing birds out of step with their environment and threatening breeding success.  

The Path Forward

To further understand the effects of artificial light at night on birds and how to reduce negative impacts, the researchers are conducting a follow-up study to see whether some types of light are more disruptive than others. For example, past studies have found that changes to the quality of nighttime lighting can reduce the impact on wildlife. The team will also be attaching chips to the birds that will measure birds’ nighttime activity levels and migratory activity to see if migration is also affected by artificial light at night.

Updated June 24, 2022