Disrupted sleep cycles are a common concern for human health and functionality, and recent research indicates that insects, too, are affected. A new study reveals that artificial light interferes with the circadian rhythms of honey bees, posing a significant risk to their vital role as pollinators.
In today’s digital age, sleep experts caution against using screens in bed, sounding the alarm that the light emitted by phones and other devices disrupts our sleep cycles. This highlights how science is beginning to understand the broader health implications tied to circadian biology and our everyday sleep-wake routines.
The University of California San Diego research team has discovered that the adverse effects of light disruption extend beyond humans. A study spearheaded by PhD candidate Ashley Kim and Professor James Nieh from the School of Biological Sciences shows that artificial light disrupts the circadian rhythms of honey bees, threatening their essential role in pollination.
“Our findings illustrate just how sensitive honey bees are to environmental changes, especially to something as seemingly harmless as artificial light,” Kim stated regarding their publication in Scientific Reports. “Disruption of their circadian rhythms leads to noticeably shorter sleep durations, which raises serious concerns regarding bee health and the health of ecosystems that rely on them for pollination.
Honey bees are vital pollinators for wild plants and significant crops, providing essential services that help sustain ecosystem stability and ensure global food security. The loss of pollination could jeopardize crops valued in the tens of millions of dollars.
Usually, honey bees prefer dark nesting areas, though some light may seep in through the hive entrance. While sleeping, bees commonly remain still but may show slight movements if disturbed by fellow bees. However, bees will sleep outdoors while swarming or when creating “bee beards” on warm evenings, a behavior that is becoming more common due to climate change. The exposure of sleeping bees to artificial light at night (ALAN), or light pollution, fluctuates by region, yet urban areas are increasingly subjected to these artificial lighting conditions, particularly with rising temperatures. With the resurgence of urban beekeeping efforts in numerous locales to support bees and their crucial pollination services, bees in warmer climates are now more likely to encounter ALAN.
Just like humans, when bees suffer from inadequate sleep and disrupted circadian rhythms, behavioral and functional issues arise. Sleep is vital for the health and fitness of honey bee colonies, which rely on a complex communication system called the “waggle dance” to inform hive mates of nearby food sources. Bees perform less effectively and communicate poorly due to lack of adequate sleep.
Through extensive experimentation over several years, the researchers from UC San Diego compared normal sleeping bees in darkness with those exposed to continuous artificial light. The findings revealed that prolonged light exposure significantly disrupted honey bees’ circadian rhythms, leading to compromised behaviors. As the bees were filmed around the clock during the studies, Kim was able to easily observe the consequences of disrupted sleep.
“Even before analyzing the data, it was apparent that something was off the bees exposed to constant light didn’t sleep as much,” Kim remarked. “The impact of light pollution on biological systems is largely unknown and isn’t often considered, making it a rapidly advancing field of research.”
According to the details outlined in the study, bees exposed to continuous light exhibited less sleep and were disturbed more often by their hive mates compared to those kept in darkness. Furthermore, bees under constant light showed a stronger preference for darker areas within their experimental environment.
“Grasping the factors affecting bee health, such as light pollution, is critical for devising strategies to safeguard pollinator populations,” Nieh commented. “Light pollution is an escalating problem, with artificial lighting now occupying a quarter of the Earth’s surface, and this research illuminates how these disturbances might be detrimental to pollinators.”
Two co-authors of the study, Aura Velazquez (Universidad La Salle México) and Belen Saavedra (Berea College), were undergraduate students involved in the research through UC San Diego’s ENLACE initiative, a summer program where students engage in research projects over seven weeks.
“It’s gratifying that the ENLACE summer research program played a crucial role in offering research opportunities for the student authors of this study,” remarked Olivia Graeve, the ENLACE Program director at UC San Diego and a professor in the Department of Mechanical and Aerospace Engineering, Jacobs School of Engineering. “By facilitating collaboration between students from Latin America and the United States, we help aspiring researchers acquire valuable hands-on experience while building relationships that transcend borders. This project exemplifies the impact of ENLACE, uniting diverse viewpoints to tackle global challenges like pollinator health and environmental sustainability.”
Nieh and co-author Benjamin Smarr, a faculty member in the Shu Chien-Gene Lay Department of Bioengineering, Jacobs School of Engineering, and Halıcıoğlu Data Science Institute, recently received a related grant — which examines human impacts as well — from the new Chancellor’s Interdisciplinary Team Catalyst Fund. “Harmonizing the Pulse of Life: Pioneering Circadian Insights for Human and Ecosystem Health at UC San Diego” further investigates circadian biology and ecosystem wellness. The Nieh and Smarr labs will collaborate to explore circadian rhythms across various scales, from individual bees to entire ecosystems.
“The Catalyst Grant enables us to relate research on honey bee circadian rhythms to broader issues regarding biological synchronization across ecosystems and human health,” Nieh stated. “This program encourages interdisciplinary collaboration, bringing together specialists in biology, data science, and medicine to confront urgent issues like light pollution and its effects on pollinator health. Our efforts with the Catalyst Grant bolster UC San Diego’s contributions to advancing solutions for both environmental sustainability and human health.”
