Climate Change and Ecological Effects on Circadian Rhythm

Sleep is one of the most fundamental aspects of being alive. Despite its prevalence, the neurological underpinnings of the process behind sleep are very complex. Dr. Dan Cavanaugh gave a talk at the neuroscience seminar at Loyola University Chicago describing this process in detail, and what factors can affect it. Animals have adapted to the 24-hour rotation of the Earth to appropriately time their wake/sleep cycles. Clock cells found in the brain seem to be what are responsible for this internal clock. By recording activity levels in the fruit fly (Drosophila melanogaster), different peaks of activity were observed (Guerrero et al., 2025). When testing in light and dark (LD) vs. fully dark (DD) conditions, similar activity levels were observed, confirming the existence of this internal clock. 

One factor that is correlated with this internal clock is temperature. It is found that temperature is highly regulatory for the main clock neuron discussed by Cavanaugh, the Lateral Posterior Neuron (LPNs). They receive inputs from sensory afferent neurons and are thus activated by heat stimuli (Guerrero et al., 2025). At the end of his talk, Cavanaugh mentioned the relationship between temperature and the circadian rhythm, specifically in the Drosophila, and how this could potentially have ecological consequences. This immediately struck me, and my mind went to climate change and how that could now have potential neurological impacts on organisms. At the end of the paper provided by Cavanaugh, a majority of the future directions involved studying the effect of temperature further.

To investigate the specific issue of climate change and its potential impact on circadian rhythm further, I looked into the evolution of the circadian rhythm and thus how it could react to the increasing temperatures on Earth. It was found that there is an increasing temporal mismatch between the internal clock and environmental cues such as temperature (Jabbur & Johnson, 2022). While selective forces would cause a natural evolutionary process to take place to adapt to these unnatural temperatures, the rate at which the temperature increase is occurring makes it nearly impossible to keep up. Regardless, it will complicate the circadian cycle as specific clock genes related to photoperiods, or the length of day over the seasons, could be selected for. These changes nonetheless will not occur fast enough, leading to a mismatch between organic cycles in animals and on the Earth. The effects of this are yet to be seen, but will likely not be great. If we needed more reasons to combat climate change, look no further!

            Guerrero, C. Y. P., Cusick, M. R., Samaras, A. J., Shamon, N. S., & Cavanaugh, D. J. (2025). The cell-intrinsic circadian clock is dispensable for lateral posterior clock neuron regulation of Drosophila rest-activity rhythms. Neurobiology of Sleep and Circadian Rhythms, 18, 100124. https://doi.org/10.1016/j.nbscr.2025.100124

            Jabbur, M. L., & Johnson, C. H. (2022). Spectres of Clock Evolution: Past, Present, and Yet to Come. Frontiers in Physiology, 12. https://doi.org/10.3389/fphys.2021.815847