Street light choice matters: impacts of presence and color on wild plants

Anthropogenic light at night (ALAN) is rapidly expanding, affecting wildlife and ecosystems. Color is an important factor in designing responsible outdoor lighting strategies, yet color choice effects on plants remain largely unknown. We investigate how different colors of street lighting influence the morphology and nighttime assimilation rates of two wild plant species, Hypochaeris radicata and Rumex acetosa. Using a semi-natural mesocosm setting, plants were exposed to nightly red, green, and white streetlights, with a dark control, over an eight-week period. Red light significantly increased leaf length and petiole elongation compared to other treatments. Nighttime transpiration and stomatal conductance also strongly increased under both red and white light. These findings highlight that ALAN, particularly red and white light, can disrupt plant growth and physiological processes, which can potentially affect overall ecosystem dynamics. Theres also a species-specific effect to morphological parameters which is absent for the assimilation parameters. Striking a balance between functionality and ecological impact is challenging, given that certain light colors negatively affect plants, while those same colors may be preferred by other organisms. A deeper understanding is needed to guide informed decisions on plant and wildlife protection.