Festive lights are a permanent feature of Polish cities and can play a positive social role, but they also contribute to light pollution, with their environmental impact depending largely on where and how they are installed, an expert from the Wrocław University of Environmental and Life Sciences has warned.
Magdalena Zienowicz, PhD, from the Department of Landscape Architecture, said that assessing the impact of festive lighting requires taking into account multiple factors, including intensity, direction of emission, duration and location.
“It is impossible to equate all types of such decorations, assuming that each additional portion of light is equally harmful,” she said.
Zienowicz added that lighting and illumination should not be treated as the same thing. Lighting is functional and designed to ensure safety, visibility and the efficient operation of cities after dark, while illumination serves an interpretative and aesthetic role by highlighting architecture and creating atmosphere.
“Holiday decorations typically emit light with low photometric values. Their purpose is not to illuminate the street or sidewalk, but to create atmosphere. However, this does not mean they are always neutral.
“Introducing intense festive lights can mean a sudden and significant interference with the environment, leading to the creation of an artificial ‘light ecosystem’. Such a contrast can be particularly noticeable for nature,” Zienowicz said.
According to the researcher, the negative effects primarily include disruption of circadian rhythms and natural behaviours of animals, as well as impacts on humans and plants.
Scientific studies show that even small light sources at inappropriate times can inhibit melatonin secretion in humans and disturb animal circadian rhythms.
She identified areas around bodies of water, green spaces, rooftops and church towers as particularly problematic locations for luminous decorations, as they may serve as habitats or shelters for wildlife.
In large cities, however, the impact is usually smaller. “Based on current research, it can be stated with great probability that festive lights in large cities like Warsaw usually cause less damage than similar installations in rural areas. This is primarily due to the nature of the space, which has long been heavily transformed by humans,” Zienowicz said.
She added that in urban settings illuminated streets, buildings and squares are already part of the nightscape, meaning festive illuminations do not necessarily worsen environmental conditions. “However, proper design is essential to limiting their impact. They should be tailored to the specific location: taking into account the urban layout, perceptual conditions, and the needs of residents and tourists,” she said.
Timing is also critical, she said, with light decorations needing to be switched off at specific night-time hours. The use of controllers, dimming systems and energy-saving solutions should be standard.
“If these factors are not taken into account, a situation may arise in which illuminations take over the nightscape,” Zienowicz warned. “In cities, nighttime spaces are already heavily saturated with street, advertising, and architectural lighting. Adding additional sources without a clear purpose and control can lead to visual chaos, further disrupt people’s natural circadian rhythms, and have a significant impact on urban flora and fauna.”
Despite the risks, Zienowicz said thoughtful planning can balance environmental impact with positive effects on residents’ mental well-being, encouraging walks, use of public spaces and social interaction during winter months.
“Research also indicates that limiting light intensity enhances the engagement of multiple senses, which in turn contributes to a deeper sense of self, promotes self-reflection, and builds inner balance and self-esteem,” she said.
She argued that the best results are achieved by illuminating only a small number of carefully selected elements, using warm LED light sources and avoiding excessive brightness or complexity.
“Too much light, even in urban environments, can be a form of visual violence,” Zienowicz said. “My research shows that a low brightness contrast between the observer and the surroundings makes a space feel more relaxing and cohesive.”
In her view, illumination becomes destructive when moderation is lost. “As a result, we not only ‘spoil the night’, but also degrade the very concept of light, forgetting that nighttime lighting should enhance the space, not dominate it,” she said.
“Perhaps the time has come in many cities to no longer add light, but shade,” Zienowicz concluded. “Ensuring a good night’s sleep is therefore becoming one of the key challenges of modern cities.”
Nauka w Polsce, Katarzyna Czechowicz (PAP)
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