The Night Stolen by the City

Modern cities have radically transformed the night. What for millennia was a dark mantle of stars, moon, and silence has become a luminous, noisy, and always active stage. This transformation — the expansion of artificial night light, urban light pollution — is not merely aesthetic or cultural: it has profound ecological, physiological, and social consequences. In his “Manifesto for Darkness,” Johan Eklöf warns that “artificial light is not only a form of pollution, but an invisible weapon that transforms the nocturnal ecology of the planet.” But these consequences are not limited to other species: we pay the price too.

The phenomenon of light pollution, the constant glow caused by streetlights, signs, windows, cars, and urban lights, has grown exponentially. According to Eklöf, each year the nights become “a little less night;” many people in urban areas never see the Milky Way and can barely distinguish a handful of stars. What some consider convenience, for the planet represents a radical denaturalization of the day-night cycle. The writer Antonio Muñoz Molina (2025) expresses it forcefully: “An abolished night is as much a calamity as a felled forest.”

But this alteration is not a mere visual change. The natural night, with its darkness, has been an essential part of the evolution of countless species. Permanent and poorly directed artificial lights disrupt natural rhythms of light and darkness, with effects ranging from the cellular level to entire ecosystems.

One of the central points Eklöf highlights is the disruption of the human biological clock. In natural conditions, the day-night cycles regulate functions such as hormone production, sleep, body repair, and immune system regulation. With excess nighttime light, this rhythm is broken. Eklöf warns that “excessive light can affect our hormones, weight, and mental health” and that darkness is not a luxury but an ecological and biological necessity.

In particular, melatonin production is inhibited by continuous exposure to night light. The writer Henry David Thoreau, back in the 19th century, sensed this vital connection between night and deep well-being: “The night is more alive and more richly colored than the day.” His observation was not only aesthetic but philosophical: night as a source of introspection, of pause, of intimate nature.

It has been documented that white light, like that of many urban LEDs, has a stronger effect on the biological mechanisms that regulate circadian rhythms. Thus, cities, with their constant glow, alter not only the view of the night but also our internal biology, undermining one of the pillars of sustainability: human well-being.

Eklöf emphasizes that light pollution disrupts the natural cycles of countless species: insects, birds, bats, plants. Among the effects observed in urban environments are alterations in the activity cycles of nocturnal species, significant changes in insect communities, which are key for processes like pollination and nutrient recycling, disruptions in reproductive and migratory cycles of various species, and a general ecosystem imbalance that compromises the urban environment’s resilience to environmental changes. This represents a real loss: a city that loses biodiversity, that interrupts basic ecosystem functions, and that becomes hostile to life cannot sustain or regenerate itself over time. It is a city indebted to its surroundings.

Beyond the physical and biological, the loss of natural night implies a cultural rupture. Eklöf emphasizes that darkness has historically been part of our narratives. Furthermore, cities that never sleep, with constant lighting and continuous activity, reinforce a logic of uninterrupted productivity. But night is also part of stability — rest, silence, space for introspection.

“When the night goes, so too does the possibility of daydreaming,” wrote Octavio Paz, evoking that symbolic and creative dimension that is also lost with the disappearance of darkness. A city that marginalizes the night also marginalizes the emotional and mental balance of its inhabitants.

The night is not an absence of productivity and business, it is a vital component of human, animal, and plant life. For example, plants that perform nocturnal photosynthesis belong to the CAM group (Crassulacean Acid Metabolism). These plants are adapted to arid environments and conserve water by opening their stomata at night, when they capture carbon dioxide and store it as acids. During the day, with their stomata closed, they use that CO₂ to perform photosynthesis. This mechanism allows them to survive with very little water, making them ideal for cities with dry climates or water-saving policies. Some CAM plants include cacti, aloe vera, agave, orchids, and succulents.

Light pollution weakens human health, degrades ecosystems, destroys biodiversity, and interferes with natural rhythms. As Eklöf warns, each unnecessarily lit night is a loss of health, balance, and future.

If we want healthy cities, we must return the night to its place and listen to Van Gogh:

“Look at the sky. It’s not dark, or black, or without character. The black, in fact, is a deep blue. And over there, a lighter blue... And blowing through that blue and that darkness, the wind swirls through the air and then, shining, blazing, bursting ... the stars! Can you see how they roar with light? Wherever we look, the complex magic of nature blazes before our eyes.”