Ever since humans discovered fire, they have never been able to do without light. Light is a source of energy, warmth and life. But, as with all things, an excess of light sources can have serious effects on the lives of living beings. Light pollution, which spreads into the sky from our cities, disrupts the biological rhythms of plants, animals and even humans.

It disorientates animals

Light pollution caused by excessive use of artificial light in cities has extremely serious consequences for the biological cycles of animals. The biorhythm of mammals, reptiles, amphibians and birds is affected by the absence of darkness during the night. Turtles and migratory birds mistake city lights for the glow of the moon, losing their way to the sea and veering off their migratory routes. Continuously distracted by artificial light, animals fail to perceive the transition from day to night, altering — as in the case of certain amphibians — their reproductive cycles.

It transforms plants

Artificial light is a threat to trees living in cities. The spread of light during the night-time hours alters leaf pigmentation, root development and the cyclical pattern of vegetative dormancy in plants. In cities it is common to find trees that, planted near light sources such as lamp posts, shed their leaves only on the shaded side. Moreover, the leaves exposed to light are greener and the flowers take on a different form. This mutation leads to a disruption in the metabolism of plants that affects the lives of the organisms undergoing these changes, preventing them from carrying out certain biological activities, including pollination.

It disrupts the internal clock of humans

Light pollution also has a negative impact on the metabolism of women and men. Researchers from the American Medical Association have found anomalies in insulin production and a weakening of the immune defences in individuals exposed to light pollution. Light that prevents people from perceiving the darkness of night, or that disturbs their sleep, has consequences for our "internal clock". Individuals suffer from continuous exposure to light, experiencing alterations in their emotional and psychological states, as well as digestive and eating disorders.

To monitor the effects and find a solution, some researchers from the University of Exeter, led by Jonathan Bennie, director of the Environment and Sustainability Institute, have conducted studies on the behaviour of animals and plants exposed to artificial light. The scientists demonstrated that continuous exposure to light sources has serious consequences for the lives of all living beings.

Furthermore, these findings reveal that amber light is more harmful than white light, such as LED. A reassuring finding for local authorities that have adopted LED technology for urban lighting.