Christmas lights damage plants

When Christmas comes, cities around the world are decorated with colorful Christmas lights, creating a visual spectacle that attracts residents and tourists alike. Many cities compete to be the best, and during the holidays they transform into dazzling places with streets, squares, parks and gardens bathed in colored lights.

However, this tradition, although aesthetically attractive to many, raises questions about its impact on the environment, especially on urban flora.

Changes in plant physiology and behavior due to Christmas lights

The metabolism of most plants and animals is closely related to the light cycle. Therefore, the effect of Christmas lights would not exactly generate a "festive climate" for plant species.

Many of the behaviors of plants, such as when they germinate and when they shed their leaves, depend on the photoperiod, that is, the number of hours of light per day, or more correctly, on the variation in the number of hours of light day after day. .

If the photoperiod increases, the days will lengthen and spring will arrive, the optimal time for germination; while in autumn, the days with daylight begin to shorten, that is, the photoperiod is reduced and the plants enter a period of dormancy.

Therefore, artificial night light induces changes in the life cycle of plants, in the signaling of their photoreceptors regarding sprouting, senescence of leaves and flowers.

When plants are artificially illuminated with points of light very close to their leaves, the photoperiod perceived by the plant changes and its phenology also changes. These changes, in turn, can affect leaf sprouting and slow their color change.

A study conducted by Lin Meng of Iowa State University and published in the scientific journal Proceedings of the Academy of Natural Sciences in 2022 found that artificial night light accelerates the appearance of leaf buds by an average of almost 9 days and slows down the color change process by about 6 days.

To our eyes they may seem like small changes, but these will alter important functions and ecosystem services that plants provide.

Some plant species are more sensitive to the artificial light of Christmas lights at night. In 2021, Professor Benedikt Speisser and colleagues at the University of Konstanz, Germany, found that some invasive species increase their biomass in response to light pollution, which can lead to a faster spread than in urban areas.

christmas lights

Relationship between plants and animals

If there is a change in the budding or flowering process, there may be an imbalance in the coordination between insects and plants, so this type of night lighting will impact the relationships in the urban ecological system.

For example, if the pollinators are not synchronized with flowering, plant reproduction will be affected. Species that rely on nocturnal insects may lose their ability to pollinate as animals interpret nocturnal behavior based on available light. If a tree is lit, don't go near it.

It is worth remembering that interactions between animals and plants are essential to maintain healthy ecosystems, and given that artificial night lighting significantly alters this dynamic, its consequences will affect the development of trophic flows on a larger scale than expected.

According to research conducted by Dirk Sanders and his colleagues at the University of Exeter in the United Kingdom and published in 2015 in the journal Scientific Reports, depending on nature, light seriously affects the behavior of some species of aphids, reducing their populations by a 20% for 5 generations. Although the effects of these insects are harmful to plants because they consume their sap, they also act as pollinators and compete with other, even more harmful pests.

If the balance of this relationship is disturbed, the biomass of infected plants will decrease significantly. This shows that the impact of artificial night lighting extends through the food chain and has far-reaching impacts on entire ecosystems.

A new approach to Christmas lighting

There is no doubt that Christmas lights are a real spectacle for children and adults and serve as a tourist attraction. However, available scientific evidence suggests that, while these are ancient and visually impressive traditions, they may have unintended negative effects on urban vegetation.

If we want to avoid this damage, it is necessary to rethink the type, intensity and location of Christmas lighting, looking for less invasive and more sustainable lighting solutions that balance the celebration of Christmas with the protection of the urban environment.

Choose softer lighting, perhaps focused on iconic buildings and monuments rather than highlighting trees or other forms of vegetation. Critical reflection and technological advances can create a Christmas tradition that respects and protects the health of our urban ecosystems.

References:

  • Macgregor, C.J. et al. 2019. Effects of street lighting technologies on the success and quality of pollination in a nocturnally pollinated plant. ecosphere.
  • Meng, T.-T. et al. 2022. Light at night effect on the phenology of woody plants. Urban Forestry & Urban Greening.
  • Parker, E.T. et al. 2011. Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment. Proceedings of the National Academy of Sciences, 108(14), 5526-5531. DOI: 10.1073/pnas.1019191108
  • Sanders, D. et al. 2015. Nighttime changes in aphid-parasitoid population dynamics. Royal Society Open Science.
  • Singhal, R.K. et al. 2019. Responses to artificial night light pollution in plants. Journal of Plant Physiology.
  • Speißer, O. et al. 2021. Biomass responses of widely and less widely naturalized alien plants to night-time light pollution. Global Ecology and Biogeography.

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