In cities, plants experience notable changes in their natural cycles due to the constant presence of artificial light at night, which is far removed from the conditions found in rural areas. This phenomenon, which has recently been studied by international teams, highlights how urban night lighting It modifies the usual rhythm of sprouting and falling of leaves and, consequently, extends the growing season of the vegetation that we find in urban environments.
Research based on satellite data from 428 cities in the northern hemisphere, collected over seven years, have shown that the The green season for urban plants extends for up to three more weeks than in the countryside. This early spring and late fall not only transforms the landscape but also has implications for urban health and ecosystems.
Urbanization and its consequences on the plant environment
The development of cities has not only brought with it more housing and services, but also a greater presence of light and heat throughout the yearMaterials such as concrete and asphalt, along with heating systems, contribute to generating the so-called urban heat islands. The artificial light from streetlights, shop windows and buildings has grown by an average of 10% in the last decade, significantly affecting the regulation of plant biological cycles.
Experts have observed that exposure to higher levels of nighttime lighting directly determines the beginning and end of the growing season. In fact, it has been proven that Plants in cities sprout an average of 12,6 days earlier that in rural areas and keep their leaves some 11,2 more days in autumn. This phenomenon generates a longer growing season in urban environments.
The differences are not only found between cities and rural areas, but also between continents. Europe shows a more marked advance in plant cycles, followed by Asia and, finally, North America, although in the latter, cities are noticeably brighter. In temperate and cold climates without a dry season, the influence of artificial light is greater on the advancement of the cycle, while a prolonged end is a common pattern in all the regions analyzed.
Artificial light: A dominant factor in the plant cycle
The most striking thing about the latest research is that, although urban temperature has an influence, Artificial light at night proves to have an even greater impact in the extension of the growing season of plants, especially by delaying the end of the cycle in autumn. increase in the intensity and duration of light perceived by plants It alters its internal signals, as if the day never really ended, thus causing greater photosynthetic activity and postponing leaf senescence.
These changes in plant phenology not only affect urban aesthetics or the immediate surroundings of cities. Experts warn that they can increase the risk of frost damage when early shoots coincide with unexpected cold spells or cause leaf fall to be so delayed that the plants are not adequately prepared for winter. In addition, this mismatch can influence the pollination and the presence of allergens, especially pollen, with consequences for people's health.
Another relevant aspect is the technological transition towards LED lighting, which has been replacing traditional sodium lamps. LEDs are more efficient, but emit a light richer in blue tones, to which plants may be especially sensitive due to the functioning of their natural photoreceptors, such as cryptochromes. Research is still needed to understand the impact of this new type of light on urban vegetation, but everything indicates that it could intensify the observed effects.
Ecological implications and future proposals
El increase in the growing season can translate into increased carbon sequestration and increased plant productivity in urban areas, which can have positive effects in certain contexts. However, a desynchronization of the life cycle of plants and animals It could disrupt food chains, harm pollinators—essential for the reproduction of many species—and encourage the expansion of non-native species, affecting local biodiversity.
Researchers highlight the importance of rethinking lighting systems in cities. It is recommended to look for solutions that combine functionality and security with the protection of the biological cycles of urban vegetationThis would help reduce the negative impacts resulting from both technological advancements in lighting and the continued expansion of urbanized areas.
La global expansion of artificial night light It's already a reality, so the design of sustainable solutions, along with studies that delve into the responses of different plant species, will be essential to achieving healthier and more ecologically balanced cities. The challenge lies in finding a balance between modern life and respect for the natural rhythms that accompany urban vegetation, which is essential for the well-being of cities and their inhabitants.
