Artificial night light toughens tree leaves, threatens urban ecosystems

Sub: Env

Sec: Pollution

Impact of Artificial Light at Night (ALAN) on Urban Trees and Insects:

High levels of ALAN make tree leaves tougher and harder for insects to eat, threatening urban food chains.
Researchers from the Chinese Academy of Sciences found that ALAN increases leaf toughness and reduces herbivory in common street trees in Beijing.
Light pollution disrupts migrating birds, sea turtles, wilderness experiences, landscape beauty, and human health.

Study Findings on Leaf Toughness:

ALAN has species-specific effects on leaf nutrients, size, and defence substances.
Plants under high ALAN prioritize defence, producing tougher leaves with more chemical compounds, which are less appealing to insects.
In Beijing, ALAN increased leaf toughness and reduced herbivory in the Japanese pagoda tree and green ash.
For Styphnolobium japonicum, increased leaf carbon and toughness correlated with decreased herbivory, while higher leaf nitrogen increased herbivory.
For Fraxinus pennsylvanica, herbivory decreased with increased leaf toughness.

Ecological Implications:

Higher leaf toughness hinders herbivore feeding, resulting in lower herbivory levels and slower leaf decomposition, affecting nutrient cycling.
ALAN can reshape herbivorous insects’ feeding preferences and negatively impact energy flow and biodiversity in urban ecosystems.

Light Pollution and Global Trends

The 2016 New World Atlas of Artificial Night Sky Brightness found that over 80% of the world’s population lives under light-polluted skies, hiding the Milky Way from many.
A 2023 study in Science reported the night sky is rapidly getting brighter, reducing star visibility.

Dark-Sky Movement:

The growing movement to establish dark-sky places aims to minimize light pollution and protect the night sky.
In January 2024, the Pench Tiger Reserve in Maharashtra was designated as India’s first International Dark Sky Park, promoting night sky conservation and astronomy.

Source: DTE