Artificial light at night can modify ecosystem functioning beyond the lit area.

Area of Science:

• Ecology
• Environmental Science
• Conservation Biology

Background:

• Artificial light at night (ALAN) is a growing global change driver with documented adverse effects on biodiversity.
• The spatial extent of ALAN's impact on ecosystem functioning, particularly in areas adjacent to illumination, remains poorly understood.

Purpose of the Study:

• To investigate whether ALAN affects ecosystem functioning in areas adjacent to directly illuminated sites.
• To assess the impact of ALAN on plant reproductive output and seed predation.

Main Methods:

• Phytometer species were exposed to three ALAN treatments: directly illuminated, adjacent to illuminated, and dark control sites.
• Reproductive output and pre-dispersal seed predation were measured for two plant species.
• Laboratory experiments assessed seed predator behavior in relation to varying light intensities.

Main Results:

• A trend for reduced reproductive output was observed in one plant species on directly illuminated sites.
• Seed predation significantly increased in dark sites adjacent to illuminated areas, leading to reduced relative reproductive output.
• Laboratory observations showed the primary seed predator avoided light, preferring darker areas to interact with host plants.

Conclusions:

• ALAN can negatively affect ecosystem functioning in areas not directly illuminated, extending its ecological impact.
• The behavioral response of seed predators to light contributes to reduced plant reproductive success in adjacent dark habitats.
• ALAN's ecological consequences may be more widespread than previously assumed, necessitating broader consideration in conservation efforts.