Researchers at Macquarie University have completed a three-year study documenting how artificial light affects wildlife in Sydney, finding that light pollution significantly alters behaviour, reproduction, and survival of most native species in urban areas.

The study used acoustic monitors, camera traps, and direct observations across 80 sites in Sydney ranging from dark parks to brightly lit commercial districts. Two-thirds of the 120 species monitored showed significant behavioural changes correlated with light levels.

Dr. Theresa Jones, who leads Macquarie’s urban ecology program, said the results were more severe than expected. “We knew some species like sea turtles are affected by light pollution, but we found impacts across entire urban ecosystems, from microbats to large owls.”

Artificial light at night, often called ALAN in scientific literature, has increased dramatically over the past century. LED lighting has accelerated the trend because LEDs are cheap to operate, leading to more extensive lighting than older technologies.

Light pollution affects wildlife through multiple mechanisms. It can disrupt circadian rhythms, interfere with navigation, alter predator-prey dynamics, and affect reproduction cues tied to day length or moon phases.

The Macquarie study found that insectivorous bats avoided brightly lit areas despite higher insect concentrations near lights. This appears to be predator avoidance behaviour; bats feeding near lights become more visible to owls and other predators.

Conversely, some urban-adapted birds like magpies and noisy miners extended their activity into night hours in well-lit areas, potentially gaining competitive advantages over light-sensitive species.

Powerful owls, Australia’s largest owl species, showed particularly interesting responses. They hunt in urban areas but avoid well-lit hunting grounds, even when prey is abundant. This constrains their foraging areas and may limit urban owl populations.

Possums showed complex responses. Common brushtail possums, which are highly urban-adapted, showed little sensitivity to light. But sugar gliders avoided lit areas, likely because they’re more vulnerable to predation when visible while gliding between trees.

The study also monitored microbats, which are difficult to study because they’re small, fast-moving, and active only at night. Acoustic monitoring revealed that bat activity and species diversity declined sharply in areas with light levels above 5 lux, roughly equivalent to a dimly lit residential street.

Frogs and nocturnal insects also showed strong light sensitivity, with calling activity and abundance declining in lit areas. This has cascading effects because these species are prey for many other animals and play important roles in ecosystem function.

The research found that light spectrum matters. Warm-coloured lights (amber or red-shifted) caused less behavioural disruption than cool white or blue-rich lights. This is consistent with other studies showing that blue wavelengths suppress melatonin production and disrupt circadian rhythms more than longer wavelengths.

Many Australian cities have been transitioning to LED street lighting. While LEDs save energy, most produce blue-rich white light that may be more ecologically damaging than the warmer-toned sodium vapour lights they replace.

The study recommends that cities adopt amber or warm white LEDs for outdoor lighting and implement shielding to direct light downward rather than letting it spill into trees and habitat areas.

Reducing overall light levels through dimming or selective lighting that keeps pedestrian areas lit while darkening adjacent habitat is another recommendation. Some European cities have implemented adaptive lighting that dims when no pedestrians or vehicles are detected, reducing light pollution while maintaining safety.

Sydney’s urban planning policies don’t currently address light pollution systematically. Some local councils have policies about light spill from developments, but there’s no coordinated strategy for managing ecological impacts of public lighting.

The research team is working with several Sydney councils to pilot wildlife-sensitive lighting approaches. These trials will test whether changing light colour, intensity, or timing improves habitat quality for sensitive species without compromising public safety.

Public attitudes toward lighting are important. People associate bright lighting with safety, though evidence for this connection is mixed. Many perceived safety benefits come from visibility rather than light level per se, and well-designed lower-level lighting can provide adequate visibility with less ecological impact.

The study received $2.1 million in funding from the Australian Research Council and the NSW Environmental Trust. That supported extensive field monitoring and analysis that wouldn’t have been possible with typical research grant budgets.

Light pollution research in Australia has generally lagged behind Europe and North America, where some cities have implemented dark sky policies and lighting regulations to protect wildlife and astronomical observations. The Macquarie research provides evidence base for similar policies in Australian cities.

Beyond terrestrial wildlife, light pollution affects marine environments. Hatchling sea turtles use natural light cues to navigate to the ocean, and artificial lighting causes disorientation that reduces survival. Coastal lighting near turtle nesting beaches is increasingly managed to reduce impacts.

Urban light also affects plants. Street trees near lights maintain leaves longer in autumn and bud earlier in spring, potentially reducing cold hardiness and affecting interactions with insects that depend on seasonal cues.

Whether cities will implement meaningful light pollution reductions depends on political will and public support. LED technology makes reductions more economically feasible because LEDs can be precisely controlled and dimmed without reducing bulb life, unlike older lighting technologies.

The research team is developing guidelines for wildlife-sensitive lighting design that they hope will be incorporated into Australian Standards and building codes. That would mainstream light pollution mitigation rather than leaving it to voluntary initiatives.

One interesting aspect of the research is public engagement. The team conducted citizen science programs where Sydney residents monitored wildlife in their neighborhoods, contributing to the dataset while learning about urban ecology.

That engagement helps build support for conservation actions and reveals that urban residents generally want to share cities with native wildlife. Finding ways to maintain biodiversity in cities while meeting human needs is increasingly important as urbanisation continues.

The complete study results are being published in a series of papers throughout 2025 and 2026, covering different taxonomic groups and developing recommendations for different urban contexts.