Lost in the glow: navigating the crisis of light and wildlife

For most of human history, sunset was the hard boundary after a day of activity. The night was not at all a void; it was a velvet curtain that signalled the body to rest and the nocturnal world to wake up. Today, that boundary has blurred. From glaring intense white streetlights and headlights to the persistent blue glow of handheld devices, people are living in a permanent artificial noon. So the quest to banish the shadows have inadvertently led to an environmental crisis — light pollution.

Light pollution is an ecological pollutant caused by the inappropriate use of artificial light outdoors. In the past 20 years, the use of LEDs exploded, as it became so cheap and energy-efficient. Since 2010, earth’s lit surface has been increasing in both intensity and extent by approximately 2-6% per year. Dark skies over the forests of the Western Ghats are rapidly disappearing as unnecessary high-intensity lighting spreads near forests.

Physiological toll

Life on Earth evolved over millions of years under stable day-night and seasonal cycles. So any sudden disruptions to this rhythms is catastrophic. Human eyes regulate sleep through cells that are highly sensitive to blue light. Many common white lights (4,000-6,500 kelvin), emit strong blue wavelengths, mimicking daylight, leading to reduced night vision acuity, suppressed melatonin and disrupted sleep. Similar negative effects are observed in animals as well.

The eyes of many animals, especially nocturnal animals, are most sensitive to blue and ultraviolet light, which at high energy can damage photoreceptor cells. Slightest levels of illumination can alter behaviours, affecting waking cycle, foraging and food intake, and disrupts reproduction.

Impact on wildlife

The night time is a critical ecological niche necessary for the survival of a majority of living organisms. Artificial light at night (ALAN) disrupts wildlife across taxa by altering behaviour, physiology, movement, and reproduction. Migrating birds become disoriented by city lights, leading to fatal collisions and exhaustion in photic trap events. Sea turtle hatchlings, guided by the brightest horizon, are misled by ALAN and move away from the ocean, while adult females avoid nesting on illuminated beaches. Insects are drawn to lights in large numbers, causing mass mortality, disrupting pollination and collapsing ecological balance, with cascading effects on predators; fireflies fail to communicate and reproduce; and moth-mediated pollination declines. Light also alters circadian rhythms, extending activity in diurnal species and even affecting neural physiology. Amphibians reduce or stop calling and mating under slightest artificial illumination, impairing their behaviour and reproduction.

Light-adapted predators, like leopards or bats or spotted owlets, gain an advantage, while dark-dependent species decline. Even very low light levels can delay activity and reduce foraging in nocturnal mammals and forest-floor species. Artificial light disrupts aquatic life by altering vertical migration of zooplankton, triggering trophic cascades, causing algal blooms, reduced oxygen, and degraded water quality. It also affects soil, altering microbial communities, reducing nutrient cycling, and destabilising food webs.

Glow trap

Illuminated linear infrastructure such as roads acts as a psychological barriers for many mammals. While some species such as elephants become light-habituated, others such as leopards avoid brightly lit areas and shift to darker routes through villages or agricultural lands, increasing the risk of human-wildlife conflict.

Repeated exposure to light can reduce an animal’s natural aversion to light, causing them to associate light with high-energy food sources. Habituated elephants, for instance, may be attracted to night glows/halos originating from distant towns and cultivated fields, increasing the likelihood of negative interactions with people. High-beam headlights from vehicles can also startle animals, escalating stress and conflict. Such incidents are routinely observed on roads that pass through our forests. Growing light pollution is likely contributing to human-wildlife negative interactions in landscapes such as Wayanad.

Light pollution policy

For a sustainable transition to a “low glow” Kerala, a comprehensive state policy on light pollution is essential, as no regulations currently mandates correlated colour temperature (CCT) limits based on ecological sensitivity.

Regulations supported by a mix of mandates and incentives, can bring about systematic reduction in CCTs, and promote the use of full-cut-off, shielded, and low-intensity lighting for outdoor applications, including streetlights and public illumination. Establishing ecological lighting standards (ELS) by zone-based limits and prescribing appropriate spectral quality standards (in CCTs) based on ecological sensitivity offer a practical way to address this issue, from protected areas to urban centres.

In general, regulations requiring downward-facing, low-kelvin LED lights, and light curfews, particularly on commercial advertisements, can significantly reduce sky glow and glare. Additionally, innovations such as adaptive dimming, midnight intensity reduction, and motion-triggered lighting systems using passive infrared or advanced microwave sensors, while reducing power consumption, also improve the quality of ecosystems around them.

Regular monitoring using light meters and Sky Quality Meters, remote sensing, ecological surveys, and citizen science initiatives is essential to track progress and compliance.

Critical ecological zones, from protected areas to high-value biodiversity areas, must shift to deep amber (1,800 K), amber (2,200 K) lights and reduce unnecessary illuminations. In surrounding interface zones, warm lighting (up to 2,700 K) is recommended. Across the rest of the state, wherever possible, lighting should be limited up to 3,000 K or warmer, favouring dim, low-intensity white light to reduce ecological impact.

Establishing dark corridors can help reconnect fragmented forests by reducing lighting durations, dimming or switching them off after midnight, thereby facilitating the movement of wildlife, from elephants to tiny moths. A single brightly lit road cutting through a traditional migratory path can cause fragmentation. Without the corridors, these patches become biological prisons, leading to inbreeding and local extinction.

Creating dark zones around high-value biodiversity areas can prevent sky glow that otherwise spills into the night and acts like welcome sign for habituated wildlife. By doing so, they can preserve true darkness as an asset, supporting conservation while attracting niche, high-value tourism. At the same time, targeted incentives for individuals, LSGDs and government agencies that comply with these standards can accelerate its adoption and acceptance. Introducing these measures also reduce the likelihood of light-induced behavioural changes in wildlife that contribute to human-wildlife conflict.

It is time to recognise ALAN as a legally defined form of disturbance in the Environmental (Protection) Act, 1986, and mandate light impact assessment for all development activities in and around key ecological zones as well as high value biodiversity areas.

Reclaim the night

Individual habits, culture and preferences are driving this problem. People celebrate with light, often turning night into day and illuminating the surroundings with artificial brightness, from buildings to towering trees. In doing so, they are reshaping the natural world, without realising the cost. The solution to this crisis is simple, and does not require a massive budget or decades of efforts. It takes only the humility to admit that not everything needs to be seen all the time.

The night is not a void to be filled; it is a heritage to be protected. Preserving its sanctity safeguards human health, while allowing wilderness and wildlife to remain truly wild.

Nafin K.S. is a conservation biologist at the Periyar Tiger Conservation Foundation, Kerala Forest Department; and Pramod G. Krishnan is the Chief Wildlife Warden of the Kerala Forest Department. The views expressed are personal.