Taking away from the Darkness

Light has always been one of humanity’s finest discoveries. It was the burning of oil, after all, that lit the long nights of learning and labor, helping us become what we are intellectually and technologically today. Stories of great thinkers burning the midnight oil remind us how light became a necessary companion of knowledge, achievements and of the civilizations itself.

But before oil lamps, candles and, much later, the invention of light bulbs and LEDs, Earth was an entirely different place for a creature to survive. The only illumination one could imagine at night would come from the stars, milky way, phases of the moon and yes, the fires lit by nature and our ancestors. For the past 3–4 billion years, life evolved under conditions of dark nights and bright days (1).

Everything from the instincts of insects to the sleep of humans is attuned to these patterns of light and darkness. One crucial requirement of darkness among others is, in the production of melatonin, a hormone that synchronizes the day–night rhythm in both animals and humans. It helps them adapt to changing seasons, influencing reproduction, hibernation, and migration patterns.  

In many ways, ecological side of darkness has shaped how creatures move, hunt, rest, migrate, reproduce and just be themselves.

The overlooked darkness of light

However, this pattern has changed forever. With the advent of modern lighting, we have extended brightness deep into the night — even into places once touched only by starlight or the moon. This phenomenon, known as Artificial Light at Night (ALAN), refers to the illumination humans create and leave on after sunset. From streetlights and car headlights to glowing billboards and city skylines, this light reaches forests, coasts, and even oceans. Research on the ecological effects of artificial night lighting indicates direct mortality, altered reproductive behaviours, and disrupted interactions between species.

Images: The illustration on the left shows how different types of light affect fish behavior; naturalist William Beebe noted how ultraviolet light irresistibly drew juvenile fish toward it (Drawing by John and Helen Tee Van). The image on the right captures a critical moment in the life of a sea turtle hatchling. Instead of heading seaward guided by the moon, it turns inland toward artificial lights from nearby buildings, placing it at great risk of predation and exhaustion. (Photo by Blair Witherington).

For migratory birds, bright lights can be deadly. During their long journeys, they often rely on natural cues like the stars and moon to navigate. But in over-lit skies, these cues get masked, leaving birds disoriented. At a lighthouse in Canada, researchers once recorded more than six hundred bird deaths in just one migration season (2). Across North America, it is estimated that 4–5 million birds perish every year after colliding with illuminated towers, their supporting wires, or even with one another in disoriented flight (3). Many of these are already species under population stress (4), and among them, twenty species of conservation concern together lose more than 10,000 individuals annually (5).

Image: During New York’s 9/11 Tribute in Light, thousands of migrating songbirds become disoriented by the powerful beams, circling within them for hours. In this image, the birds appear as illuminated streaks flying through the lights of high intensity. (Photo by Debra Kriensky).  

Festivals and Darkness

In India, bird migration occurs throughout the year. However, winter migration is particularly significant, bringing species from thousands of kilometres away to the country’s comparatively warmer regions.

Delhi alone hosts around 191 migratory bird species each year including 66 species which are included under Schedule I of the Wildlife Protection Act. What makes this movement especially critical is its timing. It coincides with Diwali, when the cityscape glows not with the gentle light of diyas and candles, but with the harsh brilliance of modern LED strings and floodlights.

Recent studies have shown that decorative lighting for festivals and increased evening or night-time activities during major festivities are key drivers of global patterns in artificial night illumination. Massive social festivals such as Christmas, Ramadan, and Diwali contribute prominently to annual peaks in global night light emissions (6).

Image 3: While evaluating how macro-cultural activities, such as social gatherings and the use of artificial lights, shape annual lighting patterns globally. Researchers found that night-time light peaks in Hindu-majority countries are concentrated in October–November, aligning with the festivities of Diwali. (Source: Ramirez et al.)

While there is limited secondary data from India, especially from Delhi, evidence from elsewhere as discussed above paints a worrying picture. If similar disruptions occur in Indian cities during festival periods, the implications could be deeply troubling for migratory birds. In addition, the use of firecrackers during such festival months only aggravates the threat.

Interdisciplinarity and Introspection

This is a call for two key insights: ecologically backed solutions to behavior change communication; and ecologically sound technical standards. As city planners, designers, and citizens, our policies must take an interdisciplinary approach. One that makes cities equitably comfortable for both present and future generations while remaining conscious of the other species in these landscapes.

A change in lighting type itself can eliminate up to 80% of bird mortality (7) which we read above. Literature suggests that the effects of light pollution can be reduced by adjusting the intensity of light sources to suit their actual purpose, and illumination can be avoided in places and at times when it is not needed. Through the use of shields and adequate lamp design, light can be directed precisely where it is required. Further, reducing the emission of harmful blue wavelengths is a crucial step toward mitigating the ecological impacts of nocturnal illumination (8). So much can, in fact, be done.

But first, the change must begin with ourselves. We must ask, do we honestly require such over-illumination to celebrate? Do our festivals and rituals call for this exuberant orchestra of light? What purpose does this exhibition serve us, beyond spectacle?

We have made light an essential ingredient of our celebrations, without acknowledging the value of darkness. And yet, in our intimacy with light, we remain blinded.

References:

1. Nelson RJ, Chbeir S. Dark matters: effects of light at night on metabolism. Proc Nutr Soc. 2018 Aug;77(3):223–9.

2. Jones J, Francis CM. The effects of light characteristics on avian mortality at lighthouses. Journal of Avian Biology. 2003 Dec;34(4):328–33.

3. Longcore T, Rich C, Mineau P, MacDonald B, Bert DG, Sullivan LM, et al. An Estimate of Avian Mortality at Communication Towers in the United States and Canada. Krkosek M, editor. PLoS ONE. 2007;7(4):e34025.

4. Banks RC. Human related mortality of birds in the United States [Internet]. 1979. (Special Scientific Report  - Wildlife). Report No.: 215. Available from: https://pubs.usgs.gov/publication/5230238

5. Ramírez F, Cordón Y, García D, Rodríguez A, Coll M, Davis LS, et al. Large‐scale human celebrations increase global light pollution. People and Nature. 2023 Oct;5(5):1552–60.

   
   

6. Gehring J, Kerlinger P, Manville AM. The role of tower height and guy wires on avian collisions with communication towers. J Wildl Manag. 2011 May;75(4):848–55.

7. Karan S, Saraswat S, Anusha BS. Light pollution and the impacts on biodiversity: the dark side of light. Biodiversity. 2023 Oct 2;24(4):194–9.

8. Dominoni DM, Nelson RJ.  2018. Artificial light at night as an environmental pollutant: An integrative approach across taxa, biological functions, and scientific disciplines.  Journal of Experimental Zoology A,  329: 387-393. doi: 10.1002/jez.2241. PMID: 30371014