4 May 2026
There are more than a septillion (10²⁴) stars in the observable universe. It is a number far beyond what we can truly comprehend. On a clear night, far from the glow of cities, a few thousand of them, roughly up to 6,000, should be visible to the naked eye. But how many do we really see today, from our terraces, our balconies, our backyards? A handful, perhaps.
It wasn’t always this way. Just a few decades ago, the night sky told a very different story. So where did the stars go?
The answer lies not in the sky, but on the ground. In the way we light our cities, our streets, and our homes. In a form of pollution we rarely speak about: light pollution.
In an age where most of us are absorbed in the glow of our screens, the disappearance of stars often goes unnoticed. But this is not just about losing a celestial view. It is about something far more profound. Light pollution disrupts ecosystems, affects human health, wastes energy, and challenges the very foundations of sustainability.
From a sustainability perspective, the implications are significant. A substantial portion of outdoor lighting, often estimated at around 30 percent, is wasted as upward or misdirected light. This is not just lost illumination. It represents unnecessary energy consumption, avoidable carbon emissions, and money that could have been saved through better lighting design.
Lighting Impact Snapshot
| Metric | Value |
|---|---|
| Outdoor lighting wasted | ~30% |
| Energy loss (US) | $3.3 billion annually |
| CO₂ emissions | 21 million tons/year |
| Trees needed to offset | 875 million/year |
| Energy saving potential | 60–70% |
According to DarkSky International, at least 30 percent of all outdoor lighting in the United States alone is wasted, largely due to unshielded fixtures. This translates to approximately 3.3 billion dollars in energy loss and the release of 21 million tons of carbon dioxide every year. To offset these emissions, an estimated 875 million trees would need to be planted annually.
Environmental responsibility is closely tied to how we define sustainability itself. At its core, sustainability is about using resources efficiently today so that they remain available for the future. In lighting, saving energy also means saving money, while preserving resources for generations to come.
In this context, responsible lighting becomes not just a design consideration, but a critical component of sustainable development, linking energy efficiency, environmental protection, and human wellbeing.
Installing quality outdoor lighting can reduce energy use by 60 to 70 percent, resulting in significant cost savings while cutting carbon emissions. Fully shielded luminaires, which direct light downward only where it is needed, can provide the same level of illumination on the ground as unshielded fixtures, but with far greater efficiency and control.
At its core, light pollution is the presence of artificial light where it is neither needed nor intended. When poorly designed lighting sends light upward or outward, it interacts with molecules and particles in the atmosphere, scattering in all directions and creating a luminous haze known as skyglow, veiling the night sky beyond.
This misdirected light also manifests as glare and light trespass, reducing visual comfort and spilling into spaces where it is neither wanted nor appropriate.
While other forms of pollution dominate global conversations, light pollution remains largely overlooked. Yet, it stands apart in one crucial way. It is perhaps the only form of pollution that can be reversed almost instantly, simply by lighting more thoughtfully.
More Than Just Stars: What We Are Losing
“Only in the darkness can you see the stars.”
This widely attributed quote to Martin Luther King Jr. resonates deeply in today’s context. We have designed our cities to remove darkness. In doing so, we have not lost the stars, but we have made them invisible. And in that process, we have lost something very fundamental. There is even a term for this growing sense of loss. Noctalgia describes the grief and longing people feel for the natural darkness that has been replaced by artificial light. For centuries, the night sky has guided explorers, inspired science, and shaped our understanding of the universe. Today, that connection is fading.
Why Light Pollution Matters
Understanding light pollution leads to a more important question. Why does it matter? It is not just about losing stars. It affects far more. Light pollution disrupts ecosystems, wastes energy, and impacts both human and wildlife health.
Impact Across Systems
| Area | Impact |
|---|---|
| Human health | Sleep disruption, metabolic issues |
| Wildlife | Navigation and behavioural disruption |
| Marine life | Hatchling disorientation |
| Agriculture | Increased pesticide dependency |
| Environment | Energy waste and emissions |
Disruption of circadian rhythms does not just affect sleep. It also has a direct impact on metabolic health. Research has shown that prolonged exposure to artificial light at night can alter glucose metabolism and reduce insulin sensitivity, increasing the risk of conditions such as obesity and Type 2 diabetes.
Over time, this imbalance can place stress on the body’s natural regulatory systems, affecting energy levels, hormonal balance, and overall wellbeing. What was once a natural cycle governed by daylight and darkness is now increasingly influenced by artificial environments. In response, many people turn to supplements such as melatonin to restore sleep patterns. However, this raises an important question. Instead of adapting our bodies to disrupted environments, should we be designing our environments to better support our biology?
For the environment, much of this light is wasted, increasing energy consumption and carbon emissions. For wildlife, the consequences are profound. Sea turtle hatchlings, which once navigated toward the ocean guided by moonlight, are now disoriented by artificial lighting and often move toward cities instead. Birds, which rely on celestial navigation, become disoriented by illuminated skylines. Many are drawn toward buildings, where they collide with glass or circle in confusion until exhaustion. It is estimated that hundreds of millions of birds die each year due to such collisions.
Even plant life is affected. Trees exposed to artificial light at night may bud earlier and shed leaves later, disrupting natural cycles. Many ecosystems depend on nocturnal pollinators such as bats and moths, whose behaviour is altered by artificial lighting. A bat might not excite you, unless you are a Batman fan. But its role in our ecosystem is far more significant than we often realise. Before artificial lighting became so widespread, bats played a crucial role in agriculture by feeding on insects and pests, naturally controlling their populations and reducing the need for chemical pesticides.
With increasing light pollution, this balance has begun to shift. Artificial lighting alters the natural behaviour of bats. Many species avoid illuminated areas, changing their flight paths or remaining closer to their roosts, reducing their feeding activity. As a result, pest populations can increase, leading to a greater dependence on pesticides in agriculture. And this is where the impact comes full circle. No matter how thoroughly produce is washed, traces of these chemicals often remain. Over time, this contributes to exposure that affects not just individuals, but entire populations across generations.
It is a reminder that we are not separate from nature. We are part of a deeply interconnected system.
Lighting, Design, and Responsibility
Organizations like DarkSky International continue to advocate for the protection of our night skies. Each year, International Dark Sky Week serves as a global reminder of the importance of preserving natural darkness.
In 2026, International Dark Sky Week was observed from April 13 to 20, coinciding with the new moon to maximize visibility of the night sky while promoting awareness of light pollution and celebrating the beauty of natural darkness. As part of this initiative, the Society of Light and Lighting (SLL) and TRILUX collaborated with academia to raise awareness among students on responsible outdoor lighting, integrating both international and regional perspectives, and fostering the next generation of advocates in the region. On 13 April 2026, at Manipal Academy of Higher Education (MAHE), Dubai, the session unfolded through three key perspectives: Experience, Performance, and Responsibility.
It began with a simple but important idea: Design is not just visual. It is measurable. Lighting is where art meets engineering. We do not just place lights. We simulate performance. When we walk into a space and feel that it is welcoming or comfortable, it is not by chance. There is always a design intent, guided by standards, tools, and careful calculations.
The session started with fundamental lighting terms, introducing students to design tools and industry guidelines, and exploring how to balance ideal lighting design with optimized energy consumption. It also addressed carbon emissions, both operational and embodied, along with the importance of circularity in lighting design. This also extends to the concept of circularity in lighting, where design considers not just performance, but lifecycle impacts, including material use, longevity, and end-of-life reuse.
We explored real-world applications, including the redesign of a residential park in Mumbai in collaboration with the DarkSky India Chapter. Lighting levels were reduced and fixtures were optimized to minimize glare and spill light, demonstrating that lower light levels did not compromise safety, but instead enhanced visual comfort and the overall nighttime experience.
We also examined thresholds defined by green building frameworks such as LEED, reinforcing how sustainability targets translate into real design decisions.
Understanding and Measuring the Problem
A key part of the session focused on understanding light pollution at a global scale. We explored world light pollution maps, observing how urban expansion directly correlates with increasing sky brightness.
Tools such as the Bortle Scale and Sky Quality Meter help quantify what was once invisible. We also examined luminaire performance using the BUG rating system, which evaluates backlight, uplight, and glare.
The message was simple. If we can measure it, we can design to improve it.
From Awareness to Action
Another simple yet often overlooked aspect is indoor lighting. In many buildings, lights remain on long after occupants have left, with blinds left open. This allows light to spill into the outdoor environment, contributing to skyglow and ecological disruption. A simple action, such as closing blinds or turning off unnecessary lighting, can significantly reduce this impact. This reinforces an important idea: responsible lighting is not always about complex solutions. Sometimes, it begins with small, conscious decisions.
Designing Responsibly
Dark sky does not mean dark ground. It means the right amount of light, at the right time, in the right direction. The discussion then extended to practical implementation, focusing on lighting zones, boundary conditions, and exemptions, which help define where and how lighting should be applied to minimize spill light and environmental impact. Lighting zones play a critical role in translating intent into practice. They classify areas based on their environmental sensitivity, ranging from naturally dark zones with minimal human activity to highly urbanized environments. Each zone defines acceptable lighting levels, controls, and design limits, ensuring that illumination is appropriate to its context.
This helps prevent overlighting in sensitive areas while allowing functional lighting where it is needed. In practical terms, lighting zones guide decisions such as how much light is required, where it should be directed, and when it should be reduced or switched off. They provide a structured framework that connects design intent with measurable outcomes. Equally important is how lighting is installed. Even well-designed luminaires can contribute to light pollution if they are not installed as intended. Incorrect tilt, orientation, or mounting can lead to unintended uplight, glare, and light spill, undermining the design itself.
To guide responsible outdoor lighting practices, organizations such as the Illuminating Engineering Society and DarkSky International promote the Five Principles for Responsible Outdoor Lighting.
These principles encourage us to ensure lighting is useful and necessary, direct light only where it is needed, use the lowest effective light levels, control lighting through timers and sensors, and choose warmer color temperatures to reduce ecological impact.
These are not just guidelines, but practical strategies grounded in science. They were discussed in depth during the session, reinforcing an important idea: we do not always follow rules unless we understand why they matter. When that understanding is in place, these principles evolve from restrictions into tools for better, more responsible design.
While global principles provide direction, regional policies help translate these ideas into enforceable design practices.
The Abu Dhabi Dark Sky Policy, launched by the Department of Municipalities and Transport, reflects this approach by setting clear and measurable objectives for outdoor lighting across the Emirate, focusing on reducing light pollution, promoting sustainable and environmentally responsible lighting systems, and protecting ecosystems and native wildlife.
It also recognizes the broader impact of lighting on society, supporting research in astronomy, improving public health and well-being, and contributing to long-term sustainable development.
In this way, lighting becomes part of a larger sustainability strategy, aligning urban development with environmental and social responsibility. Rather than viewing lighting purely as a technical requirement, it positions lighting as a multidisciplinary responsibility, one that connects environmental protection, human health, and our relationship with the night sky. Through requirements such as shielded, downward-facing fixtures, defined color temperature ranges, and the reduction of nonessential lighting after midnight, these objectives are translated into real design decisions across both public and private developments.
Beyond regulation, the intent is clear: to enhance the well-being of both people and wildlife while restoring the visibility of the night sky. In doing so, Abu Dhabi is positioned among the first cities in the region to align with the global dark sky movement, taking a meaningful step toward reconnecting people with the stars.
Image: Implementation of the Abu Dhabi Dark Sky Policy through practical lighting design, illustrating the difference between acceptable and unacceptable lighting fixtures in terms of shielding, direction, and light control.
A Responsibility That Extends Beyond Design
Sustainability does not succeed through policies or frameworks alone. It succeeds when people understand the intent behind decisions. Lighting is not just something we see. It shapes how we feel, function, and interact with our environment.
As designers, architects, and engineers, we are not just shaping spaces. We are shaping environments, ecosystems, and experiences. The night sky is part of our shared heritage. And while we may have dimmed it, we have not lost it completely.
The session concluded with a simple yet powerful call to action. Students were encouraged to become advocates for responsible lighting, to question design decisions, and to carry this awareness forward into their future work. Because advocacy does not begin with large-scale change. It begins with individuals who understand the impact of their choices and are willing to do better.
Organizations like DarkSky International continue to build a global community of such advocates, working toward a future where responsible lighting becomes the norm. Because in the end, this is not just about lighting design. It is about what we choose to preserve. And perhaps, if we begin to light our world more responsibly, future generations will once again look up and see a sky full of stars.
