In the 21st century, the notion of “sustainable lighting” is closely associated with LED technology. In the past ten years, municipalities and private light users worldwide have installed light-emitting diodes in urban spaces and public streets to save energy. Yet an increasing body of interdisciplinary research suggests that supposedly sustainable LED installations are in fact unsustainable, because they increase light pollution. Paradoxically, blue-rich cool-white LED lighting, which is the most energy-efficient, also appears to be the most ecologically unfriendly. Biologists, physicians and ecologists warn that blue-rich LED light disturbs the circadian day-and-night rhythm of living organisms, including humans, with potential negative health effects on individual species and whole ecosystems. Can the paradox be solved? This paper explores this question based on our transdisciplinary research project Light Pollution—A Global Discussion. It reveals how light pollution experts and lighting professionals see the challenges and potential of LED lighting from their different viewpoints. This expert feedback shows that “sustainable LED lighting” goes far beyond energy efficiency as it raises complex design issues that imply stakeholder negotiation. It also suggests that the LED paradox may be solved in context, but hardly in principle.

Concerns about the potential negative effects of artificial light at night on humans, flora and fauna, were originally raised by astronomers and environmentalists. Yet, we observe a growing interest in what is called light pollution among the general public and in the lighting field. Although lighting professionals are often critical of calling light ‘pollution’, they increasingly acknowledge the problem and are beginning to act accordingly. Are those who illuminate joining forces with those who take a critical stance towards artificial light at night? We explore this question in more detail based on the results of a non-representative worldwide expert survey. In our analysis, we distinguish between “lighting professionals” with occupational backgrounds linked to lighting design and the lighting industry, and “light pollution experts” with mostly astronomy- and environment-related professional backgrounds, and explore their opposing and shared views vis-à-vis issues of light pollution. Our analysis reveals that despite seemingly conflicting interests, lighting professionals and light pollution experts largely agree on the problem definition and problem-solving approaches. However, we see diverging views regarding potential obstacles to light pollution mitigation and associated governance challenges.

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