X, Y, and Z: A bird's eye view on light pollution

1. The global increase in light pollution is being viewed with growing
concern, as it has been reported to have negative effects ranging from the
individual to the ecosystem level. 2. Unlike movement on the ground,
flying and swimming allows vertical motion. Here, we demonstrate flight
altitude change is crucial to the perception and susceptibility of
artificial light at night of airborne organisms. Because airborne species
can propagate through the airspace and easily across ecotones, effects
might not be small-scale. Therefore, we propose including airspace as a
vital habitat in the concept of ecological light pollution. 3. The
interplay between flight altitude and the effects of light pollution may
not only be crucial for understanding flying species but may also provide
valuable insights into the mechanisms of responses to artificial light at
night in general.