Artificial light at night disrupts animal behavior, navigation, and physiology across species, causing welfare harm at a massive but largely invisible scale.
Light pollution welfare impacts are pervasive but invisible: animals adapted to dark night skies face continuous circadian disruption, navigation failures, and behavioral interference from anthropogenic lighting. Sea turtle hatchlings disoriented toward human lights instead of moonlit ocean are condemned to death from dehydration and predation. Migratory birds collide with lit structures during nocturnal flight. Solutions — shielded fixtures, motion sensors, red-spectrum lighting — reduce harm without eliminating human use of light.