Artificial light at night disrupts the behavior and physiology of nocturnal and crepuscular wildlife, causing welfare problems across many species.
Light pollution causes both direct welfare harm and ecosystem-level disruption. Sea turtle hatchlings crawling inland toward artificial lights instead of the ocean die of dehydration or predation - a direct welfare consequence of lighting choices near nesting beaches. Migratory birds killed in building collisions number in the billions annually. Nocturnal mammals, reptiles and insects whose entire behavioral ecology evolved in darkness are forced to cope with an artificial environment for which they are not adapted. Chronic disruption of melatonin cycles and circadian rhythms causes physiological stress with welfare consequences. The good news is that wildlife-friendly lighting - shielded, amber-spectrum, motion-activated - dramatically reduces impacts.