Firefly populations are declining globally from light pollution, habitat loss, and pesticide use, with their bioluminescent courtship displays disrupted by artificial light at night affecting mating success.
Firefly welfare centers on their ability to complete reproductive behavior - the flash signaling that enables mating is a fundamental biological need. Light pollution that masks female flash responses effectively prevents males from finding mates, reducing reproductive success without any direct physical harm. The welfare of individual fireflies that cannot successfully mate in light-polluted environments may be limited given their short adult lifespan, but population-level impacts from reproductive failure are profound. Fireflies as a potential sentience consideration are uncertain given their simple nervous systems, but their ecological value and beauty justify conservation regardless.