By the end of the century, rising CO2 levels will cut fishes’ sense of smell by nearly half, new research finds. And the impaired olfaction will threaten marine ecosystems and our food supply. That’s according to a report Monday in Nature Climate Change.

Fish need a sharp smelling sense because many species spawn offshore, forcing newly hatched fish to find their way home by following their noses. Smell also helps fish locate food, communicate with their pals and recognize predators.