CENTURIES AGO, manatees were symbols of dreams. Early explorers mistook them for mermaids. Now the gentle mammals are symbols of nightmare. Last year 1,100 manatees—around a seventh of those in Florida—died, the worst year since record-keeping began in the 1970s. Pollution-fuelled algal blooms have killed the seagrass they eat, leaving many to starve to death. Concerned researchers on the east coast Indian River Lagoon have started to feed manatees lettuce to sustain them. The manatees’ deaths shocked Floridians, but they are an “even bigger event than people realise, because it means that the environment has reached a tipping point”, says Craig Pittman, author of “Oh, Florida!: How America’s Weirdest State Influences the Rest of the Country”.