The number of manatees in Florida has increased greatly since they were protected, so the question is whether to designate them as "threatened" rather than "endangered".

A species can't survive if its habitat is wiped out. The US often protects one endearing endangered species as a way of protecting the whole ecosystem, including many other species, that it lives in. It seems that manatees are an example of this. The existing restrictions enable manatees to coexist with human water activities, but this redesignation would permit land development that could wipe out all of them.