From the World Heritage inscription:
Everglades National Park is the largest designated sub-tropical wilderness reserve on the North American continent. Its juncture at the interface of temperate and sub-tropical America, fresh and brackish water, shallow bays and deeper coastal waters creates a complex of habitats supporting a high diversity of flora and fauna. It contains the largest mangrove ecosystem in the Western Hemisphere, the largest continuous stand of sawgrass prairie and the most significant breeding ground for wading birds in North America.
It is amazing how abruptly the urban Miami area ends and how fast the Everglades begins. The Everglades is a sea of grass and if you visit, you will not have difficulty finding the star of the park: the alligator. I saw dozens of alligators sunning themselves on bike paths and in the water near the road. Despite their appearance, they really pose no threat to humans. If you are ever in South Florida, take a day to visit the Everglades as it is the premier natural attraction in the state.