Angelfish photo: Florida Keys National Marine Sanctuary

The Keys environment is a magnificent array of coral reefs, seagrass beds, shallow-water flats, mangrove islets, and hardwood hammocks extending from the southern tip of the Florida mainland to the remote Dry Tortugas. Home to the world's third-largest coral barrier reef--the marine equivalent of a tropical rainforest--Keys' waters sustain more than 6,000 species of marine plants and animals. A remarkable diversity of threatened and endangered species, including the tiny Key deer, West Indian manatee, American crocodile, and five species of sea turtle, depend on the archipelago. The islands themselves still harbor remnants of once-extensive tropical hardwood hammocks and pine forests.

"I doubt that anyone can travel the length of the Florida Keys without having communicated to his mind a sense of the uniqueness of this land of sky and water," wrote renowned environmentalist Rachel Carson in The Edge of the Sea. "This world of the Keys has no counterpart elsewhere in the United States, and indeed few coasts of the earth are like it."

Did You Know? The amazing American alligator can grow to be up to 18 feet long and weigh up to 500 pounds. As a result of unregulated hunting, this species almost became extinct. Thanks to dedicated conservation efforts the American alligator was removed from the endangered species list in 1987.

The waters of Florida Bay - including lush expanses of the Northern Hemisphere's most extensive seagrass meadows, an essential nursery and feeding grounds for spiny lobster, queen conch, dolphins and more than 100 species of fish - link the Keys to the Everglades. One of the planet's only rainfall-driven wetlands, the Everglades are the only site in the Western Hemisphere recognized as a World Heritage Site, a UNESCO Biosphere Reserve, and a RAMSAR Wetland of International Importance. This famed "River of Grass" originally flowed from the Kissimmee Chain of Lakes just south of Orlando to Florida Bay and the Keys, creating South Florida's rich mosaic of sawgrass prairies, sloughs, tree islands, hardwood hammocks, cypress stands and coastal mangroves.

These diverse Everglades habitats sustain more than 11,000 species of seed-bearing plants (25 different orchids alone), 350 kinds of birds, 150 types of fish, and innumerable invertebrates. Among those species that make their home here are alligators, pygmy rattlesnakes, tree snails, zebra butterflies, least killifish, snail kites and elegant wading birds - herons, egrets, wood storks, spoonbills, ibises - that once formed spectacular colonies numbering in the hundreds of thousands: enough birds, when taking wing, to blacken the sky. South Florida also provides habitat for the Florida panther, of which fewer than 90 are thought to survive in the wild, making it one of the most critically endangered large mammals in the world.