The South Florida rocklands ecoregion, in the tropical and subtropical moist broadleaf forests biome, occurs in southern Florida and the Florida Keys in the United States, where they would naturally cover an area of 2,100 km2 (810 sq mi). These forests form on limestone outcroppings with very thin soil; the higher elevation separating them from other habitats such as coastal marshes and marl prairies. On mainland Florida, rocklands exist primarily on the Miami Rock Ridge, which extends from the Miami River south to Everglades National Park. South Florida rocklands are further divided into pine rocklands and rockland hammocks.