The Great Barrier Reef World Heritage Area has been divided into 70 different areas. These are called bioregions. Each bioregion has its own special plants and animals. There are 30 reef bioregions, and 40 are non-reef bioregions. In the northern part of the Great Barrier Reef, there are ribbon reefs and deltaic reefs. These kinds of reef do not exist in the rest of the Great Barrier Reef system.