The island has rainforests, eucalyptus woodland, mangrove forests, wallum and peat swamps, sand dunes and coastal heaths. It is made up of sand that has been accumulating for approximately 750,000 years on volcanic bedrock that provides a natural catchment for the sediment which is carried on a strong offshore current northwards along the coast. Unlike on many sand dunes, plant life is abundant due to the naturally occurring mycorrhizal fungi present in the sand, which release nutrients in a form that can be absorbed by the plants.[6] Fraser Island is home to a small number of mammal species,[7] as well as a diverse range of birds, reptiles and amphibians, including the occasional saltwater crocodile. The island is part of the Fraser Coast Region and protected in the Great Sandy National Park.