Kelp forests are a type of marine ecosystem that is present around colonies of kelp; they contain rich biodiversity. Kelp can stretch 2-30 meters or more (up to 60 m in "Macrocystis pyrifera") from their anchors on the sea floor to the surface. It provides a vertical infrastructure that is home to many fish and invertebrate species. Kelp forests also often attract mammalian visitors, including whales, sea lions, sea otters, and SCUBA-diving humans.