Such trees really exist, and it is very dangerous to humans. But many do not know that it is the main food to many kinds of animals. Spines instead of leaves have mostly defensive purposes but also used for storage of water for the dry season without rain .. One thing is for sure not to climb on them .. Acacias is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian Acacias are not. They are pod-bearing, with sap and leaves typically bearing large amounts of tannins. The generic name derives from greece, the name given by early Greek botanist-physician to the medicinal tree. This name derives from the Greek word for its characteristic thorns. The species name nilotica was given by Linnaeus from this tree’s best-known range along the Nile river. Acacias are also known as thorntrees, whistling thorns or wattles, including the yellow-fever acacia and umbrella acacias. Until 2005, there were thought to be roughly 1300 species of acacia worldwide, about 960 of them native to Australia, with the remainder spread around the tropical to warm-temperate regions of both hemispheres, including Europe, Africa, southern Asia, and the Americas. However, the genus was then divided into five, with the name Acacia retained for the Australian species, and most of the species outside Australia divided into Vachellia and Senegalia.