 The cultivation of plants that give textile fibers (Cannabis sativa, Linum usitatissimum), the cultivation of sugar beet ("Beta vulgaris"), cereals, potatoes, orchards, vineyards and olive groves have almost replaced the natural vegetation.The actions of man since Roman times have resulted in the destruction of most of the lowland forests and hills, the expansion of pastures, and the extinction of many species and in the introduction of exotic species which are then naturalized.For example, the Indian fig opuntia (Opuntia ficus-indica), is now common in the warmer parts of the Southern Italy.