Sicily is an often-quoted example of man-made deforestation, which has occurred since Roman times, when the island was turned into an agricultural region. This gradually dried the climate, leading to a decline in rainfall and the drying of rivers. The central and southwest provinces are practically devoid of any forest. In Northern Sicily, there are three important forests; near Mount Etna, in the Nebrodi Mountains and in the Bosco della Ficuzza Natural Reserve near Palermo. The Nebrodi Mountains Regional Park, established on 4 August 1993 and covering , is the largest protected natural area of Sicily; and contains the largest forest in Sicily, the Caronia. The Hundred Horse Chestnut (Castagno dei Cento Cavalli), in Sant'Alfio, on the eastern slopes of Mount Etna, is the largest and oldest known chestnut tree in the world at 2,000 - 4,000 years old.