Before revision: Biospheres and the IUCN classification 238x238px|The Province of León in Spain holds the greatest concentration of Biosphere Reserves in the World with nearly 17% of its territory declared.
After revision: Biospheres and the IUCN classification 238x238px|The Province of León in Spain holds the greatest concentration of Biosphere Reserves in the world with nearly 17% of its territory declared.