The Eucalyptus is primarily used for the extraction of cellulose and its essences have medicinal applications, especially those of E. globulus (Tasmanian blue gum). The wood is hard and freshly cut has a reddish or greenish color that becomes dark with air. It has been used in construction, posts, and more recently to build ecological or similar gateways. Eucalyptus trees are fast growing trees and tall, in fact, they are the tallest trees in the Real Alcázar of Seville, around 35 m though they may reach 60 m. These plants were introduced in the early nineteenth century in Spain so as to obtain large amounts of paper pulp fast. Because of their great adaptability to our climate, their efficiency and absorption of large amounts of water, they were also introduced to clean low marshy land. These short term economic criteria have caused many environmental problems, even in the nearby Doñana National Park, also World Heritage whose protection was initiated, among other things, due to the removal of natural vegetation for the mass planting of this species.