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The evergreen Cork Oak (Quercus suber) is native to the western and central Mediterranean region, but is cultivated elsewhere, e.g., in California and the southeastern United States. The bark covering the trunk and branches (i.e., the cork), which can be 30 cm thick in older trees, is harvested commercially in southwestern Europe. Portugal is the world’s biggest cork producer (and cork is Portugal's most important forest product). At various times, developing commercial cork production in the Mediterranean climate of central California (U.S.A.) has been explored.
Cork Oak is well-adapted to the challenges of the Mediterranean climate, such as high summer temperatures, limited water availability, and fire. Adaptations range from root and water transport system architecture and function to phenology, leaf morphology and physiology, fire-related protective structures (e.g. thick cork), and resprouting ability.
Cork Oak woodlands occupy around 1.7 million ha in the western Mediterranean Basin. Portugal (with 713,000 ha of Cork Oak-dominated forest) and Spain (with 550,000 ha) account for much of this area, but Cork Oak is also present elsewhere in southern Europe (France and Italy), as well as in northern Africa (Algeria, Morocco, and Tunisia).
Throughout the lifespan of a Cork Oak (which may exceed two hundred years), the tree maintains the ability to regenerate the cork layers after each harvest through many cork production cycles, provided the vascular cambium has not been damaged. Although cork has been sustainably harvested and used by humans for thousands of years, the cork industry grew substantially with the broad use of glass bottles in the 17th century, creating a growing demand for cork stoppers. The widespread use of stoppers for glass bottles capitalized on cork’s resistance to deterioration and its high coefficient of friction. (Although cork stoppers are by far the most economically important use of cork, cork has a range of uses, some less broadly familiar than others, e.g., pruned cork oak tree branches or bark provide a highly desirable media for growing orchids and other epiphytes.) In recent years, as the wine industry has been promoting alternatives to cork stoppers, environmentalists have become increasingly concerned that reduced demand for cork may threaten the sustainable cork industry, which has been relatively effective in protecting the unique cork oak ecosystems of southwestern Europe and North Africa. WWF has initiated a campaign to promote the use of cork and to protect the Cork Oak landscapes.
(Brooks 1997; Sibley 2009; Oliveira and Costa 2012 and references therein)