Sian Ka'an is a biosphere reserve in the municipality of Tulum in the Mexican state of Quintana Roo. It was established in 1986 and became a UNESCO World Heritage Site in 1987.
With the participation of scientists, technicians, students, fishermen, farmers, rural promotors and administrators, together with regional and international partners, have successfully carried out more than 200 conservation projects basing all conservation actions on scientific and technical information for planning and implementing environmental policies and the proposal of viable solutions for sustainable use of natural resources and focusing their efforts established within eight protected natural areas that include the reefs of Banco Chinchorro, and Xcalak at South of Quintana Roo, Sian Ka'an Biosphere Reserve, Cancun, the island of Cozumel that is located in front of Xcaret and Contoy Island up North, covering 780,000 acres (3,200 km2). These areas lie in parts of all seven Caribbean Sea coastal municipalities of the state, with the largest part being in eastern Felipe Carrillo Puerto Municipality, where the vast majority of Sian Ka'an Biosphere Reserve lies.
Part of the reserve is on land and part is in the Caribbean Sea, including a section of coral reef. The reserve has an area of 5,280 km².
The reserve also includes some 23 known archaeological sites of the Maya civilization including Muyil.
Within the Amigos de Sian Ka'an project objectives are the identification, protection and management of additional areas with high biodiversity value as well as those critical for maintenance of the life cycles of endangered, threatened and migratory species in the Riviera Maya and providing environmental education through books, journals and pamphlets and giving technical assistance and training to Mayan communities working with ecotourism.
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Coordinates: 19°30′N 87°45′W / 19.500°N 87.750°W