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Sian
Ka'an Biosphere
reserves are a new concept in ecological terminology, intending
to preserve the flora, fauna and ecosystems of an area while still
satisfying the needs of the local population. In biosphere reserves,
conservation is not conceived of as prohibiting use of the land,
but rather as the rational and long term sustainable use of the
natural resources.
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Facts About Sian Ka’an
The Sian Ka’an Biosphere Reserve was established on the 20th of January 1986 by presidential decree (under President Miguel de la Madrid Hurtado) and became part of UNESCO’s Man and the Biosphere (MAB) program that same year. In 1987 the reserve was declared a UNESCO World Heritage Site. As part of the MAB program, Sian Ka’an faces the greatest challenge of conservation: to find a way to integrate human activities without compromising other forms of life contained within its boundaries. Sian Ka’an is approximately 1.3 million acres in size and spans 120 kilometers from north to south (comprising almost one third of the Caribbean coast of Mexico). In 1994 an area of over 200,000 acres to the south of the Reserve was named a Protected area of Flora and Fauna of Uaymil, increasing the continuous area of protected land.
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The reserve contains three large core zones where human activity is limited by permission to scientific research. These areas, known as the Zonas Nucleares of Muyil, Cayo Culebras, and Uaymil, cover a total area of almost 700,000 acres. Low-impact human activities and sustainable development occur in the area of the reserve known as the buffer zone. The human population is estimated at 2,000 inhabitants, the majority of which are located in the coastal regions, especially in the fishing villages of Punta Allen and Punta Herrero. Approximately one percent of the land within the reserve is privately owned. There are five entrances to the reserve, located at Pulticub, Santa Teresa, Chumpón, Chunyaxché and Chac Mool. Guards employed by the governmental SEMARNAP organization are stationed at every entrance to enforce the Reserve regulations. “Sian Ka’an” is translated from Mayan as “where the sky is born” or “gift from the sky”. The reserve is thought to have been inhabited in the pre-Classic and Classic periods as part of the chieftanships of Cohuah and Uaymil. There are twenty-three known archeological sites inside the reserve. Discoveries of human remains, ceramic pieces, and other artifacts have been dated up to 2,300 years old. The northernmost section of Sian Ka’an contains what is thought to be an ancient trade route through lagoons and mangrove channels between the cities of Tulum and Muyil. Parts of what is now the Reserve were once areas of chicle production and trade through the middle of the twentieth century, and the fishing industry is still one of the most important economic activities of the Reserve’s population. Common species include spiny lobster (Palinurus espinosa) tarpon, grouper, permit, nurse shark, hammerhead, black tipped shark, and snapper. Tourism is a another source of income for fishermen in Sian Ka’an, hired to run boat trips to see the reefs and lagoon systems. Approximately 36,000 tourists entered the reserve in the year 2000, and those numbers are expected to increase significantly for the year 2001. There is no fee charged to enter the Reserve.
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Geographical Information The Reserve is situated on the Yucatan Peninsula, which is an area of limestone bedrock with very little change in elevation and no real surface rivers. The annual rainfall in this area is between 44 and 48 inches, approximately seventy percent of which falls in the rainy season between May and October. Much of the rainfall filters through the sandy soils and limestone bedrock and is contained within an underground aquifer which extends throughout the entire peninsula. A large portion of the Reserve is wetland areas, which become inundated during the rainy season and contain a superficial, nutrient poor, calciferous topsoil. Habitats found in Sian Ka’an
Coral Reef The boundaries of the Sian Ka’an Biosphere Reserve include 110km of the second largest barrier reef in the world, which extends onward past Belize and Honduras. The reef is home to many important and several endangered species. Uncontrolled development along the Caribbean coast of Mexico has placed the reef in grave danger, as it is easily damaged and not so easily restored.
Beaches The beaches of Sian Ka’an constitute a very important habitat and nesting grounds for many species of wildlife, as well as serving as an important transition between land and ocean. Most notably during the months of May through August, the beach is a nesting ground for 4 endangered sea turtle species that have lost important nesting sites along many parts of the Caribbean coast. Dunes The coastal dune is an important protector of inland habitats, especially during storms. Coastal vegetation includes Coccoloba uvifera, Tournefortia gnaphalodes, Suriana maritima, Sesuvium portalacastrum, Ambrosia hispida, Ipomoea and many other species. (For a more complete list, refer to flora link)
Wetlands Mangroves, savannas, swamps and marshes are all included within the classification of “wetland”. Water plays a vital role in the existence of each of these habitats, whether it be fresh, salty, or brackish. Wetlands line the coast of Sian Ka’an, playing an important protective role as a type of buffer between the ocean and the land that can absorb the impact of storms. Wetland areas contain immense biological diversity and are home to a number of endangered species. Evident in all inundated wetlands is a conglomeration of algae known as periphyton that is believed to play an important role in the dissolution of calciferous soils, as well as being an invaluable source of food for many species of fish, mollusks, and insects.
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Mangroves Four species of mangrove line the coastal areas of Sian Ka’an. The mangrove communities are critical for the survival of many species of fish, birds, insects, reptiles, and other plants. Many species of mangrove filter contaminated water and trap loosened sediment, making them protectors of the coral reef and other littoral habitats. The mangrove species found within Sian Ka’an are Rhizophora mangle (red mangrove), Avicennia germinans (black mangrove), Laguncularia racemosa (white mangrove), and Conocarpus erectus (buttonwood mangrove).
Savannas Coastal savannas are large areas of low-lying land with sparse, oxygen-poor soil that is inundated throughout much of the year. As few tree species have adapted to these conditions, savannas are dominated by species of grass, reeds, and rushes that rarely exceed three meters in height. Inland savannas contain shrubs and occasional trees in addition to grass, are drier and have a lower salinity. These environments are in danger of natural fires during the dry season.
Cenotes or Sink holes Fresh water contained in the Yucatan’s underground aquifer carves away at the limestone above, weakening it and eventually causing it to give way. The result of this phenomenon is a unique habitat known as a cenote or sink hole. Many cenotes remain connected with the aquifer and with other cenotes through underground passageways. Occasionally, however, cenotes are found to be completely isolated from other bodies of water and may contain fish and other wildlife that have evolved over time into completely distinct species.
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Hummocks Petenes, or hummocks, are isolated areas of forest from several meters to several kilometers in diameter that are surrounded by swamps or inundated savanna land. These formations are found only in Cuba, the Florida Everglades, and the Yucatan Peninsula. There is often a cenote at the center of the hummock, which is surrounded by concentric circles of vegetation, from hardwood trees to grasses and rushes. Common species include cedar, mahogany, and zapote in the center ring, which are surrounded by various palm trees and the poisonwood tree, and eventually mangrove, rushes, and grasses. Many species of fauna live in hummocks, from insects to reptiles, mammals, and birds.
Tasistales A tasistal is a concentrated strip found within savanna land that contains the tasiste palm (Acoellorraphe wrightii), the grass Cladium jamaicensis, and occasionally other plant species such as poisonwood (Metopium brownei), buttonwood mangrove (Conocarpus erectus), and cocoplum (Chrysalobanus icaco). The tasiste palm is extremely fire-resistant, and will survive natural fires that often strike savanna.
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Fresh water lagoons The fresh water lagoons of Sian Ka’an are supplied with fresh water from the subterranean aquifer by small springs or cenotes. Found mostly inland, the fresh water filters toward the ocean in channels or through the surrounding wetlands. The lagoons are home to a number of species of fish and vegetation not found in the coastal areas.
Brackish water lagoons Ocean water and fresh water from inland and the aquifer meet and mingle in the brackish water lagoons along the coast of Sian Ka’an. These lagoons are lined with salt tolerant mangrove and grass species which provide a home to fish and mollusk species that make the area an attractive nesting ground for wading birds and residence of two crocodile species, Crocodylus moreletii and C. acutus. Low tropical forest Many of the mammal species found within Sian Ka’an reside within the low tropical forest land which is located in the westerly portions of the reserve. The forests contain many hardwood species, including chechem, chicozapote, mahogany, tsalam, and other valued hardwoods. The environmental importance of these areas is increased by the international demand for hardwood that is pressuring many countries in the neotropics. |
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