Location and General Description
This ecoregion lies on a vast plateau located on the Atlantic coast of the Mexican state of Quintana Roo. Soils are shallow and rocky and derive from sedimentary rocks, primarily limestone. When limestone suffers weathering, it hardens and forms surface plates known as lajas. The climate is tropical subhumid with summer rains; precipitation levels are high (1300 mm/year). The location of these mangroves on the Yucatan Peninsula makes them very susceptible to hurricanes; in the last 88 years, the region received 11 hurricanes (SEMARNAP 1996).
Two different types of mangroves grow in Quintana Roo. The smaller, appropriately called "pygmy mangroves", are composed of trees no taller than 2 m. The fringe mangrove on the other hand, grows on the edge of coastal lagoons, and sometimes reach 12 m in height. The dominant species in both types are: Rhizophora mangle, Laguncularia racemosa, Avicennia germinans and Conocarpus erectus. The pygmy mangrove also includes Cladium jamaicensis and Elaocharis cellulosa. As in most mangroves, herbaceous vegetation is not abundant in these communities, because it is intolerant of permanent floods (Janzen 1985; Lot et al. 1993).
There are 96 species of mammals in the area, and 322 species of birds, approximately two thirds of which nest in the ecoregion. In addition, 21 of 23 species of the order Ciconiiformes of Mexico inhabit these mangroves (López-Ornat 1992). The mangroves are the second most important place in Mexico for endangered birds such as Jabiru, wood stork, and white ibis and are the most important site for the reproduction of the great white heron. They also receive a number of flamingos during the winter. CONABIO has identified a terrestrial priority site within this ecoregion: Sian Ka’an-Uaymil-Xcalak (Arriaga et al. 2000). There are also two important bird area’s here: Sian Ka’an and U yumil C'eh, A.C. (Benitez et al. 1999).
Mammals found in the mangroves of this ecoregion include jaguar (Panthera onca), puma (Felis concolor), ocelot (Leopardus pardalis), manatee (Trichecus manatus). Birds are the most numerous fauna in the ecoregion with lesser yellow-headed vulture (Cathartes burrovianus), ocellated turkey (Agriocharis ocellata), white-crowned pigeon (Columba leucocephala), black catbird (Melanoptila glabrirostris), reddish egret (Egretta rufescens), anhinga (Anhinga anhinga), clapper rail (Rallus longirostris) cormarant (Phalacrocorax spp.), roseate spoonbill (Ajaia ajaja), greater flamingo (Phoenicopterus ruber), and jabiru (Jabiru mycteria) listed as a sampling. Reptiles are represented by green turtle (Chelonia Mydas), hawksbill turtle (Eretmochelys imbricata), loggerhead turtle (Caretta caretta), leatherback turtle (Dermochelys coriacea), Morelet's crocodile (Crocodylus moreletii), and American crocodile (C. acutus).
Together with the coral reefs, the mangroves constitute the only intact habitat in Quintana Roo. The state is recognized for the low degree of disturbance to native vegetation (Flores-Villela & Gerez 1994). 68% of the state has suffered from some degree of disturbance, but the rest is intact, which explains the well-preserved state of ecosystems in the ecoregion.
The Biosphere Reserve of Sian Ka’an protects a vast area of coastal formations, mangroves, and some patches of dry forests. The reserve is well preserved because it lacks roads making access to the area difficult.
Types and Severity of Threats
It is highly probable, however that mangrove tourism will increase in the next few years, which could cause significant disturbances to native vegetation if appropriate measures are not taken. Exotic species of plants (e.g. Casuarina) have been introduced directly in the coastal ecosystems, without knowledge of the potential effects of these plants on the native flora. In fact, the so-called pine tree (Casuarina) is responsible for displacing plant species that have a specific function as soil retention, including mangrove trees (Rzedowski 1988; Tomlinson 1994). Moreover, soils in this area are rocky, lowering their potential as cultivable lands, and the abundance of flooded lands deters logging activities. One of the main threats to the area is intensive exploitation of wildlife: native villagers have hunted the manatee in high numbers, and extract iguanas, and turtles and other reptiles to sell as food. In general, better law enforcement is needed to control the illegal wildlife trade.
Justification of Ecoregion Delineation
Classification and linework for all mangrove ecoregions in Latin America and the Caribbean follow the results of a mangrove ecoregion workshop (1994) and subsequent report (Olson et al. 1996).
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Benitez, H., C. Arizmendi y L. Marquez. 1999. Base de datos de las AICAS. CIPAMEX, CONABIO, FMCN y CCA. Mexico.
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Tomlinson, P.B. 1994. The Botany of Mangroves. Cambridge University Press. Pp. 166-168.
World Conservation Monitoring Center, Protected Areas Programme. Data sheet for the Sian Ka'an Biosphere Reserve: http://www.wcmc.org.uk:80/protected_areas/data/wh/sianka'a.html
Prepared by: Alejandra Valero
Reviewed by: In process