The Wetlands of Centla and Términos are one of the most valuable ecological landscapes in Mesoamerica. These wetlands are part of a delta system formed by the Mezcalapa, Grijalva and Usumancinta rivers - one of the largest hydrological watersheds in Mexico, with an average yearly runoff of 117,000 million cubic meters. Wetlands comprise approximately 5,000 km2 of the area, making them an important source of biodiversity and primary productivity and one of the 15 most important wetlands worldwide.
The geological region of the Wetlands of Centla and Términos is one of the most important in Mexico, for it is the center of convergence of different tectonic alignments in the Yucatan Peninsula. The landscape is composed of low, undulating hills interspersed with depressions of alluvium deposits. With respect to its edaphological or soil characteristics, the region is composed of well drained soils classified as Gleysol, Solonchak, Vertisol and Fluvisol.
The Wetlands of Centla and Términos are flooded alluvial plains, where hydrological, geomorphologic and pedological processes have created a vast mosaic of , aquatic and terrestrial plant communities, providing critical habitat for various species, and a vital nesting site for marine turtles and migratory birds.
The Wetlands of Centla and Términos were formed as a result of over flooding of the Usumacinta River and changes in slope, thereby creating the floodplains. The only areas of firm land are natural damns or banks up to 1-2 m high and 100-500 m wide. These banks are aligned with those of the major rivers in the region, and cross the Usumacinta River and the San Pedro and San Pablo River and their tributaries.
The Wetlands of Centla and Términos region contains several landforms representative of the Tabasco lowlands: floodplains, palustrine plains, freshwater lagoons, plains made up of a series of berms, and coastal lagoon plains. These comprise about 110 permanent and temporal freshwater bodies in the region.
The weather is characterized by hot and sub-humid climate, with abundant summer rain. Annual temperatures average 26-28oC, with 1200-2000 mm of mean annual precipitation.
The region is characterized by a variety of plant communities. Here, a flora of 569 different species in 118 families has been identified within the mangrove forests and wetlands. The aquatic plant community includes emerging rooted hydrophytes, such as popal, carrizal, tular and rooted hydrophytes with floating leaves.
The mangrove forests that border the Wetlands of Centla and Términos are classified as tropical ecosystems with high biodiversity. These forests are the most representative, developed and extensive in the region. Some of the mangrove trees grow up to 25-30 m and are over 1 m in diameter, making them the most developed within their latitude. The mangroves are characterised by 4 main species: Rhizophora mangle (red mangrove), Aviceennia germinans (black mangrove), Laguncularia racemosa (white mangrove) y Conocarpus erectus (button mangrove).
Eighty-three families of molluscs have been identified, with a total of 207 species. Additionally, 15 species of crustaceans, and 125 species of fish from 101 families have been reported in the region, some of which have an important economic and nourishment value.
The herpetofauna community is comprised of 134 species, including river crocodile, Morelet's crocodile, caiman crocodile, white turtle, white-lipped mud turtle, (Kinosternon leucostomum), freshwater turtles (Pseudemys scripta), giant musk turtle (Staurotypus triporcatus), snapping turtle (Chelidra serpentina), and in lesser numbers, the furrowed wood turtle (Rhinoclemys areeolata). Additionally, hawksbill turtle (Eretmochelys imbricata), green turtle (Chelonia mydas) and Kemp's ridley turtle (Lepidochelys kempi) can be found on Términos lagoon's beaches.
The wetlands also provide a refuge for a variety of migratory and resident bird species. About 33% of the bird population that use the Mississippi migration route is estimated to use the Wetlands of Centla and Términos. Among those species are the Jabiru (Jabiru mycteria), wood stork (Mycteria americana), boat-billed heron (Cochlearius cochlearius), Muscovy duck (Cairina moschata), black-bellied whistling duck (Dendrocygna autumnalis), blue-winged teal (Anas discors), peregrine falcon (Falco peregrinus), roseate spoonbill (Ajaia ajaja) and white ibis (Eudocimus albus).
Overall, 49 families and 328 species of birds have been reported to use the Wetlands of Centla and Términos, 69% of which are year-round residents and 31% are resident during the winter months.
Of particular interest is the Jabiru (Jabiru mycteria), which is in danger of extinction. Jabiru mycteria is one of the biggest species in Mexico and the Americas, with a 3 m wingspan and a height of over 1.5 m.
Of the mammals, 124 species have been reported. Some of these mammals are protected, including manatee (Trichechus manatus), jaguar (Panthera onca), ocelot (Leopardus pardalis), margay (Leopardus weidii), and howler monkey (Alouatta palliate), tapir (Tapirus bairdii), agouti (Agouti paca), spider monkey (A. geoffroyi yucatanensis), Central-American woolly opossum (Caluromys derbianus), Mexican porcupine (Coendou mexicanus) and jaguarondi (Herpailurus yagouaroundi). Additionally, two mammals of particular appeal to the area are the bottlenose dolphin (Tursiops truncatus) and the nutria (Lontra longicaudis), which can be found at the mouth of the Términos Lagoon.
Justification de la Valeur Universelle Exceptionelle
These wetlands were formed by the rivers in the deltaic system, which have created dikes or levees erected by the vertical accretion of sediments. This phenomenon occurs when water rises above the principal canal and the fluvial sediments carried by the water are deposited on the adjacent plain. This arrangement of levees along the rivers explains the geomorphologic characteristics of the Tabasco and Campeche floodplains, which are made up of many distributaries and depressions. This geomorphology determines the level of flooding experienced and establishes a gradient from the drier areas of the region to the perennial lagoons and wetlands.
The costal levees in the delta are another landscape feature of the Wetlands of Centla and Términos. The levees are a system of banks with small crests of 1-3 meters high and separated by depressions 20 to 100 m long. These structures are made up of contiguous succession of banks and depressions created in the last 5,000 years, once the current sea level stabilized at the end of the Holocene transgression. The system of levees dammed the adjacent sea and gave way to the formation of the lagoons perpendicular to the coast line, such as the lagoons of Carmen, Machona, Mecoacán, Pom, Atasta, and Términos.
As the delta progresses into the sea, the gradient and carrying capacity of the rivers decreases. This in turn impedes the flow of the principal canal and forces its currents to overflow at the lowest points, and subsequently changes the trajectories of the distributaries. Thus, Tabasco and Campeche's deltaic plains show signs of innumerable closed fluvial channels, which indicate a series of changes to the hydrologic network that were repeated throughout the Quaternary period.
The Wetlands of Centla and Términos form one of the most productive ecosystems of the world. The ecosystem includes mangrove forests, numerous lagoon estuaries, marshlands, aquatic grasslands, freshwater wetlands, rivers, swamp forests, flooded low forests and freshwater lagoons. These dynamic ecosystems are interconnected, and interact with each other in different ways. They are a source of rich biodiversity, manifested by the innumerable species of plants and animals whose subsistence depends on the wetlands as an important source of water.
The mangrove forests and marine grasslands provide the best example of integrated landscape ecosystems: together they form a mosaic of interrelated and interacting subsystems that link physical and biological processes.
The wetlands contain important flooded areas that give life to a rich biodiversity of plant communities. The system of wetlands and mangrove forests within the area has high structural and functional biodiversity, is a major source of primary productivity, and maintains a high level of water quality along the coastline.
The Wetlands of Centla and Términos form an ecological unit that contains unique habitats indispensable for the conservation of a rich biodiversity. The aquatic communities are the most developed and extensive of the region, and considered the most important source of vascular plants in Mesoamerica, with 569 different species. This spectacular diversity of hydrophytes makes the wetlands home to 328 species of birds.
Within the Wetlands of Centla and Términos, the mangrove forests are considered critical habitat for many species. The mangroves grow up to 25-30 m high with an average diameter of over 1 m, due to the physiological and climatic characteristics of the region, thus becoming one of the most valuable assets for conservation and scientific research.
The wetlands are refuge of diverse species of birds, mammals, fish, reptiles and amphibians considered threatened or at risk of extinction. Examples of these include the Jabiru (Jabiru mycteria), wood stork (Mycteria Americana), peregrine falcon (Falco peregrinus), osprey (Pandion haeliaetus), jaguar (Panthera onca), two howler monkey species (Alouatta pigra y A. palliata), manatee (Trichechus manatus), sea turtles (Caretta caretta, Lepidochelys kempii, Eretmochelys imbricada and Chelonya mydas), among others.
In particular, the Jabiru (Jabiru mycteria) is the largest bird in Mexico and North America, measuring 150 cm in height with a 250 cm wingspan. This bird is considered endangered under the NOM 059-SEMARNAT-2001 in Mexico, and in Appendix 1 of CITES. Only 100 individuals are estimated remain, and the areas under which they are protected in Mexico is diminishing. These areas are restricted to the Protected Areas of Sian Ka'an, and Pantanos de Centla and the Términos Lagoon, the majority of which are located in the Wetlands of Centla and Términos.
Satements of authenticity and/or integrity
This area is recognised by the IUCN under the Usumacinta and Tabasco Laguna Delta. This region of wetlands and/or marine zones has utmost importance and should be considered as a World Heritage. In: R. Ferster and T. Sigaty. 1997. Una visión de conjunto de las áreas protegidas de humedal y marinas en la lista de Patrimonio Mundial. World Heritage Program. IUCN, Gland, Switzerland. The Wetlands of Centla and Términos are part of the Pantanos de Centla Biosphere Reserve and the Laguna de Términos Wildlife Protected Area, created in 1992 and 1994 respectively. The wetland boundaries and regulations that protect them, were established by the General Ecological Balance and Environmental Protection Law.
With respect to the protection of its flora and fauna, the protection and conservation of the wetlands have been reinforced by the Mexican Environmental Law NOM-059-SEMARNAT-2001. This law identifies species of flora and fauna or their populations classified at risk in Mexico. Additionally, this law establishes the criteria for inclusion or changes in category of risk for species or their populations in Mexico, and evaluates their risk of extinction.
A Conservation Management Program was established for each protected area, and published in the Official Journal of the Federation; in 1997 for the Laguna de Términos and in 2000 for Pantanos de Centla. These programs develop criteria and strategies to insure ecosystem conservation in these areas located along the Gulf of Mexico coast.
The Ramsar Convention of Wetlands recognised the Pantanos de Centla Wetlands in 1995, and the Laguna de Términos wetlands in 2004. Ramsar considers these wetlands of international importance. Moreover, the Pantanos de Centla Biosphere Reserve has been included in the World Network of Biosphere Reserves - Man and Biosphere Program (MAB), UNESCO, in September 2006.
Comparison with other similar properties
Wetlands and costal zones are the most productive environments in the world, maintaining important ecological processes and providing vast socioeconomic benefits. They are a source of genetic diversity and are vital in sustaining fisheries. Moreover, they provide critical habitat for vulnerable species, which make them one of the world's most endangered habitat. The Wetlands of Centla and Términos have similar qualities to those of other World Heritage sites. They contribute to the conservation of mangrove forests, protection of threatened and endangered species, and maintenance of hydrological cycles similar to the Everglades in the USA, the Plátano River in Honduras, the Sundarbarns in India and the Gran Pantanal in Brasil.
The Everglades, USA, have exceptional variety of fluvial ecosystems (riverine, lacustrian, estuarine and marine) that provide critical habitat for a large number of birds, reptiles and endangered species such as the manatee (Trichechus manatus).
The Plátano River's coast, Honduras, provides a wide range of habitat containing a high diversity of wildlife. This habitat is critical for many rare and endangered species and is an important source of genetic diversity.
The Sundarbarns, India, have extensive mangrove forests that are well conserved, are part of one of the largest deltas in the world, and are inhabited by many threatened and endangered species.
The Gran Pantanal, Brasil, has a wide diversity of landscapes, ecosystems and species, and demonstrates as well a great geological and hydrological complexity at a national scale. Additionally, it provides critical habitat for many threatened and endangered species, both migratory and endemic.