Consisting of a series of lagoons, the Enriquillo wetlands ecoregion represents the remains of an ancient marine channel that divided the island of Hispaniola (Dominican Republic and Haiti) into two paleo-islands more than 5000 years before present. The largest lake in this ecoregion, Lake Enriquillo in the Dominican Republic is the largest and most hypersaline lake in all of the Antilles. It consists of a depression that is approximately 44 metres (m) below sea level, surrounded by thorny subtropical mountains and dry forests of great biological importance. The lake surface is the lowest topographic point in the entire Caribbean Basin.
This lake is home to the largest population of American crocodile (Crocodylus acutus), although currently its the populations of this reptile are at risk. It is also the habitat for the Iguana cornuda (Cyclura cornuta), which is endemic to the island of Hispaniola and the Iguana de Ricord (C. ricordi), the latter being at risk of extinction due to its limited distribution. In addition, it is a resting, feeding, and reproductive location for the Greater flameningo (Phoenicopterus ruber) and many other species of migratory birds. There are also other smaller lakes near Enriquillo that hold extremely important biota, including the Manatí in lake Saumatre and the island's endemic Hispaniolan slider (Trachemys decorata), particularly in Lake Rincón .
Location and general description
Lake Enriquillo in the southwestern portion of the Dominican Republic is located at 18°30'N and 71°40'W, occupying the lowest part of the basin known as Hoya del Lago Enriquillo between the Neyba and Bahoruco ranges, and has geomorphological characteristics that are unique in the Caribbean region. It is the largest lake in the Caribbean Basin; it is approximately 35 kilometres (km) long and about twelve km wide and has a maximum depth of 24 m. There are three islands on the lake: Cabritos Island, Islita, and Barbarita Island; however, as of the year 2015 only Cabritos is above water, since the other two islands have become totally submerged due to rising lake levels of the last two decades. Cabritos is the largest island and is approximately twelve kilometres (km) long and an average of two km wide. Water temperature in the lake varies from 23.9 to 29°C, salinity is twice that of the sea and its waters are sulfurous. Rocks in the zone are coral limestones and remains of mollusk shell because in past geological eras the ecoregion corresponded to the marine channel that divided the island of Hispaniola into two paleo-islands. Annual precipitation in this ecoregion is between 400 and 500 millimetres (mm), representing one of the most arid areas on the island. Hurricanes and tropical storms are generally beneficial to the lake biota, by providing a surge in freshwater input.
The lake is fed by subterranean and surface influents, but its volume only increases significantly with the hurricanes, cyclones, and tropical storms that lash the island. In the Dominican Republic, other less important lakes with origins similar to those of Lake Enriquillo are Rincón Lagoon (Cristóbal or Cabral), Lake Caballero. Rincón Lagoon is 47 square kilometres (km2) and is the largest surface body of freshwater (albeit hypersaline) in the Dominican Republic. In Haiti, Saumatre Lagoon (Étang Saumatre or Lago Azuei) is the country's largest lake. It occupies another concavity ten km west of Lake Enriquillo, separated from it by the Jimaní anticline. It covers an area of approximately 120 km2 and is located in the far east of the Cul-de-sac Valley. Another smaller lake on the Haitian coast and close to Saumatre is Trou Cayman, measuring approximately 15 km2.
The shores of Lake Enriquillo, as well as the three islands on the lake and the smaller lagoons, have dry subtropical forest and subtropical thorny mountain that is very valuable because it has some species with very restricted distributions. Vegetation consists chiefly of bayahonda (Prosopis juliflora), cambrón (Acacia macracantha), Lignum vitae (Guaiacum officinale), almácigo (Bursera simarouba), baitoa (Phyllostylon brasiliensis), and spiny shrubs (cactáceas) such as the guazábara (Cylindropuntia caribaea), cayucos (Pilosocereus polygonus), melón espinoso (Melocactus lemairei), alpargata (Opuntia moniliformes) and bombillito (Neomammillaria prolifera) . Common palm trees are the Hispaniolan endemic Yarey (Copernicia berteroana) and the Florida cherry palm (Pseudophoenix vinifera). In the wetter areas the baría (Callophylum calaba), Pitch apple (Clusia rosea), Mangle rojo (Rhizophora mangle), and Mangle botón (Conocarpus erecta) predominate.
An inventory of the flora on Cabritos Island shows that there are 105 species of plants, primarily herbaceous (57 species), followed by trees, cactus, shrubs, and creepers; with regard to fauna, there are 292 vertebrates in the ecoregion. To be noted are the limited numbers of palm and epiphyte species. More than ten percent of the species on Cabritos Island are endemic to Hispaniola or the ecoregion. This habitat of subtropical dry forest and subtropical thorny montane vegetation is of great interest due to the abundance of xerophytic vegetation on the island of Hispaniola.
Both terrestrial and aquatic fauna in the ecoregion are also of great biological value. In the wetter areas, we find amphibians like the Cane toad (Rhinella marinus); the Endangered Hispaniolan endemic Ruth's robber frog (Eleutherodactylus ruthae); the Vulnerable Hispaniolan endemic Tiburon whistling frog (Eleutherodactylus wetmorei); and the Vulnerable Hispaniolan endemic Gunther's Caribbean toad (Peltophryne guntheri).
Within the ecoregion there are numerous reptile taxa, with 13 species of snakes (Epicrates spp., Uromacer catesbyi, and others); the Endangered Haitian endemic Thomas' worm snake (Typhlops hectus) occurs in the Enriquillo Wetlands. Of the two iguana species, Ricord's rock iguana (Cyclura ricordi) is critically at risk of extinction and lives only in this lake, in the Jaragua National Park. Also to be noted is the largest snake on the island, the Hispaniola Island endemic Hispanioa racer (Alsophis anomalus). Aquatic reptiles are represented by the American crocodile (Crocodylus acutus), the Hispaniola endemic turtle the Hispaniolan slider or "jicotea" (Trachemys decorata) endemic to the island; with its largest population in Lake Rincón. Current populations of American crocodile on the island of Hispaniola are only found on Lake Enriquillo, Manzanillo Bay, and Lake Saumatre (Haiti) and Lake Enriquillo has the largest natural population of this species in the world (estimated population of 400).
Fish fauna in the Enriquillo Wetlands are represented by the Hispaniola endemics Blackbanded limia (Limia melanonotata); the Hispaniolan gambusia (Gambusia hispaniolae); and the Hispaniola pupfish (Cyprinodon bondi). The Dominican Republic endemic Sulfur limia (Limia sulphurophila) is also found in the Enriquillo basin, chiefly in sulfur springs influent to the Lake Enriquillo.
Of the 35 species of non-aquatic birds reported in the Enriquillo Wetlands, the most representative are the Broad-billed tody (Tordus subulatos), Burrowing owl (Athene cunicularia), the Near Threatened Hispaniolan palm crow (Corvus palmarum), and Vervain hummingbird (Mellisuga minima). Of the 62 species of aquatic birds present here, many of them migratory, one notes the Greater flamingo (Phoenicopterus ruber), Roseate spoonbill (Ajaia ajaja), Green-backed heron (Butorides striata), Lttle blue heron (Egretta caerulea), Tricoloured heron (Hydranassa tricolor) and Bahama pintail (Anas bahamensis).
Terrestrial mammals are represented by the greater bulldog bat (Noctilio leporinus) and Mexican free-tailed bat (Tadarida brasiliensis). It is important to emphasize the presence of Sea cows or Manatees (Trichechus manatus) in Lake Saumatre. A number of bat species are found in the Enriquillo wetlands, an example of which is the Brazilian free-tailed bat (Tadarida brasiliensis).
This ecoregion is outstanding in regional terms, with a vulnerable conservation status and maximum conservation priority (I). There is sufficient taxonomic and geographic data on the ecoregion to implement an appropriate conservation strategy. The succulent vegetation endemic to this area is extremely vulnerable to human activities and thus presents a plant community at risk.
There are three National Parks in the ecoregion with IUCN management category II, all of them on the Dominican Coast. In 1974, the Cabritos Island National Park was created with an area of 26 km2. In 1995, the Enriquillo Lake National Park was created with 320 km2, and in 1997 Rincón Lagoon's category was changed from Wildlife Refuge to National Park, increasing the protected area of the park to 240 km2. Enriquillo Wetlands has been given the ecocode NT0903 by the World Wildlife Fund. The ecoregion is classified within the Flooded Grasslands and Savanna biome in the Neotropical Realm.
One of the most significant threats to Lake Enriquillo is its extremely high salinity at certain times of year as a result of the diverting of freshwater influent by pipes emptying into the lake for use in the area's agriculture. Another threat, particularly to crocodiles, is indiscriminate hunting as well as altered habitat due to reduced vegetation. Also detrimental is the drilling of tubular wells in communities close to the lake, overgrazing of livestock, and gathering of firewood. The most pressing causes of the degradation of Lake Saumatre and its surroundings involve the inflow of human and animal waste, sediments coming from mountain rains, contamination from detergents and other chemicals and the burning of trees. Insular ecosystems are very fragile and once altered it is difficult for them to revert to their original state.
There is only a single ecoregion tangent to the Enriquillo wetlands; in fact, that ecoregion, the Hispaniola dry forests totally surrounds and engulfs the Enriquillo wetlands.
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CitationFund, W., & Hogan, C. (2015). Enriquillo wetlands. Retrieved from http://www.eoearth.org/view/article/51cbedba7896bb431f69377c
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