Greater Antilles mangroves
Because of their location on large islands, the Greater Antilles mangroves support relatively high levels of endemic flora and fauna, and are often part of complex assemblages of habitats that are as diverse as the conditions found in various parts of these islands. Mangroves are also a particularly important feature of Caribbean shores, as they form a barrier that helps to protect the coastal area from tropical storms and hurricanes that some observers think have become more intense in recent decades. They are also important as barriers against salinization of coastal soils and groundwater and support fisheries upon which most of the population is dependent.
Location and General Description
The Greater Antillean mangroves vary in their ecological development, from scrub vegetation found as coastal fringe, to well developed stands with heights of up to 25 meters (m) found at river mouths. This variation depends on levels of rainfall and freshwater input from riverine and groundwater systems, the tidal range, salinity levels, degree of shoreline protection from high wave energy, the accumulation of fine-grained sediments, and localized conditions in the various parts of these islands. For example, mangrove distribution is often restricted by the lack of large rivers, and they are primarily found in the low depositional areas of the coastline that have a constant flow of both tidal and fresh water. Mean rainfall varies throughout the region, ranging from 800 millimeters (mm) per annum in parts of Jamaica, to over 5000 millimeters in parts of Puerto Rico. The mean tidal range also varies, but is in the vicinity of .34 meters, the level found in Cuba, where springtides reach up to .90 meters. Offshore salinity levels vary because of the mixing of Atlantic waters with the massive outflows of the Orinoco and Amazon Rivers from South America.
Depending on localized conditions, various assemblages of mangrove species may be found as parts of a complex mosaic of terrestrial and marine habitats that include wetland forests and marshes, peatlands, sedge marshes, riparian swale, swamp and riparian forests; aquatic vegetation and coastal dunes, as well as seagrass beds and coral reefs. Mangrove communities found in "morasses" or large wetland areas may be in basins isolated from the sea by sand barriers, and are usually associated with various forms of swamp vegetation. Those found along rocky coasts are typically associated with coral reefs and seagrass beds. Although they tend to be found where fine grained sediments have accumulated, in Discovery Bay in Jamaica, mangroves are also found growing on limestone substrates inhabited by algae and molluscs. There, they support large communities of plants and animals that attach to mangrove roots.
Situated on large islands, the Greater Antillean mangroves have relatively high levels of endemic wildlife, including the Cuban Crocodile (Crocodylus rhombifer) found on the Zapata peninsula of Cuba, and several bird taxa. Some protected areas that are important centers of both floral and faunal endemism are the Desembarco del Granma National Park, also a World Heritage Site, where mangroves are part of an assemblage of habitats that include coral reefs and sea grass beds, that are all located within a system of marine terraces that create altitudinal and climatic diversity within a small area. Endemic flora are also found in the Black River Lower Morass in Jamaica, which contains mangroves and is important habitat for both wetland and migratory birds.
Coastal mangroves together with coral reefs and seagrass beds are often interdependent and, together, form a highly diverse and structurally complex ecosystem in which the reefs act as a barrier that shelters seagrass beds and mangroves from high wave energy and strong coastal currents typical of the Caribbean environment. These in turn provide foraging and nursery habitats for many reef species. At La Parquera in southwestern Puerto Rico, large seagrass beds consisting of turtle grass Thalassia testudinum can be found in the channels between coastal fringe mangroves. Among the species found here are the Upside-down Jellyfish (Cassiopeia frondosa), Cushion Sea Star (Oreaster reticulatus) and the Donkey Dung Sea Cucumber (Ludwigothuria mexicana).
Mangrove species found in this ecoregion are: Red mangrove (Rhizopora mangle), Black Mangrove (Avicennia germinans, White Mangrove (Laguncularia racemosa), and the Buttonwood Mangrove (Conocarpus erectus). R. mangle is generally found at the seaward fringe and in the margins of creeks and lagoons, and A. germinans and L. racemosa further behind R. mangle, followed by C. erectus. Dwarf R. mangle can also be found far from the coast in association with C. erectus. Mangroves are associated also with various seaweeds, and extensive prairies of seagrass Thalassia testudinum can often be found adjacent to mangrove roots. Some species associated with C. erectus forests in Cuba are: Batis maritima, Dalbergia ecastaphillum, Acrostichum aureum, and Bucida sp. In the Black River morass in Jamaica, there are assemblages of Rhizopora-Conocarpus, a Cladium-Conocarpus assemblage in the transition between mangroves and freshwater swamp, and a mix of Rhizopora, Avicennia, Laguncularia, and Conocarpus in the back of a coastal barrier.
Among the endemic birds associated with mangroves are the Cuban Green Woodpecker (Xiphidiopicus percussus), the Jamaican Tody (Todus todus), and an endemic subspecies of the mangrove warbler (Dendroica petechia gundlachi), as well as the Caribbean Clapper Rail (Rallus longirostris caribaeus). Endemic mammals and reptiles include several species of Hutia (Capromys spp) found in Cuba, and the Anolis Lizard (Anolis spp.).
Other birds most associated with this mangrove ecoregion include: Spotted Sandpiper (Actitis macularia,), Roseate Spoonbill (Ajaja ajaja), Cattle Egret (Bubulcus ibis), Striated Heron (Butorides striatus). Belted kingfisher Ceryle alcyon, Mangrove cuckoo Coccyzus minor, White crowned pigeon Columba leucocephala, Crescent-eyed pewee Contopus caribaeus, Puerto Rican pewee Contopus portoricensis, West-Indian whistling duck Dendrocygna arborea, Mangrove warbler Dendroica petechia gundlachi, Little blue heron Egretta caerulea, Reddish egret Egretta rufescens, Snowy egret Egretta thula, Common moorhen Gallinula chloropus, Least bittern Ixobrychus exilis, Wood stork Mycteria americana, Yellow-crowned night heron Nyctanassa violacea, Black-crowned night heron Nycticorax nycticorax, Greater flamingo Phoenicopterus ruber; Pied-billed grebe Podilymbus podiceps, Greater Antillean Grackle Quiscalus niger, Clapper rail Rallus longirostrus caribaeus, Northern waterthrush Seirus noveborensis, Jamaican tody Todus todus, Black-whiskered vireo Vireo altiloqua, Cuban Green Woodpecker Xiphidiopicus percussus,
Mammals which frequent these mangroves include: several species of Hutia: Capromys pilorides, C. sanfelipensis, C. garridoi, C. angelcabrerais, C. auritus and West Indian manatee Trichecus manatus .
Estimates of total mangrove area in this ecoregion are: 5569 square kilometers (km2) in Cuba or 4.8%; 134 km2 in Haiti; 325 km2 in the Dominican Republic; and 106 km2 in Jamaica. Between 1812 and 1959 when their importance began to be recognized, forest cover in Cuba decreased from 90 to 14%. Since 1980, 25,700 hectares (ha) of mangroves have been replanted and management plans are being developed for 15 protected areas. In Puerto Rico, over 75% of mangroves were destroyed in the 1970’s to reduce malarial mosquitoes, and were drained and filled for urban development, but have also increased in the 1980’s. The Jamaican government intends to establish a chain of marine protected areas around the island that include mangrove areas, and to declare 14 national parks, marine parks and marine protected areas within the decade.
Types and Severity of Threats
Mangroves are exploited for timber, fuel-wood and charcoal, shrimp and lobster which are exported, and oysters and other fish sold in domestic/international markets. Mangrove bark is also in demand for leather tanning, and crocodiles are hunted for their skin. More general environmental problems that have impacts on mangroves include expansion of tourism facilities in the coastal areas, development of ports and harbors, expansion of agricultural and urban areas that increase the transport of sediment to coastal areas, discharge of mining, industrial and domestic wastes, and damming and diversion of rivers which decreases freshwater inputs to mangroves. In Jamaica, forest clearance in coastal watersheds brought about the erosion of 80 million tons of topsoil a year. This is believed to be reducing the flows of many rivers that mangroves rely upon for freshwater inputs. Because of prevailing wind patterns, Jamaican mangroves are also vulnerable to oil spills.
A particular concern in the Caribbean is an apparent increase in the frequency and intensity of tropical storms and hurricanes that may be associated with climate change, and which damage mangroves. The two strongest hurricanes on record for the Western Atlantic, Allen and Gilbert, both occurred in the 1980s, and George occurred in 1998.
Topic Editor for this article is J. Emmett Duffy
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