Location and General Description
This ecoregion is perhaps best characterized by estuarine conditions most conducive to mangrove development because of a salinity gradient ranging between 34 and 36%, created by massive outflows from the Amazon and Orinoco rivers, particularly during the rainy season. Much of this water flows around the islands of Trinidad and Tobago and enters the Caribbean sea through the islands of the Lesser Antilles. The climate is tropical humid, with mean annual rainfall of 1556 mm (Laydoo et al, 1998; Agard and Gobin 2000).
Mangroves of this ecoregion range in height from 3-4 m scrub to tall basin forests of Avicennia germinans that reach 23m in height, and Rhizopora racemosa at 17m height. They are found in a variety of conditions ranging from freshwater to hypersaline, and in association with a variety of other habitats. Mangroves are found on all coasts of the island of Trinidad and are predominantly estuarine but they are also found in association with lagoons, in coastal fringe areas, in basins, and around salt ponds. Various types may also be interconnected by small channels, as occurs between the fringe mangroves around the Bon Accord lagoon, and the basin mangroves found behind beach barriers in the Buccoo Bay, for which a small channel to the lagoon provides the only drainage outlet. Along the Atlantic coast and the Gulf of Paria they are associated with complex wetland systems and perennial river mouths. Although coral diversity is lower than islands further north in the Caribbean because of lower salinity levels, mangroves are also found in association with coral reefs and sea-grasses.
7 mangrove species are reported for the area: Rhizopora mangle, R. harrisonii, R. racemosa, Avicennia germinans, A. Schaueriana, Laguncularia racemosa, and Conocarpus erectus (Bacon 1993). R. mangle is the most widespread. In general, R. harrisonii and R. racemosa are more abundant in the east coast swamps, A. schaueriana is uncommon, and L. racemosa and C. erectus are found in small stands. Rhizopora species are found along the margins of tidal channels, sometime mixed with Avicennia germinans, which is also found in pure stands in basins behind levees. L. racemosa has a patchy distribution, A. schaueriana is more common in dry areas, and C.erectus is found on the margins of swamps and along artificial channels. Associated species in brackish marshes are Eleocharis mutata, Fimbristylis, Cyperus odoratus and Phragmites spp.; in swamp wood with Symphonia globulifera, Virola surinamensis, Pterocarpus officinalis; in freshwater marshes with Cyperus giganteus, Gynerium sagittatum, Montrichardia arborescens as well as patches of floating marsh and Palm swamp forest (Bacon 1993).
Resulting from the proximity to, and recent geological split from, the South American mainland, Trinidad and Tobago have a high species to area ratio. The two islands have approximately 175 families and 2,500 species of plants, 110 that are believed to be endemic to the island, including numerous palms. There are also reported to be over 400 species of birds, 100 species of mammals, 85 species of reptiles, and 30 species of amphibians (Huber and Meganck 1987; Kenny et al., 1997).
Tropical rain forest covers much of this ecoregion. In this forest type there are several tiers of vegetation interlaced with lianas and vines while epiphytic orchids, bromeliads and ferns are common. Typical plant species include Carapa guianenis, Ceiba pentandra, Spondias monbin, Pentaclethra macroloba, and Brownea latifolia (French 1991). One notable type of forest found extensively in east Trinidad, especially near Matura and Mayaro, is Mora forest - dominated largely by Mora excelsa.
Birds constitute the largest group of vertebrates. Sixty-six families in twenty orders are represented in Trinidad and Tobago. The dominant order, as it is in many other parts of the world is the Passeriforms, accounting for almost a third of the families represented. A little over 400 species have been reported in Trinidad. As with other vertebrate groups, there are substantially fewer species in Tobago. About 170 species have been recorded for Tobago (French 1991).
Nine orders and about 27 families of mammals are represented and all are typical of the adjacent mainland and the wider Neotropics. There are approximately 100 indigenous species but the bats and rodents predominate. Bats account for over half of the mammalian fauna. The rest of the mammalian group includes the marsupials, edentates, a single armadillo species, several rodents, primates, a few carnivores, and deer. About 40 species of snakes in six families can be found in Trinidad. In Tobago, there are fewer families and numbers of species. There are five families of lizards and about 25 species in Trinidad and Tobago. Of the amphibians in Trinidad, there are about 30 species in nine families, all in a single order. Tobago has only about one-third the number of species. All are frogs or toads of the anuran order. The golden tree frog (Phyllodytes auratus) is a notable endemic frog species of the montane forest in Trinidad.
There are over 7,000 ha of mangroves at 35 sites on the Island of Trinidad, an additional 10 sites on the island of Tobago, and 2 on the offshore island of Chacachacare. The single largest area is over 3,000 ha in the Caroni Swamp. Mangroves are included in the system of protected areas but actual protection is minimal in that there is no active management nor are there explicit mangrove protection policies (Bacon 1993).
Types and Severity of Threats
In general, mangroves are directly used for timber and charcoal, and their bark is used to extract tannin. They also support the harvesting of oysters, crabs, shrimp and fish. Concerns include the reclamation of large areas for agricultural uses, discharge of industrial effluents and petroleum residues as well as sewage and solid waste, residential development. Pesticide runoff has been found at the Caroni Swamp, illegal rice farming is taking place in the Nariva Swamp, now brought under control , there is illegal felling of mangroves for bark used by the tanning industry, illegal settlement and livestock grazing, unsustainable harvesting of oysters and crabs. Oysters are harvested by cutting the entire prop-roots of the red mangrove on which they settle (Agard and Gobin 2000; Frazier 1999, Bacon 1993). A particular concern is slash and burn farming on steep slopes with highly erodable soils, and deforestation rate of 3000 ha/yr which increases sedimentation in coastal areas. Another general concern is that Trinidad and Tobago are sites of intense industrial development including several petrochemical plants. Oil spills and loss of oil to the marine environment through effluents and produced water are routine and are estimated to total 120,000 barrels a year. Although it did not go ashore, the largest oil spill ever recorded occurred 30 km northeast of Tobago as a result of a tanker collision in 1979, which spilled 90,000 tons (Agard and Gobin 2000).
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).
Agard J.B.R., and J.F. Gobin 2000. The Lesser Antilles, Trinidad and Tobago. C. Sheppard, editor. Seas at the millenium: An environmental evaluation. Elsevier Science Ltd. Oxford.
Bacon, P.R. 1993. Mangroves in the Lesser Antilles, Jamaica and Trinidad and Tobago. L.D. Lacerda, editor. Conservation and sustainable utilization of mangrove forests in Latin America and Africa Regions. Part I: Latin America. International Society for Mangrove Ecosystems and the International Tropical Timber Organization.
Censky, E.J., and H. Kaiser 1999. The Lesser Antillean fauna. B.I. Crother, editor. Caribbean amphibians and reptiles. Academic Press, New York.
Ecoregional Workshop: A Conservation Assessment of Mangrove Ecoregions of Latin America and the Caribbean. 1994. Washington D.C., World Wildlife Fund.
French R. 1991. A Guide to the Birds of Trinidad and Tobago. Ithaca: Cornell University Press.
Frazier, Scott. 1999. Editor. A directory of wetlands of international importance designated under the Convention on Wetlands of International Importance (Ramsar, 1971). Compiled by Wetlands International for the Seventh Meeting of the Conference of Contracting Parties to the Ramsar Convention, San José, Costa Rica, May 1999. Retrieved from http://www.wetlands.agro.nl/ramsar_database/ramsar_quick.html
Laydoo, R.S., K. Bonair, G. Alleng. 1998. Buccoo reef and Bon Accord Lagoon, Tobago, Republic of Trinidad and Tobago. B. Kjerfve, editor. CARICOMP – Caribbean coral reef, seagrass and mangrove sites. Coastal region and small island papers 3, UNESCO, Paris, xiv + 347 pp.
Olson, D.M., E. Dinerstein, G. Cintrón, and P. Iolster. 1996. A conservation assessment of mangrove ecosystems of Latin America and the Caribbean. Final report for The Ford Foundation. World Wildlife Fund, Washington, D.C.
Raffaele, H., J. Wiley, O. Garrido, A. Keith , and J. Raffaele 1998. A guide to the birds of the West Indies. Princeton University Press, Princeton New Jersey.
Prepared by: Sylvia Tognetti and Christine Burdette
Reviewed by: In process