Location and General Description
This ecoregion runs along the Pacific coast of Central America beginning just south of the Golfo de Fonseca in Nicaragua then continuing south to the Gulf of Nicoya in Costa Rica (Olson et al.1996). This southern dry pacific coast ecoregion encompasses the Gulfo de Nicoya that marks the transition zone from dry to moist on the pacific coast (Spalding et al. 1997). The mangroves in this ecoregion is structurally less developed than that further south as a result of its orientation within the dry tropical climate zone. Also there is lower annual rainfall, than further south of the transition line, ranging from 1300 mm in Nicaragua to 2000 mm in Costa Rica, but mostly falling during the short wet season resulting in a longer dry season from December to April. Annual temperature fluctuates between 25° C and 27° C with lean high or low depending on northern or southern areas of the ecoregion (Polanía 1993; Polanía and Mainardi 1993).
Because of high evapotranspiration rates and severity of the dry seasons, there is high salinity and a water deficit most of the year. Two kinds of zones can be distinguished in this ecoregion external and internal. The external areas are directly exposed to estuarine waters. The internal areas are isolated from the estuaries’ waters mostly however, seasonally the tides inundate these areas. There is a strong salinity gradient between the mouth and the inland areas where salt pans may form. Evapotranspiration, marine water, and a supply of freshwater from rainfall, river discharge and surface runoff regulate these salinity variations in the soil. In areas of seasonal climate fluctuation, salinity concentrations increase towards the internal side of the forest. With greater distance from the tidal channels, and diminishing intensity of tidal inundation’s, salt accumulates in the soil as freshwater evaporates, leaving salt pans in the driest areas. The dry internal zone receives freshwater input during the dry season through runoff, which may come from small wetlands that function as reserves. Throughout the ecoregion fine sediment dominates most sites soil types but sandy areas are also found (Jimenez 1999).
Vegetation in this ecoregion is mainly represented by mangrove ecosystems including species, which grow in association with mangroves and some aquatic plants. Dominant mangrove species such as Rhizopora mangle, R. harrisonii, R. racemosa, Avicennia germinans, A. bicolor, A. tonduzii, Laguncularia racemosa, Pelliciera rhizophorae and Conocarpus erecta in less flooded areas (Polonía 1993). The dryness of the region is associated with a clear zonation pattern among the mangrove species Rhizopora species are found at the seaward edge, and Avicennia along the inland fringe (Jimenez 1999).
Vegetation that grows in moist areas in association with mangrove species include ferns Acrostichum aureum, Tabebuia palustris while Canavalia maritima, Ipomoea pescaprae, Caesalpinia bonduc, Prosopis juliflora, Sesuvium portulacastrum, Plutapapron vermiculare, Jouvea straminea, Fimbristylis spadicea, Capparis odoratissima, Randia sp and Tamarindus indica grow in dry zones (Polonía 1993).
Forests in the dry internal zone are composed of Avicennia subspecies bicolor, which are nesting areas for the yellow-naped parrot (Amazona auropalliata) (Jimenez 1999). A faunal inventory at the Juan Venado Natural Reserve counted 95 species of birds, 24 reptiles, 23 mammals, 14 fishes and 6 amphibian species (IRENA 1992, cited in Polonía and Mainardi 1993). This ecoregion is said to be extremely important for nesting, staging and wintering birds (Ramsar, 1993). Birds most specific to mangroves include the Panama flycatcher (Myiarchus panamensis), whimbrel (Numenius phaeopus), yellow-crowned night-heron (Nyctanassa violacea), black-crowned night-heron (Nycticorax nycticorax), scaly-breasted hummingbird (Phaeochroa cuvierii), black-bellied plover (Pluvialis squatarola), prothonotary warbler (Protonotaria citrea), northern waterthrush (Seiurus noveboracensis), northern scrub-flycatcher (Sublegatus arenarum), mangrove swallow (Tachycineta albilinea) and greater yellowlegs (Tringa melanoleuca) just to name a few.
Mammals, although not as numerous as birds, also utilize the resources available in this mangrove ecoregion including the paca (Agouti paca), mantled howler monkey (Allouatta palliata), white-faced capuchin (Cebus capucinus), pygmy anteater (Cyclopes didactylus), nine banded armadillo (Dasypus novemcinctus), Central American otter (Lutra annectens), white-tailed deer (Odocoileus virginianus), northern raccoon (Procyoon lotor), crab-eating raccoon (P. cancrivorus), which can be found both on the ground and in the canopy consuming crabs and mollusks and the Mexican anteater (Tamandua mexicana). The great false vampire bat (Vampyrum spectrum) is also found in this ecoregion and is considered the largest bat in the new world.
Reptiles such as the Basilisk lizard (Basiliscus basiliscus),snakes (Boa constrictor) American crocodile (Crocodilus acutus), spectacled caiman (Caiman crocodilus), Ctenosaur (Ctenosaura similis), iguana (Iguana Iguana) and a few species of sea turtle such as the Pacific Ridley sea turtle (Lepidochelys olivacea) (species lists from Jimenez 1999, Polanía 1993, Polanía and Mainardi 1993, and Ramsar 1993).
Areas with the highest remaining concentrations of mangroves in this ecoregion, in Costa Rica are Puerto Soley (near NI border; Tamarindo (400 ha), Golfo de Nicoya (15,173 ha), and Puntarenas (Polanía 1993). In Nicaragua: Estero Padre Ramos (4,590 ha), Aserradores-Poneloya (10,700), Las Peñitas to Salinas Grandes (2,420), and Estero Ciego to Puerto Sandino (1,990 ha) (Polanía and Mainardi 1993).
Types and Severity of Threats
In general, the river basins that drain into this ecoregion are of high relief, therefore seasonally intense rainfall and highly erodable soils make them prone to erosion caused the removal of vegetation for agricultural practices, timber, fuelwood and livestock grazing. The direct result is high sedimentation of nutrients that are naturally brought to the mangrove areas but in much lower concentrations, during the rainy season (Jimenez 1999).
Major threats include the pressure to convert mangroves to agricultural uses even though mangrove soils are too poor for agricultural purposes and have problems of drainage, salinity and acidity. Converted lands are often then abandoned because of high maintenance costs. In this ecoregion in particular vast areas of mangrove have been destroyed to construct salt ponds, which also requires cutting of mangroves for fuelwood to crystallize the salt. Also, urban encroachment, runoff of pesticide residues and eutrophication (Polanía 1993; Ramsar 1999).In the Gulf of Nicoya, between 1964 and 1989, 633 ha of mangroves were lost to shrimp culture and 115 to salt production (Polanía 1993).
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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Prepared by: Sylivia Tognetti and Christine Burdette
Reviewed by: In process