Location and General Description
It is located in northern Colombia in the Department of Magdalena encompassing the Gulfo de Urabá then east to just past the Sierra Nevada de Santa Marta at the base of the Guayjira Peninsula, at 10°30’ and 11° north latitude. The ecoregion is particularly arid with an average isomegathermic climate of 27°C, a notably seasonal pattern of precipitation of 400-760 mm and high annual evapotranspiration of 1400 mm; three times higher than precipitation (Sánchez-Páez et al. 1997). The latitudinal movement of the intertropical conversion front (ICF) defines the two rainy seasons, which are from March to May and from October to November, representing 70% of total annual volume. Two dry seasons lie between these rainy season months (Pro-Ciénaga 1995).
The estuarine plain that these mangroves grow on is a flat intramountainous system that was created gradually due to a relative rise in the sea of about two meters over the last 2,300 years. This quaternary plain was formed by the post-orogenic clastic depositing of sediment, derived from adjacent tectonic uplifts deposited in the basin of the lower Magdalena River that formed a platform of peat intercalated with sand and clay beds. This platform is now submerged and gradually being covered by recent lacunar sediments. It intermixes with the lateral floodplain of the Magdalena River that shows a tendency to become disconnected. In the southwest it is spread under the alluvial colluvial fan of the Tucurinca, Aracataca and Fundación Rivers; in the east it borders on the high alluvial terrace of the "Zona Bananera"; and in the north it extends into the Caribbean Sea (Pro-Ciénaga 1995). Hydrodynamic processes are governed by the Magdalena River, which has an effect on the western section of the ecoregion and by the rivers on the western slope of the Sierra Nevada de Santa Marta, which exclusively feed the Ciénaga Grande.
Mangrove forest is the most notable plant characteristic of this ecoregion. Its maintenance depends on the flow of waters and the entry of nutrients from adjacent ecosystems such as those contributions from the Magdalena River and the rivers of the Sierra Nevada (Pro-Ciénaga 1995). The species present by order of occurrence, importance and utility are red mangrove (Rhizophora mangle), black mangrove (Avicennia germinans), white mangrove (Laguncularia racemosa) and buttonwood (Conocarpus erecta), which is not a mangrove species but often occurs in the same areas (Sánchez-Páez et al. 2000). They form mixed forests that do not exceed 20-25 m in height without associated higher plants reported. Their zoning is not homogeneous; variations in their structural development depend on environmental factors prevailing in the Caribbean Sea such as coastal geomorphology, amplitude of tides, salinity gradients, nutrient contributions, supply of freshwater and climatic conditions (Sánchez-Páez et al. 1997). Mangrove species in general have developed special adaptations to tolerate tidal flooding and high salinity. However, disproportionate increase in salinity, or decline in incoming freshwater, sedimentation and contamination have caused the slow death of 55% of the mangrove forest in this ecoregion over the last 40 years and with it a decline in biodiversity.
The high primary productivity of this ecoregion provides habitats to shelter numerous marine and freshwater species, as well as a number of birds and reptiles. Santos-Martínez and Acero (1991) recorded 130 species of fish residing in the mangrove forest patch near the Santa Marta area, including those of great commercial importance (mullet, sea bass, shad). Pro-Ciénaga (1995) reports 114 fish and 98 mollusks, making this the third most important source of the country’s fishing and hydrobiological resources, after the basins of the Orinoco and Magdalena Rivers. The ostra de mangle (Crassostrea rhizophora) is also endemic.
Many birds and reptiles depend on these mangrove forests and swamps of the Caribbean at some point in their lives and this ecoregion is the most representative of the coast. It provides sites for the temporary stay of migratory birds, many of which are water birds suxh as herons, ducks and ibis. It harbors important populations of crested screamer (Chauna chavaria), listed as vulnerable on IUCN red list (Naranjo 1998). Exclusive to the area are the bare-throated tiger-heron (Tigrisoma mexicanum) and the continential subspecies of the yellow warbler (Dendroica petechia) (Sánchez-Páez et al. 1997). Although endemism is not a characteristic of aquatic birds, sapphire-bellied hummingbird (Lepidopyga lilliae) has been reported as endemic to the mangrove forests of this ecoregion and is seriously at risk of extinction (Stattersfield et al. 1998) and Colombian bronzed cowbird (Molothrus armenti) has been reported as vulnerable (Sánchez-Páez et al. 1997). For reptiles, the best represented species are the American crocodile (Crocodylus acutus) at risk of extinction in the country, narrow-snouted spectacled caiman (Caiman crocodylus), the iguana (Iguana iguana) and the snakes Corallus sp. and Boa constrictor. Mammals notably include large cat species (Felis spp.), otters (Lutra sp.), crab eating raccoon and raccoon (Procyon cancrivorus and P.lotor), deer (Mazama spp.), capybara (Hydrochaeris hydrochaeris), three-toed sloth (Bradypus variegatus), red howler monkey (Alouatta seniculus) and west indian manatee (VU) (Trichechus manatus) (Sánchez-Páez et al. 2000 b, 1997).
From an ecological and socioeconomic perspective, this ecoregion holds the most degraded estuarine complex in Colombia. Construction of highways to the north between the cities of Ciénaga and Barranquilla in 1956-1960 and on the eastern shore of the Magdalena River in the 1970s has lead to the disruption of most of the ecoregion from its natural state. Decline in mangrove forest during the period between 1956-1987 was 40.6%; by 1993 it had increased to 56.6% and in 1995 reached 63.8% of the total alive in 1956 (Gónima et al. 1998). In addition to the deterioration of the landscape, the decline in the mangrove forest has created effects throughout the lacunar system such as the loss of habitats for a large number of species of fish, birds and bentonic organisms.
The Pro-Ciénaga Project of the Ministry of the Environment and Corpamag has succeeded in opening and dredging various channels that allow freshwater to enter the complex of swamps, as an approach to the comprehensive management of hydric and fishing resources. An initial contribution was made to reducing salinity and to regrowing and repopulating some mangrove forests (Sánchez-Páez et al. 2000 a). It has been seen that the mangrove forests have great ability to recolonize, including in areas that are sedimentated and exposed to the action of the tides. The Manglares de Colombia Project is carrying out the restoration of mangrove areas, through natural regeneration and production in community nurseries. Nonetheless, given the climatic conditions of the Caribbean region, a slow and long-term recovery is anticipated that will take from 8 to 30 years (Sánchez-Páez et al. 1997).
It contains two protected areas in the System of Natural National Parks. The Isla de Salamanca Natural National Park is located in the southwest of the island and covers approximately 300 km2. The Ciénaga Grande de Santa Marta Flora and Fauna Sanctuary covers 450 km2 and is the largest lagoon in the ecoregion and in the country, and one of the most important fishing areas in the Caribbean basin (Gónima et al. 1998). The Isla de Salamanca Natural National Park covers 100 km2, is located in the northwest of the ecoregion, shows many environments typical of the ecoregion, and is under great marine influence (Pro-Ciénaga 1995).
Types and Severity of Threats
The diversion of water by building channels and dikes to prevent flooding on the major rivers as well as the resulting silting of water flow due to the high loads of sediment from erosion allowed by deforestation, which has led to the breakdown of the hydric balance throughout the entire ecoregion (Gónima et al. 1998). The resulting hypersalination together with overfishing and social pressures have had a direct effect on productivity resulting in the gradual disappearance of mangrove forest belts (Donato 1998). The enrichment of masses of water with organic matter from the rivers, from nearby human population centers and from chemical fertilizers (eutrophication), creating anoxic conditions leading to the death of massive numbers of fish and other organisms (Mancera and Vidal 1994) and generally the decline and variation in time and space of the primary productivity of the ecosystem (Hernández and Márquez 1991), which continues to be a threat and problem to prevent futher events of this kind and stature.
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: Maria Paula Buverte
Reviewed by: Emilio Constantino