Location and General Description
The Marabi mangrove forests are halophyte forests distributed along the Ecuadorian Coast and located at the mouths of river systems converging on the Pacific Coast of South America (Suárez & Silva 1996). In the province of Manabí (about 0° 15’ north latitude to about 2° 0’ south latitude), these forests are represented in two subregions. The Cojimíes subregion (88.77 km2) is bound on the north by the Muisne River, on the south by the town of Pedernales and on the east by adjacent land formations (dry forest, wet forest and various human settlements). The Chone subregion encompasses an area of 14.78 km2 and is found in the central part of the coastline of the province of Manabí. It is bound on the extreme north by the town of Bahía de Caráquez and the Chone River and on the south by the Portoviejo River (PATRA & CLIRSEN 1999)
The climate is homogeneous with fluctuating salinity: with an average of 1,410 mm/year for Cojimíes and 501 mm/year for the Chone subregion. The strong influence of the warm El Niño currents, the cold and dry Humboldt current and the effects of the intertropical convergence zone produce a broad fluctuation of tides, strong climatic pressure and sporadic formations of frost (CLIRSEN 1991; Dinerstein et al. 1995). The soil is characterized by unstable swampy structure and complex woody forms that define four distinct landscapes depending on topographical forms: deltas, estuaries, carbonated platforms and lakes (Fundación Natura 1990; Dinerstein et al. 1995). In the Cojimíes subregion, the principal river systems include the Muisne River to the extreme north, with a flow of 22m3/sec., and the Cojimíes River. The Chone River flows through the second subregion with a flow of 31m3/sec. In some sites there is high sedimentation that produces a low shoreline, low wave energy and a reduced number of estuaries (CLIRSEN 1991; Bodero 1993).
Mangrove forests are generally forests that appear homogeneous on the surface, with few land species but enormous aquatic and marine wealth. The principal characteristics of these tree species is their high tolerance to salinity; most of them are represented in three subtypes of mangrove: border, strip and coastal (Bodero 1993; Dinerstein et al. 1995). In wet areas, there is a predominance of the black mangrove (Avicennia germinans) and red mangrove (Rizophora mangle L., R. harrisonii R), except where there is sedimentation. Behind these formations, also dominant is the button mangrove (Conocarpus erectus) and other mangrove species like Laguncularia racemosa and Pelliciera rhizophora. Together with epiphytic herbaceous communities (orquedeae, bromeliaceae, cacti and mosses), and rhodophytes, the mangroves form complex forests responsible for providing a physical buffer against sea swells and winds on the coast, purifying the salt in marine breezes, enriching the coastal profile and producing soil recovery (CLIRSEN 1991).
The mangrove forests are important because they provide habitats for various species of birds, mammals, reptiles, mollusks, crustaceans and fish (Suárez & Silva 1996). Although endemism is not considered high in this region, it is estimated that it has high alpha diversity, meaning a high wealth of species within a particular locality (Dinerstein et al. 1995). The few endemic species include Pelliciera rhizophora (piñuelo), confined to the Chone subregion (Bodero 1993). In addition, these mangrove forests shelter a large number of species in certain groups such as 42 species of birds, including Pelecanus occidentalis, Columbina sp., Fregata magnificens, (Ortiz 1990); carious mammals such as crab-eating raccoon (Procyon cancrivorus), mantled howler monkey (Alouatta palliata), white-faced capuchin (Cebus capucinus), and jaguar (Panthera onca), and reptiles like Iguana iguana. The region is particularly rich in certain taxons: fish of the genus Mugil as well as post-larva shrimp of the family Penaeidae (Bodero 1993).
Active migrations of numerous species of fish and shrimp occur according to reproductive cycles near the coastal shields. In addition, birds and mammals move between the mangrove and dry land, and between patches of mangroves along the entire coast (Dinerstein et al. 1995). The cattle egret (Bubulcus ibis) increased its range of distribution early in the last century and now lives in these mangrove forests and the rest of the continent (indirect introduction). The most important ecological and evolutionary processes in the mangrove forests are maintained by plants adapted to these ecosystems that have managed to survive thanks to viviparism and their great ability to spread through the water (CLIRSEN 1991). Other ecological processes are influenced by the El Niño phenomenon that with warm waters bringing changes in climate and in the intensity of the rains, producing serious ecological disturbances that are more intense from time to time. However, energetic fragmentation in the system is the largest ecological event maintaining biodiversity in these mangrove forests: fungi, bacteria, cilia, nematodes, amphipods, bivalves, gastropods, polychetes and oligochetes, and others, that are responsible for breaking down detritus and converting it to protein. Fish that take nourishment from organic detritus are in turn food for large aquatic and land carnivores seeking a spot that provides shade, substrate, refuge, reproduction and nourishment (Bodero 1993). Unfortunately, there are no habitats that could be considered intact in both regions; 38 % of their total surface is in critical condition and at risk due to the high degree of fragmentation (Dinerstein et al. 1995). In these regions, bird species such as the mangrove finch (Camarhynchus heliobates) are classified as seriously at risk of becoming extinct (Granizo et al. 1997).
In Manabí, the momentary and final conservation status of the mangrove forests is critical and the threats are considerably high (Dinerstein et al. 1995). The mangrove forests maintain a strong ecological relationship with other regions of the coast and dry land, including adjacent areas affected by various human activities (Bodero 1993). In Cojimíes, for example, deforestation is evident and critical and its specific effects are closely related to shrimping activities. In 1985, the government implemented a prohibition on building shrimp farms in or near coastal mangrove forests (CLIRSEN 1991). However, the nearby low water plains are used for shrimp-farming as an alternative. In the region of Cojimíes there are extensive shrimp farm building activities and development of grazing lands while in Chone there is the added disturbance caused in the rivers and sedimentation processes (Bodero 1993). The mangrove forests of Manabí were declared a priority within the new strategies adopted by the National System of Protected Areas and the Fundación Natura in 1989, but on the Ecuadorian coast there are only four protected areas covering marine and coastal environments, and none of these includes the Manabí mangrove forests (CPPS/PNUMA/PSE/IE(97) 3). Nonetheless, some non-governmental organizations operating in the country have devoted their attention to major areas of research and training in the environmental management of these and other mangrove forests in the country (Suárez & Silva 1996).
Types and Severity of Threats
In addition to the advance of construction of shrimp farm pools (an industry in decline since 1988), the factors with direct impact on ecosystems are urban development, construction of highways and ports, drainage works, waste elimination. Indirect effects are produced by over-grazing on high lands, affecting sedimentation in the mangrove forest (Suárez & Silva 1996).
In the Cojimíes subregion there are serious habitat fragmentation events. Data from 1999 indicates the loss of a total of 1,162 hectares of the original mangrove forests and an increase of 6.68 km2 in the area covered by shrimp farms. However, the reverse has been seen in the Chone subregion: a reduction of 3.83 km2 in the area occupied by shrimp farms and an increase of 2.59 km2 in the coverage of the mangrove forests. Despite this figure, the totals indicate a loss of 9.03 km2 of mangrove forest and in increase of 2.85 km2 in the coverage of shrimp farms (PATRA & CLIRSEN 1999).
However, the construction of shrimp farms near the mangrove forests has a positive indirect effect. It causes the rate of sedimentation to increase, which in turn favors colonization by the forest in new shallow areas (Bodero 1993). Possibly this explains the increase in the coverage of mangrove forests in the Chone subregion, although that increase is well below the rate of habitat alteration in Cojimíes. The threats represented by construction activities and settlement by human populations in areas adjacent to the mangrove forests bring increased exploitation of wildlife, the introduction of exotic species and the degradation of the habitat in general. As part of an evaluation of the conservation status of the mangrove ecosystems in 1995, Dinerstein refers to these two regions and suggests that future conservation plans should consider them in their management as forest regeneration areas, a criterion applied to areas with critical conservation status.
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).
Bodero A. 1993. en Conservation and sustainable utilization of mangrove forests in Latin America and Africa regions, (2), Part I, Latin America. ITTO/ISME, International Society of Mangrove Ecosystems, 1993. pp 55-73.
Briones E., A. Flachier, J. Gómez, D. Tirira, H. Medina, I. Jaramillo, and C. Chiriboga. 1997. Inventario de humedales del Ecuador. Primera Parte: Humedlaes Lénticos de la provincia de Esmeraldas y Manabí. EcoCiencia/INEFAN/ Convención Ramsar, Quito.
CLIRSEN 1991. Inventario de Manglares del Ecuador continenetal. Ministerio de Agricultura y Ganadería (MAG) y Subsecretaría de Áreas Forestales y Recursos Renovables (SUFOREN), DINAF. Quito.
CPPS/PNUMA, 1997. Estudio Nacional de la diversidad biológica marina y costera del Parque Nacional Machalilla – Ecuador. CPPS/PNUMA/PSE/IE(97)3.
Dinerstein E., D.M. Olson, D.J. Graham, A.L. Webster, S.A. Primm, M.P. Bookbinder, and G. Ledec. 1995. Una evaluación del estado de conservación de las ecoregiones terrestres de América Latina y el Caribe. WWF y Banco Mundial de Washington, D.C., U. S. A.
Ecoregional Workshop: A Conservation Assessment of Mangrove Ecoregions of Latin America and the Caribbean. 1994. Washington D.C., World Wildlife Fund.
Fundación Natura, 1995. Determinación de áreas de bosques remanentes en la región occidental ecuatoriana. Serie Estudios No. 1. Quito, Ecuador.
Fundación Natura. 1993. Bosques Occidentales Remanentes (del Ecuador). 1:1’000.000. Quito, Ecuador.
Granizo T., M. Guerrero, C. Pacheco, R. Phillips, M.B. Rivadeneira, and L. Suárez. 1997. Lista de aves amenazadas de extinción en el Ecuador. UICN-Sur. CECIA, INEFAN, EcoCiencia, Birdlife International, Quito. 31 p.
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.
Ortiz D 1990. Estudio socioeconómico de la comunidad salinas de Bahía de Caráquez, en la provincia de Manabí. Quito.
PATRA & CLIRSEN 1999. Actualización del estudio multitemporal de los manglares, camaroneras y áreas salinas del Ecuador continental a 1999 con base en información satelital. Quito.
Suárez L., and P. Silva. 1996. en Conservation Atlas of Tropical Forests. The Americas. (27 - Ecuador), pp. 260-269.
Prepared by: Paola U. Carrera, Pilar G. Jiménez, and Xavier Viteri
Reviewed by: In process