Location and General Description
The Gulf of Panama mangroves include those on the eastern side of the Pacific coast of the country, from the Parita Bay to the San Miguel Gulf, and include the Chame Bay and the Panama Bay in between. There is great variability found within this region. Annual rainfall varies from an average of 1,070 mm in the western part of the ecoregion to 3,000 mm in the eastern part, where mangroves are better developed. Tidal amplitude ranges from 2-6 meters (D’Croz 1993). Rainfall covers the region between May and December, which is the rainy season. The dry season occurs from January to April. The low pressure systems strengthen winds coming from the east, which bring stronger storms, and winds that are capable of damaging mangroves, paired with higher freshwater inputs that keep the mangroves inundated for prolonged periods. Another regular disturbance is from El Ninós, which severely reduces rainfall, disturbing mangrove reproductive cycles by limiting available freshwater.
Because of high evapotranspiration rates and the severity of the dry seasons, there is a water deficit in this ecoregion most of the year. Thus, extreme values are more important than the mean values of river discharge to get an understanding of the effects of seasonal rainfall on river load and its influence on mangroves. In general, the river basins are of high relief and therefore prone to erosion caused by agricultural practices, livestock grazing and deforestation, together with steep slopes, seasonally intense rainfall, highly erodible soils, and high concentrations of people and livestock; the direct result of which is high sedimentation and nutrient loading. Therefore, sand and mud are abundant. Coral reefs are not associated with the mangroves in this ecoregion because of the heavy sediment load, though some are found further offshore near islands. Mangroves are better developed where there is a greater supply of freshwater reducing salt accumulation in the mangroves. Evapotranspiration, marine water, availability of freshwater, rainfall, river discharge and surface runoff regulate salinity variations in the soil. Small wetlands in the ecoregion function as reservoirs, slowly releasing water during the dry season. In areas of seasonal climate, salinity concentrations increase towards the internal side of the forest. With greater distance from the tidal channels, diminishing intensity of inundation, salt accumulated in the soil through evapotranspiration as freshwater creates salt pans. In the rainier climates, freshwater input is so high that it is impossible for salt to accumulate. In this case, a transition zone can be found in which mangrove vegetation mixes with that typical of freshwater wetlands such as palms and swamp forests (Jimenez 1999).
The mangrove forests also have high variation, corresponding with the tremendous variation in climatic conditions. Two principal zones can be distinguished: external and internal. The external areas are directly exposed to estuarine waters; the internal are isolated from them but are seasonal inundated by the tides. Red mangroves (Rhizopora mangle and R. brevistyla), which reach up to 40 meters in height dominate brackish areas of the Pacific Coast. Other species found along the salinity gradient are: black mangroves (Avicennia germinans and A. bicolor), white mangrove (Laguncularia racemosa), mora (Mora oleifera) and castaño (Montrichardia arborescens). Also, mangle piñuelo (Pelliciera rhizophorae) (D’Croz 1993) and Avicennia tonduzii a mangrove species that is only found along the coasts of Costa Rica, Panama and slightly into northeastern Colombia.
Birds most specific to mangroves include roseate spoonbill (Ajaia ajaja), gray-necked wood rail (Aramides cajanea), rufous-necked wood rail (A. axillaris), mangrove black-hawk (Buteogallus subtilis), yellow-billed cotinga (Carpodectes antoniae) (now rare), green kingfisher (Chloroceryle americana), Amazon kingfisher (Chloroceryle amazona) lesser nighthawk (Chordeiles acutipennis), rufous-browed peppershrike (Cyclarhis gujanensis) (Jimenez 1999, CSP bird book pertaining to Central America) and many others.
Also contributing to the immense diversity are the many types of mammals which both live in and around this ecoregion. Including arboreal mammals such as the Mexican anteater (Tamandua mexicana), pygmy anteater (Cyclopes didactylus), mantled howler monkey (Allouatta palliata), white-throated capuchin (Cebus capucinus), raccoon (Procyoon lotor), crab-eating raccoon (P. cancrivorus). In A. bicolor and L. racemosa mangrove forests, white-tailed deer (Odocoileus virginianus) can be seen feeding on the rich foliage. Reptiles found in the branches of the canopy include (Boa constrictor), Iguanas (Iguana iguana), and the ctenosaur (Cthenosaura similis) (Jimenez 1999; Reid 1997).
The role of mangrove ecosystems as nurseries for fish, invertebrates and crustaceans leads to higher levels of diversity especially in water associated species of birds. These immature species including the 30 fish species reported to be found in their juvenile stages are part of the basis for this ecoregion’s foodchain. Fish and crustacean species dominant for the ecoregion are those traditionally found in estuarine and arid environments such as Serranidae (sea basses), Gerreidae (ray-finned fishes) and Mugilidae (mullets). Crabs play an important role in the pathways of leaf decomposition and also, through selective predation on propagules, the mangrove species that are found in this ecoregion. 3 species of shrimp are particularly abundant; they spawn offshore but live in the mangroves as juveniles for 4-5 months where they grow from 12 mm to as long as 80 mm before migrating back to the ocean (D’Croz 1993).
Mangroves of the Gulf of Panama ecoregion cover approximately 892.78 km2 of this region’s total 2,424 km2. 21.45 km2 have been converted to salt flats, shrimp ponds, crops, cattle farming, tidally flooded land, non-vegetated land and agriculture. Most of this decrease has occurred on the Pacific Coast in the Chiriqui area – the greatest losses to shrimp farming have occurred in the more saline areas (D’Croz 1993).
Management is complicated by the tremendous variation found within this region and within small areas. There is heavy economic dependence on the mangroves. Many families exist solely on mangrove resources, and 70% of the population relies on fuelwood for energy. Most of the country’s income from fishing is from mangrove related fish species, and shrimp is, economically, the most important fishery. Also important are anchovies (Centengraulis mysticetus), for which the largest catches are in the areas with the greatest mangrove cover (particularly in Gulf of Panama), because they feed on detritus or organic debris from the mangroves. Artisanal fisheries are also associated with mangroves include snappers (Lutjanus spp.), corvinas (Micropogon altipinnis), and robalos (Centropopmus spp.) (D’Croz 1993).
Types and Severity of Threats
Mangrove ecosystems are threatened by conversion to agricultural areas that are used for low productivity crop and part of these areas often remains unvegetated because of regular inundation. Pressures from urbanization occur around Panama City. A special concern is with the potential for oil and chemical spills because of the amount of oil and other freight that is transported through the Panama Canal and also through pipelines. The destruction, conversion and utilization of mangrove ecosystems for use as fuelwood, salt flats, shrimp ponds and cattle grazing are a continual threat as the surrounding human population largely relies on these resources and this ecoregion to help supply them (D’Croz 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).
D’Croz L. 1993. Status and uses of mangroves in the Republic of Panamá. L.D. Lacerda, editor. Conservation and sustainable utilization of Mangrove Forests in Latin America and Africa Regions. Part 1; Volume 2.
Ecoregional Workshop: A Conservation Assessment of Mangrove Ecoregions of Latin America and the Caribbean. 1994. Washington D.C., World Wildlife Fund.
Jimenez, Jorge A. 1999. Ambiente, distribucíon y características estructurales en los manglares del Pacífico de Centro América: contrastes climáticos. Yáñez-Arancibia, Alejandro and Ana Laura Lara-Domínguez, editors. Ecosistemas de Manglar en América Tropical. Instituto de Ecologia, A.C. Xalapa, México; UICN/ORMA Costa Rica; NOAA/NMFS Silver Spring MD USA.
Reid F. A. 1997. A field guide to the mammals of Central America and Southeast Mexico. Oxford University Press, New York.
Prepared by: Sylivia Tognetti and Christine Burdette
Reviewed by: In process