Covering the lowland Atlantic slopes at chiefly below 500 meters (m) elevation in southern Nicaragua, northern Costa Rica, and most of Panama, the Isthmian-Atlantic moist forests represent the epitome of wet, tropical jungle. This forest ecoregion evolved from unique combinations of North American and South American flora and fauna, which came together with the joining of these continents three million years ago. Currently, much of this ecoregion has been converted to subsistence and commercial agriculture.

Bocas del Toro, Panama (Photograph by David Olson)

Location and General Description

This ecoregion located at the juncture of Central and South America. Condensation over the warm land produced by moisture-laden air from the Caribbean Sea hitting the mountains produces constant high humidity and precipitation. Rainfall ranges from about 2500 millimeters (mm) in central Panama to over 5000 m in southern Nicaragua. These forests are distinguished from the cooler subtropical Central American Atlantic Moist Forest ecoregion to the north by their distinct geologic history and consistent annual temperatures above 24°C.

Until recent geologic times, the isthmus south of central Nicaragua was discontinuous, volcanically active and topographically and environmentally diverse. Basalt bedrock is the parent material of the residual and often unconsolidated soils covering the hilly areas of this ecoregion. Old alluvial terraces form the base of the swamp forests and flat lands in the lowest elevations and near the Caribbean Coast. The northern section of this ecoregion is formed of a wide, relatively flat alluvial plain, with a gradual elevation change from sea level to 500 (m), while south into Panama, steep slopes rise up from the Atlantic Ocean, significantly narrowing the ecoregion to only 5-10 kilometers (km) in width.

This ecoregion is characterized by a lush, tall tropical evergreen forest of huge, buttressed canopy trees reaching 40 meters (m) in height and an extremely rich epiphyte flora. The palm component includes many subcanopy and understory species. Abundant subcanopy palm species are Welfia georgii, Socratea durissima and Iriatea gigantea and in permanently flooded areas, Raphia taedigera. Seasonal swamp forests occur in the lowest and flattest areas in Nicaragua and northern Costa Rica, particularly along the coast where they grade into mangrove forests. In these forests, Gavilán (Pentaclethra macroloba) dominates the canopy, along with Caobilla (Carapa nicaraguensis). The almendro (Dipteryx panamensis) and the monkey pot tree (Lecythis ampla) are two outstanding and rapidly disappearing canopy emergents, which are regional endemics of the lowlands, below 250 (m).

Biodiversity Features

Honduran white bat. Photo: David Olson

While biologically very diverse, this ecoregion supports low levels of endemism. The high species richness is derived in great part from the mixing of North and South American floras and faunas on this land bridge. The resident fauna, including butterfly, reptile, amphibian, bird, and mammalian taxa are for the most part wide-ranging representative species of a wet tropical forest ecoregion that extends from southern Mexico to northern South America. Strict endemism among fauna is almost non-existent: between 80-100% of the mammal species that occur in northern Costa Rica also occur in Panama, Nicaragua, Honduras, and Colombia. However, a number of restricted range birds are shared with the Central American Atlantic moist forests ecoregion to the north, together forming an Endemic Bird Area. The Caribbean slope is a major migration route; neotropical and altitudinal migrants comprise about 30% of the avifauna, particularly against the foothills.

Few large expanses of primary rain forest remain intact, occurring only in large reserves, particularly the Indio-Maiz Biological Reserve (approx. 400,000 ha) along Nicaragua's coast and in eastern [[Panama] along La Amistad International Park. These blocks retain nearly all vertebrate species of this ecoregion, including most large predators though increasing isolation threatens their long-term viability. Although small in size, the 1500 hectares (ha) La Selva Biological Station in Northeastern Costa Rica hosts permanent populations of large predators (Panthera onca) and herbivores (Tapirus bairdii) probably because its connection to the upper montane forests of Braulio Carrillo National Park. In fact, this connection represents the last intact gradient of primary forest from near sea level to 2,900 (m) elevation in Central America. Tortuguero National Park, along the Caribbean coast of northern Costa Rica, acts as an isolated refuge to many species (as does Barra de Colorado Wildlife Refuge). Although, enforcement of protection remains a challenge to both areas.

Logging and clearing of remaining forests threaten many species of slow-growing trees, such as the almendro and monkey pot tree. Four species of marine turtles nest on the coastal beaches. The Atlantic lowlands and middle elevations contain some of the rarest butterfly species in Central America and some of the world's highest butterfly species richness. Scarlet and great green macaws (Ara macao, A. ambigua) nest in the lowland forests; great green macaws also move seasonally to higher elevations within the ecoregion. Other endangered restricted range species that migrate seasonally to this ecoregion are the three-wattled bellbird (Procnias tricarunculata) and the bare-necked umbrella bird (Cephalopterus glabricollis).

Current Status

Chunk-headed snake (''Imantodes cenchoa''), Costa Rica (Photograph by Jan Schipper)

Although a few large blocks of intact habitat still exist, the once vast Atlantic lowland forests have been seriously fragmented in recent years. The tropical evergreen forests are among the least well represented in Costa Rica's protected areas system, although large reserves exist in southern Nicaragua and eastern Panama. Only about 130,000 (ha) in the lowland Atlantic zone are currently protected and difficult economic conditions offer little likelihood that the area in protection will be significantly expanded.

The lack of protection of the Atlantic lowlands and the heavy bias toward deforestation at elevations of < 1,000 (m) contribute to the fragmentation and elimination of these forests. With gradual slopes and relatively good access, much of Costa Rica's remaining Atlantic slope forest has been intervened or exists in small fragments. Nicaragua's lack of access and the until-recently inaccessible steeper slopes of western Panama's Atlantic lowlands and foothills have left these areas relatively forested.

Types and Severity of Threats

Flat areas with alluvial soils are under banana cultivation, while the less fertile hilly basaltic soils have more recently been logged and converted to cattle pasture. New access roads, malaria control, and incentives for migration to these areas in the last few decades have encouraged settlement and resource extraction from the area. The last remaining intact forests in this ecoregion are currently under tremendous logging pressure and are being felled, rapidly. Squatting and other property claims are resulting in unregulated destruction in many areas despite the legislation in place to protect forests. Clear-cuts have even been made illegally within many parks - including Tortuguero National Park - which now provides ready access for poachers to the once isolated second largest Green Turtle (Chelonia midas) nesting beach in the world.

While future threats in this ecoregion vary among the three countries, destruction of forest habitat through logging and conversion to cattle pasture are the most widespread and significant. Illegal logging and squatting is making in-roads into the remaining large forest blocks in Nicaragua, while in the already fragmented Costa Rican forests; the principal threat is clearing for cattle production. In Panama, the Atlantic slopes are steeper and less likely to be converted to agriculture; however, new roads in this region will certainly increase human settlement and cutting of accessible forests. The Mesoamerican Biological Corridor project, which aims to enhance connectivity among the Atlantic slope habitats, may provide some needed support for new or expanded protected areas or for payments for environmental services provided by private lands.

Justification of Ecoregion Delineation

Panama (Photograph by WWF/A. Dartfelt)

The delineations for this ecoregion were derived from two separate national vegetation maps. In Costa Rica we followed the delineations of life zones by Tosi. In this case we lumped the following ecoregion of the Pacific slope catchment, south of the Central Valley: Tropical Wet Forest, Premontane Wet Forest, Tropical Moist Forest (TMF), TMF Perhumid Province Transition, and TMF Premontane Transition Belt. The western delineation is marked by the continental divide, or where it does not abut to montane forests at higher elevations. In Panama we relied on the UNDP vegetation map, again, lumping the following lowland and premontane moist forest components on the southern portion of the continental divide: Tropical Moist Forest, Premontane Rain Forest, and Tropical Wet Forest. The northern delineation, which separates this ecoregion from the Central American Atlantic moist forests to the north, was determined by expert opinion due to distinct species associations. This ecoregion hosts many endemic species.

Additional Information on this Ecoregion

• For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.

Further Reading

• Asociación Nacional Pro Medio Ambiente y Recursos Naturales (ProAmbiente). 1998. Evaluación Ecológica Rápida: Corredor Biológico Talamanca-Caribe. The Nature Conservancy.
• Barborak, J. R., A. F. Carr III, and L. D. Harris. 1994. Recomendaciones para la consolidación territorial y conectividad de las áreas protegidas de Costa Rica. A. Vega, editor, Corredores Conservacionistas en la Región Centroamericana: Memorias de una Conferencia Regional auspiciada por el Proyecto Paseo Pantera. Florida: Tropical Research and Development, Inc.
• Boza, M.A. 1996. El Corredor Biológico Mesoamericano. In Informe de la reunión de la comisión técnica sectorial binacional de recursos naturales, Proyecto Binacional de Manejo y Conservación de la Reserva de la Biósfera La Amistad Costa Rica-Panamá. Boquete, Panama.
• Cardenal Sevilla, L. 1994. Informe de País Nicaragua: Diversidad y Prioridades. In A. Vega, editor. Corredores Conservacionistas en la Región Centroamericana: Memorias de una Conferencia Regional auspiciada por el Proyecto Paseo Pantera. Florida: Tropical Research and Development, Inc.
• Davis, S.D., V.H. Heywood, O. Herrera MacBryde, J. Villa-Lobos and A.C. Hamilton, editors. 1997. Centres of Plant Diversity. A Guide and Strategy for their Conservation. Volume 3. The Americas. IUCN Publications Unit, Cambridge, U.K. 562 pp.
• Delgado, F. 1985. Present situation of the forest birds of Panama. In A. W. Diamond, and T.E. Lovejoy, editors, Conservation of tropical forest birds. ICBP Technical Publication No. 4. UK: International Council for Bird Preservation. ISBN: 0946888051
• DeVries, Philip. 1987. The butterflies of Costa Rica and their natural history. Volumes 1 and 2. Princeton: Princeton University Press.
• Dinerstein, E., et al. 1995. An Evaluation on the status of conservation of terrestrial ecoregions of Latin America and the Caribbean. DC: World Wildlife Fund-US.
• Emmons, L. 1990. Neotropical Rainforest Mammals. Chicago: University of Chicago Press. ISBN: 0226207218
• Gómez, L. D., editor. 1986. La vegetación de Costa Rica (map series). Vol. I, In Vegetación y clima de Costa Rica. Ed. UNED. Costa Rica. cited in R.García, 1997. Biología de la conservación y áreas silvestres protegidas: situación actual y perspectivas en Costa Rica. INBio. Costa Rica.
• Guyer, C. 1990. The Herpetofauna of La Selva, Costa Rica. In A. H. Gentry, editor, Four neotropical rainforests. Yale Univesity Press. ISBN: 0300054483
• Hartshorn, G. 1983. Plants Introduction. In D. H. Janzen, editor, Costa Rican natural history. Chicago: University of Chicago Press. ISBN: 0226393348
• Holdridge, L.R. 1967. Life zone ecology. Costa Rica: Tropical Science Center.
• Lieberman, D., M. Lieberman, R. Peralta, and G. S. Hartshorn. 1996. Tropical forest structure and composition on a large-scale altitudinal gradient in Costa Rica. Journal of Ecology 84: 137-152.
• Mendez, E. 1994. Estado de la Conservación de Biodiversidad en Panamá. In A. Vega editor, Corredores Conservacionistas en la Región Centroamericana: Memorias de una Conferencia Regional auspiciada por el Proyecto Paseo Pantera. Florida: Tropical Research and Development, Inc.
• Powell, G. 1999. Personal communications regarding linework for ecoregional deliniations.
• Powell, G., J. H. Rappole, and S. A. Sader. 1992. Neotropical migrant landbird use of lowland Atlantic habitats in Costa Rica: a test of remote sensing for identification of habitat. In J.M. Hagan III, and D.W. Johnston, editors. Ecology and conservation of Neotropical migrant landbirds. DC: Smithsonian Institution Press.
• Palminteri, S., G. Powell, A. Fernandez, and D. Tovar. 1999. Talamanca Montane-Isthmian Pacific Ecoregion-Based conservation plan: Preliminary reconnaissance phase. Report to WWF-Central America.
• Raven, P. H. 1985. Research, Tropical ecology, and the future of Panama. In W. G. D'Arcy and M. D. Correa, editors. The botany and natural history of Panama. Saint Louis: Missouri Botanical Garden. ISBN: 0915279037
• Reid, F. 1997. A field guide to the mammals of Central America and Southeast Mexico. New York: Oxford University Press. ISBN: 0195064011
• Rich, P. V. and T. H. Rich. 1983. The Central American dispersal route: biotic history and paleogeography. In D. H. Janzen, editor, Costa Rican natural history. Chicago: University of Chicago Press. ISBN: 0226393348
• Ridgely, R. 1976. A guide to the birds of Panama. Princeton, New Jersey: Princeton University Press.
• Sánchez-Azofeifa, G. A., C. Quesada-Mateo, P. Gonzalez-Quesada, S. Dayanandan, and K. S. Bawa. 1999. Protected areas and conservation of biodiversity in the tropics. Conservation Biology 13: 407-411.
• Stattersfield, A.J., M.J. Crosby, A.J. Long, and D.C. Wege. 1998. Endemic bird areas of the world: Priorities for biodiversity conservation. Birdlife Conservation. Series No. 7. Birdlife International, Cambridge, UK.
• Stiles, F.G. 1985. Conservation of forest birds in Costa Rica: problems and perspectives. In A. W. Diamond, and T. E. Lovejoy, editors. Conservation of tropical forest birds. ICBP Technical Publication No. 4. UK: International Council for Bird Preservation. ISBN: 0946888051
• Stiles, F.G., and A. F. Skutch. 1989. A guide to the birds of Costa Rica. New York: Cornell University Press.
• Stiles, F.G., and D.A. Clark. 1989. Conservation of tropical rain forest birds: a case study from Costa Rica. In American birds. Vol. 43. No. 3. UK: International Council for Bird Preservation.
• Tosi Jr., J.A. 1969. Republica de Costa Rica: mapa ecológico. Map 1:750,000. Tropical Science Center, San Jose, Costa Rica.
• UNDP. 1970. Mapa ecólogico de Panama. Map 1:5,000,000. Programa de las Naciones Unidas para el Desarrollo, Panama City, Panama
• Vásquez Morera, A. 1983. Soils. In D. H. Janzen, editor. Costa Rican natural history. Chicago: University of Chicago Press. ISBN: 0226393348
• Wille, C. 1999. Personal communication.
• Wilson, D. E. 1990. Mammals of La Selva, Costa Rica. In A. H. Gentry, editor, Four neotropical rainforests. New Haven: Yale Univesity Press. ISBN: 0300054483
• World Wildlife Fund-Central America. 1999. Concept Paper for a reconnaissance of the Talamancan Montane Forest Ecoregion in Costa Rica and Panama.