Introduction

Corcovado National Park, Costa Rica(Photograph by John Morrison)

Covering the lowland Atlantic slopes at mainly 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 3 million years ago. The resultant mixing has produced one of the richest and most diverse assemblages of plants and animals of any area of comparable size. Currently, much of this ecoregion has been converted to subsistence and commercial agriculture.

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 2,500 millimeters(mm) in central Panama to over 5,000 mm 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 24o 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 meters(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 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

Red-eyed treefrog (Agalychnis callidryas), Costa Rica(Photograph by Jan Schipper)

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 rainforest remain intact, occurring only in large reserves, particularly the Indio-Maiz Biological Reserve (approx. 400,000 hectars(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 1,500 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. The ecoregion is extremely important for great green macaw, a vulnerable species, which moves 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

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. Most lowland wet forest parks are too small and isolated to maintain viable populations of large-ranging species; the only one connected to highland forest is La Selva in Costa Rica (just over 1,700 ha), which is too small to protect much of the avifauna and other larger taxa. 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

Vermiculated screech-owl (Otus guatemalae), Costa Rica(Photograph by Jan Schipper)

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

The delineation’s for this ecoregionwere derived from two separate national vegetation maps. In Costa Rica we followed the delineation’s 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 either the continental divide or where it abuts 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 due to distinct species associations and seasonal climatic factors. This ecoregion also hosts several endemic species.

Additional information on this ecoregion

• For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
• To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
• World Wildlife Fund Homepage

Further Reading

• Baldospino, I. 1999. Personal communication.
• 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. 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.
• Clark, K. L., R. O. Lawton, and P. R. Butler. 2000. The Physical Environment. In N. M. Nadkarni, and N. T. Wheelwright, editors, Monteverde: Ecology and conservation of a tropical cloud forest. New York: Oxford University Press.
• Correa, M. 1999. Personal communication.
• Davis, S. P., V. H. Haywood, O. Herrera-MacBryde, J. Villa-Lobos, and A. C. Hamilton. 1997. Centres of plant diversity-Volume 3: The Americas. UK.: WWF and IUCN.
• 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.
• DeVries, Philip. 1987. The butterflies of Costa Rica and their natural history. Volumes 1 and 2. Princeton: Princeton University Press. ISBN: 0691028893.
• Dinerstein, E., D. Olson, D. Graham, A. Webster, S. Primm, M. Bookbinder, and G. Ledec. 1995. A conservation assessment of the terrestrial ecoregions of Latin America and the Caribbean. Washington DC.: World Wildlife Fund-US.
• 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 García, R. 1997. Biología de la conservación y áreas silvestres protegidas: situación actual y perspectivas en Costa Rica. INBio. Costa Rica.
• Haber, W. A. 2000. Plants and vegetation. In N. M. Nadkarni, and N. T. Wheelwright, editors, Monteverde: Ecology and conservation of a tropical cloud forest. New York: Oxford University Press.
• Hartshorn, G. S., and L. J. Poveda. 1983. Checklist of trees. In D. H. Janzen, (editor), Costa Rican natural history. Chicago: University of Chicago Press.
• Mendez, E. 1994. Estado de la Cde la 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.
• 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.
• Powell, G. 1999. Limits to using ecological classification schemes to assess biodiversity representation. Presentation at Society for Conservation Biology annual meeting.
• Powell, G., J. Barborak, and M. Rodriguez. 2000. Assessing representativeness of protected natural areas in Costa Rica for conserving biodiversity: a preliminary gap analysis. Biological Conservation 93 (2000) 35-41.
• Quesada, F., Q. Jiménez, N. Zamora, R. Aguilar, and J. González. 1997. Arboles de la Peninsula de Osa. Costa Rica: INBio.
• Reid, F. 1997. A field guide to the mammals of Central America and Southeast Mexico. New York: Oxford University Press. ISBN: 0195064011.
• Ridgely, R. 1976. A guide to the birds of Panama. New Jersey: Princeton University Press. ISBN: 0691025126.
• Stattersfield, A.J., M.J. Crosby, A.J. Long, and D.C. Wege (in press). A global directory of Endemic Bird Areas. BirdLife Conservation Series. BirdLife International, Cambridge, U.K.
• 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.
• Stiles, F. G., and A. F. Skutch. 1989. A guide to the birds of Costa Rica. New York: Cornell University Press. ISBN: 0713635126.
• 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.
• Young, B. E., G. Sedaghatkish, E. Roca, and Q. Fuenmayor. 1999. El estatus de la conservación de la herpetofauna de Panamá. Resumen del Primer Taller Internacional sobre la Herpetofauna de Panama. The Nature Conservancy y Asociación Nacional para la Conservación de la Naturaleza (ANCON).