Central American dry forests
Central American dry forest, northwest Costa Rica. Source: C.Michael Hogan
Tivives, Costa Rica. Source: Linda Farley The Central American dry forests is an interesting dry forest ecoregion, which stretches along the Pacific Coast, corresponds to a tropical habitat that has a prolonged dry season of five to eight months and is home to important plant and animal species, as well as a significant degree of endemism. This totally fragmented ecoregion, represented in less than two percent of the original habitat, is threatened by strong pressures from man, including cattleovergrazing, burning, agricultural expansion, and hunting operations. The dry tropical forests are now much more rare than tropical rain forests, although the latter are also disappearing at a very rapid rate. A bright spot in the region is the Guanacaste National Park, which, even though small, provides a protected dry forest in Costa Rica that also serves as a biological migration corridor connecting Pacific coast to the moist forests toward the east.
Location and general description
Up to the mid-twentieth century, thedry tropical forest of Central America ecoregion originally extended in a continuous strip from the Pacific Coast of southwestern Mexico (southern Chiapas), through Guatemala, El Salvador, Honduras and Nicaragua to northwestern Costa Rica. The dry forest previously formed a continuous strip in lowland and premontane areas from zero to 800 metres (m) in elevation along the Central American Pacific Coast from southern Chiapas to Guanacaste. In addition, there are multiple fragments of dry forest from this ecoregion scattered in low altitude areas removed from the coast and even some relatively large fragments in interior lowland areas close to the Caribbean Sea in Honduras. In the Pacific strip area, the dry forest could also be found at higher elevations along the mountain system up to 2000 metres. The fact that this ecoregion extends along a large stretch of the Pacific Coast of Central America means that the confluence of flora and fauna from similar ecoregions of North and South America would be important. The climate of the region is tropical with a prolonged dry season of five to eight months, with average annual precipitation between 1000 and, 2000 millimetres (mm) and a generally bimodal pattern of rainfall, with a briefer and a longer seasonal dry period. Given that the prevailing winds in the ecoregion originate from the northeast or east to the southwest or south and most of the ecoregion has mountain systems running from northwest to southeast, the Pacific versant of Central America receives a lesser amount of rain than the Caribbean side. These dry forests can be found in a wide variety of soils.
A low stature semi-deciduous forest with two tree stories characterizes this dry forest, although there are variations in terms of structure and composition. Depending on water conditions, the trees of the canopy can measure approximately 30 metres in height and usually have fine, compound leaves that are shed seasonally. Most tree taxa belong to the leguminosae superfamily, many of which are associated with nitrogen-fixing bacteria (Nitrogen) and various species of ants. The trees in the lower story usually include more evergreen species and members of the Rubiaceae family. Mostly deciduous trees compose the canopy. Common trees in the southern part of the ecoregion include the Ceiba tree (Bombacopsis quinata), Degame (Calycophyllum candidissimum),Raspa Lengua (Casearia arguta), Tom Bush (Chomelia spinosa), Croton reflexifolius, Elephant Ear Tree (Enterolobium cyclocarpum), Eugenia salmensis, Erythroxylon havanense, Eugenis salamensis, Pigeon Wood (Guazuma ulmifolia), Jacuqinia pungens, Tabebuia ochracea, T. rosea, Thouinidium decandrum, Trichilia colimana, and Zanthoxylum setulosum . Underneath the canopy, thorny trees make up the understory of the forest. Also common are woody lianas and epiphytes. The small dry forest fragments that are now extant contain species that are endangered and at risk of extinction such as the Yauco (Cordia gerascanthus), Coyote (Platymiscium parviflorum), Quira (P. pinnatum), "Tempisque" Syderoxylon capiri, Swietenia humilis and mahogany (S. macrophylla), "lignum vitae" (Guaiacum sanctum), "cocobolo" Dalbergia retusa, "ronrón" Astronium graveolens. Other interesting, unique or rare plants in the region are "guachipelín blanco" Myrospermum frutescens, brazilwood (Haematoxylon brasiletto), "tamarindo de monte" Lysiloma divaricatum, Cedrela odorata and Bombacopsis quinatum.
Biodiversity features
Sphinx moth (Xylophanes chiron), Costa Rica. Source: S. E. Cornelius The dry forest on the Pacific Coast of Central America corresponds to an ecoregion of biological interest because elements of both South and North America are mixed. This ecoregion also contains a large percentage of endemic flora and fauna. At least 50 plant species are endemic to the region such as Myrospermum. A Costa Rican endemic is Rehdera found in the northern Guanacaste Province. Many plant species have evolved effective adaptive strategies to survive in these forests. During the dry season, for example, many species lose their leaves and drop their fruits, allowing them to limit evapotranspiration. There are also numerous adaptation examples of succulent sclerophyllous species with photosynthetic stalks or bark, short and synchronous flowering periods, and large deep roots all. This can be considered an ecosystem intimately associated with the human species for at least the last 11,000 years. As a result the ecosystem has suffered anthropogenic disturbances for considerable time. It has some vegetation in semi-arid zones and on lands with special geologic conditions and thus some endemic vegetation can be found, such as high-density stands of Encino Prieto (Quercus oleoides), and Morrito (Crescentia alata). Although it is a seasonal environment, there are some fungi that have adapted to the dryness and high temperatures. New records of bryophytes and pteridophytes have emerged in Costa Rica. There are still entire groups of plants and fungi in the biological environment that remain unknown.
Scarlet macaw (Ara macao). Source: David Olson Considered a Central American area of interest by Harcourt et al., due to the endemism of its avifauna, this area also includes part of the wet forests of the Pacific adjacent to the dry forests outside of this ecoregion. According to Stattersfield et al. this ecoregion falls within the North Central American Pacific slope Endemic Bird Area with four restricted range species, three of which are endemic including the White-bellied Chachalaca (Ortalis leucogastra), the blue-tailed hummingbird (Amazilia cyanura) and the giant wren (Campylorhynchus chiapensis). The Pacific parakeet (Aratinga strenua) although not endemic this ecoregion is part of its restricted range.
Large numbers of mammals live in these forests including endangered species of spider monkey (Ateles geoffroyi) which use the corridors of rivers through the dry forest, as well as various cats such as Felis onca, F. concolor, F. pardalis, F. wiedi and F. yaguaroundi, tapir (Tapirus bairdii), anteaters (Tamandua mexicana) and many others. Mention should be made of the aquatic fauna of the Pacific coast that, depending on the zone, is home to up to five different species of marine turtles, numerous fish, amphibians and other endangered reptiles.
Current status
In Honduras, the dry forests are very deteriorated. The principal cause has been migratory agriculture. With the country’s demographic explosion, the future is expected to bring a greater reduction in the few remaining dry forest habitat areas. Indiscriminate hunting and fishing, and trafficking in wildlife also threats this ecoregion. None of the small patches of dry forest in existence are found in protected areas. In Nicaragua, the Pacific Coastal area is the most populated region, with the most infrastructure and urban development. In addition, for the last 40 years large areas have been devoted to the growing of cotton, sugar cane or banana, and to a lesser extent coffee. Most of the hydrographic basins are contaminated and experience frequent droughts. Deforestation is due to the conversion of forestlands to extensive cattle-raising and migratory agriculture. In addition, forests are cleared for firewood, which represents nearly 50% of all of the country’s energy sources. However, a few remnants of dry forest remain at elevations below 500m, with average annual precipitation of less than 1500 mm. Some of the characteristic species are boxwood (Phyllostylon brasiliensis), lignum vitae (Guaiacum sanctum) and Haematoxylum brasiletto. Costa Rica is the country that has implemented the most conservation strategies for this ecoregion, although very little of the original habitat is protected. This forest is affected primarily by the extraction of precious woods and many agricultural activities.
The highest priority in the ecoregion is the need for rehabilitation, formulation of management strategies including fire control and prevention, and absolute protection of the last remaining fragments, as small as they may be. If an action plan is not established according to each country’s socioeconomic and political structures, the dry forests could be wiped out completely in a short time, leaving only tiny remnants. The action plan should not only conserve but also work on the recovery of contiguous areas in the ecoregion.
Biological corridor
In 1989 the Government of Costa Rica established the Guanacaste National Park, part of the Area de Conservación Guanacaste World Heritage Site as a protected habitat in northwestern Costa Rica, This unit effectively serves as a biological corridor connecting moist forested topography on the slopes of the Orosí and Cacao Volcanoes west to the Pan-American Highway, where it joins Santa Rosa National Park. This migration corridor between the dry forest and rain forest areas allows many fauna species to move seasonally. This protected area embodies a holding of about 340square kilometers, and boasts 140 species of mammals, more than 300 bird species, 100 amphibian and reptile taxa, and over 10,000 species of insects.
Types and severity of threats
The threats to this highly decimated ecoregion vary in each country. In Guatemala, inadequate economic structures, large numbers of poor people with basic needs, expansion of the agricultural frontier and many other factors have an effect on the amount and rate of habitat destruction. In El Salvador, conservation of the dry forest has been difficult due to the lack of sectional planning, organization, institutional coordination, policies, legislation, and governmental financial capacity. El Salvador's natural resources and wildlife are highly endangered. The crimes of usurping and usufruct of state areas threaten the existence of natural areas. While this country once had abundant flora and fauna, the only remaining Park with dry forest is Deininger National Park covering 7.32 square kilometres.
Justification of ecoregion delineation
The delineation’s for the Central American dry forests were derived from a variety of maps and other sources, and the final linework was a result of combining this data with expert opinion at a number of workshops. The linework for Costa Rica follows the Holdridge system and is derived by lumping the tropical dry forest and tropical dry forest transition to humid life zones. The delineation’s for the dry forests of Nicaragua were derived from national vegetation and coverage maps. Within Honduras, Holdridge line zones were again used and linework was derived by lumping lowland dry forest, lowland arid forest, and premontane dry forest. In El Salvador, the Instituto Geográfico Nacional "Ingeniero Pablo Arnoldo Guzmán" map was utilized and expert opinion helped place the lines. In Guatemala, Junio was utilized for linework and then expert opinion was consulted for the final product. Some assumptions were made based on climate and elevation to map historic ranges in areas were original habitat has long since been degraded. Linework in Mexico was based on Flores et al., and modified by expert opinion resulting from several workshops. Justification for the ecoregion is based on endemic bird areas and both floristic and faunistic range limits to "dry forest" species, associations, and processes.
Further reading
- For a terser summary of this entry, see the WWF WildWorld profile of this ecoregion.
- Bellefontaine, R., A. Gaston, and Y. Petrucci. 1997. Aménagement des fôrets naturelles des zones tropicales sèches. Cashier FAO conservation: 32. Roma, Italia.
- Bullock, S., H. Mooney, and E. Medina, editors. 1995. Seasonally dry tropical forests. Cambridge University Press, Cambridge, U.K. ISBN: 0521435145
- Carrillo, E., and C. Vaughan, editors. 1994. La vida silvestre de mesoamérica: Diagnóstico y estrategia para su conservación. Editorial Universidad Nacional, Heredia, Costa Rica.
- Dinerstein, E., D.M. Olson, et al. 1995. A Conservation Assessment of the Terrestrial Ecoregions of Latin America and the Caribbean. The World Bank in association with WWF, Washington, D.C. ISBN: 155963734X
- Flores, M.G. L.J. Jiménez, S.X. Madrigal, T.F. Takaki, X.E. Hernández, and R.J. Rzedowski. 1971. Mapa de tipos de vegetación de la República Mexicana. Map at a scale of 1;2,000,000. Secretaría de Recursos Hidráulicos.
- Gentry, Alwyn. 1995. Diversity and floristic composition of neotropical dry forests. S. Bullock, H. Mooney and E. Medina, editors. Seasonally dry tropical forests. Cambridge University Press, Cambridge, U.K.
- Harcourt, C., and J. Sayer, editors. 1996. The conservation atlas of tropical forests: The Americas. Simon & Schuster, NY. ISBN: 0133408868
- Hartshorn, G. 1983. Plants Introduction. D. H. Janzen, editor. Costa Rican natural history. University of Chicago Press, Chicago.
- Holdridge, L.R. 1962. Mapa ecológico de Honduras. Map 1:1,000,000. OAS, Washington, D.C., USA.
- Instituto Geográfico Nacional "Ingeniero Pablo Arnoldo Guzmán". 1987. Mapa básico de la República de El Salvador. San Salvador, El Salvador.
- Instituto Nicaraguense de Recursos Naturales y del Ambiente (IRENA). 1992. Ordenamiento Ambiental del Territorio plan de accion forestal. IRENA, Managua, Nicaragua.
- Inventario Nacional de Recursos Fisicos. 1966. Nicaragua: vegetation. U.S. Army Corps of Engineers, AID/RIC GIPR No. 6, Washington, DC, USA.
- Janzen, D. 1986. Guanacaste national park: tropical ecological and cultural restoration. Ed. Universidad Estatal a Distancia, San José, Costa Rica. ISBN: 9977643164
- Janzen, D.H., editor. 1983. Costa Rican Natural History. The University of Chicago Press, Chicago, IL. ISBN: 0226393321
- Jiménez Q. 1999. Árboles maderables en peligro de extinción en Costa Rica. Instituto Nacional de Biodiversidad, San José, Costa Rica.
- Jiménez, Q., Poveda L. 1997. Lista actualizada de los principales árboles maderables nativos de Costa Rica. Aportes al desarrollo sostenible #2. Universidad Nacional, Heredia, Costa Rica.
- Junio, C.A. 1982. Mapa de cobertura y uso actual de la tierra República de Guatemala. Instituto Geográfico Nacional Guatemala, Guatemala City, Guatemala.
- La Bastille, A. 1978. Conservación de áreas silvestres en Centroamérica. CATIE, Turrialba, Costa Rica.
- León, J., and L. Poveda. 2000. Nombres comunes de las plantas en Costa Rica. Ed. Guayacán, San José, Costa Rica.
- McCarthy, R., and A. Salas. 1998. Las áreas protegidas de Centroamérica. Área de conservación de bosques y áreas protegidas. UICN/ORMA.
- Reid, F.A. 1997. A field guide to the mammals of Central America and Southeast Mexico. Oxford University Press, New York, NY.
- Sabogal, C. 1992. Regeneration of tropical dry forests in Central America, with examples from Nicaragua. Journal of Vegetation Science 3: 407-416.
- Sistema de Integración Centroamericana: Dirección ambiental, con el apoyo técnico de UICN-ORMA y WWF Centroamérica. 1999. Lista de fauna de importancia para la conservación en
- Centroamérica y México: listas rojas, listas oficiales y especies en apéndices CITES. WWF, UICN, SICA, San José, Costa Rica.
- Stattersfield, A.J., M.J. Crosby, A.J. Long, and D.C. Wege. 1998. Endemic bird areas of the world: priorities for conservation. BirdLife International, Cambridge, UK.
- Tosi Jr., J.A. 1969. Republica de Costa Rica: mapa ecológico. Map 1:750,000. Tropical Science Center,San Jose, Costa Rica.
- Wege, D.C., and A.J. Long. 1995. Key areas for threatened birds in the Neotropics. Birdlife international, Smithsonian, Washington, DC.
- WWF, Museo Nacional de Costa Rica. 1999. Identificación de vacíos de información botánica en Centroamérica. Taller de análisis de información.. San José, CR
- WWF. 1996. Identificación de vacíos de información botánica para la conservación de la biodiversidad en América Latina y El Caribe. Memorias del taller. Washington, D.C.
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