Panamanian dry forests
Buttressed tree and dry forest, Panama. @ C. Michael Hogan
The Panamanian dry forests ecoregion occupies approximately 2000 square miles of coastal and near-coastal areas on the Pacific side of Panama, around portions of the Gulf of Panama.
Four disjunctive elements of the Panamanian dry forests. Source: World Wildlife Fund
Originally, the Panama dry forests were distributed exclusively in the lower and premontane portions of the Pacific versant (0-800 metres in elevation), around the Gulf of Panama;. This ecoregion has a dry climate and intermediate flora diversity, which is distributed in distinct areas, such as small residual deciduous and semi-deciduous forests and gallery forests along the rivers.
Habitat destruction of this ecoregion has been extensive, with overgrazing, agricultural conversion and urbanization and resultant fragmentation, strong pressure for cattle ranching, burning, and hunting.This process of habitat destruction began in earnest with the Spanish exploration and settlement period of the mid 1800s.
This neotropic ecoregion is one of the least well conserved in the region with a scant 0.52 percent of the land area under some type of protection.
Resident species are highly adapted to living with little availability of water and high solar radiation, and they demonstrate defenses against herbivory. Plant endemism is intermediate, and vertebrate species richness is also quite high in the Panamanian dry forests.
This important ecoregion is highly threatened from its extensive ongoing exploitation. Beyond the high endemism and species richness, the ecoregion is further significant since it offers a biological corridor from the moist forests to the coastal mangroves.
Contents
Geography and climate
The entirety of this terrestrial ecoregion lies between sea level and elevation 800 meters, and encompasses a land area of approximately 5200 square kilometers. There are four disjunctive units of the Panamanian dry forests. (World Wildlife Fund). The most extensive element is along the western part of the Gulf of Panama flanking the eastern Azuero Peninsula and wrapping crescent shaped around the northwest margin of the Gulf of Panama. This unit includes the near coastal portions of Los Santos, Herrrera and Cocle Provinces, which in some reaches extends about fifty kilometers from the coast. Parts of the immediate coastline are actually designated as South American mangroves ecoregion, with the dry forests beginning one to three kilometers inland. The Herrera Province portion includes all of the area surrounding Parita Bay except for the coastal fringes that are designated as mangroves.
The next largest element of the Panamanian dry forests lies in the near coastal portion of the northern Gulf of Panama near the capital Panama City; the Parque Natural Metropolitano is an important easily accessible protected area within this element of the dry forests. A third coastal element lies disjunctively along the eastern side of the Gulf of Panama, specifically along the southern shore of the Gulf of San Miguel in the Darien Province. A small interior portion of the Panamanian dry forests lies in Chiriqui Province.
Temperatures are relatively constant throughout the year with a mean average of about 27 degrees Celsius. Rainfall is minimized by the shielding effects of the continental divide and the Azuero Peninsula highlands, both of which intercept much of the rain fronts which come from the Caribbean side of the country. Rainfall in this ecoregion is typically below 1500 millimeters per annum, which is approximately one half of the precipitation on the Caribbean side, only a modest distance away. Hurricanes are absent from this ecoregion.
Looking up to the canopy top, Panamanian dry forest. @ C. Michael Hogan
Flora diversity
Plant endemism is high within the Panamanian dry forests, likely due to the (a) isolation of this ecoregion from the surrounding and intervening moist forest habitat; (b) arid conditions which likely enhanced speciation and hence species richness; and (c) absence of prehistoric glaciation, which has extinguished many species in more extreme latitudes.
Many of the plants are well adapted to herbivory defense through such morphologies as spiny exteriors and other features. Forest canopies are typically less than twenty meters, with a few of the highest species exceeding that benchmark. Caesalpinia coriaria is a dominant tree in the Azuero Peninsula portion of the dry forests, while Lozania pittieri is a dominant tree in the forests near Panama City. (Kricher) The vegetative palette is well adapted to the dry season, where water is a precious commodity.
Faunal diversity
Plantation Glass Frog. Source: Justin Touchon/EoL Faunal species richness is high in the Panamanian dry forests, as in much of Mesoamerica, with a total of 519 recorded vertebrates alone within the Panamanian dry forests. Special status reptiles in the Panamanian dry forests include the American Crocodile (Crocodylus acutus), the Lower Risk/Near Threatened Brown Wood Turtle (Rhinoclemmys annulata), the Lower Risk/Near Threatened Common Caiman (Caiman crocodilus), the Lower Risk/Near Threatened Common Slider (Trachemys scripta), and the Critically Endangered Leatherback Turtle (Dermochelys coriacea). There are two special status amphibian in the ecoregion: the Critically endangered plantation Glass Frog (Hyalinobatrachium colymbiphyllum) and the Vulnerable Camron mushroom-tongued salamander (Bolitoglossa lignicolor).
Threatened mammals found in the Panamanian dry forests are the: Endangered Central American Spider Monkey (Ateles geoffroyi), the Vulnerable Giant Anteater (Myrmecophaga tridactyla), the Near Threatened Handley’s Tailless Bat (Anoura cultrata), the Vulnerable Lemurine Night Monkey (Aotus lemurinus), the Near Threatened Margay (Leopardus wiedii), the Near Threatened Yellow Isthmus Rat (Isthmomys flavidus), the Near Threatened White-lipped Peccary (Tayassu pecari), and the Near Threatened Spectral Bat (Vampyrum spectrum). There are two special status bird species occurring in the ecoregion: the Endangered Great Green Macaw (Ara ambiguus) and the Near Threatened Olive-sided Flycatcher (Contopus cooperi).
Conservation
Panama urban scene, indicating a part of the extensive habitat loss. @ C. Michael Hogan This ecoregion has been highly degraded by human activity and most of the habitat has been destroyed and severely fragmented. Due to its accessible lowland and premontane elevations, even primitive humans exacted a toll on the landscape. The Spanish settlement period and twentieth century human population explosion have exacted the greatest damage due to introduction of domesticated livestock, agricultural conversion to cropland and general urbanization.
The ecological importance of the Panamanian dry forests stems from its critical location as a biological corridor for seasonal migration of species moving from the higher elevation moist forests to the coastal mangroves, or simply as a gene pool connector for species that can reside in the moist forests as well as the mangroves. In the latter case, populations of some taxa such as the Almirante Robber Frog (Craugastor talamancae) are effectively isolated by the degradation of the Panamanian dry forests. Most of the ecologically useful fraction of this corridor has been effectively severed by human activity and land cover changes exacted to accommodate the burgeoning human population; however, some bird species appear to be more tolerant of this degradation. (Lasky & Keitt) There is a pressing need to expand the protected fraction of the region above the present 0.52 percent of the ecoregion land area.
History of exploration
The early exploration of any of the ecoregions of Panama has scant recording prior to the year 1848. Coastal probing and mapping of the Caribbean shores of present day Panama occurred as early as 1501 and 1503 by Rodrigo de Bastidas and Christopher Columbus. Further recording of some basic coastal biotic conditions were made by Vasco Núñez de Balboa and Gaspar de Espinosa in the early sixteenth century, with the latter conducting interior reconaisance through the Panamanian dry forests and into the Pacific lowland forests at least as far inland as the town of Santiago.
The earliest scientific exploration of detailed recording of Panama's ecoregions began (Seeman. 1852-1857) in 1848 with the arrival of Berthold Seeman, botanist of the HMS Herald. Seeman collected and described a vast array of Panama's trees, shrubs and herbaceous species. At that time dense forests occupied two thirds of Panama's land area. On the Pacific coast lowlands Seeman described the forests, savannas and grasslands as virtually unharmed by native agriculturalists; the human population within what is present day Panama is estimated to have been 130,000 in the year 1850.
See also
References
- Bullock, S. H., H. A. Mooney, and E. Medina. 1995. Seasonally dry tropical forests. Cambridge University Press, New York
- A.J. Crawford & E.N. Smith. 2005. Cenozoic biogeography and evolution in direct developing frogs of Central America (Leptodactylidae: Eleutherodactylus) as inferred from a phylogenetic analysis of nuclear and mitochondrial genes. Molecular Phylogenetics and Evolution 35: 536-555
- Dinerstein, E., D. M. Olsen, D. J. Graham, A. L. Webster, S. A. Primm, M. P. Book-binder y G. Ledec. 1995. A conservation assessment of the terrestrial ecoregions of Latin America and the Caribbean. World Bank, WWF. Washington D. C., USA.
- C. Michael Hogan. 2012. Species account for Craugastor talamancae (Dunn, 1831). GlobalTwitcher. ed. N.Stromberg
- J.Kricher. 2011. Tropical Ecology. Princeton University Press
- Jesse R. Lasky & Timothy H. Keitt. 2009. Abundance of Panamanian dry forest birds along gradients of forest cover at multiple scales. Journal of Tropical Ecology. Vol 26 pp 67-78
- Berthold Seeman. 1852-1857. The botany of the voyage of HMS Herald. Lovell Heave. London
- United Nations Development Programme. 2007. Supporting Country Action on the CBD Programme of Work on Protected Areas: Panama.
- World Meteorological Organization. 2012. World Weather Information Service: Panama City, Panama
