Location and General Description
The ecoregion of the wet forests of Chocó-Darién extends from eastern Panama, in the provinces of Darién and Kuna-Yala, along almost the entire Pacific Coast of Colombia, in the departments of Chocó, Cauca, Valle del Cauca, and Nariño. Thus running between latitudes 9º to 1º15’ north, then down to 2° S and longitudes 79º to 76º15’ west. This ecoregion encompasses a strip of land from sea level to an elevation of approximately 1,000 meters. It lies between the Pacific Ocean and the western range of the Andes; from west of the mouth of the Atrato River, in Panama to the Patia River, in Colombia.
There are five distinct subregions (Rangel-Ch. et al. 1994). First the northern coast, with the hill country areas of Darién and Urabá. Second the coastal zone along the Pacific coast, generally up to an elevation of 500 m. Third the central strip, including the northern wet forests, the central rainforests and the San Juan River area. Fourth the hills of Carmen del Atrato and the San José del Palmar area and finally the jungles along the Pacific slope from 500 to 1,000 m in altitude. The mountainous areas include the western slopes of Cordillera Occidental and land massifs such as Cerro Torrá, Serranía del Darién and Sierra Llorona de San Blas and Serranía del Baudó .
Average annual temperature is generally 23.6ºC, with a maximum average of 30ºC and a minimum of 18.6ºC. The biogeographic Chocó is probably the only ecoregion of this size with the precipitation, from 4,000 to more than 9,000 mm per year. It is also one of the few places in the Neotropics with pluvial rainforest (Gentry 1982). Precipitation in the ecoregion varies - with less in the northern zone, higher amounts in the central region and less again in the south. Some sectors may receive more than 13,000 mm of precipitation per year. There are areas toward Panama and the Caribbean Sea to the north and then south that have short dry seasons, generally from January to March.
There are three principal geomorphologic types in the ecoregion: alluvial plains of recent origin, low mountains formed by the relatively recent dissection of sediments from the tertiary and pleistocene periods, and the complexes in mountain areas consisting of mesozoic rocks (West 1957). The high precipitation and the topography mean that the ecoregion includes a complex of great hydrographic basins, the most important being those of the Atrato, Baudó and San Juan Rivers and the Micay and Patía Rivers in the south. The force of the water in many of these rivers form deep gorges cutting through the mountains, creating spectacular rapids and waterfalls in the mountains, along the upper courses. At lower elevations, large rivers become very wide and with many meanders. Given the high precipitation in the region, it is not surprising that the soils are very leached and poor in nutrients. Most of the ecoregion has typical lateritic soils with reddish clay, although the soils are younger and less leached in some areas, especially close to the base of the Andes and in the floodplains of the major rivers. Of particular botanical interest are the white clay soils in the region of Bajo Calima in Colombia, which are associated with the gigantic sclerophyllous leafed and unusually large fruited vegetation (Gentry 1986, 1993).
Depending on the altitudinal gradient, soil water content and the effect of the sea, there are various types of vegetation that make up the ecoregion. In broad terms, in the northern part of the ecoregion, the lowland rainforests correlate to the Brosimun utilis alliance, including communities dominated by the deciduous "cuipo" or "ceiba bonga" tree (Cavanillesia platanifolia), the "aspavé" or wild cashew (Anacardium excelsum), the "táparo" (Catilla elastica), the rubber tree (Castilla elastica), Brosimum guianense, Bombacopsis spp., Ceiba pentandra, Dipteryx panamensis, and others. In the undergrowth Mabea occidentalis, Clidemia spp., Conostegia spp. and Miconia spp. are abundant. In zones that are occasionally flooded, the "cativo" (Prioria copaifera) flourishes as well. In the southern part of the ecoregion, these rainforests have multiple strata, with two layers of trees, lianas and epiphytes with vigorous growth rates. The number of deciduous plants increases in the north and south, where there is a dry season, particularly near the coast. The forests at higher altitudes, starting at 600 m, have communities with the following species: "guamos" (Inga sp.), Billia columbiana, Brosimum sp., Sorocea sp., Jacaranda hesperia, Pourouma chocoana, Guatteria ferruginea, Cecropia sp., Elaegia utilis and Brunellia sp. (Davis et al. 1997).
Chocó-Darién corresponds to one of the largest active centers of speciation and endemism in the world. The flora of Chocó is estimated at a minimum of 8,000 species of vascular plants and possibly more than 10,000 with nearly 20% strictly endemic (Gentry 1982). Although there are no endemic families, there are endemic genera, some of which have undergone a considerable amount of speciation, including Trianaeopiper and Cremosperma. Local endemism is characteristic of the region, indicating that many species have very restricted ranges of distribution and giving rise to an extraordinary β (beta) - diversity, i.e., diversity related to high variation from one location to another in the ecoregion (Gentry 1989, 1992). There is active speciation in epiphytes, vascular plants [“bijaguas”] (Heliconia, Costus), and shrubs.
In the central zone of the ecoregion, we find a mosaic of rainforests at higher elevations and very wet or wet forests in the lower coastal ranges. These rainforests of the Chocó have distinct plant life that is usually confined to cloud forests at medium elevations (about 1,000 meters ASL) yet this habitat is not. It includes characteristics such as thick moss cover and other non-vascular epiphytes on trunks and branches and the prevalence of woody hemiepiphytic lianas belonging to the families Ericaceae, Marcgraviaceae and Melastomataceae (Gentry 1986), all of which have centers of diversity in the region. In addition, there are high densities of slender and average and not very thick trees and low biomass (Faber-Langendoen et al. 1991). In the areas to the north and south of the ecoregion a different type of rainforest in terms of physiognomy and plant life occurs. These forests have large emergent trees and a high biomass. The extraordinary amount of rainfall in this area acts as a barrier to many vertebrates, and presents a gap in the distributions of many mammals, including a number of primate species.
The ecoregion of Darién-Chocó also has high diversity and endemism with regard to fauna. There are at least 127 species of amphibians (Roa and Ruiz 1993) and 97 species of reptiles have been recorded in the ecoregion with Colubridae listed as the most diverse family, with 35 species, followed by Iguanidae, with 26 species (Sánchez and Castaño 1994). There are 577 species of birds recorded; Tyrannidae is listed as the most diverse family, it contains 28 genera and 60 species (Roda and Styles 1993). This ecoregion is a center of avian endemism of the Neotropics. According to Stattersfield (1998) this ecoregion falls within two endemic bird areas one in Central America and one in South America. Between the two areas there are at least 60 restricted range species including the Chocó tinamou (VU) (Crypturellus kerriae), Baudó oropendola (EN) (Psarocolius cassini), viridian dacnis (Dacnis viguieri), crested ant-tanager (Habia cristata), Lita woodpecker (Piculus litea) and plumbeous forest-falcon (EN) (Micrastur plumbeus) just to name a few (Stattersfield 1998). Also to be noted is the presence of the harpy eagle (Harpia harpyja), the black and white crowned eagle (Spizastur melanoleucus),which are increasingly rare in many areas of the Neotropics and possibly the speckled antshrike (EN) (Xenornis setifrons) although one has not been recorded in Colombia since the 1940s (Davis et al. 1997).
The region is also known to be rich in mammals but the larger animals have received little study as yet. Many species are in danger of extinction (E) or vulnerable (V) according to the 1996 IUCN red list (Baillie et al. 1996). These include the Chocó tamarin (E) (Saguinus geoffroyi), the tapir (E) (Tapirus bairdii), the giant anteater (E) (Myrmecophaga tridactyla), the spider monkey (E) (Ateles fuscipens), the puma (V) (Puma concolor), the ocelot (E) (Leopardus pardalis) and the jaguar (E) (Panthera onca).
According to the evaluation of Dinerstein et al. in 1995, the ecoregion has lost between 10% and 20% of the original habitat. The habitat blocks are large with minimal fragmentation and high connectivity, which still allows dispersion over long distances through altitudinal and climatic gradients. The annual habitat conversion rate or percentage of intact habitat that is altered each year from during the period 1990-1995 is estimated to be 3.5%, a relatively high figure.
Protected areas are limited in size considering the size of the ecoregion and the great diversity of different ecosystems, and thus the protection system is deficient (Dinerstein et al. 1995). The existence of extensive areas of lowland forests and medium elevations represents one of the last opportunities to conserve relatively large areas of intact forest in the northwestern section of South America. In addition, this characteristic allows the natural altitudinal migration of many species of birds, mammals and invertebrates, a phenomenon that is increasingly rare in the tropics as its forests are being destroyed. The region has great potential for ecotourism and scientific research. Its forests are of great interest because some of them may be secondary forests that are nearly 500 years old, which would clearly allow for studies on the subject of the regeneration of tropical forests (Davis et al. 1997). The areas with remaining vegetation correspond to the central area of the ecoregion, while the northern areas of Darién and Urabá, in Colombia are devoted primarily to the production of bananas and cattle ranching. Southern areas of Bajo Calima and Tumaco, are devoted in part to plantations for the production of oil palm and extraction of timber for paper pulp are those that require greater urgency and efforts for their protection and conservation (Barnes 1993; Davis et al. 1997). It is estimated that the rate of deforestation is 600 km2 per year (Budowski 1990).
Originally, in Panama, this ecoregion covered approximately 13,335 km2 (Li et al. 1999). Nearly 30% of this area, about 4,000 km2, is under some type of protection in parks and reserves. The most important is the Darien National Park, covering 597,000 hectares (representing less than 10% of the entire ecoregion), with management categories II and X (Biosphere Reserve), and also a UNESCO World Heritage Site. Next there is the Kuna-Yala indigenous reserve (3,200 km2) and the Embera Wounan reserve (4,326 km2) (Li et al. 1999; IUCN 1982; CEP 1996). An additional 40% of the ecoregion is found in areas considered to be potential parks and 5% is found in mining reserves. A third section of the area of this ecoregion in the Panamanian sector is devoted to agriculture (Li et al. 1999).
In Colombia, where most of the ecoregion is found, the largest protected areas cover an area equal to only about 1% of the total original habitat, and these areas are quite distant from each other. On the Colombian side, a total of approximately 2,013 km2 of the ecoregion is protected in national parks or 2.5% of the total ecoregion (Davis et al. 1997). Bordering on the east with the Darien National Park, in Panama, is the Los Katios National Park, covering an area of 720 km2. The Utria National Park, covers an area of 543 km2 including a land and a marine sector while the Sanquianga National Park covers 800 km2 and the Gorgona Island National Park covers 16 km2 of protected land. The lowland portions of Farallones de Cali National Park and Munchique National Park are included in this figure. Additional areas must be delineated and their protection promoted (INDERENA 1993), including the area lying between the Atrato, Baudó and San Juan rivers, the area between the Calima and Patía rivers and the western lowlands of the department of Nariño.
The lack of sufficient taxonomic and geographic data on this ecoregion makes adequate management plans difficult, and thus much additional work is needed. There is information but it is insufficient or limited to small areas. More detailed flora and ecological studies are needed on the ecoregion, as well as on the patterns of distribution of plant communities. The need for conducting studies in the region is a priority, as there are still large undisturbed areas. (Olson et al. 1996).
Types and Severity of Threats
The resources in these forests have been over-exploited for years, although the benefits have not gone to local groups (Kuna, Emberá, Wounana, Eperara, Afro-descendants mestizos and other indigenous groups). Due to the numerous threats in the ecoregion, its conservation status is vulnerable although relatively stable. There are threats of habitat conversion and the degradation associated with it, in an insufficient system of conservation areas (Dinerstein et al. 1995).
The major threat to this ecoregion is deforestation. In the Darien region, the major threat is the construction of the Inter-American Highway and the degradation associated with it. The forests of Chocó, although they represent only one-sixth of Colombian forests, supply more than half of the wood in the country. This deforestation also entails serious problems of erosion, affecting the different ecosystems of the region, including the coastal areas. Another pressing threat in Chocó is industrial development. The government has built a naval base at the mouth of Málaga Bay, an important place for humpback whale reproduction. Industrial production of African palm oil (Elaeis guineensis), uncontrolled gold mining and illegal growing of coca add to the list of causes of deforestation (Budowski 1990).
Justification of Ecoregion Delineation
The delineations for this ecoregion were derived from two national vegetation maps, that of Panama (UNDP 1970) and of Colombia (Suarez-Navarro 1984). The northern limits of this ecoregion in Panama follow UNDP’s classification of humid tropical forest and very humid tropical forest, and the arching line from the Pacific to the Caribbean denoted the transition from Chocó influence in Panama to isthmanian species associations. Montane regions were then distinguished from this primarily lowland ecoregion. Within Colombia, linework was derived by combining all Pacific "heterogeneous dense forests", "piedmont cordillera forests", "hydrophilic (riparian) forest", and "escarpment cordillera forests" of the Chocó region. From this, we then separated out all mangrove forest classifications and drew the southern delineation along the Patia River, which acts as a barrier to dispersal of many species. This ecoregion is distinct in its incredible species richness and high levels of endemic species. It is also an important convergence zone for elements of South and Central American influence.
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Prepared by: Ugo D’ambrosio
Reviewed by: Emilio Constantino