Location and General Description
Located in south western Colombia and western Ecuador, most of this ecoregion’s moist forests are concentrated in the province of Esmeraldas to the north between the area of San Lorenzo (south of the Colombian Chocó) and Quinindé (Mangoya river). The ecoregions boundaries extend from the Patia River in the north then through the provinces of Manabí and Guayas to the south where it touches the Golfo de Guayaquil, ending among the foothills of the Andes Mountains in the east (Fundación Natura 1995). The ecoregion covers an area of 34,108 km2 extending over the coastal plain varying in width from about 100 to 200 km. The northern half of this ecoregion extends along the Pacific Coast except for interruption by patches of mangrove forest in areas with an inflow of freshwater. In the southern half of the ecoregion it is separated from the Pacific Coast by the Ecuadorian dry forest ecoregion. Toward the east the ecoregion becomes lost in the western foothills of the Andes, below elevations of 800 m (Suárez & Silva 1996; Sierra 1999).
This ecoregion maintains its moist forest classifaction due to the high in flux of precipitaion and the almost complete lack of a designated dry season. Annual rainfall rates fluxuate with higher averages in the north then becoming progressively drier in the south; however, these southern areas still receive more than 1000 mm of precipitation annually. More than 8,000 mm of annual rainfall has been recorded for some areas within this ecoregion, near the Colombian and Ecuadorian border (Davis et al. 1997) and these are thought to be some of the wettest places on earth (Stattersfield 1998). The northern half of the ecoregion averages more than7,000 mm while the southern half averages about 2,000 mm each year (Fundación Natura 1990; Dodson & Gentry 1993; Suárez & Silva 1996). Average annual temperatures range between 23 and 27 °C, with slight seasonal fluctuations and variations of only minus or plus 2 to 3 °C from the coldest months to the warmest months.
The history of these forests has been influenced by intense volcanic activity, resulting in formations of volcanic-sedimentary rocks that continue as far as 700-800 meters above sea level in the western foothills of the Andes. These have left volcanoclastic deposits and andesitic lavas found together with intercalated turbidic marine sediments corresponding to tertiary sedimentary formations. The soils are fertile, particularly toward the north-central region, which lies over lapilli and ashes. Geomorphological processes going from west to east such as plate tectonics, the warm el Niño current and the cold Humboldt current, increasing altitude and the influence of areas of intertropical convergence transform these wet forests into increasingly dryer formations, and the topography becomes uneven and unsuitable for the growth of wood (Fundación Natura 1990).
The vegetation is dominated by trees with a dense canopy of over 30 meters high, rich in lianas and epiphytes many of which are endemic; as well as woody climbers (lianas), mosses and lichens, ferns and palms. In these forests, 1250 plant species have been recorded corresponding to 136 families in 1 km2, and of these species 43 are endemic (Dodson & Gentry 1978). The forests of this ecoregion are shaped by dominant species of trees, palms and lesser plants throughout the structural vegetation layers. For example, Virola dixonii, Carapa guianensis, Brosimum utile and Guarea kunthiana (Davis et al. 1997) represent some of the large and dominant tree species in the canopy. Two main species of the subcanopy are the palms (Iriartea deltoidea and Wettinia quinaria) (Davis et al. 1997). Many other tree species are cited by different sources including Pseudolmedia eggersii, Clarisia racemosa, Brosimun utile, Symphonia globulifera, Matisia colora dorum, Pouriuma chocoana and Pouteria sp. (Fundación Natura 1995). Emergent species like the strangler fig (Ficus dugandii) may reach heights of over 60 m while very abundant epiphytes such as Araceae sp and Cyclanthaceae sp. cover the lower parts of tree trunks and ferns help make up the dense understory (Davis et al. 1997).
At the Río Palenque Scientific center in the province of Esmeraldas and in small patches of remnant forest there are rare species like Diliptera dorsonii Wassh and some records of extinct plants such as Carapa megistocarpa A. Gentry, Brownia sp. and Erythrochiton carinatus Kaastra & A. Gentry.
A high number of endemic species that are specific to small areas, particularly in narrow strips and on isolated mountain ridges help characterize these forests (Dodson & Gentry 1993). This ecoregion is part of a bioregion noted for some of the highest avian endemism in the world. In 1993 Dodson and Gentry identified 650 species of birds in the region. A large number of birds in the ecoregion are threatened. Some occur in the most humid parts ranging into the Chocó forest of Colombia such as Crypturellus berlepschi, Penelope ortoni, Aramides wolfi, Pyrrhura orcesi, Thalurania hypochlora, Scytalopus robbinsi, Cephalopterus penduliger, Dacnis berlepschi, Diglossa indigotica, Tangara johannae. Other species prefer less humid area nearer the bordering dry forest including Leucopternis occidentalis, Ortalis erythroptera, and, Attila torridus. Confined to the northern mangroves is Hylocharis humboldtii. Larger species that have been nearly extirpated in the ecoregion owing to fragmentation and hunting include Tinamus major, Harpia harpyja, Penelope purpurascens, Crax rubra, and Ara ambigua.
It is also unique because it has a high number of endemic plants; about 10,000 plant species have been identified and 2,500 of these are endemic (Dodson & Gentry 1978). In a part of this ecoregion north of the Guayllabamba River the endemic Humiriastrum procerum tree grows however its numbers are low due to its popularity as a building material (Davis et al. 1997). The Río Palenque Scientific Center has 26% local endemism. Here and in other parts of the ecoregion, five new mammal species and 122 orchid species have been found in recent years (Fundación Natura 1990; Dodson & Gentry 1993).
In the moist forests of the west, large radiations caused by natural fragmentation and climatic and edaphic processes facilitate dynamic speciation, which is extremely rapid, as well as adaptation for survival, with low density and rapid natural rates of extinction. An example is the disproportionate number of monocotyledoneae (28%) compared to dicotyledoneae (19%). Similarly, Gasteranthus sp. of the family Gesneraceae is highly evolved with four endemic species for the ecoregion. (Dodson & Gentry 1993). Given that the forest has been highly fragmented, this process has unleashed variations in the migration patterns of certain bird species that have extended their range of distribution to this zone. These include the harpy eagle (Harpia harpyja) and Great Curassow (Crax rubra). One of the ecological processes responsible for maintaining biodiversity in the area is the cold Humboldt current that brings cold, dry winds and regulates the transition line between moist forests to dry forests in the south (Dodson & Gentry 1993).
At present, the coastal cordillera region has only small patches of remnant forest, which are now subjected to the edge effect; however, the most intact forests in the southern part of the ecoregion are in the communities of Chongón, Jame, 10 de Agosto and Colonche. The largest remaining forests are situated in Esmeraldas Province and along the Pacific slope in Azuay and El Oro. Also recognized are small continuous, narrow strips running parallel to the mountain chain in the northern end of the coastal cordillera that still have good biotic integrity but are seriously threatened by settlement, indiscriminate felling of trees and environmental deterioration (Fundación Natura 1990). Large predator species such as Panthera onca and Crocodylus acutus (VU), are some of the threatened species in these forest remnants (Suárez & Silva 1996).
Between 1960 and 1980 there was accelerated construction of highways and oil exploration, leaving only 4.4 percent of the forests (Dodson & Gentry 1993) in western Ecuador. The zone covered by wet forest is declining from 50 percent to 1993 percentages of less than 1 percent according to Dodson & Gentry (1993).
Ecuador’s primary forest coverage is 72,000 km2 and only an area of less than 40,000 km2 is in the west. In this area, the Cotacachi-Cayapas government reserve falls within the limits of this ecoregion. Ecuador also has one of the major wet forest remnants in the western highlands between 400 and 900 meters in Machalilla National Park. Within the National System of Protected Areas (SNAP), the western forests are least represented. Other institutions or private organizations collaborate in management, protection and research, among them the Río Palenque Scientific Station (Suárez & Silva 1996).
Types and Severity of Threats
The major threats to these ecosystems are the effects of activities associated with banana plantations and extraction of palm oil and rubber (Suárez & Silva 1996). The moist forests of western Ecuador constitute one of the most threatened types of habitat on the planet. In addition, the construction of roadways also constitutes a high intervention factor and facilitator of settlement, and thus felling of the forest and conversion to pasture (Fundación Natura 1990; Dodson & Gentry 1993). According to Olson and Dinerstein (1998), the ecoregion of Ecuador’s wet forests is considered vulnerable.
Justification of Ecoregion Delineation
This western moist forest ecoregion encompasses the lowland coastal habitats and valleys of southern Pacific Colombia and Ecuador. These forests occur from approximately 800m elevation on the western slopes of the Andes, and extend to the Pacific Ocean, excluding portions of dry forests and mangrove habitats, which we classify as a separate ecoregion. The northern deliniation occurs along the Patia River, which is a formitable barrier to dispersal of many species and thus seperates this ecoregion from the wetter Chocó influences to the north. The southern boundary occurs near Guayaquil – though several fingers extend into moist valleys from this point – otherwise the western lowlands become dry to xeric to the south. In Ecuador we refered to Sierra (1999). Linework was reviewed and modified at the ecoregion workshop for the Northern Andes (Bogota, Colombia, 24-26, July, 2000).
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Prepared by: Paola U. Carrera and Pilar G. Jiménez with contributions from Xavier Viteri
Reviewed by: Neils Krabbe