Northern South America: Southeastern Colombia into Brazil

Located in the Colombian Amazon and high in rainfall, flora diversity is rich as is a transitional area between these floristic provinces of the Amazon Basin forests and the Guayana region. Fauna diversity is high although endemism is not. A few species that are endemic include the Chiribiquete emerald (Chlorostilbon olivaresi) and grey-legged tinamou (Crypturellus duidae), and tamarin (Saguinus inustus). Large-scale cattle ranching poses the most serious threat to this ecoregion. Large tracts of forest have been logged to cultivate pastures for grazing.

  • Scientific Code
  • Ecoregion Category
  • Size
    71,100 square miles
  • Status
    Relatively Stable/Intact
  • Habitats

Location and General Description
The Caquetá moist forest occurs in the Colombian Amazon. It is bound on the northeast by the Guainía, Guaviare, and Guayabero rivers and to the western extreme at the small Rio Losada, south of the Serrania de la Macarena. The southern border of the region extends southeast from the headwaters of the Rio Caguan, which then converges with the Caquetá. The region extends east just into Brazil. The Apaporis, Vaupés, and Yari rivers dissect this region, and large expanses of seasonally flooded forest occur on their banks. Geologically, the Caquetá moist forest ecoregion is part of the Guayana Shield whose rocks are among the most ancient in South America. Because of multiple and extensive times of sedimentation and low elevation, however, the forests floristically have more affinity to the Amazon Basin forests rather than those of the Guayana floristic region. Nevertheless, this is a transitional region between these floristic provinces.

Four major geomorphic groups are identified in this region. They host distinct vegetative communities: the alluvial plains of the Caquetá River, their upland terraces, a Tertiary sedimentary plain, and a unit of hard rocks that forms a consistent plateau of Palaeozoic sandstone . These plateaus, or mesetas, include the Cerro Isibukuri, Cerro Yapobodá, Cerro Araracuara, and the massif of Chiribiquete that reaches 800 m elevation. This series of low sandstone table mountains hosts a low sclerophyllous forest on the lower and middle slopes and sclerophyllous shrublands on the rocky substrate of the lowlands and on the mountaintops (Huber 1995).

The soils of the region are heterogeneous, some having high total nutrient resources and others with low nutrient resources. Forest structure and composition reflect the relative nutrient status. In forests on the poorer soils, such as in the igapó forests (seasonally inundated by blackwater rivers), the trees tend to support fewer epiphytes, and the understory is less dense. Lying between 100 and 300 m in elevation, this region has an average annual temperature of 26° C. This ranges between 20° and 32° C, depending on elevation and forest cover. This region receives some of the highest rainfall in Amazonia with an annual average of 3,000 mm and extremes to 4,000 mm.

There are three structural types of forest found here. High forest is found on well-drained soils with a canopy of 24 m and basal area of 32 m2/ha. Low forest is on poorly-drained soils with a canopy of 10 m and a 17 m2/ha basal area. Permanent swamp forests is on poorly-drained soils dominated by palms such as Mauritia flexuosa, 18 m high, with an area of 27 m2/ha . The first two types are characterized by the absence of dominant species, that is, a high very alpha diversity. The diversity of some forests here rivals the extremely high diversity of other western Amazonian regions such as those around Iquitos, Peru, and in the cloud forests of Ecuador. The most important tree famlies are Leguminosae, Sapotaceae, Lauraceae, Chrysobalanaceae, Moraceae, and Lecythidaceae. Scientists have identified 15 community types here, reflecting different drainage patterns, soil nutrients, and influence of floods .

An example of the plateau environment is the Sierra de Chiribiquete in the center of this region, situated between the Rio Apaporis and Rio Yari. The highest point is 840 m elevation. A patchwork of vegetation types corresponds to topography, soil characteristics and climatic variations. Thse include xeromorphic open vegetation with shrubs and trees to 5 m; low forest (7 to 8 m); closed-canopy medium forest with a canopy from 15 to 22 m high; and savanna vegetation (Cortés-B. et al. 1998). The vegetation has closest affinity to the Amazon region and secondly to the central Guayana region. The most common vascular plant families are Rubiaceae, Melastomataceae, Orchidaceae, Bromeliaceae, and Cyperaceae (Cortés-B. et al. 1998).

Biodiversity Features
Among the 469 birds found here with a restricted distribution are two endemics, Chiribiquete emeralds (Chlorostilbon olivaresi) and grey-legged tinamous (Crypturellus duidae). Also found here are the plain-winged antwren (Myrmotherula behni), dusky spinetail (Synallaxis moesta), lemon-throated barbet (Eubucco richardsoni), and zone-tailed hawk (Buteo albonotatus).

Mammal diversity, with 189 species, rivals that of the birds. Larger mammals include tapirs (Tapirus terrestris), collared peccaries (Tayassu tajacu), white-lipped peccaries (Tayassu pecari), 13 primates including the night monkey (Aotus vociferans), a white-faced saki (Pithecia monachus), and a regionally endemic tamarin (Saguinus inustus).

Reptiles and amphibians are abundant and include the tortoise (Geoquelone denticulata) and the more famous snakes such as fer-de-lance (Bothrops asper), palm pit-vipers (Bothriechis spp.), Philodrias viridisimun, coral snakes (Micrurus spp.), boa constrictors (Boa constrictor), and bushmasters (Lachesis muta). Iguanas (Iguana iguana) are ubiquitous and tegus lizards (Tupinambis) common.

Current Status
Large-scale cattle ranching in the western extreme of this ecoregion at the headwaters of the Vaupés River has resulted in the clearing of vast expanses of forestland. A large triangle of deforestation has occurred, fanning out from the San Jose-Calamar road south of the Rio Guayabero. In the interior of the region small settlements of indigenous people have little impact on the natural habitat ; however, colonists are now migrating down the Rio Negro, deforesting along the way for small-scale agriculture or cattle grazing. Large forested areas along the Vaupés and Apaporis rivers are also falling to coca (Erythroxylum coca) production. The one protected area in this region is the 8,550 km2 Nukak Tuhahi National Reserve in the center. The remaining intact forest is considered threatened frontier forest that may eventually be degraded by ongoing human activities.

Types and Severity of Threats
Human-induced deforestation for plantations and cattle pasture is the most severe threat to the natural habitat. Large quantities of ornamental fish, particularly arawana (Osteoglossum bicirrhosum), are harvested for international trade, although the severity of the threat of extinction’s is unknown.

Because this is a transition zone between the western Guayana and northwest Amazon floristic provinces where elements of both intermingle, the habitat of this ecoregion deserves concerted conservation effort. The administration of the national parks should be strengthened. Economic alternatives to coca production and cattle ranching should be developed for the local residents and colonists. Trafficking of wildlife, such as the ornamental fish Osteoglossum bicirrhosum, should be more strongly regulated.

Justification of Ecoregion Delineation
These moist forests stretch from the foothills of the Andes (approx. 500m) eastwards across Colombia to western Brazil, and are interspersed with patches of várzea habitats along the major waterways. The northern delineation spans the gap between the eastern Andes and the Serrania de la Macarena, then follows the Guayabero River eastwards. The southern delineation follows the Guayas River from the foothills of the Andes (aprox. 500m) eastward along the Caguan and eventually the Caqueta River. The eastern delineation’s extends from the Caqueta River (near where it becomes the Japura) northwards to encompass the Serra do Traíra, then continues northwards along the Inírida River to its confluence with the Guayabero River. This ecoregion is unique in its endemic species and shared components and species associations with the Amazon and Orinoco floristic provinces, as well as both Andean and lowland influences (da Silva 1998). Linework follows river systems for the most part, although reference was also made with various ecological maps (Navarro et al 1984, IBGE 1993). Linework was reviewed and modified at a priority setting workshop (CEAN 2000).

Complejo Ecoregional de los Andes del Norte (CEAN). Experts and ecoregional priority setting workshop. Bogota, Colombia, 24-26, July, 2000.

Cortés-B., R., P. Franco-R., and J. O. Rangel-C. 1998. La flora vascular de La Sierra de Chiribiquete, Colombia. Caldasia 20: 103-141.

Duivenvoorden, J. F., and J. M. Lips. 1995. A Land-ecological Study of Soils, Vegetation and Plant Diversity in Colombian Amazonia. Wageningen, The Netherlands: The Tropenbos Foundation.

Fundação Instituto Brasilero de Geografia Estatística-IBGE. 1993. Mapa de vegetação do Brasil. Map 1:5,000,000. Rio de Janeiro, Brazil.

Huber, O. 1995. Vegetation. Pages 97-160 in P. E. Berry, B. K. Holst, and K. Yatskievych, editors, Flora of the Venezuelan Guayana. St. Louis: Missouri Botanical Garden and Timber Press.

Navarro, A.E.S., G.H. Peña, F.C. Lemus, J.R. Baquero, R.F. Soto. 1984. Bosques de Colombia. IGAC-INDERENA-CONIF, Bogota, Colombia.

Silva, J.M. C. 1998. Um método para o estabelecimento de áreas prioritárias para a conservação na Amazônia Legal. Report prepared for WWF-Brazil. 17 pp.

Prepared by: Robin Sears and César Marín
Reviewed by: In process