Location and General Description
The Solimões-Japurá moist forest ecoregion lies on well-drained upland Tertiary alluvial plains in western Amazonia. The region straddles the Putumayo River which forms the Peru-Colombia border north extending to the Caquetá River in Colombia and south to the Amazon and Napo Rivers in Peru. The eastern flank covers the interfluve between the Japurá (Caquetá) and Solimões (Amazon) Rivers in Brazil. The western extent of the ecoregion is well before the lowest foothills of the Andes near Puerto Laguízamo, Colombia. Elevations ranges from 100 to 220 m. The major river systems that drain this region are the Caquetá, Napo, Amazon, and Putumayo. Many tributaries dissect this gently undulating terrain.
It is an area of great complexity, comprising a mosaic of soils that host a diversity of vegetation types. In a single region of Colombia, 15 vegetation types have been defined . The soils are generally nutrient-poor oxisols and ultisols and have high aluminum and iron content. This is a very humid region where the annual precipitation sometimes exceeds 3,000 mm. The region has a relatively aseasonal climate with an average annual temperature of 24° C. The combination of high rainfall, edaphic and topographic variability, and historical biogeographical patterns renders these forests some of the most species diverse in the world.
This moist forest region primarily hosts tall, dense, evergreen tropical rain forest, which is characterized by high biodiversity. Well-drained upland forests, swamp forests, well-drained floodplain forests, and poorly-drained floodplain forests are all found according to topography and soil type, each having slightly different structure and composition. The floodplain soils are more nutrient rich than the upland soils because annual inundation from the whitewater rivers (carrying suspended solids from the Andes) results in the deposition of organic and mineral sediments on the forest floor. These forests are described in the Purus Várzea ecoregion. In Peru, there are areas of white sand, similar to those of the Campinarana ecoregion in Brazil, with a distinct biota and a high level of plant and animal endemism. The vegetation on these nutrient-poor soils is sclerophyllous low scrub or low forest with a more open canopy. There are also sandstone plateaus to 500 m in Colombia hosting Amazonian shrub and savanna vegetation with a Guyanan affinity. On the uplands, the dense forest canopy reaches 35 m in height, with the tallest trees emerging to 40 meters.
The flora of these rain forests is typical of the Amazon florisic province. The most abundant tree families are Annonaceae, Lecythidaceae, Myristicaceae, Leguminosae, and Sapotaceae. The tallest trees that emerge from the canopy include Ceiba pentandra, Terminalia amazonica, Cedrelinga catenaeformis, Carapa guianensis, and Hevea guianensis var. lutea, a type of rubber tree. Many valuable timber species are native to these forests including Virola surinamensis, Cedrela odorata, and Carapa guianensis. Many of these forests host an abundance of lianas and palms, epiphytes, and many mosses and ferns, which create a dense understory.
The floristic diversity of the Solimões-Japurá moist forest ecoregion harbors a high diversity of mammals, insects, amphibians, reptiles, and birds. Many rare plants, especially herbaceous species, are restricted to these interfluves. The fauna is typically Amazonian with many species reaching the western limit of their distribution. Among the 181 mammals recorded from this region are numerous primates such as monk sakis (Pithecia aequatorialis), marmosets (Saguinus tripartitus), Goeldi’s marmosets (Callimico goeldii), jaguars (Panthera onca), margays (Leopardus wiedii), South American foxes (Pseudalopex sechurae), bats such as yellow-eared bats (Vampyressa pusilla) and little big-eared bats (Micronycteris schmidtorum); American manatees (Trichechus manatus) in the rivers, and the largest terrestrial mammals in South America, tapirs (Tapirus terrestris). Three species of ant-eaters (Myrmecophaga tridactyla, Cyclopes didactylus, and Tamandua tetradactyla), armadillos (Dasypus spp.), and deer (Mazama gouazoubira and M. americana) also inhabit this region.
Approximately 500 bird species are found in the Amacayacu National Park alone and 542 for the ecoregion as a whole. Some bird species restricted to this ecoregion or found in few other places in Amazonia include ashy-tailed swifts (an austral migrant, Chaetura andrei), blue-tufted starthroats (Heliomaster furcifer), pavonine quetzals (Pharomachrus pavoninus), white-eared jacamars (Galbalcyrhynchus leucotis), endemic ochre-striped antpittas (Grallaria dignissima), curassows (Mitu salvini), a terrestrial bird, and golden-winged tody-flycatchers (Todirostrum calopterum).
Reptiles, fish, and amphibians are abundant. The largest freshwater turtle in the world (Podocnemys expansa) inhabits the rivers along with black caimans (Caiman crocodylus) and the mighty anacondas (Eunectes murinus). Other oft-mentioned snakes that occur here include lanceheads (Bothrops atrox), palm pit-vipers (Bothriechis spp.), coral snakes (Micrurus spp.), boa constrictors (Boa constrictor), emerald tree boas (B. canida), and bushmasters (Lachesis muta). Iguanas (Iguana iguana) are ubiquitous and tegus lizards (Tupinambis) common. Many ornamental fish inhabit the rivers including arawana (Osteoglossum bichirrosum) and various tetras (Hyphaessobrycon, Bryconops). Two species of fierce piranhas (Serrasalmus) and stingrays (Potamotrygon motoro) inhabit these rivers.
Much of the native habitat in this ecoregion remains intact, but recent advances of coca (Erythroxylum coca) production, logging and mining operations, and cattle ranching have resulted in large deforested areas, particularly along the Caquetá and Putumayo Rivers. The remaining intact forest is considered threatened frontier forest that may eventually be degraded by ongoing human activities. Only two short roads (less than 20 km) currently exist in the region. The Colombian Cahuinari and Amacayacu National Parks are situated in this region together covering 8,690 km2 of rain forest. About one-third of this ecoregion, in Colombia between the Putumayo and Caquetá Rivers, is under the jurisdiction of indigenous people who practice extractive activities and small-scale shifting cultivation. Although Colombia has strong legislation to regulate timber extraction from these forests, enforcement suffers because of insufficient administrative capacity.
Types and Severity of Threats
Human-induced habitat loss threatens some species of this rich biodiversity. Expansion of cattle ranches, coca (Erythroxylum coca) plantations, and colonization along rivers results in deforestation and habitat degradation, driving the fauna away. Timber species are suffering from overharvest. Mahogany (Swietenia macrophylla) is commercially extinct. Tropical cedar (Cedrela odorata) is threatened with local extinction along the rivers, particularly the lower Putumayo and its tributaries near the Colombian City of Tarapacá on the Caquetá, and on the Amazon near Leticia.
Justification of Ecoregion Delineation
This interfluvial ecoregion is bound by the Solimões River (Amazon) to the south and the Japurá and Caquetá Rivers to the north. Linework follows the presence of várzea habitats along these rivers according to IBGE (1993) and the eastern delineation is the confluence of the Japurá with the Solimões Rivers. The western delineation’s follows the Napo River northwards, then a line was drawn between the Napo and Caquetá across the Peru-Colombia border. This westernmost line was meant to distinguish the Napo ecoregion, to the west, from these interfluvial ecoregions as an area of Pleistocene refugia and butterfly endemism (see Napo moist forest description). These classifications follow the expert opinion of da Silva’s (1998). In Colombia reference was made to Etter (1998).
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.
Etter, A. 1998. Mapa General de Ecosistemas de Colombia. Escala 1:1,500,000. Instituto de Investigación de Recursos Biológicos Alexander von Humboldt. Santa fe de Bogotá
Fundação Instituto Brasilero de Geografia Estatástica-IBGE. 1993. Mapa de vegetação do
Brasil. Map 1:5,000,000. Rio de Janeiro, Brazil.
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