Guianan Freshwater

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Cascade river in tropical rainforest, French Guiana.
© WWF-Canon / Roger LeGUEN

About the Area

The Guianan Region of South America is a unique and very special part of our planet, and ranks as one of the world’s last great wild places. Occupying roughly the northeastern third of Amazonia, it is particularly noteworthy for its endemism, unique ecosystems, and exceptionally pristine state, as well as for its cultural diversity. The coastal rivers of this ecoregion drain an area called the Guyana Shield and contain a wide range of flowing water habitats that include cataracts, rapids, and riparian flooded forests among others.
Though poorly investigated, these rivers are known to support a very diverse, highly intact, and notably endemic freshwater fauna.

The tallest waterfall in the world - the 3,200 feet (980 m) Angel Falls - is in this ecoregion along with some of the Earth's oldest land formations. In many rivers, waterfalls have created isolated bodies of water, where many endemic species have evolved.

This region may account for as much as 10-15% of the world’s freshwater, and has the largest number of pristine or near pristine river basins on Earth It also harbors large stocks of carbon in the living biomass of the forest, accounting for about a quarter of the total carbon pool in tropical forests.

The Orinoco river flows 2140 km across Colombia and Venezuela from its source in the extreme south of the Guianan massif until reaching the ocean, covering an area from the Andes to the Atlantic. The river basin represents one of the most biologically and hydrologically diverse areas of the planet.
Size:
510,000 sq. km (200,000 sq. miles)

Habitat type:
Small Rivers

Geographic Location:
Northeastern South America: Brazil, French Guiana (France), Suriname, and Venezuela

Conservation Status:
Relatively Stable/Intact
Local Species
The biodiversity of this region is particularly rich, with an estimated 20,000 vascular plant species, of which about 35% (7,000) are endemic, making it one of the three richest tropical wilderness areas on Earth. Bird richness is estimated at 975 species, with 150 endemics and 25 near-endemics; mammals at 282 species, with 27 endemics, reptiles at 280 species, with 76 endemics, amphibians at 272 species, with 127 endemics, and freshwater fish at 2200 species, with 700 endemics.

Invertebrate groups for which numbers are available include the ants, with 900 described species and 1,500 expected, of which 300 are endemic; termites with 150 described species and 225 expected, of which 10 are endemic; earthworms with 120 described species and 2,000 expected, of which 1,900 are likely to be endemic; dragonflies with 210 described species and 240 expected, of which 2 are endemic; moths with 95 species, of which 16 are endemic; stingless bees with 70 described species and 90 expected, of which 10 are endemic; and social wasps with 200 described species and 250 expected, of which 10 are endemic.

Among the numerous species found in this important freshwater system are the imperiled Arapaima (Arapaima gigas), giant South American river turtle (Podocnemis expansa), Black caiman (Melanosuchus niger), and Arowana (Osteoglossum bicirrhosum).

This ecoregion provides some of the best remaining habitat for Giant river otter (Pteronura brasiliensis).

Featured species

 / ©: WWF-Canon / Edward PARKER
South American river turtle (Podocnemis expansa), Brazil.
© WWF-Canon / Edward PARKER
Giant South American river turtle (Podocnemis expansa)

The giant South American turtle is the largest river turtle in South America. It has a broad, domed and streamlined carapace for active swimming in moderate river currents. The colour may be influenced by the algae that is attached to it, but is usually olive green to brown in colour.

It nests during the low water season, laying from 75 to 125 leathery eggs per clutch. This species is mainly herbivorous, feeding on aquatic vegetation and plant matter that falls into the water. However, it is also known to be somewhat opportunistic, feeding on small, slow-moving prey and carrion.
Mutual cleaning behaviour between individuals of this species has been observed. One turtle will position itself at right angles to a second turtle and use its jaws to pull algae from its shell. The turtles will then switch position.

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Threats
Unsustainable logging, poor mining practices, and hydroelectric projects have already impacted significant areas and could increase dramatically in the next few years. Monoculture agriculture (e.g., oil palm, soybeans) of the kind that has transformed large areas of Africa, southeast Asia and the Cerrado region of Brazil is another potential threat. Bushmeat hunting and wildlife trade are also problems.

The freshwater habitats of this ecoregion are relatively intact and support generally stable freshwater populations. However, valuable game species such as the enormous arapaima and some reptiles are imperiled as a result of over-exploitation and illegal border trade.

Further human activities such as deforestation, mining, agriculture, industrial and domestic waste discharge, and water extraction have led to serious problems such as erosion, sedimentation, cyanide spills, altered hydrologic regimes, pollution, and wildfires.
WWF’s work
The Integrated Management Programme for the Orinoco Basin seeks the conservation of this region by means of identifying and analysing the main threats faced by the basin’s ecosystems. The initiative is led by WWF Colombia in association with the Venezuelan conservation organisations, FUDENA.

The Orinoco basin covers nine ecoregions within WWF’s Global 200. José Saulo Usma, coordinator of WWF Colombia’s Orinoco Programme, stated that “the programme has allowed joint efforts between different organisations towards the conservation of resources and biodiversity in this important river basin”.

WWF Colombia (with support from WWF Switzerland) has initiated a process to identify and analyse information with a view to designating a new conservation area consisting of 600,000 ha of seasonally flooded savannas and riparian forest in the municipality of Ariporo in the department of Casanare, Colombia.

WWF Colombia, together with its partners, is working to convert conservation opportunities into concrete actions within the region. In the short, medium and long term, these actions should result in improved quality of life for local communities as well as the preservation of valuable ecosystems within the third most important river basin on the planet.

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