Map of the Month: Orinoco Delta and Eastern Guyana Highlands
Map boundaries: 0 to 10 degrees North; 56 to 64 degrees West
Countries (States, Regions, or Districts): Brazil (Amazonas, Para, and Roraima), Guyana, Suriname (Coronie, Nickerie, and Sipaliwini), and Venezuela (Amazonas, Anzoategui, Bolivar, Delta Amacuro, and Monagas).
Overview
This map area extends from the Venezuelan coast range in the northwest to the Amazon rainforest in the south. Although the region is mostly tropical moist forest, there are areas of xeric vegetation in the northwest. Grasslands and savannas are found in the lower Orinoco and southwestern Suriname, and in La Gran Sabana where Brazil, Guyana, and Venezuela come together. In the Orinoco Delta and along the coast of Suriname are swamp forests that mark the transition from coastal mangroves to higher elevation tropical forests. The Guyana Highlands are notable for the tepuys, which are about 100 dramatic flat-topped sandstone mountains scattered across Venezuela, northern Brazil, central Guyana, and central Suriname. The most well-known tepuy is Auyan in southeastern Venezuela, from which Angel Falls plunges.
This map area includes Guri Reservoir, an artificial lake in Bolivar state, Venezuela. An archipelago of hilltop islands was created by the filling of the lake. Since 1993, ecologists have studied the islands in the Connecticut-sized reservoir. From an ecological standpoint, the islands were not big enough to support large predators like jaguars, army ants, and armadillos. With the predators gone, other animals and plants took over, causing major ecological changes. For example, freed from army ants and armadillos, fungus-eating ants of the genus Atta took over, deforesting trees and allowing thorny vines to grow. The end point was a treeless island with a tangle of liana (vine) stems. Howler monkeys initially experienced a population explosion, but then ended up starving as defoliated trees began growing increasingly poisonous vegetation in defense. Based on these results, conservation scientists should focus on replacing top predators, or at least devise management interventions to substitute for the loss of the key species (Stolzenburg, 2008).
Ecoregions and Provinces/Political Subdivisions
Tropical and Subtropical Moist Broadleaf Forests
NT 117, Cordillera La Costa montane forests. Found in Monagas State, Venezuela. Evergreen moist forests on mountain tops. Gyranthera, Trophis, and Ficus at lower elevations, then evergreen montane cloud forests, then elfin forest and scrub at the mountain tops.
NT 124, Guyanan Highlands moist forests. Found in Brazil—Amazonas and Roraima; and Venezuela—Amazonas and Bolivar. Tall primary rainforest and savannas. Emergent rainforest trees are Calophyllum, Anacardium, and Manilkara.
NT 125, Guyanan moist forests. Found in Brazil—Roraima; Guyana—Barima-Waini, Cuyuni-Mazaruni, Demerara-Mahaica, East Berbice-Corentyne, Essequibo Islands-West Demerara, Mahaica-Berbile, Pomeroon-Supenaam, Potari-Siparuni, Upper Demerara-Upper Berbice, Upper Takutu-Upper Essequibo; Suriname—Coronie, Nickerie, and Sipaliwini; and Venezuela—Bolivar and Delta Amacuro. Tropical lowland forest and savannas. Bignoniaceae, Bobacaceae, Euphorbaceae trees and Calophyllum, Carapa, and Ceiba.
NT 143, Negro-Branco moist forests. Found in Brazil—Amazonas. Forested lowland plains and low sandstone table mountains. Notable plants are Virolia, Duckeanthus, Heteropetalum, and Leopoldina.
NT 147, Orinoco Delta swamp forests. Found in Guyana–Barima-Waini and Venezuela—Delta Amacuro and Monagas. Moist forests and wetlands with typical genera Carapa, Ceiba, and Dimorphandra.
NT 149, Paramaribo swamp forests. Found in Suriname—Coronie and Nickerie. A thin strip of flooded forests between mangroves and coastal mountains containing a mosaic of freshwater swamp habitats. Typical genera are Viriola, Symphonia, Euterpe, Crudia, and Macrolobium.
NT 158, Rio Negro capinarana. Found in Brazil—Amazonas and Roraima. Heath forests at the transition between the Guyana shield and Amazon basin. Savanna and thorn forests of cycads, Vochisia, Virola, Compsoneura, and Macrolobium grow on low nutrient soils.
NT 169, Tepuys. Found in Brazil—Roraima; Guyana—Cuyuni-Mazaruni, Potari-Siparuni, and Upper Takutu-Upper Essequibo; Suriname—Sipaliwini; and Venezuela—Amazonas and Bolivar. Isolated mountains with dramatic cliffs rising out of the rainforests. Various vegetation zones of montane shrublands, meadows, rock communities, and forests of Clusia, Monorobea, Miconia, and Graffenrieda.
NT 173, Uatuma-Trombetas moist forests. Found in Brazil—Amazonas, Para, and Roraima. A region of blackwater rivers north of the Amazon River in eastern Brazil. Typical plant famililies are Sapotaceae, Lecythidaceae, Bursuraceae, and Fabaceae.
Tropical and Subtropical Grasslands, Savannas and Shrublands
NT 707, Guyanan savanna. Found in Brazil—Para and Roraima; Guyana—Cuyuni-Mazaruni, Upper Takutu-Upper Essequibo; Suriname—Sipaliwini; and Venezuela—Bolivar. Located between the Amazon and Orinoco basins. Grass, shrubs, trees and forest islands, including the Gran Sabana of Venezuela. Impermeable subsoil and sandy soils are typical. Typical plant genera are Euphorbia, Humiria, and Clusia.
NT 709, Llanos. Found in Venezuela—Anzoategui, Bolivar, and Monagas. This is a transition area between the coastal xeric habitats of the Caribbean coast and the Amazon moist forests. Savannas are found in both seasonally flooded and non-flooded areas.
Flooded Grasslands and Savannas
NT 906, Orinoco wetlands. Found in Venezuela—Delta Amacuro and Monagas. Flooded grasslands and forests, buffered by mangroves.
Deserts and Xeric Shrublands
NT 1309, La Costa xeric shrublands. Found in Venezuela—Anzoategui and Monagas. Sparse dry desert shrubs, including Cactaceae, Leguminosae, and Capparidaceae.
Mangrove
NT 1411, Guyanan mangroves. Found in Guyana—Barima-Waini and Pomeroon-Supenaam; Suriname—Coronie and Nickerie; and Venezuela—Delta Amacuro and Monagas.
Freshwater Ecoregions of the World
South America Region
Tropical and Subtropical Upland Rivers
308. Orinoco Guiana Shield.
310. Essequibo
311. Guianas
315. Amazonas Guiana Shield
Tropical and Subtropical Floodplain Rivers and Wetland Complexes
307. Orinoco Llanos.
314. Rio Negro
Large River Deltas
309. Orinoco Delta and Coastal Drainages. As the Orinoco reaches the coast, the main river channel divides into a network of smaller channels.
Marine Ecoregions of the World
Tropical Atlantic Realm, North Brazil Shelf
71. Guianan
UNESCO World Heritage Sites
Central Suriname Nature Reserve. A pristine montane and lowland rain forest with 5000 vascular plants. Significant vertical relief and soil diversity in the watershed of the Coppename River. Contains Tafelberg Tepui. Found in Sipaliwini District of Suriname. Ecoregion 125, Guyanan moist forest.
Canaima National Park. An area of 100 tepuis, savannas, and waterfalls. The top of Auyan Tepui is an intricate maze of jagged sandstone with holes and caves. Includes 3211-foot-high Angel Falls, reached from Canaima, Venezuela, and Gran Sabana, reached by highway from Guayana City in Venezuela. Found in Bolivar State, Venezuela. Ecoregions 124 (Guyanan Highlands moist forests), 169 (Tepuis), and 707 (Guyanan savannas).
Other points of interest
Amazonas National Forest. Found in Brazil–Roraima. Ecoregion 124.
Anaua National Forest. Found in Brazil—Roraima. Ecoregion 158.
Bakhuys Mountains. An important bird area with crested eagle, harpy eagle,a nd blue-cheeked parrot. Found in Sipaliwini District, Suriname. Ecoregion 125.
Bigi Pan. Mudflat and swamp area with Guyanian Piculet, Blood-Colored Woodpecker, and Rufous Crabhawk. Found in Nickerie District, Suriname. Ecoregion 1411 (mangroves)
Blanche Marie Falls. Located in Sipalawini District, Suriname. Ecoregion 125.
Caracarai Ecological Station. Found in Roraima, Brazil. Ecoregion 707.
Caruachi. An important bird area on the Guri Resevoir. Found in Bolivar State, Venezuela. Ecoregion 709, Llanos.
Coppename Estuary National Park. Noted for bird colonies. Located in Coronie District, Suriname. Ecoregion 1411 (mangroves).
Delta del Orinoco National Park. Swamps and marshes of mangroves, palms, grasslands. Found in Delta Amacuro, Venezuela. Ecoregion 147 and 1411.
Gran Morichal Wildlife Refuge. Savanna with scattered trees and palms. Found in Delta Amacuro and Monagas, Venezuela. Ecoregion 906.
Guayana (city). Noted for waterfalls upstream on Caroni River. Found in Bolivar state, Venezuela. Ecoregions 125 (Guyanan moist forest) and 709 (Llanos).
Guaiquinima tepui. Tepui topped by evergreen rainforest. Found in Bolivar State, Venezuela. Ecoregion 124 (Guyana highlands moist forest) and 169 (tepuis).
Imateca Reserve. Hills of Guyana Shield; preserves evergreen rainforest. Found in Bolivar and Delta Amacura, Venezuela. Ecoregion 125 and 147.
Iwokrama Rainforest Programme. A research area with canopy walkway and hikes to mountains and petroglyphs. Located in Potari-Siparuni Region of Guyana. Ecoregion 125.
Jonestown (site). In 1978, the American cult known as the Peoples Temple committed mass suicide. The site was located southwest of Kaituma in Barima-Waini Region of Cooperative Republic of Guyana. Ecoregion 125.
Kabalebo/Arepahu. An important bird area by the Kabalebo River, noted for green ibis. Found in Sipaliwini District, Suriname. Ecoregion 125.
Kaieteur National Park. Unspoiled forest and a 100-meter waterfall five times the height of Niagara. Located in Potari-Siparuni Region of Guyana.
Maraca Ecological Station. Found in Brazil—Roraima. Ecoregion 124.
Niquia Ecological Station. Found in Roraima, Brazil. Ecoregion 158.
Nort Coronie. Important bird area and mudflats. Found in Coronie District, Suriname. Ecoregion 1411 (Mangroves).
Northwest Suriname (NWS on map). An area of grass swamps and swamp forests harboring the giant river otter and manatees. Found in Nickerie District, Suriname. Ecoregion 149, Paramaribo swamp forests.
Orinduik Falls. Located in Potari-Siparuni Region of Guyana and Roraima State, Brazil. Ecoregion 125.
Pedernales-Capure. Found in Delta Amacuro, Venezuela. Ecoregion 1411.
Raleigh vallen/Voltzberg Nature Reserve. A subunit of the Central Suriname Nature Reserve on the Coppename River. Found in Sipaliwini District, Suriname. Ecoregion 125.
Roraima National Forest. Found in Roraima, Brazil. Ecoregion 124.
Monte Roraima National Park. Encompasses the Brazilian portions of Roraima Tepui. Found in Roraima, Brazil. Ecoregion 125 and 169.
Roraima Tepui. The highest of the tepuis, this mountain is at the meeting point of Brazil, Guyana, and Venezuela. It has a 400 m cliff of quartzite with a cloud forest of ferns and an open, rocky summit. It is reached by a 5-day trek. Ecoregion 169 (tepuis)
Rupununi Savanna. Dry grassland in southern Guyana. Located in Upper Takutu-Upper Essequibo Region of Guyana.
Serra da Mocidade National Park. Found in Roraima, Brazil. Ecoregion 124 and 158.
Shell Beach. A 145-km reach of coastline from Pomeroon River to Venezuelan border in Guyana. The nesting ground of sea turtles: leatherback, green, hawksbill, and olive ridley. Found in Pomeroon-Supenaam and Barima-Waini regions, Guyana. Ecoregion 1411.
Sipaliwini Nature Reserve. Contains the Sipaliwini savanna. Found in Sipaliwini District, Suriname. Ecoregion 707.
Tucupita. Base for excursions to Orinoco Delta and Warao villages at Guyana border. Found in Delta Amacuro State, Venezuela. Ecoregion 147.
Urutani tepui. Topped by an evergreen rainforest. Located in Bolivar State, Venezuela and Roraima State, Brazil. Ecoregion 169 (Tepuis).
Virua National Park. Found in Roraima, Brazil. Ecoregion 707.
References
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Emma Beare, ed. 2006. 501 Must-Visit Natural Wonders. Bounty Books.
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Ildos, Angela S. and Bardelli, Giorgio G. 2001. Great National Parks of the World. AAA Publishing.
Olson, David M., et al., 2001. Terrestrial Ecoregions of the World: A New Map of Life on Earth. BioScience 51:933-938.
Schultz, Patricia. 2003. 1,000 Places to See Before You Die. Workman Publishing.
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Stolzenburg, William. 2008. Ecosystems Unraveling. Conservation Magazine 9(1):21-25.
World Heritage List. Accessed 5/24/09 at whc.unesco.org/en/list