Guianan moist forests

Guianan moist forests
Name	Guianan moist forests
Biome	Tropical and subtropical moist broadleaf forests
Countries	Brazil, Guyana, Suriname, Venezuela, Colombia, French Guiana
Area km2	300000
Conservation	Relatively stable/intact

Guianan moist forests are a large tropical moist broadleaf forest ecoregion in northeastern South America, spanning parts of Brazil, Guyana, Suriname, Venezuela, Colombia and French Guiana. The ecoregion forms part of the larger Amazon rainforest biome and lies adjacent to the Guiana Shield, the Orinoco River basin and the Atlantic Ocean coast, hosting extensive biodiversity and endemism. Its landscape includes lowland rainforest, tepuis, riverine systems and savanna mosaics, and it has been a focus for international conservation organizations and scientific institutions.

Geography and extent

The ecoregion occupies the eastern portion of the Guiana Shield, bounded by the Amazon Basin, the Orinoco River drainage, the Amapá region of Brazil, the coastline of French Guiana, and the borderlands of Venezuela and Colombia. Major river systems include the Essequibo River, the Courantyne River, the Maroni River, and the Río Orinoco tributaries, while upland features include the Pakaraima Mountains and isolated tepui plateaus such as Mount Roraima and Auyán-tepui. The ecoregion overlaps administrative regions like Roraima, Pará, Amapá (state), Distrito Especial de Nueva Esparta and coastal provinces of Suriname and Guyana. Protected areas within the region include Tumucumaque Mountains National Park, Kaieteur National Park, Roraima National Forest, and Mount Roraima National Park.

Climate and ecoregion characteristics

Climate is tropical humid with high annual rainfall influenced by the Intertropical Convergence Zone and Atlantic trade winds, producing wet and less-wet seasons across zones such as Llanos ecotones and coastal mangrove fringes like Cabo Orange National Park. Mean annual temperatures are moderated by elevation on tepuis and the Pacaraima Mountains while precipitation patterns reflect interactions with the El Niño–Southern Oscillation, the North Atlantic Oscillation and regional sea surface temperatures. Soil types include ancient, nutrient-poor laterite and sandy podzols derived from Precambrian shield rock, shaping lowland terra firme forests, seasonally flooded várzea and igapó forests along rivers, and montane cloud forest on high plateaus. Vegetation structure ranges from multilayered canopy and emergent trees to dense liana tangles and epiphyte-laden understories.

Flora and fauna

Floral assemblages include dominant genera such as Eschweilera, Carapa, Bertholletia, Brosimum, Iriartea and diverse families like Fabaceae, Lauraceae, Myrtaceae, Arecaceae and Bromeliaceae, with notable endemics on tepuis such as species in Heliamphora, Bonnetia and Stegolepis. Faunal diversity features large mammals including Jaguar, Giant anteater, Giant river otter, Tapir and primates such as Red howler, Squirrel monkey and Black bearded saki, alongside birds like Harpy eagle, Hoatzin, Scarlet macaw and endemic species associated with tepui summits. Aquatic systems support fisheries with species like Arapaima gigas, Pirarucu and diverse characiforms, while amphibian and reptile assemblages include taxa referenced in collections of the Smithsonian Institution, American Museum of Natural History and regional universities like the University of Guyana and Universidade Federal do Pará.

Human inhabitants and Indigenous peoples

Indigenous groups with long-standing ties to the region include the Wayana, Wai Wai, Wapishana, Makushi, Arawak, Carib and Patamona, many occupying traditional territories recognized by national constitutions and international instruments such as the Inter-American Court of Human Rights precedents. Colonial histories involve contact with Portuguese Empire, Spanish Empire, Dutch Empire and French colonial empire administrations, which influenced settlement patterns, missionary activity by orders like the Society of Jesus and resource extraction driven by companies and concessions registered in cities such as Georgetown, Guyana, Paramaribo and Cayenne. Contemporary livelihoods combine smallholder agriculture, artisanal gold mining linked to migrant networks from Brazil and Venezuela, forestry operations regulated by agencies including IBAMA and regional ministries, and eco-tourism centered on attractions like Kaieteur Falls, Roraima treks and river expeditions departing from ports such as Manaus and Macapá.

Threats and conservation

Primary threats include illegal and small-scale gold mining with mercury contamination, deforestation for cattle ranching and soybean cultivation linked to markets in São Paulo and Buenos Aires, hydrocarbon exploration within concessions sanctioned by national regulators, and the impacts of road construction altering forest fragmentation patterns as seen near the BR-319 corridor. Climate change driven by global emissions regimes negotiated under the United Nations Framework Convention on Climate Change exacerbates drought and fire risk documented by researchers at institutions like NASA, INPE and CATHALAC. Conservation responses involve international NGOs such as WWF, Conservation International and The Nature Conservancy, cross-border cooperation through initiatives like the Guiana Shield Facility and protected area networks supported by multilateral banks including the World Bank and the Inter-American Development Bank.

Research and scientific importance

The ecoregion is a key site for research on biodiversity gradients, endemism, paleoecology and biogeography, attracting scientists affiliated with the Smithsonian Tropical Research Institute, Royal Botanic Gardens, Kew, University of Oxford, University of São Paulo, Université de Guyane and regional research institutes. Long-term ecological monitoring projects include plots in the RAPELD system and inventory work by the Biological Dynamics of Forest Fragments Project, with genetic studies housed in collections of the Naturalis Biodiversity Center and molecular laboratories at Instituto Nacional de Pesquisas da Amazônia. Findings inform policy at fora like the Convention on Biological Diversity and initiatives on ecosystem services valuation advanced by the World Resources Institute and IPBES assessments.

Category:Neotropical ecoregions