Llanos

The Llanos, whose Spanish name means "The Plains," is a huge tropical grassland plain in northwestern South America, located east of the Andes across Colombia and Venezuela. This ecoregion falls under the tropical and subtropical grasslands, savannas, and shrublands biome. The lowland stretches mainly east to west, with the Andes forming its western and northwestern borders, the Venezuelan Coastal Range to the north, the Guiana Highlands to the southeast, and the Negro-Branco moist forests to the southwest. The Orinoco River, the main waterway, flows from west to east through the region and marks part of the Colombia-Venezuela border. To the east lie the Orinoco wetlands and delta swamp forests. As of a 2017 assessment, about 105,323 square kilometers—28 percent of the ecoregion—falls within protected areas, including Aguaro-Guariquito National Park, Cinaruco-Capanaparo National Park, Tortuga Arrau Reserve, and Caño Guaritico Wildlife Refuge in Venezuela, and El Tuparro National Natural Park in Colombia.

The climate is tropical savanna, shifting to tropical monsoon in the Colombian Llanos. Rainfall is seasonal: a rainy season runs from April to November, with June and July typically wettest, and a dry season from December to March. Precipitation varies widely, reaching up to 3,000 millimeters yearly in the southwest, dropping to 1,200–1,600 millimeters in Apure State, and as low as 800–1,200 millimeters in Monagas State to the northeast. The average annual temperature is 27°C, with little monthly variation; the coolest months (June, July, December, and January) are only about 2–3.6°F cooler than the hottest ones.

Plant life includes open grasslands, savannas with scattered trees or clumps, and small forest patches, especially gallery forests along rivers. There are seasonally flooded areas (llano bajo) and dry ones (llano alto). Llano alto covers about two-thirds of the Venezuelan Llanos and is common in Colombia too, featuring grasses and shrubs 30–100 centimeters tall in tussocks spaced 10–30 centimeters apart, on sandy, nutrient-poor soils. Dominant grasses include Trachypogon species, along with others like Axonopus canescens, Andropogon selloanus, and various sedges. Shrubs and herbs are often legumes from genera such as Mimosa, Cassia, and Desmodium. Common trees are manteco, chaparro, and alcornoque, growing alone or in woodland patches called matas, which range from 12 meters across to a hectare. During the rainy season, parts of the Llanos flood up to a meter, creating temporary wetlands similar to the Pantanal, which attract water birds and other wildlife. Llano bajo, with richer soils, is dominated by the grass Paspalum fasciculatum and trees like the palm Copernicia tectorum. Gallery forests include evergreen seasonally flooded types and semi-deciduous forests on higher ground. Morichales are flooded forests featuring the moriche palm, while vegas are seasonally flooded evergreen forests along the Orinoco and its tributaries, with a canopy 8–20 meters high made up of Inga, Combretum, Gustavia, and other species. Semi-deciduous forests above flood level have a 12–15-meter canopy of trees like Tabebuia billbergii, Spondias mombin, and Hura crepitans. Matorrales are deciduous or semi-deciduous shrublands 5–8 meters tall, covering large areas of the central Venezuelan Llanos, possibly as secondary growth from former dry deciduous forest, with shrubs such as Bourreria cumanensis, Randia aculeata, and Pereskia guamacho.

Grassland and savanna mammals include white-tailed deer, giant anteater, capybara, giant armadillo, Eastern cottontail, and various rats. Gallery forests host more diverse large and medium-sized mammals: collared and white-lipped peccaries, South American tapir, red brocket, wedge-capped capuchin, Venezuelan red howler, lowland paca, agoutis, Brazilian porcupine, and large cats like puma, jaguar, and ocelot.