A savanna is a biome characterized by a mix of grassland and woodland, where the open tree canopy allows sunlight to reach a continuous layer of grasses below. South America hosts some of the world’s most biologically rich and expansive tropical savannas, representing the second largest vegetation type on the continent, after the tropical forests. Their immense size and high level of species diversity make these neotropical savannas globally significant ecological systems.
Geographic Distribution and Primary Types
The South American savanna landscape is dominated by two distinct regional biomes. The most extensive is the Cerrado, which occupies the heart of the continent, covering a vast area primarily across central Brazil, and extending into eastern Bolivia and northeastern Paraguay. The second major system is the Llanos, situated further north, spanning large plains across western Venezuela and eastern Colombia. These biomes are physically separated by the Amazon rainforest. The Llanos are bounded by the Andes Mountains and the Guiana Shield, while the Cerrado rests largely on the ancient Brazilian Plateau.
The Defining Climate and Landscape
The physical structure of South American savannas is shaped by a strongly seasonal climate, marked by distinct wet and dry periods. The typical climate involves a hot, rainy summer, followed by a prolonged dry winter that can last up to five months, dictating the growth patterns of life forms. Mean annual precipitation generally falls between 800 and 2,000 millimeters, but the intense seasonality prevents the establishment of a closed-canopy forest.
Fire is a natural force that plays a role in maintaining the open landscape of these savannas. Periodic fires clear above-ground vegetation and prevent woody species from dominating the grasslands, allowing fire-adapted grasses to thrive and regenerate. The geological foundation consists of ancient, highly weathered soils, often classified as oxisols, which are typically acidic and severely nutrient-poor. This lack of soil fertility restricts the growth of large, dense forests.
Specialized Flora and Fauna
The plants and animals of the South American savanna exhibit remarkable biological adaptations to survive seasonal drought and frequent fires. Flora in the Cerrado has evolved specific traits, including thick, corky bark that insulates tissues from fire. Many species can re-sprout quickly after a fire event.
A key adaptation for enduring the dry season is the development of deep root systems, which allow plants to tap into underground water sources, sometimes reaching depths of over 15 meters. The Cerrado is renowned for its immense biodiversity, harboring over 10,000 plant species, with an estimated 4,400 found nowhere else in the world.
The fauna is equally specialized, including the long-legged Maned Wolf, which uses its height to see over the tall grasses while hunting. Large mammals like the Giant Anteater and the Giant Armadillo are also characteristic inhabitants of the savanna. The Giant Armadillo uses its powerful claws to dig extensive burrows, utilizing them to escape the heat and avoid predators. In the seasonally flooded Llanos, the Capybara, the world’s largest rodent, fills the niche of a large herbivore, navigating the fluctuating water levels.
Ecological Importance and Current Status
The South American savannas act as a significant carbon sink. They store vast amounts of carbon, sequestered below ground within their deep root systems and rich soils, rather than primarily in the trees. The Cerrado is also known as “Brazil’s water tower” because it serves as the headwaters for three of the continent’s major river systems: the Amazon, the São Francisco, and the Paraná-Paraguay basins. This role in regional water cycling provides water for human consumption, agriculture, and hydroelectric power.
Despite their importance, these ecosystems are among the most threatened in the world, facing intense pressure from human activity. The primary threat is large-scale agricultural expansion, particularly for soy cultivation and cattle ranches, causing rapid habitat destruction. Conservation efforts are challenged by the aggressive pace of conversion and the significant loss of native vegetation.