savannas

Savannas are ecosystems dominated by grasses with scattered trees or shrubs. They occur in tropical and subtropical regions where there is a distinct wet season and dry season, and where fire and grazing prevent the establishment of dense forests. Average annual rainfall typically ranges from about 500 to 1,500 millimeters, and rainfall is highly seasonal; soils are often relatively nutrient-poor.

Savannas are found across Africa, parts of South America, and large areas of Australia, with notable examples including East African savannas, the Brazilian Cerrado, and the Australian tropical savannas. They can vary in tree cover from sparse stands to more open woodlands, and fire regimes and herbivore pressure shape their structure.

The vegetation is typically a mixture of C4 grasses and drought-tolerant trees or shrubs. Grasses such as Themeda or Hyparrhenia are common, while trees can include acacias and baobabs in Africa and eucalyptus in Australia. Fire, drought, and nutrient limitations favor grasses and hinder rapid tree growth, maintaining the open landscape.

Savannas support diverse fauna, including large herbivores such as antelope, zebras, camels in some regions, and predators. Insects, birds, and smaller mammals also contribute to biodiversity. Seasonal migrations and forage availability influence ecological dynamics.

Humans use savannas for grazing, pastoralism, and, in some places, agriculture and tourism. They face threats from overgrazing, land conversion, deforestation, mining, and climate change. Conservation approaches include protected areas, fire management, restoration of degraded sites, and sustainable grazing practices.