Savanna
A savanna is a grass-dominated ecosystem with scattered trees or shrubs, shaped by seasonal rainfall, fire, grazing, soils, and climate. Savannas occur in Africa, South America, Australia, Asia, and other regions, supporting distinctive wildlife, livelihoods, and land-management challenges.
What a savanna is
A savanna is an open ecosystem where grasses dominate the ground layer and trees or shrubs are scattered rather than forming a continuous canopy. It sits between closed forest and treeless grassland in structure, but it is not just a halfway stage. Many savannas are stable systems maintained by climate, fire, herbivores, soils, and human management.
Rainy and dry seasons
Seasonal rainfall is one of the clearest features of many savannas. During wet months, grasses can grow quickly and support intense grazing. During dry months, vegetation cures, water becomes patchier, and fire risk rises. The contrast between wet and dry seasons helps explain why savannas can support abundant grasses without always turning into forest.
Fire and grazing
Fire is a natural and human-managed process in many savannas. It can recycle nutrients, reduce dead grass, and limit young trees, although too much or poorly timed fire can damage soils and vegetation. Grazers such as antelope, zebra, cattle, bison, or kangaroos can also shape plant growth. Fire and grazing often interact rather than acting separately.
Trees and grasses together
The balance between trees and grasses is one of the central puzzles of savanna ecology. Deep roots, shallow roots, soil texture, rainfall timing, browsing, fire tolerance, and seedling survival all matter. In some places, trees expand into grassland when fire or grazing changes; in others, drought, repeated burning, or heavy browsing can keep tree cover low.
Wildlife and food webs
Savannas can support rich food webs. Grasses feed large herbivores, herbivores feed predators and scavengers, and termites, fungi, bacteria, and dung beetles move nutrients through soil and detritus pathways. African savannas are famous for large mammals, but savanna biodiversity also includes birds, reptiles, insects, plants, microbes, and belowground life.
People and land use
Savannas are working landscapes as well as habitats. People use them for grazing, farming, hunting, tourism, cultural practices, fuelwood, and conservation. The same land can be claimed for food production, wildlife corridors, carbon projects, settlement, and protected areas, so decisions about savannas often involve tradeoffs rather than a single obvious goal.
Threats and change
Savannas face conversion to cropland, overgrazing, invasive plants, altered fire regimes, woody encroachment, fragmentation, mining, and climate stress. Some savannas are also misidentified as degraded forest and targeted for tree planting, even when open grass-tree structure is their natural state. Protecting savannas requires recognizing their own ecology.
Why it matters
Savannas matter because they store carbon, sustain grazing economies, protect distinctive biodiversity, shape regional fire and water cycles, and support communities with long histories of land stewardship. They challenge simple ideas about nature: more trees are not always better, and fire is not always only destructive.