The savanna is a tropical grassland biome found between the equatorial rainforest and the subtropical deserts, characterised by a pronounced wet and dry season. Open plains, scattered trees, and some of the world's richest wildlife assemblages define the African savanna, though savannas also cover large areas of South America, Australia and South Asia.
Where are savannas found?
Savannas are located in a broad band on either side of the equatorial rainforest belt, typically between 5° and 20° north and south of the equator. The major savanna regions of the world are:
- Africa: The largest area, covering roughly half the continent. Includes the Serengeti (Tanzania/Kenya), the Sahel, the Miombo woodland (southern Africa), and the savanna lands of West Africa.
- South America: The cerrado of central Brazil is the world's most biodiverse savanna, home to about 5% of all species on Earth. The llanos of Venezuela and Colombia are also savanna.
- Australia: The tropical north — the Kimberley, the Northern Territory, and Queensland — is predominantly savanna.
- South Asia: Parts of India have savanna-type environments (sometimes called "tropical dry deciduous forest").
The SEEP framework helps organise savanna geography: Social (communities who live there), Economic (agriculture, tourism), Environmental (biodiversity, fire ecology), Political (land rights, conservation policy).
What is the savanna climate?
The savanna climate has one defining characteristic: a strong seasonal pattern of rainfall and drought, not a year-round tropical wetness.
| Season | Temperature | Rainfall | What happens |
|---|---|---|---|
| Wet season (summer) | Hot, ~27–30°C | 1,000–1,500 mm concentrated here | Grasses grow rapidly; animals congregate at water sources; vegetation greens |
| Dry season (winter) | Still warm, ~21–25°C | Very little or none | Grasses dry out; many trees shed leaves; fires are common |
Annual rainfall typically falls between 500 mm and 1,500 mm, but the key factor is concentration: most rain arrives in just four to six months. The dry season lasts from around May to October in the southern hemisphere and November to April in the northern hemisphere. Temperatures remain high throughout the year — the savanna does not have a cold season, only a wet one and a dry one.
What vegetation grows in the savanna?
Savanna vegetation is specifically adapted to survive the extremes of drought, fire, and flood that characterise the biome.
Grasses dominate the ground layer. Tall grass species such as elephant grass (Pennisetum purpureum) can reach 3–4 metres. Grasses grow extremely rapidly during the wet season and die back to fire-resistant roots during the dry season.
Trees are scattered rather than forming a closed canopy. Key adaptations include:
- Deep taproots reaching the water table during drought (e.g., acacia trees)
- Thick, fire-resistant bark protecting the cambium layer (e.g., baobab trees)
- Deciduous behaviour — shedding leaves in the dry season to reduce water loss
- Water storage in trunks — the baobab stores thousands of litres
Fire adaptation is crucial. Many savanna species not only survive fire but depend on it. Grasses regenerate rapidly from root systems after burning. Fire clears dead vegetation and releases nutrients into the soil, encouraging new growth that attracts grazing animals.
What wildlife lives in the savanna?
The African savanna is famous for its diversity of large mammals, particularly the assemblage of grazing and browsing animals and the predators that follow them.
Grazers and browsers: Wildebeest, zebra, impala, Thomson's gazelle, buffalo, giraffe, and elephant all exploit the wet-season grass growth. The wildebeest migration across the Serengeti and Masai Mara — roughly 1.5 million animals following the rains — is the largest land mammal migration on Earth.
Predators: Lion, leopard, cheetah, wild dog, and hyena occupy different ecological niches within the predator community. The diversity of prey supports this predator diversity.
Birds: Over 600 bird species in the Serengeti alone, ranging from ostriches and secretary birds that stalk the grass to vultures exploiting thermals to find carcasses.
Seasonality matters: Animal populations move with the rains. During the dry season animals concentrate at permanent water sources, making them visible and vulnerable. The wet season disperses them across the landscape.
What threats does the savanna face?
Agricultural conversion is the single biggest threat. The savanna's soils are suitable for grazing and some arable farming. In Brazil's cerrado, roughly half the original vegetation has been cleared for soy farming and cattle ranching. In Africa, traditional pastoralism is being replaced by intensive agriculture that does not allow the land to recover.
Overgrazing occurs when livestock numbers exceed what the land can sustain. Overgrazed savanna loses its grass cover, leaving bare soil vulnerable to erosion and potentially tipping towards desertification.
Fire management changes can alter savanna ecology. Traditionally, communities used fire to manage pasture. Suppression of burning — which can happen when land ownership changes — allows woody vegetation to encroach on open grassland, a process called "bush encroachment."
Climate change is projected to lengthen dry seasons in some savanna regions and shorten wet seasons, stressing vegetation and reducing the carrying capacity of the land for both wildlife and people.
Frequently asked questions
How is the savanna different from the desert and the rainforest?
The savanna sits between these two biomes in terms of rainfall. The tropical rainforest receives more than 2,000 mm of rain spread year-round, producing dense canopy vegetation with very little grass layer. The hot desert receives less than 250 mm per year and has sparse, highly specialised plant life. The savanna's 500–1,500 mm of strongly seasonal rainfall creates the open, grass-dominated landscape with scattered trees that is uniquely its own.
Why do trees not form a closed canopy in the savanna?
Three factors interact. First, annual dry seasons are long enough to stress trees severely, favouring drought-resistant species that are naturally more widely spaced. Second, fires regularly kill tree seedlings before they can establish, limiting tree density. Third, browsing animals — particularly elephants — actively suppress tree growth by eating saplings and pushing over trees. Remove elephants and fire from a savanna, and it often transitions towards woodland.
What is the economic importance of the savanna?
Savannas support enormous human populations who depend on them for pastoralism (cattle, goats, and camels), small-scale agriculture, and gathering of wild food and materials. Tourism — particularly wildlife safaris in East Africa — generates significant income and creates economic arguments for conservation. The cerrado in Brazil supports large-scale commercial agriculture (soy, maize, cattle) that makes Brazil a global food exporter, though at major environmental cost to the native savanna ecosystem.
Why is fire important for the savanna?
Fire is not simply a threat to the savanna — it is a fundamental part of its ecology. Savanna has evolved with regular fire over millions of years. Fire removes dead grass and woody material, releasing nutrients. It limits the invasion of trees into grassland. Grass species regenerate rapidly from fire-resistant root systems, while tree seedlings that lack this protection are killed, maintaining the open landscape. Many African national parks use deliberate burning to manage habitats. Removing fire entirely can cause the savanna to shift towards dense bush or woodland.
Explore the savanna biome with the SEEP framework and Professor Mercator at aitutors.me.