A sea of grass
A savanna is a tropical grassland dotted with trees and shrubs. Savannas cover about one-fifth of Earth’s land, more than any other biome on land. They’re home to some of the world’s most famous animals: lions, elephants, giraffes and zebras.
Where savannas are
| Region | Example |
|---|---|
| Africa | Serengeti (Tanzania and Kenya); nearly half of Africa is savanna |
| South America | Llanos (Venezuela and Colombia); Cerrado (Brazil) |
| Australia | Northern Australia |
| Asia | Parts of India |
Savannas lie between tropical rainforests and deserts, roughly between 5° and 20° north and south of the equator.
Climate
| Feature | Savanna |
|---|---|
| Temperature | Warm to hot all year (about 20–30 °C) |
| Rainfall | About 500–1500 mm per year |
| Seasons | A wet season and a long dry season |
During the wet season, heavy rains turn the grass green and fill water holes. During the dry season, which can last half the year or more, grass turns brown, rivers shrink and fires are common.
Savannas get too little rain for a thick forest but enough to support tall grasses and scattered trees.
Plants
Savanna plants are adapted to drought and fire.
| Plant | Adaptation |
|---|---|
| Grasses (like elephant grass and Rhodes grass) | Deep roots; grow back quickly after fire or grazing because their growing points are near the ground |
| Acacia trees | Thorns protect against grazers; deep roots reach groundwater; umbrella shape |
| Baobab trees | Store huge amounts of water in their swollen trunks; drop leaves in the dry season; can live over 1000 years |
| Shrubs | Small, waxy leaves reduce water loss |
Many savanna plants are drought-resistant: they survive months without rain.
Animals
Savannas support huge herds of grazing animals and the predators that hunt them.
| Group | Examples |
|---|---|
| Grazers (eat grass) | Zebras, wildebeest, gazelles, buffalo |
| Browsers (eat leaves) | Giraffes, elephants, some antelopes |
| Predators | Lions, leopards, cheetahs, hyenas, African wild dogs |
| Scavengers | Vultures, hyenas, jackals |
| Others | Termites, ostriches, kangaroos (in Australia) |
Sharing the food
Different grazers eat different parts of plants, so they don’t compete as much. Zebras eat the tough tops of grass; wildebeest eat the leafy middle; gazelles nibble the new shoots close to the ground. Giraffes reach leaves up to 6 m high that no one else can reach.
The Great Migration
Each year, about 1.5 million wildebeest, along with hundreds of thousands of zebras and gazelles, travel in a huge loop through Tanzania’s Serengeti and Kenya’s Maasai Mara, following the rains to fresh grass. It’s one of the largest animal migrations on Earth.
Animal adaptations
- Many animals are fast runners to escape predators (gazelles) or catch prey (cheetahs, the fastest land animal).
- Zebras’ stripes may confuse predators and biting flies.
- Elephants dig for water with their tusks during the dry season, creating water holes other animals use.
- Some animals rest during the hottest part of the day and are active at dawn, dusk or night.
Fire
Fires are natural in savannas, often started by lightning at the end of the dry season. Fire:
- burns dead grass and returns nutrients to the soil
- kills young trees, keeping the savanna open
- encourages fresh grass growth
Threats
| Threat | Effect |
|---|---|
| Farming and ranching | Savanna land is converted to cropland and pasture |
| Poaching | Elephants and rhinos are hunted for ivory and horns |
| Overgrazing | Too many livestock can turn savanna into desert |
| Climate change | Shifts in rainfall patterns |
National parks like the Serengeti and Kruger help protect savanna ecosystems.
Common mistakes
- Thinking savannas are deserts. They get much more rain.
- Thinking all savannas are in Africa.
- Thinking fire is always harmful. It’s a natural part of savannas.
Try it yourself
- Draw a savanna food web with at least eight organisms.
- Compare savanna and Canadian prairie grasslands in a chart.
- Research why baobab trees are sometimes called "upside-down trees."
Quick recap
- Savannas are tropical grasslands with scattered trees.
- They have warm temperatures and distinct wet and dry seasons.
- Plants survive drought and fire with deep roots and water storage.
- Huge herds of grazers support predators and scavengers.
- Farming, poaching and climate change threaten savannas.