Vegetation of Africa and the World
Senior 3 · Geography
Vegetation of Africa and the World
Lesson 1 of 4
25 min
Let's begin
A tree is a record of the climate it grows in. A mahogany in the Congo Basin keeps broad green leaves all year because it is never short of water. A baobab in the Sahel stores water in a trunk as thick as a small room and stands bare for half the year. A welwitschia in the Namib Desert survives on scant rain and coastal fog, and grows only two leaves in its whole life, which may last centuries. In this lesson you will name Africa's vegetation types, describe each one, and explain why it grows where it does, using the climate types you learnt in Unit 4.
Definition
Vegetation: all the plant life that covers an area: trees, shrubs, grasses, herbs and mosses. Natural vegetation is the plant cover that grows without human help, and that would grow there if people left the land alone. Example: the forest of Nyungwe is natural vegetation; a tea estate beside it is not.
Climate is the strongest control, so Africa's vegetation belts line up with its climate belts: they run roughly east to west, and they repeat north and south of the Equator in mirror image.
Figure 1 shows the pattern. Compare it with the climate map of Africa in Unit 4: the belts match closely.
Figure 1: Africa's vegetation zones, drawn by Ganzaa as a simplified sketch from standard atlas maps. Real boundaries are gradual, and large areas of each zone are now farmland.
| Vegetation type | Climate it matches (Unit 4) | Where in Africa | Typical plants |
|---|---|---|---|
| Equatorial (tropical) rainforest | Equatorial, Af and Am: hot, rain in every month | Congo Basin, Gabon, Cameroon, the Guinea coast from Liberia to Nigeria, eastern Madagascar | Mahogany, ebony, iroko, sapele, obeche; lianas and epiphytes |
| Savanna (tropical grassland with trees) | Tropical wet-and-dry, Aw: one long dry season | A broad belt north and south of the rainforest, and most of East Africa | Tall grasses such as elephant grass; acacia, baobab, the miombo trees of the south |
| Semi-desert (thorn scrub) | Semi-arid, BS: short, unreliable rain | The Sahel, the Horn of Africa, the Karoo and the Kalahari | Short tufted grass, thorny bushes, low acacias, succulents |
| Desert | Desert, BW: very little rain | The Sahara and the Namib | Scattered xerophytes; date palms at oases; plants that sprout only after rain |
| Mediterranean forest and scrub | Mediterranean, Cs: hot dry summers, winter rain | Coasts and mountains of Morocco, Algeria and Tunisia; the south-western Cape | Cork oak, olive, Atlas cedar, aleppo pine; maquis scrub; fynbos at the Cape |
| Temperate grassland (the veld) | Mild highland climates, Cw and Cf, with cool dry winters | The Highveld of South Africa and Lesotho | Short grasses with few trees; frost in winter keeps trees out |
| Mountain (montane) vegetation | Mountain climate: cooler with every 1,000 m of height | Ethiopian Highlands, East African mountains, the Virunga volcanoes, Mount Cameroon, the Atlas | Belts of forest, bamboo, heath and alpine plants such as giant lobelias |
| Mangrove and swamp | Any hot climate where the ground is waterlogged | Mangroves on tidal coasts (the Niger Delta, the Rufiji Delta, Mozambique); papyrus swamps in the Sudd, the Okavango and Rwanda's valleys | Mangrove trees with stilt roots; papyrus and reeds |
Definition
Equatorial rainforest: dense, evergreen, broad-leaved forest of hot, wet lowlands near the Equator. Evergreen means the trees lose and replace leaves a few at a time, so the forest is green all year. Example: the forest of the Congo Basin, the second largest rainforest on Earth after the Amazon.
Heat and rain in every month let plants grow all year, so the forest is the richest in species of any African vegetation. Its main characteristics are:
Savanna is Africa's most widespread vegetation. It is grassland with scattered trees, and it grows where a hot climate has a long dry season.
Geodiode: The Savannah Biome. Watch for how the wet and dry seasons decide the mix of grass and trees, and for the comparison of savanna with the rainforest and the desert on either side of it.
Where rain is short and unreliable the grass is short and patchy, and bushes are thorny. In true desert, plants are far apart and are xerophytes. Some ephemeral plants survive the dry years as seeds, then germinate, flower and set seed within a few weeks of a rare storm.
Here the rain comes in the cool winter and summers are hot and dry. Trees and shrubs are evergreen but have small, hard, waxy or hairy leaves that lose little water, and thick bark such as that of the cork oak. Where forest has been cleared, a dense, aromatic scrub called maquis grows. At the Cape the scrub is fynbos, a heathland so rich in plant species that the Cape is counted as a floral kingdom of its own.
On high mountains the vegetation changes with height, in belts: you studied this on Mount Kilimanjaro in Unit 2, and you will meet Rwanda's own example on the Virunga volcanoes in Lesson 3. Mangroves grow in the salty mud of tidal coasts and deltas; their stilt roots hold them up and breathing roots poke above the mud. Inland, flat valley floors that stay flooded carry papyrus swamps.
Definition
Xerophyte: a plant adapted to survive drought. It may have deep or very wide roots, tiny, waxy or spiny leaves, or a fleshy stem that stores water. Examples: the date palm, cacti-like euphorbias and the welwitschia of the Namib.
Definition
Deciduous: describes a tree that sheds all its leaves in one season (in Africa, the dry season) and grows new ones when the rains return. Mangrove: a salt-tolerant tree or shrub of tidal coasts, with stilt roots or breathing roots. Example: the mangroves of the Niger Delta.
Worked example
Worked example 1: name the vegetation from a description. A region at 9°N in West Africa has grass up to 2 m tall with scattered trees that stand bare from December to March. Many trees have thick, fire-scarred bark. Name the vegetation and explain two features.
Worked example
Worked example 2: explain a rainforest feature. Explain why trees in the Congo rainforest have buttress roots and drip-tip leaves.
Warning
Savanna is not "grassland only", and rainforest is not "jungle". Savanna always has some trees; the mix of grass and trees is what defines it. And the floor of an old rainforest is shaded and fairly open; the tangled "jungle" of films grows only where light gets in, such as along rivers and in old clearings. In an exam, describe the layers, not a tangle.
Tip
Read the vegetation from the dry season. Ask: how many months is it dry? None: rainforest. Three to five: wooded savanna. Six or more: grass and thorn savanna. Almost all year: semi-desert, then desert. Dry in summer instead of winter: Mediterranean.
Practice
Sources and credits
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
