Grasslands of Eastern Africa: A Vital Ecosystem

Jun 11, 2025 0

African savannas are tropical grasslands spanning from 15ºN to 30ºS, covering almost half of the continent and 29 different countries. These savannas are a mixed woodland-grassland ecosystem characterized by widely spaced trees above a continuous grass understory.

The African savanna ecosystem supports some trees, shrubs, and forbs, but remains grass dominated. Notable trees include baobabs (Adansonia) and acacias (Senegalia and Vachellia).

African baobabs (Adansonia digitata) on the savanna, Tarangire National Park, Tanzania, 2019. Photo by Yoky (Wikimedia Commons, Creative Commons Attribution-ShareAlike 3.0 Unported license, image resized).

The savannas arose as rainfall progressively lessened in the edges of the tropics during the Cenozoic Era (66 million years ago to the present)-in particular, during the past 25 million years.

Dominant Plants and Their Adaptations

Africa’s iconic grasslands are dominated by plants known as “C4 grasses,” which use a photosynthetic pathway adapted for warm, arid conditions. Most grass species in the savannas are perennials.

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During the dry season, fires kill the shoot systems of the grasses, but their underground organs (roots and rhizomes) remain in the soil, and they send up new shoots during the next wet season. African savanna grasses are mostly C4 grasses, except in areas with relatively high winter rainfall.

Here are some common grass species found in African savannas:

Bermuda grass: A perennial C4 grass that grows across the African savannas and is also native to large parts of Eurasia and Australia.
Rhodes grass: A perennial C4 grass commonly found in disturbed habitats.
Red oat grass: A perennial C4 grass also found in Australia, where it is known as kangaroo grass.
Napier grass: An evergreen perennial C4 grass found in many African countries.

Climate and Seasons

The temperature remains warm throughout the year across the African savanna, with distinct wet and dry seasons. Rainfall is concentrated to around half of the year and is followed by an extended period of drought with frequent wildfires.

The dry season occurs from October to March in the southern hemisphere and from April to September in the northern hemisphere.

Wildlife in the Savanna

The savannas are home to both grazing and browsing animals, with about 45 species of mammals and 500 species of birds. Animals in the African savanna generally include the giraffe, elephant, buffalo, zebra, gnu, hippopotamus, rhinoceros, and antelope, where they rely on grass and/or tree foliage to survive.

A large acacia tree on the savanna, Amboseli National Park, Kenya, 2019. Photo by Kandukuru Nagarjun (flickr, Creative Commons Attribution 2.0 Generic license, image resized).

New Discoveries and Research

Researchers have often argued that during the early Miocene, between about 15 and 20 million years ago, equatorial Africa was covered by a semi-continuous forest and that open habitats with C4 grasses didn’t proliferate until about 8 to 10 million years ago. However, mounting evidence from paleontological and paleoclimatological research undermines this theory.

A new study sought to determine if this was an anomaly or a clue to the true diversity of ecosystems that occurred during the early Miocene. Multiple lines of evidence show that C4 grasses and open habitats were important parts of the early Miocene landscape and that early apes lived in a wide variety of habitats, ranging from closed canopy forests to open habitats like scrublands and wooded grasslands with C4 grasses.

One of the most advanced early apes, Morotopithecus, was found to inhabit open woodland environments with abundant grasses and to rely on leaves as an important component of its diet. This contradicts long-standing predictions that the unique features of apes, such as an upright torso, originated in forested environments to enable access to fruit resources.

The history of grassland ecosystems in Africa prior to 10 million years had remained a mystery, in part because there were so few plant fossils, so it was exciting when it became clear that we had phytolith assemblages to add to the other lines of evidence.

This much earlier occurrence of C4 grasses and open habitats found at the same sites as early apes also allowed the researchers to assess the kinds of environments in which the early apes were living.

For the first time, by combining diverse lines of evidence, this collaborative research team tied specific aspects of early ape anatomy to nuanced environmental changes in their habitat in eastern Africa, now revealed as more open and less forested than previously thought.

Map of tropical savannas in Africa. Map created by N. Schulberg.

Threats and Conservation

The savannas of the world currently are undergoing another phase of change as modern expansion of the human population impinges on the vegetation and fauna. Savannas are subject to regular wildfires and the ecosystem appears to be the result of human use of fire.

A number of exotic plants species have been introduced to savannas around the world. Human induced climate change resulting from the greenhouse effect may result in an alteration of the structure and function of savannas.

Alteration in soil structure and nutrient levels affects the establishment, growth and survival of plant species and in turn can lead to a change in woodland structure and composition. Large areas of Australian and South American savannas have been cleared of trees, and this clearing continues today.

The Future of Grasslands

Between 10 million and 6 million years ago, vegetation across much of the world underwent a transformation, as warmth-loving grasses displaced previously dominant plants, shrubs and trees. The new grasses carried out the chemical reactions required for photosynthesis in a distinct new way.

Increasing atmospheric CO2 levels will diminish the biochemical advantages of C4 photosynthesis over C3 photosynthesis, and that would result in a decrease of C4 biomass. Other important factors that affect all plants are temperature, disturbances like human land use, fire and invasive species, and the availability of water.