SAVANNAS: CHARACTERISTICS, TYPES, RELIEF, FLORA, CLIMATE, FAUNA, EXAMPLES - BIOLOGY - 2025

The savannas are tropical to subtropical ecosystems, dominated by grasses and trees and shrubs scarce. They are part of the so-called grasslands next to the meadows, differing from them by climate and species composition. The rainfall, fertility and permeability of soils is what determines the presence of savanna instead of tropical forest.

Savannas are distributed throughout much of tropical and subtropical America, from southern North America to South America. We find them in vast areas of sub-Saharan Africa, from the Atlantic to the Indian Oceans.

Savannah of the Serengeti (Africa). Source: Bjørn Christian Tørrissen

Similarly, there are savannas in the foothills of the Himalayas, in the north and east of Australia and in Hawaii. These plant formations have a simple structure with a herbaceous cover dominated by grasses and some scattered trees.

Savannas develop in variable soil conditions from sandy loam to clay. Among the factors that affect the ecology of these ecosystems are fires (natural and man-made) and herbivory.

Savanna plant formation is classified according to different criteria such as biogeography, by prominent biotypes, by hydric regime, floristics and height of the pastures. According to biogeographic criteria, the World Wildlife Foundation or World Wildlife Fund (WWF) has established 50 savanna ecoregions.

Savannas develop in flat or slightly undulating reliefs, which can be alluvial plains, foothills or plateaus. Being its composition of species variable depending on the region where they develop.

However, the predominant family is Poaceae, and trees of the Leguminosae family abound in wooded savannas.

This flora develops in a bi-seasonal climate with variable rainfall, from 600 to 3,000 mm and an average annual temperature is approximately 27 ºC. The dry season can last from 3 to 7 months and the rest of the year a rainy season.

The fauna in the savannas can be scarce or very abundant, depending mainly on the climatic conditions. In the African savannas there is a high diversity of species with large populations.

There are herds of wildebeest from millions of animals and hundreds of thousands of zebras and gazelles. As well as other emblematic animals such as the elephant and the giraffe and large predators such as the lion, leopard, cheetah and hyenas.

In the savannas of America we find capybaras, deer, jaguars and a great diversity of birds. In addition, fauna associated with the rivers that cross the savannah such as the anaconda, piranhas, turtles, the Orinoco caiman and the spectacled caiman.

The savannas have been traditionally dedicated to both cattle and sheep due to their relief and the predominance of pastures. Agriculture and tourism activities are also developed in these ecosystems.

Many savanna areas are protected under the regime of national parks or nature reserves. These areas allow the conservation of these ecosystems with their natural characteristics and are a good example of these ecosystems.

For example, the Serengeti national park in Tanzania stands out, representing the Acacia tree savannas in Africa. Huge herds of wildebeest and zebra live here, as well as lions, elephants, giraffes and various species of gazelles.

For its part, the Santos Luzardo National Park in Venezuela is a good example of the flooded savanna of northern South America. Here are numerous herds of capybaras or chigüires in the lagoons and rivers, as well as the jaguar and the caramerudo deer.

General characteristics

- Biogeography

Intertropical zone

The geographical delimitation of the savannas is framed in the intertropical zone, conditioned by climatic and edaphic factors (soils). The savannas develop in low tropical areas, with high average temperatures and low total rainfall.

- Geographical distribution

America

We find savannas in America from southern North America to northern South America in Colombia and Venezuela. The most representative being the Colombian-Venezuelan plains and the Guyanese savannas that limit the Amazon and the Guiana jungle to the south.

Wooded savannah in Venezuela. Source: Inti

Then there is the Cerrado, stretching through central Brazil, northeastern Paraguay, and eastern Bolivia. There is also an extensive savanna from Rio Grande do Sul (Brazil), all of Uruguay and even part of Entre Ríos (Argentina).

Africa

In Africa the savannah extends in a wide strip below the Sahara desert, from the Atlantic to the Indian Ocean, in what is known as the Sahel. To the south are savannas up to the edge of the Congo jungles and another area that includes the wooded savannas of Zimbabwe.

Indomalasia

In the Indomalaya region are the Terai-Duar savannas, in the foothills of the Himalayas. This tall grass savanna spans Bhutan, India and Nepal.

Oceania

Savannas are found in this region of the world in the north and east of Australia as well as shrubby savannas in Hawaii.

- Plant structure

Savannas have a simple structure, where trees only appear sparsely and are even absent in large areas. The dominant stratum is the herbaceous cover, mainly composed of grasses, with some subshrubs and shrubs.

The grass cover can have a height from 0.20 to 3 m. while in wooded savannas the trees have heights between 5 and 15 m.

- Floor

Although in the savannas the soils are variable, in most cases they are loamy-sandy, clay-sandy to clayey. Entisols and oxisols soils predominate in well-drained savannas; while in poorly drained savannas there are mainly vertisols and alfisols.

There are also regional peculiarities such as the volcanic ash soils of the Serengeti in Tanzania.

- burning

Fires are a characteristic component of the savannahs, being both natural and human-caused. The grasses that dominate the savanna have developed adaptations that allow them to survive burning.

These periodic burns allow the renewal of biomass to the extent that it promotes the emergence of new grass shoots.

- Herbivory

Savannas, like all herbaceous biomes in the world, have developed a process of coevolution between herbivores and herbs. Herbivores have specialized to reduce competition and some consume mainly grass while others browse the leaves of scattered trees.

- Anthropic impact

The human being has caused great negative impacts on the savannas, especially with agriculture, farming and hunting. In some cases it has expanded the limits of the ecosystem by deforesting bordering forests that are transformed into secondary savannas.

In others, the limits of the natural savannah are reduced by dedicating extensions to the cultivation of cereals or the rearing of cattle.

Loss of species

Hunting has been the main cause of the decline in large populations of herbivores in the savannas. For example, the intensification of hunting with the arrival of Europeans in Africa, substantially reduced the fauna in the Guinean and Sahelian savannas.

Types

- Biogeographic: ecoregions

The World Wildlife Foundation or World Wildlife Fund (WWF) identifies up to 50 savanna ecoregions worldwide. Each ecoregion represents a type of savanna defined by some combination of species composition, climate, and soils.

- By prominent biotypes

The biotype is the general morphological expression of the plant, of which four basic forms are recognized: grass, subshrub, shrub and tree. In the savanna the predominant biotype is grass, although there are savannas with scattered trees or with shrubs and subshrubs.

In this sense, we speak of non-wooded savannas, shrubby savannas and wooded savannas. For example, the non-wooded savannas of the Gran Sabana in Venezuelan Guiana.

On the other hand, the bush savannas of northwestern Tanzania or the wooded miombo savannas of the central Zambezi from Tanzania to Angola.

- By water regime

Flood and non-floodable savannas

Another criterion for classifying savannas is the water regime; thus there are floodable and non-floodable savannas. For example, in the Colombian-Venezuelan plains there are savannas associated with the course of large rivers that flood in the rainy season.

Seasonality

In this case we speak of seasonal savannas, hyperstational savannas and semi-seasonal savannas given by the duration of the dry and rainy seasons. The seasonal savannas alternate a rainy season of 6-8 months with a dry season of 4-6 months, have well-drained soils and do not flood.

Floodplain in Venezuela. Source: Fernando Flores

The hyperstational savannas have poorly drained soils and are periodically flooded; with a dry season of 3 to 4 months. These savannas actually have four seasons: the dry season, the rainy season, the flooding season and the rainy season.

For their part, semi-seasonal savannas are similar to hyperstational ones, but with a dry season that lasts only a few weeks.

- Floristic criteria

A criterion that is also used to define the types of savannas is the presence of characteristic species due to their abundance or representativeness. Thus, for example, in the Colombian-Venezuelan region we speak of Trachipogon savannas (not floodable) and Paspalum fasciculatum savannas (floodable).

- By pasture size

Short and intermediate grass savannas

The species of grasses of these savannas do not exceed one meter in height. They are characteristic genera Cynodon, Sporobolus, Eragrostis, Andropogon and Chloris, among others. They are characterized by having soils of medium to low fertility and a relatively long dry period.

Tall grass savannas

In this case, these are species that reach heights of 1-3 m or even more and the predominant genera are Panicum, Aristida, Sorghum, Saccharum among others. These savannas generally occur on more fertile soils and with greater water availability.

- relief

These are generally large plains or slightly undulating terrain, which can be even below sea level up to 600-700 meters above sea level. In some cases they can develop in alluvial plains (formed by the diversion of large rivers) or in plateaus and areas of foothills.

- Floodplains

A relief of low areas near the course of the rivers and an elevation gradient is formed when moving away from them. It is important to note that it may be current river courses or reliefs made up of old river derivations.

Bank-Bajío-Estero sheets

In the north of South America in these cases we speak of bank savannas (high part), bajío (intermediate) and estuary (the low flood zone near the river).

Flora

The dominant family in the savannas is Poaceae, with an enormous diversity of genera and species. Among the few subshrubs, shrubs and trees legumes (Leguminosae or Fabaceae) abound.

- American species

Grasses

Species such as Tridens texanus, Tridens muticus, Trichachne hitchcockii, Aristida roemeriana, and Bouteloua radicosa are found in the savannas of southern North America.

On the other hand, in the savannas of the Colombian-Venezuelan plains species of the Trachypogon and Paspalum genera are common. Other genera represented are Axonopus, Andropogon, Leptocoryphium, Sporobolus, and Aristida.

Further south, the Cerrado is the largest savanna region in South America and one of the most biologically rich in the world. Here are species such as Gymnopogon foliosus, Panicum campestre, Saccharum asperum, and many others.

Trees and shrubs

A representative tree of the American savanna is the chaparro (Byrsonima crassifolia and Byrsonima coccolobifolia). There are also savannas where the “arboreal” element is palms, for example the plains palm savannah (Copernicia tectorum) in Venezuela.

In the plains, the formation of tree islands in the middle of the savannah is common, associated with conditions of the water table and fertility. These islands are called "matas" and are made up of species of trees and shrubs.

Among the common species in the plain “bushes” are oil (Copaifera officinalis), carob (Hymenaea courbaril) and cane fistula (Cassia grandis).

- African species

Grasses

Short and medium grasslands predominate with species of the genera Sporobolus, Chloris, Digitaria, Eragrostis, Cynodon, Panicum, Pennisetum, among others. Although there are also taller species such as Hyparrhenia rufa up to 3 m.

In the savannas near the Sahara desert there are typical species of this desert such as Panicum turgidum and Aristida sieberana. Wooded savannas of tall grasses also develop where the dominant species is elephant grass (Pennisetum purpureum).

Trees and shrubs

Among the trees, the most characteristic species are those of the genus Acacia (legumes). Legumes are rich in protein, being highly sought after by species that browse (consume tree leaves), such as giraffes.

One of the savanna ecoregions of Africa is the Sahelian acacia savannas. They form a continuous band from the Atlantic Ocean to the Red Sea. Also this ecoregion includes the Sahara desert to the north.

Acacia savanna of the Sahel (Africa). Source: Amcaja

Common tree species in this ecoregion include Acacia tortilis, Acacia laeta, Commiphora africana, Balanites aegyptiaca, and Boscia senegalensis. While to the south of the sahel there are shrubby savannas with a predominance of Combretum and Terminalia shrubs.

Also, you can find the teak wooded savannas (Baikiaea plurijuga) of the Zambezi (Zimbabwe).

- Indo-Malay species

Grasses

Tall grass savannas are presented with Saccharum spontaneum, Saccharum benghalensis, Arundo donax, Narenga porphyracoma, among other species. Low grass savannas are also found with species such as Imperata cylindrica, Andropogon spp. and Aristida ascensionis.

- Australian species

Grasses

Present in wooded savannas of tall grasses of the genera Sorghum, Chrysopogon, Aristida, among others. There are also low grass savannas such as those dominated by Dichanthium spp.

Trees and shrubs

In the case of the Australian savannas, legumes (Acacia spp., Bauhinia spp., Albizia spp.) And myrtaceae (Eucaliptus spp.) Abound. There are also species of the Macropteranthes and Terminalia genera of the Combretaceae family.

Adaptations

Savannas are characterized by a prolonged dry season, as well as high herbivory and periodic fires. This is why the plants that live there have developed various adaptations to that environment.

The structures

Grasses in particular have a series of structures such as buds at the base of culms or stems, below ground level. As well as modified underground stems such as rhizomes and stolons.

All these structures keep growing points away from herbivores and the action of flames.

Weather

Savannas thrive in warm tropical and subtropical climates with variable rainfall. In the savannas there are two seasons: a dry period and a rainy or humid period; the duration of one and the other being variable.

In northern South America, the dry period lasts from 3 to 5 months and the rainy one from 7 to 9 months. However, in the Australian savannas the relationship is reversed, with 5 months of rains and 7 months of drought.

Precipitation

During the dry period, sporadic rainfall does not contribute more than 100 mm. While in the rainy period the rains are intense and long-lasting. The amount of water supplied varies depending on the region, even locally, and can range from 600 to 3,000 mm.

Temperature

The average annual temperature is around 27 ºC although it is variable in the extension of the biome.

In the Australian savannas, temperatures are high throughout the year with maximums of 25 to 35 ºC. In the Serengeti (Africa) the average maximum temperatures vary from 24 to 27 ºC, and the minimum from 15 to 21 ºC.

Fauna

Savannas are home to a large number of animal species, in some cases such as those in Africa with large populations. The abundance of grasses allows the development of large herds of herbivores that attract large predators.

- Africa

Herbivores

Among the herbivores, the wildebeest (Connochaetes gnou and C. taurinus) and zebras (Equus quagga, E. zebra and E. grevyi) stand out. Other grass consumers are gazelles (Gazella spp.) And savanna elephant (Loxodonta africana).

There are browsers like the giraffe (Giraffa camelopardalis), which consume the leaves of the Acacia trees. Among the omnivores is the wild pig or string pig (Hylochoerus meinertzhageni) that consumes herbs, roots, but can also be a scavenger.

Carnivores

The emblematic animal of Africa is the lion (Panthera leo) that although it is known as King of the Jungle, inhabits the savannah. Likewise, there are other cats such as the leopard (Panthera pardus pardus) and the cheetah (Acinonyx jubatus).

African lion (Panthera leo). Source: Kevin Pluck

Other carnivores are hyenas (Crocuta crocuta) and spotted wild dogs (Lycaon pictus), which hunt in packs. Additionally, there is the Nile crocodile (Crocodylus niloticus), which stalks herds of wildebeest and zebra in their migrations.

- America

The capybara or chigüire

In the savannas of the Colombian-Venezuelan plains, the most prominent animal is the capybara or chigüire (Hydrochoerus hydrochaeris). This mammal is considered the largest rodent in the world and lives in the lagoons of the savannas.

Capybara or chigüire (Hydrochoerus hydrochaeris) Source: Smabs Sputzer

Predators

Among the predators of the capybara are large carnivores that inhabit the savannah. Among them is the jaguar or yaguar (Panthera onca), the largest feline in America.

In the water the anaconda (Eunectes murinus) and the Orinoco caiman (Crocodylus intermedius). The latter were abundant in the past, but hunting for their skin and meat brought them to the brink of extinction.

The Orinoco caiman is one of the largest crocodiles in the world, reaching up to 7 m in length. For its part, the anaconda is the largest snake in the world, reaching up to 10 m in length.

In the rivers and lagoons of the plains there is an abundance of the spectacled caiman or baba (Caiman crocodilus) of relatively small size (1-2.5 m). It also inhabits an ant predator, known as the giant anteater or palm bear (Myrmecophaga tridactyla).

Other herbivores

Another inhabitant of the savannas is the plains deer or caramerudo deer (Odocoileus virginianus apurensis).

Birds

The savannas are very rich in birds, including the jabirú (Jabiru mycteria) and the red corocora or scarlet ibis (Eudocimus ruber). Among the birds of prey are the chimachimá or caricare (Milvago chimachima) and the red busardo or red hawk (Busarellus nigricollis).

- Indo-Malaysia

The savannas at the foot of the Himalayas are home to the largest number of tigers, rhinos, and ungulates in Asia.

Emblematic species

The one-horned rhinoceros (Rhinoceros unicornis) and the Asian tiger (Panthera tigris) live in these savannas, which is the second largest feline in the world. In addition, these plant formations constitute the habitat of the Asian elephant (Elephas maximus).

Ungulates

Among the ungulates are the nilgó or blue bull (Boselaphus tragocamelus) and the water buffalo (Bubalus arnee).

Other threatened species

The hispid hare (Caprolagus hispidus) is threatened while the dwarf wild boar (Porcula salvania) is critically endangered.

- Australia

The fauna of these savannas is not very diverse compared to the other regions of the biome. There is an important diversity of reptiles, including the Ctenotus rimacola.

Likewise, there are small marsupials such as the kangaroo hare (Lagorchestes conspicillatus), the yellowtail kangaroo (Onychogalea unguifera) and the bronze quat (Dasyurus spartacus).

Economic activities

farming

The soils of the savannas are variable in fertility and water availability, with wide areas useful for agriculture. Sorghum and millet are grown in parts of Africa, while soy, corn, sunflower and sesame are grown in America.

Cattle raising

Savannas are ecosystems linked to grazing, making them ideal for extensive livestock rearing. A large part of the savannahs of the Colombian-Venezuelan plains have traditionally been dedicated to this activity.

Likewise, dual-purpose cattle and sheep farming mainly for wool in the savannas of Uruguay.

tourism

There are protected savannahs such as national parks or fauna reserves and in these areas the main activity is tourism. For example, the national parks of Africa where the famous photographic safaris take place.

Hunting

A historical activity in the savannas has been hunting, leading to the extinction of many species. In the acacia savannahs of the Sahel the immense herds of ungulates were drastically reduced by hunting by European settlers.

Today, even in protected areas hunting continues. For example, an estimated 200,000 animals are killed within the Serengeti National Park annually in poaching.

Examples of savannas in the world

- Serengeti National Park (Tanzania)

Its 13,000 km2 extend through the volcanic savannas of the Serengeti in northern Tanzania, near the border with Kenya. It was created in 1951 and shelters acacia wooded savannas in flat plains and rolling areas.

Flora

The dominant tree species is the acacia (Acacia spp.) Of the mimosoid legumes. For its part, the predominant plant group is the short and intermediate grasslands of grasses.

Among the dominant species are Sporobolus spp., Pennisetum mezianum, Eragrostis tenuifolia, Andropogon greenwayi and Panicum coloratum. Also found are Cynodon dactylon, Chloris gayana, and Digitaria macroblephara.

Fauna

It is home to a huge amount of fauna, both in species diversity and population size. Here live elephants, wildebeest, giraffes, lions, hyenas, gazelles, rhinos, among others.

It is also inhabited by the black rhinoceros (Diceros bicornis) and the kaffir buffalo (Syncerus caffer).

Migrations

This region is famous for the migrations of huge herds of ungulates such as the blue wildebeest (Connochaetes taurinus) that number up to 1.3 million. For their part, Thomson's gazelles (Gazella thomsoni) displace up to 400,000 individuals and Burchell's zebras (Equus burchelli) 200,000.

Herds of herbivores in the Serengeti (Africa). Source: David Dennis from Pozuelo de Alarcón, Madrid, Spain

These animals make a long journey between this area and the Acacia - South Commiphora forest ecoregion every year.

Activities

It is the land of the Maasai, an ethnic group that traditionally practices livestock and agriculture. However, as part of the park's creation, these natives were transferred to the Ngorongoro Highlands.

For the rest, tourism is a highly developed activity that generates high income for the country. However, there are also illegal activities such as poaching that seriously affects the ecosystem.

- Santos Luzardo National Park (Venezuela)

Its 5,844 km2 extend between the Cinaruco and Capanaparo rivers until the confluence of both with the Orinoco river. It was created in 1988 and is located in the Apure state in southern Venezuela, close to the border with Colombia.

It is a representative area of ​​the flooded savannas of the Colombian-Venezuelan plains, with flat relief, except for some granite elevations.

Flora

The grass Paspalum fasciculatum (chigüirera straw) is the most abundant in these savannas. Other species of the shallows (lower parts) are Imperata contracta (viper) and Leersia hexandra (lambedora straw).

Then in the highest parts (banks) is Andropogon sealanus, Sporobolus indicus (tupuquén), Paspalum plicatulum (gamelotillo), among others. There are some shrubs (eg Cassia tetraphylla) and trees (eg Bowdichia virgilioides, the American cork oak).

Fauna

The capybara or chigüire, the jaguar and the caramerudo deer inhabit these lands. In the rivers are the Orinoco caiman, the anaconda and the piranhas. As well as the giant otter (Pteronura brasiliensis), the arrau turtle (Podocnemis expansa) and the pink or boto dolphin (Inia geoffrensis).

References

1. Calow, P. (Ed.) (1998). The encyclopedia of ecology and environmental management.
2. Duno de Stefano, R., Gerardo, A. and Huber O. (Eds.) (2006). Annotated and illustrated catalog of the vascular flora of the Venezuelan plains.
3. Purves, WK, Sadava, D., Orians, GH and Heller, HC (2001). Life. The science of biology.
4. Raven, P., Evert, RF and Eichhorn, SE (1999). Biology of plants.
5. World Wild Life (Viewed 4 Sep 2019). Taken from: worldwildlife.org/biomes/tropical-and-subtropical-grasslands-savannas-and-shrublands