In many ways a brief description of some of the main habitats for plants is really a step through the various types of environment that you'll encounter in Botswana.
As with animals, each species of plant has its favourite conditions. External factors determine where each species thrives, and where it will perish. These include temperature, light, water, soil type, nutrients, and what other species of plants and animals live in the same area. Species with similar needs are often found together, in communities which are characteristic of that particular environment. Botswana has a number of different such communities, or typical 'vegetation types', within its borders – each of which is distinct from the others. The more common include:
The dominant tree here is the remarkably adaptable mopane, Colophospermum mopane
, which is sometimes known as the butterfly tree because of the shape of its leaves. It is very tolerant of poorly drained or alkaline soils, and those with a high clay content. However, it doesn't thrive on the Kalahari's sands. This tolerance results in the mopane having a wide range of distribution throughout southern Africa; in Botswana it occurs mainly in the Okavango-Linyanti region, and throughout the eastern side of the country.
Mopane trees can attain a maximum height of 25m when growing on rich, alluvial soils. These are then called cathedral mopane, for their height and the graceful arch of their branches. However, shorter trees are more common in areas that are poor in nutrients, or have suffered extensive fire damage. Stunted mopane will form a low scrub, perhaps only 5m tall. All mopane trees are deciduous, and the leaves turn beautiful shades of yellow and red before falling in September and October.
Ground cover in mopane woodland is usually sparse; just thin grasses, herbs and the occasional bush. The trees themselves are an important source of food for game, as the leaves have a high nutritional value – rich in protein and phosphorus – which is favoured by browsers and is retained even after they have fallen from the trees. Mopane forests support large populations of rodents, including tree squirrels, Peraxerus cepapi
, which are so typical of these areas that they are known as 'mopane squirrels'.
Though not an environment for rich vegetation, a pan is a shallow, usually seasonal, pool of water without any permanent streams leading to or from it. Mopane woodlands are full of these small pans during and shortly after the rainy season, the water being held on the surface by the clay soils. They are very important to the game that will feed here during the summer, but will dry up soon after the rains cease.
A saltpan is, as its name implies, a pan that's salty. The huge Makgadikgadi Saltpans are the residues from ancient lakes. Because of the high concentrations of mineral salts found there – there are no plants there when they are dry. When they fill with water it's a slightly different story as algal blooms appear, sometimes attracting the attention of specialist filter-feeders like flamingoes.
Although this would be the natural vegetation across most of neighbouring Zambia, in Botswana miombo woodland, and its associated dambos
(see below), are uncommon. There are patches in central Chobe and the northeast of the country. It is found in areas where the soils are acid and not particularly fertile. Often they have been leached of minerals by the water run-off.
Miombo woodland consists of a mosaic of large wooded areas and smaller, more open spaces dotted with clumps of trees and shrubs. The woodland is broad-leafed and deciduous (though just how deciduous depends on the available water), and the tree canopies generally don't interlock. The dominant trees are Brachystegia, Julbernardia
species – most of which are at least partially fire-resistant. There is more variation of species in miombo than in mopane woodland, but despite this it is often known simply as 'Brachystegia woodland'. The ground cover is also generally less sparse here than in mopane areas.
is a shallow grass depression, or small valley, that is either permanently or seasonally waterlogged. It corresponds closely to what is known as a vlei
in other parts of the subcontinent. These open, verdant dips in the landscape often appear in the midst of miombo woodlands and support no bushes or trees. In higher valleys amongst hills, they will sometimes form the sources of streams and rivers. Because of their permanent dampness, they are rich in species of grasses, herbs and flowering plants, like orchids – and are excellent grazing (if a little exposed) for antelope. Their margins are usually thickly vegetated by grasses, herbs and smaller shrubs.
In a few areas of the far north of Botswana, including the northern side of Chobe National Park, the Zambezi teak, Baikaea plurijuga
, (aka Rhodesian teak) forms dry semi-evergreen forests on Kalahari sand. Often these woodlands occur on fossil dune-crests. As this species is not fire-resistant, these stands are only found where fire is rare, and slash-and-burn type cultivation methods have never been used. Below the tall teak is normally a dense, deciduous thicket of vegetation, interspersed with sparse grasses and herbs in the shadier spots of the forest floor.
The teak is a lovely strong wood, with an even texture and deep red-brown colour. It is expensive, often exported, and widely used from furniture to expensive wooden floors.
A number of trees and bushes thrive on Chobe's extensive areas of Kalahari sand, including various Acacias, Terminalias
species. 'Kalahari sandveld' is a general term that I'll use to describe any of these plant communities based on sand.
In appearance they range from a very open savannah with a few tall trees separated only by low undergrowth, to quite dense tickets of (often thorny) shrubs which are difficult to even walk through. If you want to be a little more technical about this, then biologists will often divide this into distinctive sub-groups, including:Terminalia sericea sandveld
occurs where you find deep, loose sand – these are unfertile areas which cover large areas of the Kalahari. The main species found here are the silver terminalia, Terminalia sericea
, or silver cluster-leaf as it's sometimes called, and the Kalahari apple-leaf, Lonchocarpus nelsii
. These generally occur with wild seringa bushes, Burkea Africana
, and the bushwillow, Combretum collinum
. Underneath these you'll often find the rather beautiful silky bushman grass, Stipagrostis uniplumis
.Acacia erioloba woodlands
also occur on sand, but often where there are fossil river valleys that have an underground supply of water throughout the year. Camelthorn trees, Acacia erioloba
, have exceedingly long taproots that reach this, sustaining large stands of these mature trees reaching an impressive 16–17m in height. They grow slowly but give good shade, so the bush cover beneath them is fairly sparse.Acacia tortilis woodlands
are not found on such deep sand; instead they prefer the fine alluvium soils, which water has deposited over time. Although it forms homogenous stands less often than the camelthorns, a number of the very distinctive, flat-topped umbrella thorns (Acacia tortilis
) can often be seen together. Between these you'll find low grasses rather than much undergrowth. This results in a beautiful, quintessentially African, scene which fits many first-time visitors' picture of the continent as gleaned from the blockbuster film Out of Africa
Moist evergreen forest
In the areas of higher rainfall and (as is more likely in Botswana) near rivers, streams, lakes and swamps, where a tree's roots will have permanent access to water, dense evergreen forests are found. Many species occur, and this lush vegetation is characterised by having three levels: a canopy of tall trees, a sub-level of smaller trees and bushes, and a variety of ground-level vegetation. In effect, the environment is so good for plants that they have adapted to exploit the light from every sunbeam.
This type of forest is prevalent in the Okavango and Linyanti areas, and beside the country's larger rivers. It's perhaps worth distinguishing here between two very different types of this forest:Riverine forests
(occasionally called riparian forests) are very common. They line many of Botswana's major rivers and are found throughout the Okavango-Linyanti area. Typical trees and shrubs here include the jackalberry (Diospyros mespiliformis
), African mangosteen (Garcinia livingstonei
), sausage tree (Kigelia Africana
), large feverberry (Croton megalobotrys
), knobthorn (Acacia nigrescens
), marula (Sclerocarya birrea caffra
), raintree (Lonchocarpus capassa
) and various species of figs. Move away from the river and you'll find riparian species thinning out rapidly.
Swamp forest – or something very akin to it – occurs in tiny patches on small islands in permanently flooded areas of the Okavango. These will occasionally be flooded, and might include a mixture of fig and waterberry species, plus lots of wild date palms (Phoenix reclinata
) and a few tall real fan palms (Hyphaenea petersiana
In the centre of slightly larger small islands, where the ground is salty from Trona deposits you will find only spiky sporobolus grassland (Sporobolus spicatus
) – no trees at all!
Floodplains are the low-lying grasslands on the edges of rivers, streams, lakes and swamps that are seasonally inundated by floods. The Okavango and, to a lesser extent, the Linyanti-Chobe region has some huge areas of floodplain. These often contain no trees or bushes, just a low carpet of grass species that can tolerate being submerged for part of the year. In the midst of most of the floodplains in the Okavango, you'll find isolated small 'islands' slightly raised above the surrounding grasslands. These will often be fringed by swamp forest (see above).
Sometimes the communities of vegetation will be 'zoned' to reflect the extent and frequency of the flooding. In areas that become submerged for long periods you'll find species like wild rice, Oryza longistaminata
, and the sedge Cyperus articulatus
. Grasses, like Imperata cylindrical
, often dominate places that generally spend less time under water.
Vegetation found in permanent channels includes the giant sedge, papyrus (Cyperus papyrus
), that dominates large areas of the Okavango, plus species like the distinctive cylindrical hippo grass, Vossia cuspidate
, the tall maize-like phragmites reed used for thatching, Phragmites australis
, and the unmistakable bulrush, Typha capensis
Where the water is more still, in deep lagoons and side-channels where the surface is open but the water doesn't flow much, the bottom will often be covered with fairly stable peat deposits. This gives a stable base for many species of aquatic plants. Some are strictly submerged whilst others have floating leaves. An obvious indicator of this type of environment is the presence of waterlilies.