Ecoregions

Ecoregions of Botswana

June 15, 2013, 2:32 pm
Content Cover Image

Aerial photograph of northern halophytic pans, Botswana. @ C.Michael Hogan

The ecoregions of Botswana include seven separate elements that exist entirely or in part in Botswana:

  1. Kalahari xeric savanna (orange)
  2. Kalahari Acacia-Baikiaea woodlands (Dark Yellow)
  3. Southern Africa bushveld (Light Yellow -eastern part of the country)
  4. Zambezian and Mopane woodlands (Yellow -eastern tip of the country)
  5. Zambezian halophytics (Purple)
  6. Zambezian Baikiaea woodlands (red)
  7. Zambezian flooded grasslands (Blue)

Even though much of the country of Botswana is quite arid, there are a diversity of biomes, including desert, grassland, forest and riparian habitat. There is also a considerable diversity of plants and animals across the Botswanan landscape.

Zambezian baikiaea woodlands

The Zambezian baikiaea woodlands cover much of northern Botswana near the Angola border.

Baikiaea plurijuga is the sole dominant, forming a fairly dense, dry, semi-deciduous forest with trees up to 20 metres in height.

There is a dense and shrubby understory of Combretum engleri, Pteleopsis anisoptera, Pterocarpus antunesii, Guibourtea coleosperma, Dialium engleranum, Strychnos spp., Parinari curatellifolia, Ochna pulchra, Baphia massaiensis subsp. obovata, Diplorhynchus condylocarpon, Terminalia brachystemma, Burkea africana, Copaifera baumiana and Bauhinia petersiana serpae. Lianas and climbers are also common in the understory, including Combretum elaeagnoides, C. celastroides, Dalbergia martinii, Acacia ataxacantha, Friesodielsia obovata, and Strophanthus kombe. Smaller shrubs are scattered beneath the thicket.

The herb layer is conspicuous solely during the rainy season. Grasses vary from sparse to dense and include Leptochloa uniflora, Oplismenus hirtellus, Panicum heterostachyum, and Setaria homonyma. Other conspicuous herbs are Aneilema johnstonii and Kaempferia rosa.

Zambezian flooded grasslands

caption Flooded grasslands in the north of Botswana. @ C.Michael Hogan

Most of the flow of the Okavango River dissipates within the Okavango Alluvial Fan, in an ecoregion known as the Zambezian flooded grasslands.

This ecoregion falls within the center of distribution of the globally threatened slaty egret (Egretta vinaceigula, VU). Largely restricted to this ecoregion, this species is an uncommon resident of the marshes and floodplains of the Okavango, Chobe/Kwando, and the Caprivi Strip as well as from the Zambezi River Valley northwards to the Bangweulu swamps.

 

 

 

 

 

 

 

 

Zambezian and mopane woodlands

At the southern edge of the Okavango Alluvial Fan and with a narrow finger extending north across the Namibian border is the Zambezian and mopane woodlands.

The mopane tree itself characterizes the entire ecoregion, and in many places dominates to the exclusion of other species, particularly trees. Mopane trees are ecologically valuable  as browse for numerous animals, notably elephants, and economically the wood is prized for building material and fuel. In addition, this tree is the major host for the seasonally abundant mopane worm (Gonimbrasia belina), the larval stage of a moth which is characteristic of the mopane woodlands. The mopane worm is an important human food and economic resource.

Other important taxa in the ecoregion are the families Combretaceae and Mimosaceae, which are represented by 34 and 56 tree and shrub species respectively.

 

 

Kalahari acacia baikiaea woodlands

The Kalahari acacia baikiaea woodlands ecoregion covers much of the southern portion of the Okavango Basin. Deciduous tree and bush savanna comprises most of the ecoregion in the sandveld area.

Higher canopy level trees are chiefly confined to low sand ridges and are dominated by the following taxa: Terminalia sericea, Burkea africana, Peltophorum africanum, Croton gratissimus, Rhus tenuinervis, Acacia giraffe, A. fleckii, A. luederitzii, Cobretum zeyheri, C. apiculatum, and Ziziphus mucronata.

A shrub savanna occurs on the gently rolling plains between the sand ridges and is mainly composed of Dichrostachys cinerea, Grewia flava, G. flavescens, Acacia mellifera, Bauhinia macrantha, Ximenia caffra, and Commiphora pyracanthoides.

The grass cover includes Stipagrostis uniplumis, Aristida meridionalis, A. congesta, Eragrostis pallens, E. superba, Heteropogon contortus, Cymbopogon excavatus, and Digitaria eriantha.

 

Zambezian halophytics

caption Nwetwe Pan landscape with dry lake bottom and halophytic grassland. @ C.Michael Hogan

The Zambezian halophytics stretch out within the southern portion of the Okavango Basin. This seasonal lake represents an overflow area of the Okavango, which bears surface water as a large shallow lake, the Makgadikgadi Pan, when the Okavango overflows its usual sump in the Okavango Alluvial Fan.

On the saline fringes two macrophytes predominate; Sporobolus spicatus and the spiny grass Odyssea paucinervis. Salt marshes are found scattered around the wetter fringes of the pans.

These marshes support species such as Portulaca oleracea, Sporobolus tenellus, and Saudea fruticosa.

Surrounding the pans on a larger scale (on less brackish soil) are grasslands dominated by Odyssea paucinervis and Cynodon dactylon with Cenchrus ciliaris and Eriochloa meyeriana dominating the crests of calcrete escarpments.

These grasslands have few trees, except to the west where Hyphaene palms fringe the drainage lines, extending north to Nxai Pan. The fruit of these palms is known as vegetable ivory and is used by the local people to make necklaces and heads for walking sticks. To the north and northwest of Ntwetwe Pan individual baobab (Adansonia digitata), Acacia kirkii, and Acacia nigrescens trees are found scattered throughout the grassland

Kalahari xeric savanna

 

 

 

 

 

 

 

 

 

 

 

 

 

Southern Africa bushveld

 

 

 

 

 

 

 

 

 

 

 

 

Definition of ecoregions

Ecoregions are areas that: [1] share a large majority of their species and ecological dynamics; [2] share similar environmental conditions; and, [3] interact ecologically in ways that are critical for their long-term persistence. Scientists at the World Wildlife Fund, have established a classification system that divides the world in 867 terrestrial ecoregions, 426 freshwater ecoregions and 229 marine ecoregions that reflect the distribution of a broad range of fauna and flora across the entire planet.

References

caption Elephants grazing in the Okavango Alluvial Fan flooded grassland. @ C.Michael Hogan

  • C. Michael Hogan. 2008. Makgadikgadi, The Megalithic Portal, ed. A.burnham
  • B.J.Huntley. 1978. Ecosystem conservation in southern Africa. M.J.A. Werger, editor. Biogeography and Ecology of Southern Africa. W. Junk, The Hague. ISBN: 9061930839
  • Graham McCulloch. 2003. The ecology of Sua Pan and its flamingo populations, PhD thesis, University of Dublin, Ireland
  • S.N.Stuart, R.J. Adams and M.D. Jenkins. 1990. Biodiversity in sub-Saharan Africa and its Islands. Chapter 8: Botswana. Occasional Papers of the IUCN Species Survival Commission No. 6. IUCN, Gland, Switzerland. ISBN: 2831700213
  • Thomas Tlou and Alec Campbell. 1984. History of Botswana. MacMillan ISBN 99912-74-08-7
  • M.J.A.Werger. 1978. Biogeography and Ecology of Southern Africa. Monographie Biologicae vol. 31., The Hague. ISBN: 9061930839
  • World Wildlife Fund. 2002. Zambezian flooded grasslands ecoregion
Glossary

Citation

Hogan, C. (2013). Ecoregions of Botswana. Retrieved from http://www.eoearth.org/view/article/151986

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