ECOLOGICAL DESCRIPTION OF THE KGALAGADI TRANSFRONTIER PARK
The modern Kalahari Desert, a small remnant of original dune desert, lies the Kalahari sand beds – a massive expanse of sand that covers 1 630 000 Km /2 from just north of the equator to the banks of the Orange River in South Africa. The sand originated from rocks, lying in a shallow basin, that were eroded by wind over millions of years.
The red colour of the dunes is caused by iron oxide, which covers each sand grain. The rainfall of the area is too low to reduce this iron oxide, and a wonderful variety of colours can be found in the desert sand.
The dunes of the Kalahari hide the ancient sedimentary rocks, which are believed to be rich in fossil deposits. The dunes are fixed and are no longer moved by the wind. They do, however, owe their characteristic shape to wind, which exposes the moist sand beneath. The moist sand is then eroded further. The sand that is removed is deposited on the southwest side of the dune, which results in a gentler gradient. These longitudinal dunes are called seif dunes, an Arab word meaning “sword”.
Sand overlies most of the geology of the Kalahari. Immediately beneath sand lies a vast sheet of calcareous or silicified sand, or sandstone, which contains grits and minor conglomerates thus making up the Kalahari system. This covers the blue shale’s of the Dwyka series that has occasional dolerite intrusions.
Field observations made during reconnaissance soil survey of the (former) Kalahari Gemsbok National Park showed that a variety of soils occur within the broad group of the so –called Kalahari – sands.
The soils have characteristically poorly developed profiles.
The red soils are notably infertile with low levels of phosphate, magnesium, potassium, sodium and carbon, and when less than two metres deep an incapacity to hold water.
The yellow soils of the pans and riverbeds have higher clay components, and are less permeable to water. The variability in fertility and water holding capacity between the 2 major soil types has a direct effect on the vegetation and hence animal utilisation.
The Kalahari forms part of the South West Arid biome. Two such areas occur in Africa, namely the Somali Arid and Sudan Arid.
This area is part of the Kalahari Thornveld, which is also divided into the Kalahari Thornveld Proper and the Vryburg Shrub Bushveld.
About 20% of the Kalahari – district in South Africa are conserved at present. It includes mostly the Thorny Kalahari-dune bushveld and the Shrub Kalahari bushveld.
Unfortunately, less than 1% of the other five Kalahari vegetation types are conserved at present.
In general, the Kalahari shows little habitat variation.
Although the whole area is covered with Kalahari-sand, there is a rainfall gradient that increase from the southwest to the northeast and this shows in the plant communities and species composition.
As mentioned, is rain the main factor, which influences the Kalahari System.
There are seven main habitats in this area:
Open thick tree-savannah of the lower dunes and plains
Dune valleys (-streets), pan skirts and river terraces
Calcrete banks near pans and rivers
With in these habitats the plant communities is as such:
Communities of the sand:
The vegetation of the sandy soils is an open shrub to tree savannah;
Communities, which are mostly found on the crest of dunes,
Communities found in the northern and eastern part of the Kgalagadi Transfrontier Park on the undulating to flat, red to pinky, sandy surface.
Tree savannah communities, in the northern corner of the Kalahari Gemsbok National Park (South Africa), are found on pink, compact sand.
Communities found on red sand of dune valleys or “streets” and lower slopes of dunes in the southern Kalahari.
Communities’ occurring on the pink to white sand, which is a mixture of in fertile red and calcareous white sand.
Communities found on more or less compact white to slightly pink sand probably deposited both by Aelian and fluviatile action.
Communities found on red or reddish sand on undulating flats or low dunes.
Communities common on red or reddish sand on undulating flats or low dunes. Physiognomically it represents a more shrub – dominated vegetation that is sometimes the result of overgrazing.
No clear line of separation between the more or less undisturbed shrub vegetation and that of disturbed areas could be found, in spite of extremes being quite different.
Communities of red to pink sands undulating flats or low dunes.
Communities found on pink to whitish sand especially in dunes slacks.
Communities found on red or pink sand on severely overgrazed, shifting dunes.
Communities found on red to pink sand.
Communities of the calcrete:
Communities found on the calcrete banks of the rivers.
Communities on the calcrete outcrops and white sands.
Communities of the riverbeds:
Communities found on exposed clayey or silty alluvial soils, rich in calcium and phosphate in the dry beds of the Auob or the Nossob.
Communities occurring in small patches near pans, on shallow sand over calcrete outcrops or gravel, but also occur on white compact sand away from the pans.
Most of the Flora species are also “escape-type” species, which wait out the harsh, waterless periods in the form of seeds, bulbs and dormant buds, which lie on the soil surface.
Invertebrates, reptiles, amphibians, mammals and birds found in the Kalahari Gemsbok National Park, had been surveyed, studied and classified by a number of people and researchers since 1958.
In the Kalahari Gemsbok National Park, fifty, five species of reptiles have been recorded.
Migrations do occur between the two countries, South Africa and Botswana, but in regards to the birds, migrations between South Africa and foreign countries is much more prominent. A total of 264 bird species have been recorded for the hole of the Kgalagadi Transfrontier Park, where 152 are vagrants, 16 migrants, 78 are residents and 18 nomadic. None of the bird species is endangered, but species such as the Cape vulture Gyps coprotheres , Lappet faced vulture Torgos tracheliotus, Martial Eagle Polemaetus bellicosus, Bateleur Terathopius ecaudatus, Kori bustard Ardeotis kori,
In addition, Ludwig’s bustard Neotis ludwigii, are considered vulnerable.
There are 60 mammal species that have been recorded and the Kgalagadi Transfrontier Park, the Rodentia and carnivoria are the two largest families with 27% and 33% respectively, with the Pangolin Manis emminckii, Honey badger Mellivora capensis, African wildcat Felis lybica, and Antbear Orytheropus afer considered to be vulnerable.
Most of the species found in this area are uniquely adapted to an extreme environment and climatic factors.
Most of the animals are concentrated in the riverbeds; species like the springbok, Blue wildebeest and a majority of the Gemsbok, although they also have a slight preference for the dune veld.
This is mainly because there are many water points in the riverbeds. However, species like Eland, Koedoe, Red hartebeest, Steenbok and common duiker are very scarcely seen in the riverbeds, they have a high preference for the dune veld.
The Nossob and Aoub Rivers are ephemeral rivers meaning that they only flow for a short period during very good rainy season. A portion of the Aoub River is said to flow approximately once every 11 years, the Nossob perhaps twice every 100 years.
The Nossob River last flooded in 1963 and the Aoub in 1973, 1974 and 2000. They do, however, carry rainwater in the wet season and there is moisture beneath their beds, a precious resource that is tapped to sustain life in the area.
The Nossob meanders a lot. In the north, the riverbed is wide with slightly raised alluvial plains and widely flanking dunes. Further downstream between the Nossob and Twee Rivieren rest camps, the number of trees seems to dwindle and the course suddenly cuts through calcrete deposits turning southwestward. The banks are relatively steep, narrow and rocky. The Aoub also has two discernible segments that differ in appearance and atmosphere. It is characterised by the beautiful stands of large grey camel thorn trees.
With the predominantly sandy southern Kalahari, the availability of natural supplies of drinking water is strictly seasonal, being restricted to the harder bottomed pans and fossil riverbeds, for short periods during the summer rainfall period (Knight 1995a). For the remainder of the year the region is generally devoid of drinking water, thus the indigenous wild life has to either, migrate to permanent sources of drinking water or use alternative sources such as underground storage organs or melons (tsammas).
Thus, typically migratory ungulates spend the wet season in the more arid parts of their range, which have little or no permanent surface water. During the dry periods, they move to regions with a higher rainfall and permanent surface water. This pattern has been recorded for a variety of ungulates species in different regions, including the Serengeti.
Most of the animals are not very water-dependant and can get their moisture supplements from the vegetation, thus quite adapted to the arid environment. Examples are Eland, Red hartebeest, Gemsbok and Springbok. However, Kudu and especially Blue wildebeest is water dependent.
With the clumped distribution of water by quality, with the Auob river’s water being more fresh and the water of the Nossob river being much more mineralised; animals have a higher preference to the fresh water for drinking and are attracted to the mineral deposits in the soil at water holes with saline water than the water itself.
Because this area is untouched it forms a self-sustaining ecosystem, but within this bigger picture there is a number of smaller / micro-ecosystems.
A few of these micro-ecosystems would be:
Pools of water
Burrows made by animals like ant bears and thus Sand.
Camel thorn and Sociable weavers’ nests.
1. Pools of water.
Water is a limiting factor in the Kalahari, thus pools will attract a lot of attention, mostly forming in sections of the riverbed or in pans after a rain shower.
A lot of water beetles, butterflies, bees and other insects congregate in and around these pools. Frogs will also emerge from their underground hiding and on their part will feed on these insects, as will terrapins.
With this small abundance, bird like herons will join in to utilize the water and the food supply. Other birds like vultures, lappet faced and white backed, batteleur's and tawny eagles can also be seen around these pools, the latter two maybe also feasting on the insects, but mainly enjoying the water-drinking and bathing. Smaller animals can also be found; rodents-mice, squirrels, nocturnal animals and lizards.
Over a 1000 pans occurs, scattered in the duneveld and is the focus point for many animals. Mostly the soil at these pans are white, contains calk, sandy to clay soils.
3. Burrows made by ant bears-Sand
Sand plays a very important role in the ecology of this area.
If you stop on a dune and take the time to observe it comes alive with insects, tracks, and millions of small things.
The quarts-grains of the sandy soil are easily moveable, thus it is very easy to dig a hole in it, but a hole like that can collapse just as easily.
Many adaptations on which especially the smaller animals depend for protection against the climate and predation, is characteristic of the Kalahari. The most of them survive the harsh temperatures through hiding in damp, cooler holes, which they dug themselves or by occupying holes left by other animals.
A hole like this provides shelter for numerous animals as mentioned, the minute one leave and another will move in.
In holes of example an ant bear, many different insects can make a part of it their home.
If the ant bear leaves either brown or spotted hyena can move in, and in the roof of the opening birds like the ant, eating chat will make their nests.
4. Camel thorns and Sociable weavers’ nests
The Camel thorn provides the nesting for sociable weavers and other birds, but also for lizards and tree rats.
It is not just the sociable weavers that stay in those nests, different kinds of insects can occupy vacant space and the pigmy falcon lives in commune with the weavers.
Just the bottom part of the nest which consist out of numerous chambers, is used for nesting the top part forms a hood with one large vacant chamber inside used for heat regulation. Throughout the seasons the fluctuation of the temperatures is these nests isn’t more that a few degrees.
Larger birds will also make use of these nests for nesting, just not inside but on top.
Birds of prey, secretary birds, eagles, and owls will nest on top of these nests because it provides a favourable constant temperature for their eggs to incubate and hatch.
Small spotted genets, African wildcats and even snakes like the Cape cobra on their part, prey on these birds.
Leopards will also use the Camel thorn as shelter during the day and so storing place during the nighttime if it made a kill.
5. Shepherds trees
A tree species that thrive in the dune system, important for its food supply to the organisms (leave full of protein, flowers rich in nectar and its fruit savoured by bird and other animals) and shade it provides in the hot summer against extreme sand temperatures.
Anything from lion to springhare to mice and insects congregates under these trees protecting from rays of the sun.
Its often-hollow trunk, acts as a storage tank, collecting rainwater and retaining it during the long dry periods, in the waiting for the next rains.
Beehives are also often found inside these trunks, of which the honey was used for all purposes by the Busman, and still utilised by animals that are able to gain access.
Head: Field Guiding
Kgalagadi Transfrontier Parkjan.email@example.com