INTRODUCTION

History of the Kalahari

The greater Kalahari is a basin of sand that covers an enormous 2 500 000 square kilometres. The area contains geological as well as earth history. Here the evolution of flora and fauna, including that of humans, can also be traced. 

The name, Kalahari, is derived from the Setswana word, Kgala, meaning the great thirst. 

This basin is the largest uninterrupted stretch of sand in the world with a depth of up to 200 metres, which is the result of erosion of the geological layers called the Kalahari - and Karoo Super group. It extends south to north all the way from the Orange River in South Africa to the tropical forests of the Democratic Republic of Congo [1]. The popular perception of most travellers is that the Kalahari as only a desert. It is however only partly true for the southern part, where the Kgalagadi Transfrontier Park and Central Kalahari Game Reserve are situated. The further north you go, the higher the rainfall. Nowadays, the deep sands are covered with more lush vegetation. The central part, which includes the Kafue National Park in Zambia and the Okavango Delta and the Chobe National Park, both located in Botswana, is rich in surface water due to the presence of the Okavango and Chobe Rivers. Both rivers originate on the highlands of Angola where more than 1 000 millimetres of rain fall annually. Downstream both waterways encounter the Gumare fault in Botswana.

The Okavango meanders in the Panhandle area between two parallel fault lines only, which lead the river from north to south. This upper course of the Okavango River delivers permanent water to the 80 kilometres long Panhandle. Then, it encounters the Gumare fault line and spreads out into a permanent swamp. Here it forms the UNESCO World Heritage site, the Okavango Delta, the biggest inland delta on Earth [2].

The water levels of the delta fluctuate continuously. Between the arrivals of the annual flood waters, we find temporary dry areas on the edge of the delta. These are called floodplains. Some large islands in the southern parts of the delta, like Chiefs Island and Chitabe Island, are parts of the so called Sandveld-Tongues which stretch up from the arid south. The combination of all this creates a paradise for a wide spectrum of flora and fauna, big and small.

The Kwando River becomes the Linyanti after entering Botswana. Like the Okavango, it is also spread out into a swamp by the fault line, only on a much smaller scale. The main outlet from the Linyanti is called the Chobe River. It flows along the Gumare fault in an easterly direction and forms the northern border between Botswana and Namibia. After flowing through the Chobe National Park, it joins the great Zambezi River near the Zambian and Zimbabwean borders with Botswana. The modern day course of the great Zambezi River, as will become clear in the next part of the introduction, was directly influenced by geological activity in the Kalahari and in the East African Rift Valley, 1 000 kilometres to the east.

A brief geological history of the Kalahari Basin

Africa was born as a continent approximately 100 million years ago (mya). Before Gondwanaland started to break up during the Triassic period about 200 mya, Africa was still connected to Madagascar and four other future southern continents: India, Antarctica, Australia and South America [3]. Once Antarctica and the rest finally drifted away, each on its own tectonic plate, Africa finally stood alone. At that time reptiles were the dominant animals on Earth, having evolved after the insects, fish and amphibians. Mammals were tiny and nocturnal, hiding from the predatory dinosaurs that ruled the world. Soon after standing free and alone, the continent was uplifted due to activity deep inside the earth. Three great basins were f