Title:

Aspects of ecological change in the Botswana Kalahari

Publication Year:
1998
Abstract:

The Botswana Kalahari has sustained a number of changes in land-use, for instance heavy grazing by cattle and smallstock in addition to accelerated land clearing, over the past thirty years. This work attempts to demonstrate the possibility that these changes have become manifest as changes in the nature and type of vegetation cover occurring across the Kalahari region. Measurement of the extent of change was undertaken using initially visually interpreted satellite imagery from 1975, 1984 and 1994. Results from 1975 showed that during this time of particularly good rains the majority of the country was covered by relatively dense natural vegetation. During the 1980s drought about 433,212 km² remained under some form of natural vegetation cover. The effects of drought were widespread and not necessarily ecosystem dependant. The 1994 analysis demonstrated that natural vegetation cover had regenerated over around 542,128 km² (or 93.5% of Botswana). However, in this post major drought period, significant areas have either failed to recover fully or for some reason have continued to show negative trends. Specific areas of vegetation change in 1994 were discerned using digital imagery along the Botswana Kalahari Transect (BKT) moisture gradient. This combined with field analysis showed a general overall increase in both woody and alive herbaceous cover along the gradient. Within the overall trend fluctuations included an extensive zone of sparse savanna and grassland in the northern Kalahari tree and bush savanna zone. In this area the tree/litter ration and total organic carbon (TOC) are relatively low compared to the northern and southern margins of the gradient. This may suggest high decomposition rates and therefore relatively positive post drought recovery rates in comparison to the extreme south-west and the mophane belt. Alternatively, the relatively high grass cover may be due to edaphic effects.

Publication Title:

Botswana Notes and Records

Volume:
30
Pages:
121-138
Item Type:
Journal Article
Language:
en