Abstract
AbstractDual‐scale analyses assessing farm‐scale patterns of ecological change and landscape‐scale patterns of change in vegetation cover and animal distribution are presented from ecological transect studies away from waterpoints, regional remotely sensed analysis of vegetation cover and animal numbers across the southern Kalahari, Botswana. Bush encroachment is prevalent in semi‐arid sites where Acacia mellifera Benth. is widespread in communal areas and private ranches, showing that land tenure changes over the last 40 years have not avoided rangeland degradation. Herbaceous cover is dominated in intensively grazed areas by the annual grass Schmidtia kalahariensis Stent and in moderately grazed areas by the perennial grass Eragrostis lehmanniana Nees. Nutritious perennial grass species including Eragrostis pallens Hack. Ex Schinz remain prevalent in Wildlife Management Areas. Other ecological changes include the invasion of the exotic Prosopis glandulosa Torr. and dense stands of Rhigozum trichotomum Kuntze. in the arid southwest. Regional patterns of wildlife species show that the expansion of cattleposts and fenced ranches has led to large areas of low wildlife conservation value even in areas where cattle production is not practiced. Findings show the need for integrated landscape‐scale planning of land use if the ecological value and biodiversity of the southern Kalahari is to be retained.
Highlights
Concerns are growing over dual threats of rangeland degradation, notably through bush encroachment with extensive dense stands of Acacia mellifera Benth. and an associated loss of nutritious perennial grass species (Moleele et al, 2002; Thomas & Twyman, 2004; Reed, Dougill & Taylor, 2007), and increasing rural poverty levels (Atlhopheng et al, 1998; Chanda et al, 2003)
The dynamic nature of vegetation cover is shown in the annual variability in Normalized Difference Vegetation Index (NDVI) anomalies over the period 2000–2013 which are greater than any impact associated with land use or rangeland management (Fig. 3 for snapshot of this variability from 2008 to 2013)
The spatial and temporal variability in rainfall means that satellite data studies alone cannot identify ecological changes affecting the pastoral productivity of rangelands (Behnke, Scoones & Kerven, 1993), a factor exacerbated by the difficulties in using NDVI to record changes in vegetation structure, such as the bush : grass ratio (Dougill & Trodd, 1999)
Summary
An associated loss of nutritious perennial grass species (Moleele et al, 2002; Thomas & Twyman, 2004; Reed, Dougill & Taylor, 2007), and increasing rural poverty levels (Atlhopheng et al, 1998; Chanda et al, 2003) This matches concerns raised globally for semi-arid rangeland systems (Reynolds et al, 2007; UNDP, 2011). Our study explicitly assesses the links between land use and degradation in the Kalahari across the southern portion of Kgalagadi District, Botswana (Fig. 1). It provides new ecological analyses along ‘piosphere’ grazing gradients away from borehole waterpoints for three main land uses: communal grazing lands, private cattle ranches and private game ranches
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