Bush encroachment has been recognised in southern Africa since the late nineteenth century. Our review of 23 studies showed that the rate of woody cover change has ranged from −0.131 to 1.275% y −1 . Encroachment was most rapid on small protected areas, intermediate under commercial tenure, and slowest under communal tenure and large, natural environments with mega-herbivores present. Several drivers of bush encroachment, which interact and change over time, have been proposed. Fires, for example, were actively suppressed during the early twentieth century. However, rainfall interacts with fire and the rate of woody increase under fire exclusion is linearly related to mean annual rainfall. A reduction in browsing herbivores from the nineteenth century would have had a positive cumulative effect on woody cover whilst an increase in grazing herbivores would have reduced the competitive effect of grasses. Encroachment was most rapid during the high rainfall, mid-1970s, which followed the 1960s drought when cattle numbers were at their peak, and the grass layer was degraded. Increasing atmospheric [CO 2 ] and climate change have emerged as important drivers in the recent literature. Bush encroachment depends on the interplay of history, environment, management and vegetation, recognition of which is essential for containing encroachment.
Linear structures include fences, roads, railways, canalised water ways and power lines, all man-made. Fencing as a way of managing livestock began in the late 1800s, and by the early twentieth century was almost fully implemented throughout the Karoo sensu lato. The advent of these fences, and now in many instances, 'game proof' (∼2 m high) and electric fences have impacted native flora and fauna in various ways. Roads influence the quality and quantity of vegetation along corridors throughout the Karoo, with impacts on wildlife through increased mortality, but also provide foraging opportunities. Road-side structures, such as transmission poles, offer nest sites and perches in otherwise treeless landscapes, benefiting certain avifauna. Railway lines create similar corridors, carrying ungrazed vegetation along them. Their associated structures - culverts and (historically) steel frame bridges - provide nest sites for birds and some mammals. Transmission cables and pylons along power lines have mixed benefits to conservation, providing bird nest and perch sites, but can also cause bird mortalities. Unquestionably, these linear structures have had marked effects on the biota of the Karoo, through their effects on wildlife and livestock movement and mortality, plant demography and the spread of native and alien species.
The success of different rehabilitation treatments following surface mining on the arid west coast of South Africa was assessed. Treatments consisting of one or a combination of topsoil addition, plant translocation and seeding were applied to experimental rehabilitation sites in 2001, while the treatment of another site in 2008 combined all three techniques. Vegetation and species cover, species richness, diversity and evenness, and grazing capacity of rehabilitation sites were sampled during winter 2009 and summer 2010, and compared with a reference site. All rehabilitated sites achieved the objective to attain a minimum grazing capacity of 20 ha per small stock unit. Rehabilitation trials were successful in establishing a vegetation cover, but were unable to return species richness and diversity to reference levels and did not resemble the reference site in species composition. Common species in reference sites were absent or only occurred in low numbers. No treatment outperformed the others and further experimentation is needed to determine the most suitable combination. It is recommended that rehabilitation should be done in multiple stages in future to improve seedling survival and to return species that are unable to establish in the adverse conditions present at the onset of rehabilitation.
Tierberg-LTER is a research site established in 1987 in the semi-arid Succulent Karoo near Prince Albert in the Western Cape province, South Africa. The original purpose for its establishment was to study ecosystem dynamics and the drivers of vegetation in the context of historical land use. The large body of work that has materialised from Tierberg-LTER is grounded on extensive baseline data and has greatly influenced the broader Karoo literature. It stands as the only long-term ecological research facility for the semi-arid region of South Africa. The Karoo environment faces several new developments centred largely on the expanding energy sector. Under a changing climate, ecosystems will have to further adapt to the impacts of such developments. The future research programme for Tierberg-LTER will accordingly continue to focus on understanding Karoo ecosystem dynamics and drivers of climate and anthropogenic change at local scales, thereby informing management and mitigation of future development impacts. Among a growing network of Karoo research sites, Tierberg-LTER maintains a unique role for long-term and intensive research that will contribute significantly towards the South African Environmental Observation Network's vision of furthering ecosystem integrity, societal prosperity and sustainable development.
This article explores some themes in the agrarian and environmental history of the Karoo since 1800. It argues that environmental change cannot be understood without incorporating social, economic and political history. This is especially so in the case of the Karoo because the landscape and ecology was transformed by intensive commercial livestock production in the nineteenth and twentieth centuries. The scale and economic significance of sheep farming and wool production up to the 1960s is generally underestimated in histories of the Cape and South Africa. The article outlines the patterns of economic growth and also the technologies required, such as fencing and water provision. The environmental impact of intensive livestock farming was recognised from the late eighteenth century and new scientific approaches helped to define understandings of environmental change. Environmental degradation was at its height in the first half of the twentieth century; simultaneously, conservationist ideas were developed and gradually implemented. In the second half of the twentieth century, these approaches, together with socio-economic factors that led to lower levels of stocking, resulted in a stabilisation and even some environmental recovery.
Conflict between predators and small-livestock farmers is a global phenomenon adversely impacting the preservation of wildlife, the well-being of livestock and human livelihoods. Such conflict is pervasive in the Karoo region of South Africa but its contemporary history and various causes remain poorly understood. In this study, we interviewed 77 small-livestock farmers in the Central Karoo between July 2014 and March 2015 to (1) assess the spatio-temporal distribution and severity of the reported predation problems with the main regional predators of livestock (black-backed jackal, caracal and baboon) and (2) describe the perceived reasons for changes in predator numbers. Farmers reported that serious predation problems have increased since the 1990s for all three predators. Jackal predation appears to have re-emerged, particularly since the 2000s, while baboon predation seems to have escalated rapidly since 2014 for select farmers. Farms with more rugged terrain were more likely to experience serious problems with baboons and caracal but ruggedness did not predict the year of onset of problems. Farmers perceive predator numbers to be increasing and attribute this trend to declining government support for predator management, changes in farming practices and the associated increase in suitable predator habitat, from which they can recolonise commercial farms.
We used several large data sets at a range of temporal and spatial scales to document the land-use/land-cover change (LULCC) dynamics of the semi-arid Succulent Karoo and Nama-Karoo biomes of South Africa. More than 95% of the Karoo is comprised of land classified as Natural, which has been relatively stable since 1990. Over the last 100 years cultivation, as well as the number of domestic livestock, has declined significantly in both biomes. Protected areas have increased since 1980 to comprise nearly 8% of the Succulent Karoo biome, although they only cover 1.6% of the Nama-Karoo biome. There has been a significant recent increase in renewable energy installation applications, which cover 4% of the Karoo drylands. The trend in vegetation productivity (NDVI; 1982-2015) is unchanged over 90% of both biomes, while nearly 10% of the Karoo has shown a significant increase in NDVI trend. An analysis of repeat photographs shows that vegetation cover has either remained unchanged or has increased at most locations. Although the Karoo drylands appear less degraded than they were in the mid-twentieth century, on-going monitoring at different temporal and spatial scales is essential to evaluate the future impact of LULCC on these semi-arid environments.
Rainfall and grazing are primary drivers of vegetation composition in the Nama-Karoo. Increased rainfall increases grassiness, to where Nama-Karoo transitions to grassland. Severe grazing treatments (e.g. continuous or summer-only) increase abundance of grazing-tolerant dwarf shrubs and annual grasses, and decrease perennial grasses. Grootfontein, which is ecotonal between the Nama-Karoo and Grassland Biomes, houses long-term grazing trials. The area has experienced higher-than-average rainfall in recent decades. Plant basal cover data from the 1960s and 2010s allow several hypotheses to be addressed: (1) historical severe grazing (until 1985) will limit subsequent grassiness (grazing legacy effect); (2) severe grazing will preclude increases in grassiness, independent of rainfall (herbivore trap effect); and (3) historically leniently-grazed sites will transition to grassland with increased rainfall (biome shift effect). Rainfall was lower from 1957-1966 (350 mm) than from 2003-2012 (490 mm). The grazing legacy effect was supported based on the abundance of Aristida diffusa, despite all sites becoming much grassier. The herbivore trap effect was not supported. The biome shift effect was supported in that shifts to grassland sometimes occurred. Results suggest that increasing rainfall has prompted a shift to much increased grassiness and decreased abundance of dwarf shrubs, and that grazing had a smaller secondary effect.
Although wildlife production is widely considered beneficial for semi-arid environments, few studies have reported on the long-term environmental effects of converting from livestock production to game ranching. Asante Sana Game Reserve in South Africa was stocked with domestic livestock for centuries. However, after 1996 game ranching was adopted in the reserve. We investigated the long-term (1987-2017) spatial and temporal change in vegetation productivity and type on the reserve using Landsat multispectral data and soil adjusted vegetation index (SAVI), and explored the relationship between changes in vegetation productivity and the potential drivers. The results show that while Thicket has decreased overall, it has expanded into parts of Grassland and Shrubland, and Bare-ground has expanded into parts of Shrubland and Thicket. Overall vegetation productivity increased over time, with the greatest increases in Thicket and Grazing lawn and the lowest in Shrubland and Bare-ground. Changes in rainfall, fire and stocking rates were all significant predictors of the observed changes in vegetation productivity, but rainfall had the strongest effect. This research highlights some of the complex responses that arise in semi-arid vegetation when domestic livestock production is replaced by game ranching, and points towards key issues that can be addressed by management.
The disc pasture meter (DPM) is a tool that is widely used to estimate aboveground standing grass biomass (ASB) in a rapid and non-destructive manner. Depending on the species composition, rangeland condition and local climate, available DPM calibrations may fail in providing precise measurements for a certain area. We calibrated a DPM for the arid dunefield savanna of the south-western Kalahari as found in the Northern Cape province of South Africa and bordering Namibia and Botswana. Assessments were done at 30 sites and restricted to inter-dune areas. The site selection accounted for different grazing conditions to ensure a better representation of the variability in ASB in the region. We determined grass species composition, basal cover and dry matter production in relation to height readings of the DPM. The grass sward was dominated by the species Stipagrostis ciliata, S. obtusa and Schmidtia kalahariensis, with a mean density of 25 cm point-to-tuft distances. Based on 90 paired observations of ASB and disc height (x; cm), the equation ӯ (kg ha −1 ) = 213.37(x) + 103.36 (r 2 = 0.760) was established. In comparison to other models, the equation avoids an overestimation of ASB in this vegetation type, and thus leads to more accurate estimations.
We tested whether holistic planned grazing (HPG) and four-camp grazing (FCG) rotational grazing approaches influence beef cattle parasites counts compared with continuous, season-long (SLG) grazing. We expected that parasite counts would increase linearly with increasing camp occupancy by cattle from 1 d (70-camp, HPG) to 21-28 d (four-camp, FCG) to 180 d (one-camp per season, SLG). Tick and faecal egg counts were observed across seasons on 30 steers raised on a private farm in Cedarville, South Africa. Tick species identified were Rhipicephalus evertsi evertsi, Rhipicephalus (Boophilus) decoloratus, Hyalomma spp. and Amblyomma hebreaum with respective prevalences of 32%, 29%, 20% and 19%. Unidentified roundworms had the highest faecal worm egg counts (81.2%) followed by Coccidia (16.4%), Nematodirus (1.2%) and strongyles (1.2%). Overall, prevalence and mean counts for ticks and faecal worm eggs were highest in the hot wet season, with the SLG having greater (P ≤ 0.05) values than either of the rotational approaches. However, increasing camp number and animal densities above four camps did not reduce (P > 0.05) parasite loads compared with HPG. Current results suggest that rotational grazing is a potential strategy to reduce livestock losses caused by high tick and worm loads in cattle, especially in the hot wet season.
Adopting a systems view and regenerative philosophy can indicate how to regenerate ecosystem function on commercial-scale agro-ecological landscapes. Adaptive multi-paddock grazing management is an example of an approach for grazinglands. Leading conservation farmers have achieved superior results in ecosystem improvement, productivity, soil carbon and fertility, water-holding capacity and profitability. Their method is to use multiple paddocks per herd with short grazing periods, long recovery periods, and adaptively changing recovery periods, residual biomass, animal numbers and other management elements as conditions change. In contrast, much research on grazing management has not followed adaptive research protocols to account for spatial effects, for sufficient time to produce resource improvement, sound animal production, and socio-economic goals under constantly varying conditions on rangelands. We briefly review what management has achieved best outcomes and show how previous reviews of grazing studies were limited in scope and applicability to larger, more complex landscapes. We argue that future research can provide better understanding of how multi-paddock grazing management can improve socio-ecological resilience in grazing ecosystems, while avoiding unintended consequences of possible management options, by involving realistic scale and context, partnering with innovative land managers on real operations, applying adaptive treatments, and combining field studies with modelling approaches.
It has been claimed that Holistic Planned Grazing™ (HPG), a type of rotational grazing, can increase productivity in rangelands and reverse climate change while doubling the stocking rate, mainly through the impact of densely bunched animals on primary production. Previous reviews have found similar or greater plant and animal production in continuous (season-long) compared with rotational grazing. Here season-long continuous grazing is compared with HPG alone to explore the evidence for animal impact. Three quantitative meta-analysis models were used to assess data sets from literature between 1972 and 2016. Weighted mean differences (effect sizes) between HPG and continuous grazing showed that there was no difference in plant basal cover, plant biomass and animal gain responses (p > 0.05). Thus, from the balance of studies, if animal impact is occurring during HPG, it has no effect on production. As interesting as the overall result is the significant between-study heterogeneity assessed using Cochran's Q (p = 0.007 to <0.0001). Studies with positive effect sizes tended to have higher precipitation (p < 0.05), suggesting that only some rangelands have the resources to support HPG. Furthermore, there is scope for investigating the impact of HPG on socio-ecological aspects of rangelands, such as management.
Plant growth forms likely respond differently to disturbances such as trampling. We investigated the trampling effect of 1 600 sheep encamped at night in temporary enclosures (kraals, corrals or pens), which were relocated weekly. To examine trampling effects and regeneration rates of the various growth forms we compared vegeta- tion composition, canopy cover and foliar nitrogen inside and outside kraals, between one and 12 months after the trampling event. We predicted that inside kraals (1) succulent and non-succulent shrubs would be affected more severely than grasses, (2) perennial plant cover would decrease compared with annual plant cover, (3) foliar nitrogen concentrations would increase, and (4) vegetation recovery would be affected by time and rainfall since last use of the kraal. Grasses and shrubs (succulent and non-succulent) responded differently to kraaling. Density and diversity of succulent and non-succulent shrubs decreased, while annual and perennial grass cover inside and outside kraaling areas did not differ. Foliar nitrogen was greater inside kraals. Both succulent and non-succulent shrub cover increased over time after kraaling irrespective of the rainfall. Our study demonstrates that short-term intensive trampling and dunging creates nutrient-rich, heterogeneous patches that may enhance restoration of degraded production landscapes.
Because vegetation change in arid ecosystems is slow, long-term data are essential to gain an understanding of how the vegetation responds to short-term, inter-annual variation in rainfall; long-term cyclic rainfall patterns; and grazing pressure. The point intercept method was conducted annually over a period of more than 20 years at five transects in the plains habitat on the Goegap Nature Reserve in the Northern Cape, South Africa. Vegetation change was assessed in terms of vegetation cover, species composition, species abundance, growth form composition, range condition and plant diversity. Non-metric multidimensional scaling was used to illustrate the trajectories in floristic data and to determine the strength of the correlations with rainfall and grazing variables. The effects of the high grazing pressure on the plains were apparent in the overall decrease in total plant cover and reductions in the cover of grazing-sensitive species over the monitored period. Diversity parameters, of especially the annual component, were strongly related to rainfall. A directional change, which supports the equilibrium concept, was evident in changes in perennial species composition over time. The annual component, however, showed no directional change, but displayed eventdriven, non-equilibrium dynamics by fluctuating in reaction to the timing and quantity of rainfall.
Impacts of livestock farming include effects on arthropods and a range of related ecological processes. Grazing by sheep may indirectly affect web spider populations by changing vegetation structures available for web construction, or directly by trampling the spiders or their webs. We tested these two potential impacts by surveying spiders along transects and found that web spider abundance was 52% lower in a sheep grazing area compared with inside the adjacent Tierberg-LTER (Long Term Ecological Research) sheep exclosure. This reduction in web-spider abundance could be due to the 10% lower shrub cover in the sheep pasture than in the exclosure. Further support for the hypothesis that web spider abundance is affected by shrub cover came from spider abundance being higher on densely vegetated mounds, termed heuweltjies, than in the surrounding shrub matrix in both the exclosure and the sheep pasture, with heuweltjies showing cross-fence differences, consistent with grazing impacts. In addition, there may be a direct effect of trampling, as suggested by experimental removal of webs. By depressing spider populations, sheep grazing may affect a number of ecological factors, such as trophic relationships or nutrient cycling.
In common with arid and semi-arid areas worldwide, South Africa's Karoo has experienced significant population shifts over the last 100 years. These have been caused by a range of considerations related to advances in farming technology and changing labour needs, transport improvements, environmental considerations and contextual economic variables. This paper pays attention to how, in the twentieth century, these factors catalysed net population loss in the Karoo's rural areas but population gain in all categories of urban settlement, particularly the larger centres. An exception to this was the phenomenon of 'shrinking towns', which became discernible in the late twentieth century. In the twenty-first century the process has become more complex, as small towns' decline has now been reversed and all towns are now attracting rural and inter-regional migrants in the post-apartheid years. We comment on the potential causes, nature and effects of these variations in the Karoo, and discuss the key role of these towns as they reflect the dynamic socio-economic and environmental shifts witnessed in the region.
Karoo landscapes today are replete with evidence of recent human impacts. The Karoo is relatively pristine in the South African imaginary, but it is not untouched. Social and historic change in the last 300 years has been dramatic. The article looks to the evidence of human lifeways and land-use patterns in Karoo landscapes from the deeper past, from before this modern era. In contrast to the 'fabric heavy' traces of the colonial period - farmsteads and SKA dishes - those reflecting earlier human inhabitation are generally 'fabric-light' and ephemeral, with the odds stacked against their survival in the archaeological record. The Karoo also has a relatively low level of archaeological survey coverage. Yet, where studies have been conducted, research testifies to a remarkable richness in archaeological and rock art heritage, a millennia-long record of non-farming stone-tool-using people. The nineteenth-century Bleek-Lloyd archive of |Xam folklore from the region contains insights into precolonial animist perspectives on living in these landscapes, perspectives which also challenge the distinction conventionally made between 'the social' and 'the ecological'.
This study used a fence-line contrast approach to investigate the long-term impact of high grazing pressure on the vegetation at a site in Namaqualand, South Africa. Forty pairs of permanently marked plots were surveyed in 1996, 2006 and 2016. The main objective was to investigate changes in the vegetation structure and species composition between the near-continuously grazed communal rangelands and the relatively lightly grazed commercial rangelands over the 20-year period. The results showed a decline in total vegetation cover in both commercial and communal rangelands in 2016 relative to the two earlier sampling periods. This can be attributed to the low rainfall in 2016 and was due largely to a reduction in annual plant cover, especially on the communal rangeland. Perennial shrub species provide a fodder bank that can be utilised by livestock in times of drought and can buffer short-term deficits in forage supply. However, the annuals that dominate the vegetation of the communal rangeland do not form such fodder banks and consequently do not have the same multi-year buffering capacity as perennial shrubs. This provides the mechanism whereby long-term continuous grazing decreases resilience to rainfall fluctuations and increases livestock variability, thereby promoting non-equilibrium-type dynamics in the system.
The Succulent Karoo is characterised by a dense coverage of biological soil crusts (biocrusts) belonging to different types and successional stages. Whereas the Soebatsfontein region hosts cyanobacteria-dominated and minor amounts of lichen- and bryophyte-dominated biocrusts, the Knersvlakte comprises a rich cover of hypolithic crusts growing on the sides and undersides of quartz pebbles. Apart from dominating photosynthesizers used to classify biocrusts, each crust type hosts a rich and specific fungal and bacterial community and also diverse protists. In a remote-sensing mapping approach, soil-inhabiting biocrusts of the Soebatsfontein region covered ∼27% of the surface area, whereas in the Knersvlakte soil-inhabiting biocrusts covered ∼16% and hypolithic biocrusts ∼42% of the region. Combining these data with biomass contents, results suggested that the Knersvlakte, despite somewhat harsher environmental conditions, harboured about 65% more biocrust biomass per surface area. In physiological measurements we observed that biocrusts emit the reactive nitrogen compounds nitric oxide and nitrous acid, showing water pulse-dependent emission patterns. In addition, CO 2 gas fixation showed characteristic type-specific patterns depending on climatic conditions. Long-term microclimate measurements along a gradient revealed that forecasted climate and land-use change may be detrimental for biocrusts with potentially adverse effects on soil stability and overall fertility of the Succulent Karoo.