Nama Karoo Research Articles

Identifying the Substrate and Vegetation Characteristics Driving Population Densities in the Buckspoor Spider, Seothyra schreineri

ABSTRACTBuckspoor spiders (Araneae: Eresidae: Seothyra Purcell) are a distinct lineage of burrow‐inhabiting web‐building spiders endemic to the arid and semi‐arid parts of southern Africa. We investigated the role of substrate and vegetation characteristics on site selection in Seothyra schreineri Purcell in the xeric Nama Karoo of the western Free State Province, South Africa. We studied web densities in two 0.5 ha plots in an open habitat grazed by sheep and found declining web densities with increasing distance from the border fence. Web densities in the 1 m2 plots were negatively correlated with increasing grass density, positively correlated with increasing percentage fine gravel, whereas shrub cover, litter, hard soil and stones had a very weak effect. Our results indicate that the spatial distribution of fine gravel in Nama Karoo landscapes is a key factor determining the occurrence of S. schreineri, a finding that can guide future sampling efforts, leading to a more complete prediction of the species' distribution and, ultimately, its overall conservation status.

Spectral Discrimination of Common Karoo Shrub and Grass Species Using Spectroscopic Data

Rangelands represent about 25% of the Earth’s land surface but are under severe pressure. Rangeland degradation is a gradually increasing global environmental problem, resulting in temporary or permanent loss of ecosystem functions. Ecological rangeland studies aim to determine the productivity of rangelands as well as the severity of their degradation. Rigorous in situ assessments comprising visual identification of plant species are required as such assessments are perceived to be the most accurate way of monitoring rangeland degradation. However, in situ assessments are expensive and time-consuming exercises, especially when carried out over large areas. In situ assessments are also limited to areas that are accessible. This study aimed to evaluate the effectiveness of multispectral (MS) and hyperspectral (HS) remotely sensed, unmanned aerial vehicle (UAV)-based data and machine learning (random forest) methods to differentiate between 15 dominant Nama Karoo plant species to aid ecological impact surveys. The results showed that MS imagery is unsuitable, as classification accuracies were generally low (37.5%). In contrast, much higher classification accuracies (>70%) were achieved when the HS imagery was used. The narrow bands between 398 and 430 nanometres (nm) were found to be vital for discriminating between shrub and grass species. Using in situ Analytical Spectral Device (ASD) spectroscopic data, additional important wavebands between 350 and 400 nm were identified, which are not covered by either the MS or HS remotely sensed data. Using feature selection methods, 12 key wavelengths were identified for discriminating among the plant species with accuracies exceeding 90%. Reducing the dimensionality of the ASD data set to the 12 key bands increased classification accuracies from 84.8% (all bands) to 91.7% (12 bands). The methodology developed in this study can potentially be used to carry out UAV-based ecological assessments over large and inaccessible areas typical of Karoo rangelands.

Phylogeny and historical biogeography of the southern African lacewing genus Afroptera (Neuroptera: Nemopteridae: Nemopterinae)

Abstract The lacewing genus Afroptera Abdalla & Mansell (Neuroptera: Nemopteridae: Nemopterinae) is endemic to southern Africa, predominantly found in the Fynbos and Succulent Karoo biomes. The taxonomy of the genus has been recently resolved. However, the monophyly and evolutionary history of the genus has never been addressed. This study employs an integrative phylogenetic approach, by incorporating three ribosomal genes (16S, 28S and 18S) and two protein‐coding genes (cytochrome oxidase subunit I and carbamoyl‐phosphate synthetase‐aspartate transcarbamoylase‐dihydroorotase), and morphological data to examine the monophyly and historical biogeography of Afroptera. We use Bayesian, parsimony and maximum likelihood phylogenetic methods to assess the monophyly and relatedness of Afroptera within the Nemopterinae. We also use ancestral range reconstruction and diversification analysis to infer the historical biogeography of the genus. Our analyses reveal the genus as a monophyletic lineage. The genus Afroptera originated during the Pliocene (5.24–3.13 Mya) in a desert environment, experiencing rapid speciation during the Pleistocene, primarily within the Fynbos and Succulent biomes; and secondarily dispersed into the Nama Karoo and Savannah (Kalahari) biomes. The current distribution patterns of Afroptera species likely stem from intensified aridification in the southwest during the Plio‐Pleistocene, consistent with the dry‐adapted nature of Afroptera's ancestors. Therefore, our findings suggest a climatically driven diversification model for the genus Afroptera.

A conservation assessment of birds in the Karoo region of South Africa: densities, populations, ranges, and trend estimates

The Karoo region of South Africa, which includes the Succulent and Nama Karoo biomes, supports a unique avian fauna, with ten bird species occurring exclusively in this arid-zone region and many others exhibiting a strong preference for this habitat. To better determine the conservation status of these birds, we conducted point counts to estimate population densities of bird species occurring in the South African Karoo region in 2017 and 2018. We also used data of the South African Bird Atlas Projects (SABAP2) to estimate the species’ ranges and to determine population trends. Although the population densities are naturally low for most species, their ranges are very large, and reporting-rate trends appear stable for most species. Our analysis reveals that none of the Karoo bird species are currently of serious conservation concern. However, the Red Lark Calendulauda burra and Sclater’s Lark Spizocorys sclateri should be considered regionally Near Threatened as they are habitat specialists with inferred declining populations and are not currently protected within any designated conservation areas. Given the rapid transformation of landscapes linked to mining and alternative energy developments currently underway in the Karoo, combined with the poor representation of bird species in protected areas, it is imperative that special attention be paid to the conservation of bird species endemic to the Karoo, and that appropriate mitigation measures be taken by developers.

Rhythms of time and place

This research investigates the density and distribution of quartz deposited over an area measuring 70,000 m 2 at Kurukop in the Nama Karoo, South Africa. Relationships between quartz artefacts, engraved depictions, water features and rock abrasions in archaeological sites has been hypothesised. However, despite other comparable engraved sites in the region, Kurukop comprises an unusual number of quartz artefacts and intra-site associations. To investigate possible relationships between features I used a combination of techniques. These include, first, mapping the engravings, water features and rock rubbings during a ground survey and by means of drone imaging. Second, obtaining quartz samples from two squares (SA1, SA2), counting and weighing them. Last, intercalating these data with measurements provided by the aerial map and ground survey. A number of trends can be observed indicating that the remains of previous activities probably influenced subsequent decisions, thereby determining spatial organisation of the site and markings. Moreover, I applied a rhythm analysis to the ethnoarchaeological dimensions of the study to consider the production of space in terms of permanence, returns and abandonment (temporality). The conclusion I draw is that the presence and absence of water appears to have influenced the way in which hunter-gatherers, and later herders, chose to interact with and mark the site.

Influence of Environmental Factors on Species Richness and Diversity in a Semi-Arid Environment, South Africa

The Nama Karoo biome is one of the least well-studied biomes in the semi-arid region of South Africa, and essential baseline biodiversity data for this region are lacking. The aim of the present study was to examine the influence of environmental factors on the species diversity and richness of Mountain Zebra National Park, South Africa, which includes this vital biome. Vegetation data were obtained using the step-point method. Both species richness and diversity were unaffected by slope, aspect, coarse fragments, and soil texture. Multiple linear regression analyses indicated that a combination of four variables (nitrogen, clay, and sand contents, and longitude) should be included in the optimal model for species richness, and the optimal model for species diversity also revealed four influencing variables: soil organic carbon, clay and sand contents, and longitude. Overall, both species richness and diversity could be predicted by a combination of climatic, topographic, and soil properties. The findings of this study can be used as a reference for the effects of environmental factors on plant species richness and diversity in semi-arid environments.

The effects of habitat loss and fragmentation on the relative abundance and conservation of Ludwig’s Bustard Neotis ludwigii in South Africa

Ludwig’s Bustard Neotis ludwigii is near-endemic to the semi-arid shrublands of southwestern southern Africa and is listed as Endangered. The primary threat to this species is collisions with overhead powerlines; however, loss and fragmentation of its habitat may contribute to its population decline. The 1990 and 2020 land-use land-cover (LULC) maps prepared for South Africa were used to determine the LULC categories that best describe suitable habitat for Ludwig’s Bustard using beta regressions and data on exact localities, as recorded in the real-time BirdLasser logging app. Optimized Hot Spot Analysis was used to determine the priority areas for conserving Ludwig’s Bustard and its habitat. Beta regression models were compiled using the reporting rate for this bird and the total surface area of suitable habitat, and three other landscape metrics, calculated using the per pentad LULC categories considered suitable habitat for the bird. These analyses revealed that, between the first and second Southern African Bird Atlas Projects, the distribution range of Ludwig’s Bustard increased by 153 quarter-degree grid cells, whereas the reporting rate for the species declined by 5.6%, along with a small net decline in its quarterdegree-grid-cell-based area of occupancy, its pentad-based area of occupancy and habitat. The habitat of Ludwig’s Bustard is dominated by shrubland with limited grassland, in primarily the Nama Karoo and Succulent Karoo biomes, and the Grassy Karoo Biome in the eastern part of its distribution. In the relative abundance hot spot of Ludwig’s Bustard, there does not currently appear to be any significant loss or fragmentation (distance between patches) of its habitat. A landscape-based approach to conserving Ludwig’s Bustard can be achieved by expanding the current network of protected areas and conserving critical biodiversity areas and ecosystem support areas, especially in the bird’s relative abundance hot spots in the Nama Karoo and Succulent Karoo biomes.

Alternative Strategies for Controlling the Brown Locust, Locustana pardalina (Walker)

Regular and often intense outbreaks of the brown locust, Locustana pardalina (Walker), in the semi-arid Nama Karoo region of South Africa present a formidable pest control problem. Outbreak patterns over a 64-year period (1941–2005) were reviewed indicating a very high frequency of outbreak years with regular ‘plague’ periods being experienced, while a more detailed analysis of the numbers of locust targets controlled during a 22-year period (1983–2005) described the intensity and scale of the outbreaks. The operational constraints associated with the traditional ground-based control strategy employed against the thousands of individual roosting brown locust hopper band and swarm targets in the Karoo are discussed. A brief review of laboratory and field trials of alternative methods of controlling the brown locust, such as insecticide baits, barrier treatments and the Green Muscle® myco-insecticide, as an alternative to broad-spectrum pyrethroid insecticides are described. In addition, alternative control strategies to the current ‘Commando’ system of ground-based control operations are discussed. The recommendation is for a modernised and technology-equipped integrated brown locust management strategy (IPM), combining ground and aerial tactics that will have the flexibility and the capacity to deal effectively with outbreaks. The integrated management strategy should focus on ground-based control of hopper bands and fledgling swarms in the Upper and eastern Karoo, while outbreaks over most of the Central Karoo and arid Bushmanland areas should be left to fledge and coalesce into large-sized swarms that could then be targeted by spray aircraft as they migrate along their known swarm flight paths. The introduction of electronic reporting and GIS mapping technologies for brown locust campaign management is essential.

Drivers of change in vegetation and soil in the Gamka Karoo: grazing versus rainfall

The Gamka Karoo is a low-lying vegetation type in the semi-arid Nama Karoo in the south-western part of South Africa with extensive rangelands used for livestock ranching and wildlife. Although the Nama Karoo is generally resilient to grazing and most responsive to variable rainfall, chronic overstocking, particularly in the driest regions and around water points, could degrade vegetation and soils. The interactive effects of rainfall (MAP) and grazing (stocking rate, percentage overstocking, resting system) on plant species composition and soil chemical characteristics were examined on 36 farms across a regional rainfall gradient (120–300 mm y−1) and around water points (n = 3) on farms. Multivariate direct gradient analyses revealed regional species compositional differences were related most strongly to MAP (r = 0.736), but not to grazing, with no MAP × grazing interaction. On a smaller scale, grazing intensity (1/distance from water point) had a weak negative impact on the vegetation (r = 0.36) and soil chemistry (r = 0.49) with nutrient enrichment around water points in paddocks. Our findings suggest that the Karoo is responsive to rainfall, but loosely coupled to grazing. Adaptive management with livestock numbers matched to rainfall and forage supply is recommended to sustain animal production, vegetation and soils.

Mapping soil organic carbon stocks and trends with satellite-driven high resolution maps over South Africa

Estimation and monitoring of soil organic carbon (SOC) stocks is important for maintaining soil productivity and meeting climate change mitigation targets. Current global SOC maps do not provide enough detail for landscape-scale decision making, and do not allow for tracking carbon sequestration or loss over time. Using an optical satellite-driven machine learning workflow, we mapped SOC stocks (topsoil; 0 to 30 cm) under natural vegetation (86% of land area) over South Africa at 30 m spatial resolution between 1984 and 2019. We estimate a total topsoil SOC stock of 5.6 Pg C with a median SOC density of 6 kg C m−2 (IQR: interquartile range 2.9 kg C m−2). Over 35 years, predicted SOC underwent a net increase of 0.3% (relative to long-term mean) with the greatest net increases (1.7%) and decreases (−0.6%) occurring in the Grassland and Nama Karoo biomes, respectively. At the landscape scale, SOC changes of up to 25% were evident in some locations, as evidenced from fence-line contrasts, and were likely due to local management effects (e.g. woody encroachment associated with increased SOC and overgrazing associated with decreased SOC). Our SOC mapping approach exhibited lower uncertainty (R2 = 0.64; RMSE = 2.5 kg C m−2) and less bias compared to previous low-resolution (250–1000 m) national SOC mapping efforts (average R2 = 0.24; RMSE = 3.7 kg C m−2). Our trend map remains an estimate, pending repeated measures of soil samples in the same location (time-series); a global priority for tracking SOC changes. While high resolution SOC maps can inform land management decisions aimed at climate mitigation (natural climate solutions), potential increases in SOC are likely limited by local climate and soils. It is also important that climate mitigation efforts such as planting trees balance trade-offs between carbon, biodiversity and overall ecosystem function.

Geospatial analysis of meteorological drought impact on Southern Africa biomes

ABSTRACT Within Southern African biomes, droughts are recurrent with devastating impacts on ecological, economic, and human wellbeing. In this context, understanding the drought impact on vegetation is of extreme importance. However, information on drought impact on natural vegetation at the biome level is scanty and remains poorly understood. Most studies of drought impact on vegetation have largely focussed on crops. The few existing studies on natural vegetation are based on experiments and field measurements at individual tree level which are not representative of biomes. In this study, we mapped the spatial extent and severity of drought using the Standardized Precipitation Evapotranspiration Index (SPEI) and then quantified the drought impact on Southern African biomes using the Vegetation Condition Index (VCI) for the period 1998 to 2017. To compare drought impact across the biomes, we computed the percentage area of the biome with seasonal VCI <30. The drought trend for each biome was computed for each pixel using a linear regression model in R software using the seasonal VCI images from 1998 to 2017. Our result showed that extreme drought impact on vegetation was mainly confined to the southwestern biomes (i.e. the Nama karoo and desert biomes) with most drought occurring during the first half of the season. We also observed an increasing trend of VCI (1998 to 2017) across all biomes and this increasing VCI trend might be explained by woody encroachment which is prevalent in the Savannah and Grassland biomes. The results of this study provide baseline information on drought hotspots.

Leopards and mesopredators as indicators of mammalian species richness across diverse landscapes of South Africa

Leopards and mesopredators as indicators of mammalian species richness across diverse landscapes of South Africa

Late Quaternary palaeoenvironments in the central semi-arid region of South Africa from pollen in cave, pan, spring, stream and dung deposits

Late Quaternary palaeoenvironments in the central semi-arid region of South Africa from pollen in cave, pan, spring, stream and dung deposits

Overview of the horseflies (Diptera: Tabanidae) of South Africa: assessment of major collections for spatiotemporal analysis

Abstract Tabanidae, commonly known as horseflies, is a large, cosmopolitan family with approximately 4400 described species, of which about 400 occur in southern Africa. Both sexes feed on nectar or pollen and some species are important pollinators. Females usually require a bloodmeal to produce eggs, implicating them as vectors of disease‐causing agents. Despite their importance, they have been largely neglected by science, especially in the Afrotropics. In this study, we aimed to elucidate some fundamental spatiotemporal aspects of horsefly biology in South Africa by centralising digitised data from the major natural history museums in the region. Approximately 6 000 records have been digitised and collated into a Specify database from an approximate 17 000 specimens housed in 10 museums in the region. The collections from the 10 institutions, including six collections in neighbouring countries are briefly discussed. Spatiotemporal analysis according to biomes (Albany thicket, desert, forests, fynbos, grassland, Indian Ocean belt, Kalahari savannah sub‐biome, Central Bushveld sub‐biome, Lowveld savannah sub‐biome, Nama Karoo and Succulent karoo) revealed baseline information regarding their biology within the biomes. The majority of the records are from north eastern KwaZulu‐Natal, followed by Kruger National Park and areas surrounding Cape Town, indicative of uneven sampling. The database is represented by a total of 195 species of which 83 species were recorded in only one biome, with grassland home to 28% of the biome endemic species. A species list to the region, supplemented by records from previous authors, totals to 203 species occurring in the region. Future studies should aim to digitise the remaining specimens in order to create species pages with brief descriptions, high‐resolution photographs, distribution maps and spatiotemporal patterns available online.

Vegetation of the Square Kilometre Array (SKA), South Africa: A baseline to measure local and global change

Phytosociological studies provide plot-based vegetation data which can be used for numerous purposes. Recently, the potential of historical phytosociological plot data has been emphasised as a means to study vegetation change over time. Vegetation change occurs naturally but also as a result of land use and climate change. In order to quantify change, the current vegetation has to be compared with the vegetation that occurred historically at a site. The objectives of this study were to describe the vegetation on two properties (Losberg and Meysdam) purchased by the National Research Foundation on which the Square Kilometre Array (SKA) will be developed, and publish, in the scientific arena, the vegetation and landscape unit descriptions of these properties to promote awareness that baseline data exists before significant land use change occurred on the properties.One hundred and eighty Braun Blanquet surveys were conducted in units stratified using satellite images, topography, land type, geology and drainage information. The plot data were analysed using standard Braun Blanquet methodology. Ten plant communities and 2 sub-communities were identified. These plant communi-ties and sub-communities were used, together with landforms and associated environmental parameters, to produce five landscape units for decision making and management purposes.The data shows the past effect of disturbance. Historical overgrazing is speculated to have resulted in large patches denude of vegetation and the densification of the naturally occurring spinescent shrubs Rhigozum trichotomum and Lycium cinereum over large areas as in other parts of the Karoo. Significant soil erosion is evident. Soil conservation infrastructure erected in the past to combat further erosion, together with the highly disturbed vegetation and soils, has enabled the alien invasive tree species Prosopis glandulosa to proliferate in exceptionally large numbers, particularly on the flats and drainage areas. This highlights the importance of limiting disturbance to the natural vegetation and soils during the construction of SKA infrastructure. The study provides baseline vegetation data to inform the management of the proposed SKA protected area and for researchers working at this site. These data will also prove useful for ongoing monitoring efforts to detect the impact of local and global change on the vegetation of the Nama Karoo.

Biome stability predicts population structure of a southern African aridland bird species.

Environments are heterogeneous in space and time, and the permeability of landscape and climatic barriers to gene flow may change over time. When barriers are present, they may start populations down the path toward speciation, but if they become permeable before the process of speciation is complete, populations may once more merge. In Southern Africa, aridland biomes play a central role in structuring the organization of biodiversity. These biomes were subject to substantial restructuring during Plio‐Pleistocene climatic fluctuations, and the imprint of this changing environment should leave genetic signatures on the species living there. Here, we investigate the role of adjacent aridland biome boundaries in structuring the genetic diversity within a widespread generalist bird, the Cape Robin‐chat (Cossypha caffra). We find evidence supporting a central role for aridland biomes in structuring populations across Southern Africa. Our findings support a scenario wherein populations were isolated in different biome refugia, due to separation by the exceptionally arid Nama Karoo biome. This biome barrier may have arisen through a combination of habitat instability and environmental unsuitability, and was highly unstable throughout the Plio‐Pleistocene. However, we also recovered a pattern of extensive contemporary gene flow and admixture across the Nama Karoo, potentially driven by the establishment of homesteads over the past 200 years. Thus, the barrier has become permeable, and populations are currently merging. This represents an instance where initial formation of a barrier to gene flow enabled population differentiation, with subsequent gene flow and the merging of populations after the barrier became permeable.

The Keimoes 3 desert kite site, South Africa: an aerial lidar and micro-topographic exploration

Abstract

A Case for Springbok Hunting with Kite-Like Structures in the Northwest Nama Karoo Bioregion of South Africa

In the Levant and some arid zones of Central Asia, desert kites are well-known hunting structures often thought to have been used for the large-scale harvesting of gazelles during the Holocene. Until recently, such structures were unknown from the southern hemisphere. However, three kite sites have now been identified in Keimoes in the arid hinterland north of the Gariep River where the northwest Nama Karoo (the geographic area and ecology otherwise known as Bushmanland [Mucina and Rutherford 2006]) and Kalahari Duneveld bioregions meet. Here we use aspects of gazelle behavior, and local ethnographical and ethno-historical records, to explore the possibility that the stone-built kites or funnel chains of South Africa may have been used to hunt springbok (Antidorcas marsupialis), southern Africa’s only gazelle. We argue that seasonal herds of gazelles, colloquially known as trekbokken (large springbok herds on the march), were a possible target of precolonial hunters who used their intimate understanding of the animals and their landscape to design the kites.

Description of a new species of Rhinocoeta Burmeister, 1842 (Scarabaeidae, Cetoniinae) from the South African Northern Cape.

Rhinocoetanamaquasp. nov. is recognised as a separate species from its closest relative, R.cornuta (Fabricius, 1781) after a review and close analysis of specimens recently collected in the semiarid region of the Northern Cape Province, South Africa. The new species can be readily separated from R.cornuta by the drastically reduced tubercle and associated depression on its anterior pronotal margin, particularly in the male. In addition, the general body shape of R.namaqua is more globose than that of R.cornuta, its average total length is larger, and its elytral costae are generally reduced and poorly visible, particularly at the level of the umbones. These characteristics make it practically impossible to separate the two sexes of R.namaqua, without inspection of the internal reproductive organs, as their external morphologies are virtually identical, unlike in R.cornuta. Finally, the aedeagal parameres of R.namaqua exhibit a narrower apex than those of R.cornuta and, in particular, lack the subapical hook-shaped lateral expansions that are so typical of all the other Rhinocoeta s. str. species. The new species appears to be restricted to specific bioregions of the Succulent and Nama Karoo biomes of the Northern Cape, and like all other species of the genus is generally found on or under mammal herbivore dung. Adult activity is limited to short periods immediately after rainfall events, during which individuals fly around and mate, but do not feed on either fruits or flowers.

Diet selection and preference of small ruminants during drought conditions in a dryland pastoral system in South Africa

Diet selection and preference of small ruminants during drought conditions in a dryland pastoral system in South Africa