Environmental History and the Desertification of the Karoo,South Africa

Abstract

This paper reviews the desertification debate in South Africa and emphasizes the methods that have been used to understand the environmental history of the semi–arid rangelands in the eastern Karoo during the last 500 years. These mixed grass/dwarf shrub rangelands, with mean annual rainfall totals typically between 300–400 mm, are described and the main driving variables discussed. A brief historical account of the European settlement of the region is also presented. The desertification debate has focussed on three main issues. Firstly, because arid and semi–arid lands appear to be heavily influenced by climate, the changing climatic regime during the Holocene and particularly during the last two hundred years has been the subject of intensive investigation. While all studies conclude that there is no evidence in the historical record to support the popular perception that rainfall totals have decreased this century, the question of changing rainfall seasonality has not been adequately explored. Although mean annual temperatures over the last 50 years have not changed there have been significant increases in mean monthly maximum temperatures and significant decreases in mean monthly minimum temperatures for some of the stations investigated. The second issue of great interest in the South African desertification literature is that of the nature of pre–colonial environments. A wide variety of archaeological, historical and ecological techniques have been used, including analyses of fossil mammal bones in owl pellets, fossil pollen in hyrax middens, notes from traveller's accounts of the region and stable carbon isotopes in soil as well as fossil mammal bones. While all authors agree that the eastern Karoo was more grassy at some stage in the past there is disagreement as to both the timing and cause of the changes to a more shrubby vegetation. The final issue of great concern to the desertification debate in South Africa concerns the rate of change during the last 100 years. Satellite imagery, matched ground and aerial photography, survey data and an analysis of historical stock records cannot agree as to whether the Karoo is degrading or not. Certainly, the classic view of an annually expanding desert margin has been replaced in recent years by a more realistic understanding of the seasonal dynamics of the vegetation. The recent trend to detailed modelling of the demographic process in key species holds much promise for our understanding of the degradation process. The vibrant community of researchers, employing a range of archaeological, historical and ecological techniques, will make important contributions to South Africa's National Action Plan to Combat Desertification.     

Lystrosaurus species composition across the Permo–Triassic boundary in the Karoo Basin of South Africa

Lystrosaurus is one of the few therapsid genera that survived the end-Permian mass extinction, and the only genus to have done so in abundance. This study identifies which species of Lystrosaurus have been recovered from Permian and Triassic strata to determine changes in the species composition across the Permo–Triassic (P–T) boundary in the Karoo Basin of South Africa. Data generated from museum collections and recent fieldwork were used to stratigraphically arrange a total of 189 Lystrosaurus specimens to determine which species survived the extinction event. Results reveal that L. curvatus and L. maccaigi lived together on the Karoo floodplains immediately before the extinction event. L. maccaigi did not survive into the Triassic in South Africa. L. curvatus survived, but did not flourish and soon became extinct. Two new species of Lystrosaurus , L. murrayi and L. declivis , appeared in the Early Triassic. It is possible that L. murrayi and L. declivis occupied different niches to L. maccaigi and L. curvatus , and had special adaptations that were advantageous in an Early Triassic environment. We suggest that L. maccaigi may be used as a biostratigraphic marker to indicate latest Permian strata in South Africa and that, in support of previous proposals, the genus Lystrosaurus should not be used as a sole indicator of Triassic-aged strata. Our field data also show that L. curvatus may be regarded as a biostratigraphic indicator of the P–T boundary interval.     

Evaluation of Restoration Techniques for the Succulent Karoo, South Africa

Abstract Possible constraints on the passive recovery of bare areas in the Karoo, a semiarid region in South Africa, include inadequate supply of seed, availability of suitable microsites for plant establishment, altered soil properties, and the truncation of key soil biotic processes. Here we investigate the possibility of initiating the restoration of bare areas by soil surface treatments with gypsum (CaSO₄) and/or organic mulch. We also apply an exogenous seed source to test the hypothesis that seed availability limits autogenic recovery. Both gypsum and mulch improved rain water infiltration, gypsum more so than mulch, and both treatments resulted in significantly higher numbers of reseeded seedlings compared with controls. Gypsum also improved the survival of the cohorts of seedlings of the larger seeded Tripteris sinuata. Tripteris showed the highest number of seedlings (maximum count of 150 seedlings/1,000 viable seeds sown) and surviving plants of the three reseeded species, which included two small‐seeded species, Ruschia spinosa and Chaetobromus dregeanus. Throughout the study period significantly higher plant volumes of naturally seeded annuals and perennials were recorded in the gypsum and/or mulch treatments compared with the controls. Germination and emergence of reseeded and naturally seeded plants appears to be determined by the availability of cool season (autumn to spring ) soil moisture, whereas follow‐up rainfall during this time is important for plant survival. Mulching of bare areas in the Succulent Karoo has the potential to re‐create vegetated areas that will further capture and conserve water, soil, and nutrients. Gypsum also showed positive results but might not be a cost‐effective option because of transport costs to these remote arid areas.     

Occurrence of fungal endophytes in cultivars ofTriticum aestivum in South Africa

Fungal endophytes were isolated from leaves, roots and stems of four wheat cultivars and a breeding line at three different sampling dates during the 1993 growing season. Of the 55 different fungal taxa encountered, 19 were present at relative importance values of more than 5%. No cultivar-related differences in the assembleges of endophytes were observed.Phoma glomerata was not restricted to only one tissue type, whereasAlternaria alternata, basidiomycete sp. 1,Pleospora herbarum andEpicoccum nigrum occurred primarily in the leaves, andFusarium avenaceum was extremely frequent in roots. In general, colonization by endophytes increased with the age of the plants. Most endophytes were isolated from wheat leaves. Successional colonization of a given tissue type was quantitative rather than qualitative, with a given fungal taxon increasing or decreasing over the period sampled, rather than replacing the fungi initially encountered.Present address: Téra d'Sott 5, CH-6949, Comano, Switzerland.     

Mokola virus involved in a human contact (South Africa)

Isolations of Mokola virus (MOKV) are rare, but in South Africa and Zimbabwe this genotype 3 lyssavirus variant has been occasionally found in domestic mammals (cats and a dog) with a total of 17 virus isolates (South Africa 10, Zimbabwe 7) having been recovered during the past 30 years. We report the identification of a MOKV isolate involved in a human contact in Grahamstown (Eastern Cape, South Africa) and a genetic comparison with previously characterized isolates. This reported MOKV case was in a previously immunized cat. While the continual recovery of MOKV isolates in domestic cats is speculative of the existence of a reservoir host species among bats or rodents, the lack of protection with currently used vaccines is discussed and the need for biologicals with a wider spectrum of protection against this lyssavirus variant is highlighted.     

The distribution and biology of nomadic birds in the Karoo, South Africa

Dryland nomadic bird species, as a proportion of all bird species in a biome in southern Africa, are highest in the arid grassland and arid and semi-arid Karoo in South Africa. Nomadic birds, of which the most widespread species is the greybacked finchlark Eremopterix verticalis (Smith), are most frequently observed in the north-central and north western Nama Karoo. The species richness of nomadic species is inversely correlated with species richness of all bird species in the Karoo. Since the distribution of nomadic birds is in areas where rainfall is patchy, low (<250 mm per year) and aseasonal, this supports the idea that fewer species are able to cope with resources that are patchy in time and space, and that there has been selection for nomadism in the species that are able to use patchy environments. Species richness and abundance of nomadic birds is negatively correlated with rainfall amount but positively correlated with the coefficient of variation of the rainfall and with rainfall in autumn. The frequency of nomadic birds is inversely correlated with altitude range; nomadic species are most often recorded in structurally simple habitats (shrubland and grassland) on open plains. Most nomadic bird species in the Karoo are granivorous. Perennial desert grasses are important components of the habitat and diet of small nomadic granivores, and also provide nest sites and nest material. Nomadic birds can breed throughout the year, without a clearly defined ‘season’ in both the Succulent and Nama Karoo. Average clutch sizes do not differ significantly between resident and all nomadic species in the arid and semi-arid Karoo. Nomadism is an evolutionary stable strategy for individual species only when extremes in environmental conditions are frequent enough, and unpredictable enough, to maintain movements to high resource patches or to maintain dispersal away from low resource patches. If high rainfall years are too regular or infrequent, or peaks in fluctuations of resources in the environment too low, or rainfall patches are randomly distributed, nomadism would not be maintained as part of the individual behaviour pattern.     

New species of Crotonia (Acari: Oribatida) from South Africa

Four new species of oribatid mites of the genus Crotonia , ( C. pauropelor sp. nov., C. dicella sp. nov., C. lyrata sp. nov. and C. ecphylla sp. nov. ) are described from soil and plant litter from South Africa. Crotonia pauropelor, C. dicella and C. ecphylla are allied to the 'capistrata' species-group, previously known only from Queensland, Australia, in that they possess the full complement of c setae on the notogaster. They differ in having eight pairs rather than nine pairs of genital setae. In addition, C. ecpylla is unusual in the genus Crotonia in that it appears to possess two pairs of setae on each of the second epimera. Crotonia lyrata has only two pairs of c setae and is allied to the 'cophinaria' species-group. This is only the second published record of the genus Crotonia from South Africa, and the first of any named species. A key to the African Crotonia species is provided, which includes the only two previously known species C. alluaudi and C. rothschildi (Berlese, 1916).     

Cerium negative anomaly just before the Permian and Triassic boundary event — The upward expansion of anoxia in the water column

A negative excursion of Ce and a succeeding steep decline in δ¹³C found just before the Permian and Triassic boundary (PTB) of Julfa area offer a geochemical constraint on the cause of the mass extinction event of PTB. The geochemical studies of recent anoxic basins like the Black Sea strongly suggest that the Ce negative excursion of these carbonate platform sequence indicates the buildup of anoxic water in the offshore realm. The suboxic water mass associated with the Ce negative anomaly zone migrated and invaded into shallow carbonate shelf around 600 thousand years before the PTB. This was followed by an anoxic water mass without Ce anomaly, and resulted in a steep decline in δ¹³C and then mass extinction of marine shelf biota.     

Diversity and distribution of entomopathogenic nematodes (Steinernematidae, Heterorhabditidae) in South Africa

A total of 1506 soil samples from different habitats in seven geographic regions of South Africa were evaluated for the presence of entomopathogenic nematodes (EPN). Nematodes were isolated from 5% of the samples. Among the steinernematids, four Steinernema sp. were recovered including Steinernema khoisanae and three new undescribed species. Although steinernematids were recovered from both humid subtropical and semiarid regions, this family accounted for 80% of EPN recovered from the semiarid climate zones characterised by sandy, acidic soils. Eight isolates of S. khoisanae were recovered from the Western Cape province. One of the new undescribed steinernematids (Steinernema sp. 1) was recovered only from the Free State and KwaZulu-Natal provinces where humid subtropical conditions prevail and soils are generally less acidic with higher clay content. A high level of adaptation, however, was noted with Steinernema sp. 2, which was recovered from a wide range of soil conditions and habitats ranging from semiarid (Western Cape province) to humid subtropical (KwaZulu-Natal province). A third undescribed steinernematid, Steinernema sp. 3, seemed better adapted to heavier soils with more than 80% of isolates recovered from fruit orchards in the Free State province. Heterorhabditis bacteriophora was the only heterorhabditid recovered during this survey. This species was particularly prevalent in four provinces ranging from humid subtropical to semiarid regions. Isolation of EPN directly from insect cadavers included Steinernema sp. 2 and one H. bacteriophora from an unidentified white grub (Scarabaeidae) cadaver (i.e., dual infection) and H. bacteriophora from the black vine weevil, Otiorhynchus sulcatus.     

Grasshopper assemblage response to a restored national park (Mountain Zebra National Park, South Africa)

Twelve grassland sites were sampled inside and outside the Mountain Zebra National Park (MZNP), South Africa to assess changes in grasshopper assemblages to grazing by indigenous mammals inside the park compared to grazing by domestic cattle outside. The MZNP has been restored from cattle-grazed farmland to indigenous mammal parkland for 62 years. The number of grasshopper species and families inside the park was not significantly different from outside the park, but the number of individuals inside the park was significantly higher. Multivariate statistics did not reveal any strong site groupings based on simple inside/outside comparisons, but there were clear groupings of sites based on vegetation characteristics and other environmental variables. The park boundary, therefore, does not significantly determine grasshopper assemblages, although intensity of grazing does. The indigenous mammals inside the park had the same effect on grasshoppers as the domestic cattle outside, and it was the level of defoliation and trampling that was important rather than the type of mammal. Intensive livestock grazing and trampling leads to bush encroachment and reduction in grass cover and/or disappearance of several grass species. In response to this pressure, grasshopper populations dropped, with localized extirpation of some species. Vegetation composition and structure, particularly grass height and percentage cover, had a significant effect on grasshopper assemblages. The MZNP is thus an area of localized, elevated grasshopper abundance in comparison with the surrounding farms, and presumably represents a situation prior to the current, intensive farming activities. Such elevated grasshopper abundances are important for maintaining soil quality and hence ecological integrity of this landscape which is poor in organics and nitrogen. The MZNP could be viewed as a centre where species with high mobility may seek refuge from anthropogenic pressures. The MZNP also serves as a reference illustrating the differences between restored-through-natural-succession and anthropogenically disturbed habitats, and compares desirable with undesirable ecosystem changes for herbivorous invertebrates such as grasshoppers.     

Adolescent Social Attitudes in South Africa and Swaziland

A content analysis was undertaken of stories written by adolescents in urban townships in South Africa and in an urban setting in Swaziland. The findings concerning the nature of the actors and the relationships between actors in the stories suggest that though South Africans in their early years encounter more elements of modernity than do the Swazis, in their present situation they view the world as having less rational elements, fewer psychological satisfactions, and more threats to their physical welfare than do the Swazis.     

Orphanhood and fertility in young adults: Evidence from South Africa

I study the relation between orphanhood and fertility patterns in young adults using a longitudinal survey from the city of Cape Town, South Africa. The data set combines two survey waves with a year-by-year life history calendar that records key outcomes (e.g., schooling, work, fertility). It also provides information on so-called ‘parental investments’ (time and material support), family background, and literacy and numeracy test scores. I find that orphans exhibit significantly higher rates of teenage pregnancy. In particular, teenage motherhood is 19% points more likely among (female) orphans. These results suggest that orphanhood may leave a long-lasting ‘imprint’ in terms of premature fertility, especially in teenage females.     

Local responses to conservation in the Richtersveld National Park, South Africa

Local notions of conservation deserve closer scrutiny. We cannot assume that they naturally coincide with those of the tourist core; nor that they are automatically given higher priority when local populations are induced to participate in practices which conserve flora and fauna. A case study of the establishment of the Richtersveld National Park in Namaqualand, a remote arid region of South Africa, is used to argue that local attitudes to conservation and development (associated with tourism) can become increasingly cynical and ambivalent in the context of ecotourism. Furthermore, such attitudes are shaped less by economic inducements than by the often contradictory messages about conservation that are being communicated daily.     

Disturbances in semi-arid shrubland and arid grassland in the Karoo, South Africa: mammal diggings as germination sites

Mammals (mainly aardvark Orycteropus ufer , porcupine Hystrix austro-africanae , bat-eared fox Otocyon megalotis and Cape fox Vulpes chama ) which excavate holes in hard-capped soils in Karoo shrubland and inter-dune pans create microsites where seeds, detritus and water accumulate, and seeds germinate. Holes with seedlings were significantly deeper (6.7 ± 0.4 cm) than holes without seedlings (4.5 ± 0.3 cm). In open, inter-shrub sites, significantly more seedlings germinated in diggings than on the flat soil surface, but there was no difference in the proportion of seedlings germinating under shrubs and in diggings. In inter-dune pans, 96% of all seedlings found were growing in diggings.

Résumé

Les mammifères (surtout l'oryctérope Orycreropus afer , le porcépic Hystrix austro-ajricanae , l'otocyon Otocyion megalotis , et le renard du Cap Vulpes chama ) qui creusent des trous dans les régions buissonneuses du Karoo et dans les creux entre les dunes créent des microsites où les semences, les déchets et l'eau se rassemblent, et les semences germent. Les trous où elles germent sont significativement plus profonds (6,7 ± 0,4 cm) que ceux où elles ne germent pas (4,5± 0,3 cm). Aux endroits buissonneux ouverts, il pousse plus de jeunes plantes dans des creux qu'à la surface du sol, mais il n'y a pas de différence entre les proportions de celles qui poussent sous les buissons et dans les creux. Dans les creux entre les dunes, 96% des jeunes pousses croissent dans les excavations.     

Tissue banking in South Africa: a 19-year history

The establishment of a Tissue Bank and the science of Tissue Banking in South Africa started in the 1960s and is still developing. This article describes the development and growth of Tissue Banking in South Africa. The current emphasis is to supply viable bone products that have been produced under the best possible quality controlled circumstances; with the collaboration between different Organ Donation Organisations. Through collaboration, a dramatic increase in the number of donors was noted over the years. Concurrently, there was a dramatic increase in the usage of different allograft products and now necessitates the development of new graft materials for expanding patient options. As an ongoing concern, the Tissue Bank in South Africa experienced an ever increase in costs to enhance quality/safety controls: increase in historical patient information, documentation and serological testing in a population struggling to control HIV. To date, the South African Tissue Bank has not experienced any untoward patient incidence since the 1960s and currently is getting over 500 donors per year.     

The Politics of Ecology in South Africa on the Radical Left

The South African ecologist and political activist Edward Roux (1903–1966) used evolutionary biology to argue against racism. During the cold-war, he transformed his communist beliefs into advocacy for scientific rationalism, management, and protection of nature against advancing capitalism. These pleas for saving the environment served as a vehicle for questioning the more risky issue of evolution and racial order in society. The link between ecological and political order had long been an important theme among the country's ecologists and politicians alike. The statesman Jan Christian Smuts' holistic theory of evolution and racial order inspired the nation's ecologists to sanctify an ecologically informed racial policy. This idealist informed methodology stood in direct opposition to the materialist approach to ecology of Roux. These methodological debates reflected differing political support from within the Union Party and people on the radical left, respectively. Ecology was of concern to politicians because understandings of the order of nature had direct implications for the racial order of the South African society. This revised version was published online in July 2006 with corrections to the Cover Date.     

An analysis of the mole rats (Mammalia: Rodentia) from Langebaanweg (Mio-Pliocene, South Africa)

A study of the taphonomy and age profiles of the mole rat population from Langebaanweg ‘E’ Quarry was undertaken in order to see if these subterranean rodents had been accumulated by predation (coprocoenosis hypothesis) or as a result of drowning in their burrows during a flood event (catastrophocenosis hypothesis). Previous research has cited the bathyergids as being the most common rodent at Langebaanweg, however, a comprehensive study of new micromammal material indicates that murids, rather than mole rats, dominate most of the assemblages. The concentration of mole rat remains in many of the fossil-bearing levels at Langebaanweg is, nevertheless, still extremely high compared to other fossil sites or predation assemblages in the area. A taphonomic examination of mole rat incisor surfaces indicates that digestion occurs on between 44% and 54% of incisors in the different assemblages, and this, together with the degree of digestion suggests that category 1 and category 2 predators had been responsible for the accumulation of the fossil mole rat assemblages. The absence of rounding, polishing or weathering on the fossils indicates that there has been little or no transport by water, and that burial of the bones was rapid. Breakage and damage to the anterior portion of many of the mandibles made it impossible to accurately assess the age of the older mole rats, and the majority of mandibles could provide only a minimum age of the animal at the time of death. The age profile indicates that very young individuals are missing from the assemblages. This allows for refutation of the previously made suggestion that flooding was responsible for the death of the majority of Langebaanweg mole rats and also introduces the possibility that Bathyergus hendeyi may have been a social animal, unlike extant bathyergids which are solitary.     

Last Interglacial Hominid and Associated Vertebrate Fossil Trackways in Coastal Eolianites,South Africa

Two Late Pleistocene hominid footprint sites are known in South Africa, one on the west coast (Langebaan) and the other on the southeast coast (Nahoon). Both trackways occur in calcareous eolianites and are dated to the Last Interglacial (～120 ka). The chief objective is to infer anatomical features of these early anatomically modern hominid footprint makers, about which little is known. At Nahoon, trackways of at least five species of vertebrates, including three hominid footprints, are preserved as casts. One footprint preserves excellent detail, appearing in all respects to be modern, but possibly with a deformity of the small toe. The impressions are shallow and suggest slight build. The stature of the footprint maker, as estimated from foot length (19.2 cm), is ～127 cm, considerably less than modern adult Khoi-San and was probably made by a juvenile. The step length is short relative to foot length, a consequence of walking uphill on a yielding substrate. The Langebaan trackway (preserved as natural impressions) comprises two intact prints and remnants of a third. Pronounced push up mounds flank the prints and preservation of toe impressions is poor. The foot length is 22.8 cm, indicating a stature of ～1.57 m. This falls within the range of modern adult Khoi-San, lending some support to the notion that Middle Stone Age people were of small stature. The depth of the prints and clumsy progression are suggestive of heavy build.     

Lopingian (Late Permian) brachiopods around the Wuchiapingian-Changhsingian boundary at the Meishan Sections C and D, Changxing, South China

The strata below the defined Wuchiapingian-Changhsingian boundary GSSP are mostly covered and obscured by faulting at the Meishan Section D. Therefore, it is very difficult to collect fossils there. After an intensive excavation at Meishan Section C, a diverse fauna based on high-resolution biostratigraphy comprising brachiopods, ammonoids, conodonts, fusulinids and small foraminifers were found. Among these fossils, brachiopods are the most dominant. Eleven species of 10 genera based on more than 1300 specimens are identified. This brachiopod fauna is of late Wuchiapingian-Changhsingian of Lopingian (Late Permian) in age as well constrained by the associated ammonoid Pseudogastrioceras sp., Jinjiangoceras and Konglingites sp., the fusulinid Palaeofusulina and the conodont lineage from C. longicuspidata to C. wangi. In terms of the changes of brachiopod fauna composition around Wuchiapingian-Changhsingian boundary, it clearly indicates a continuous transgression from the upper part of the Lungtan Formation to the lower part of the Changhsing Formation. A new species, Neochonetes (Huangichonetes) meishanensis, is described and some other species are discussed based on the new collection from Meishan Sections C and D.