Scielo RSS http://www.scielo.org.za/rss.php?pid=0038-235320090001&lang=en vol. 105 num. 1-2 lang. en http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100001&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100002&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100003&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100004&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100005&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100006&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100007&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100008&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100009&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100010&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100011&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100012&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100013&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100014&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100015&lng=en&nrm=iso&tlng=en http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100016&lng=en&nrm=iso&tlng=en Arid environments remind one of the punctuated equilibrium theory of evolution: they experience long periods of stasis and low productivity, interrupted with episodic rainfall which spurs reproduction and movement. Birds, as highly dispersive organisms, are among the most dramatic indicators of these fluctuations. Here we review birds' two main strategies, residency and nomadism, and the trade-offs faced by individuals in uncertain times. In general, wet years stimulate higher densities of nests (i.e. smaller territories), larger clutch sizes, unseasonal breeding, and at some times of year, higher breeding success. Rainfall above a certain threshold triggers breeding in resident species and an influx of nomadic species which breed and then move on. The environmental cues which trigger nomadism are sometimes poorly understood, but include distant thunderstorms for aquatic species, and perhaps for insectivores. Environmental cues that draw nomadic granivores to areas that have had recent rain are not known. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100017&lng=en&nrm=iso&tlng=en Droughts can have serious ecological and economic consequences and will pose an increasing challenge to rangeland users as the global climate is changing. Finding ways to reduce ecological and economic impacts of drought should thus be a major research thrust. Resilience, defined as the amount of perturbation a social or ecological system can absorb without shifting to a qualitatively different state, has emerged as a prominent concept in ecosystem ecology and more recently as a conceptual framework for understanding and managing complex social-ecological systems. This paper discusses the application and relevance of resilience to understanding and managing ecosystem change, and enhancing the capacity of land users to adapt to droughts. Drought can trigger vegetation change and factors such as grazing management can influence the likelihood of such transitions. Drought can cause differential mortality of perennial plants and this could provide an opportunity for rangeland restoration by opening up establishment sites for desirable species. The capacity of land users to cope with drought is influenced by the resilience of their agro-ecosystems, the diversity of livelihood options, access to resources and institutional support. By these criteria, current agricultural development approaches in South Africa, particularly in communal rangelands and areas of land reform, are unlikely to enhance land users' resilience to drought and other perturbations. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100018&lng=en&nrm=iso&tlng=en Human adaptation and response to drought is primarily through evasion or endurance. A review of historical agricultural practices in southern Africa demonstrates evidence of drought evasion response strategies in well-established transhumance routes, where herders move livestock on a seasonal basis in order to exploit resources subject to different climatic regimes. European settlers to the arid regions of South Africa quickly recognised the necessity of these evasion options to survive drought, and adopted the transhumance practices of indigenous farmers. Areas of geographically diverse resource bases became hotly contested by settlers and indigenous farmers. The success of evasion systems are shown to hinge on good social and institutional support structures. When movement is not an option, drought endurance is pursued by attempting to limit the damage to the natural resource base. This is through a number of means such as forage conservation, varying livestock types and numbers, water and soil conservation and taking up alternative livelihood options. State responses to drought over the last century reflect the general South African pattern of racially divided and unjust policies relating to resource access. Historically the state provided considerable support to white commercial farmers. This support was frequently contradictory in its aims and generally was inadequate to enable farmers to cope with drought. Since the advent of democracy in 1994, the state has intervened less, with some support extended to previously disadvantaged and poor communal farmers. Climate change predictions suggest an increase in drought, suggesting that the adoption of mitigating strategies should be a matter of urgency. To do this South Africa needs to build social and institutional capacity, strive for better economic and environmental sustainability, embed drought-coping mechanisms into land restitution policy to ensure the success of this programme, and acknowledge the diversity of the agricultural sector. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100019&lng=en&nrm=iso&tlng=en The Klein Karoo is situated in the Western Cape, South Africa, and is characterised by low rainfall (100-450 mm yr-1). The Klein Karoo is situated in the primary catchment of the Gouritz River. The mean annual runoff (MAR) for the three major tributaries of the Gouritz River arising in or feeding the Klein Karoo (Touws, Gamka, Olifants) is 540 Mm³ yr-1. Groundwater recharge in the three Klein Karoo catchments is ±257 Mm³ yr-1, but only a portion of this reaches the rivers. The very variable flows result in low 1:50 year yield of 161 Mm³ (30% of MAR). The current demand for water in these catchments is 182 Mm³ yr-1, which exceeds the yield, and demand is projected to increase between 23% and 150% by 2025. Changes in the approach to water management are required, including improving the efficiency of irrigation and land restoration to improve water infiltration and reduce soil erosion. We believe that it is time to change to a water management approach that is designed to anticipate and manage the inherent variability in water resources in the Klein Karoo, thereby placing the region on a path to sustainable development. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100020&lng=en&nrm=iso&tlng=en This paper is concerned with how changes in the global economy, triggered by actions undertaken in one part of the world, can affect the lives and the prospects of poor rural people, as well as the environment they live in, in another very distant part of the world. It analyses the linkages between changes in the European Union (EU) sugar regime and the economic fortunes and the environmental future of a very poor and highly water-stressed area in southern Africa-the Incomati River Basin-where sugar production is the single most important economic activity. The case study epitomises the complex interactions between trade liberalisation on the one hand and poverty and the environment on the other. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100021&lng=en&nrm=iso&tlng=en For the winter-rainfall region of South Africa, the frequency of drought is predicted to increase over the next 100 years, with dire consequences for the vegetation of this biodiversity hotspot. We analysed historical 20th century rainfall records for six rainfall stations within the succulent karoo biome to determine if the signal of increasing drought frequency is already apparent, and whether mean annual rainfall is decreasing. We found no evidence for a decrease either in mean annual rainfall or in the incidence of drought, as measured by the Standardised Precipitation Index (SPI) over the 20th century. Evidence points to a drying trend from 1900-1950 while no significant trend in rainfall and drought was found at most stations from 1951-2000. In a second analysis we synthesised the information concerning the response of adult succulent karoo biome plants and seedlings to extended drought conditions. General findings are that responses to drought differ between species, and that longevity is an important life history trait related to drought survival. Growth form is a poor predictor of drought response across the biome. There was a range of responses to drought among adult plants of various growth forms, and among non-succulent seedlings. Leaf-succulent seedlings, however, exhibited phenomenal drought resistance, the majority surviving drought long after all the experimentally comparative non-succulent seedlings had died. Our synthesis showed that previous studies on the impact of drought on succulent karoo biome plants differ greatly in terms of their location, sampling design, measured values and plant responses. A suite of coordinated long-term field observations, experiments and models are therefore needed to assess the response of succulent karoo biome species to key drought events as they occur over time and to integrate this information into conservation planning. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100022&lng=en&nrm=iso&tlng=en South Africa in general has been approximately 2% hotter and at least 6% drier over the ten years between 1997 and 2006 compared to the 1970s. The use of water has also increased greatly over this same period. By 2000, 98.6% of that year's surface water yield and 41% of the annual utilisable potential of groundwater was allocated to use. Irrigation agriculture, comprising 60% of total consumption, is by far the largest single consumer of water. Given these climatic and water use changes as a backdrop, we employed a panel data econometric model to estimate how sensitive the nation's agriculture may be to changes in rainfall. Net agricultural income in the provinces, contributing 10% or more to total production of both field crops and horticulture, is likely to be negatively affected by a decline in rainfall, especially rain-fed agriculture. For the country as a whole, each 1% decline in rainfall is likely to lead to a 1.1% decline in the production of maize (a summer grain) and a 0.5% decline in winter wheat. These results are discussed with respect to both established and emerging farmers, and the type of agriculture that should be favoured or phased out in different parts of the country, in view of current and projected trends in climate, increasing water use, and declining water availability. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100023&lng=en&nrm=iso&tlng=en A disproportionately large number of young (<50 years) black patients present with colorectal cancer (CRC) in South Africa. Although a phenomenon previously described elsewhere in Africa, its specific molecular basis, whether sporadic or hereditary, has not been established. Molecular analysis of these tumours could link them to the features known to be associated with specific types of hereditary colorectal cancer, specifically through examination of levels of microsatellite instability, promoter methylation and the presence or absence of KRAS and BRAF mutations. The molecular features of cancer tissue samples from 44 CRC cases of black and white patients in South Africa were accordingly retrospectively analysed without knowledge of family history. Compared with samples from older blacks (>50 years), those from young black patients presented more often with a low methylation phenotype (CIMP-L) and high levels of microsatellite instability (MSI-H). Furthermore, as determined by real-time PCR using probe technology, the tissues from 35% of young blacks showed mutations within exon 1 of the KRAS gene. The BRAF-V600E mutation was only evident in the case of a single young black patient. Based on these results it seems likely that a proportion of CRC cases in young black patients from South Africa develop through the accumulation of mutations resulting in a mismatch repair deficiency linked to MSI-H and, possibly, germline mutations in the mismatch repair genes. The features in these patients are consistent with a diagnosis of the Hereditary Non-Polyposis Colorectal Cancer (HNPCC) syndrome. This finding has important implications for patient management and suggests that family members may be at high risk for CRC. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100024&lng=en&nrm=iso&tlng=en The practice of dry sex is reportedly common among young black women in South Africa. The aim of this study was to explore the relationship of women's preference for dry sex with condom use and the prevalence of Chlamydia trachomatis (CT), Neisseria gonorrhoea (NG) and Trichomonas vaginalis (TV) infections. Between January 2006 and December 2007, 446 women completed a behavioural survey in isiXhosa which assessed demographic information, sexual behaviours, condom use behaviour and other potential correlates. In total, 159 (36.72%) women indicated preferring dry sex. A multivariate logistic regression model indicated that participants who preferred dry sex were more likely to report past STI episodes and to have a partner who also preferred dry sex. The findings indicate that dry sex behaviour was not directly associated with condom use and STI (CT, NG, and TV) prevalence but may have been associated with relationships in which sexual preferences of the male partner were dominant. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532009000100025&lng=en&nrm=iso&tlng=en Nanocrystalline silicon (nc-Si) films were deposited by hot-wire chemical vapour deposition (HWCVD) in the presence of varying H² concentrations and their structural and interfacial character investigated by X-ray diffraction, small-angle X-ray scattering (SAXS) and Raman spectroscopy. The crystalline fraction was around 30-50% and the nc-Si crystallite size was in the range 20-35 nm. The SAXS results were analysed by Guinier plot, scaling factor, and correlation distance. The nc-Si grains displayed a mass fractal appearance, and the interfacial inhomogeneity distance was ~2 nm.