A short-range weather prediction system for South Africa based on a multi-model approach

The accurate prediction of rainfall events, in terms of their timing, location and rainfall depth, is important to a wide range of social and economic applications. At many operational weather prediction centres, as is also the case at the South African Weather Service, forecasters use deterministic model outputs as guidance to produce subjective probabilistic rainfall forecasts. The aim of this research was to determine the skill of a new objective multi-model, multi-institute probabilistic ensemble forecast system for South Africa. Such forecasts are obtained by combining the rainfall forecasts of 2 operational high-resolution regional atmospheric models in South Africa. The first model is the Unified Model (UM), which is operational at the South African Weather Service. The UM contributes 3 ensemble members, each with a different physics scheme, data assimilation techniques and horizontal resolution. The second model is the Conformal-Cubic Atmospheric Model (CCAM) which is operational at the Council for Scientific and Industrial Research, which in turn contributed 2 members to the ensemble system based on different horizontal resolutions. A single-model ensemble forecast, with each of the ensemble members having equal weights, was constructed for the UM and CCAM models, respectively. These UM and CCAM single-model ensemble predictions are then combined into a multi-model ensemble prediction, using simple un-weighted averaging. The probabilistic forecasts produced by the single-model system as well as the multi-model system have been tested against observed rainfall data over 3 austral summer 6-month periods from 2006/07 to 2008/09, using the Brier skill score, relative operating characteristics, and the reliability diagram. The forecast system was found to be more skilful than the persistence forecast. Moreover, the system outscores the forecast skill of the individual models

Markedly Divergent Tree Assemblage Responses to Tropical Forest Loss and Fragmentation across a Strong Seasonality Gradient

We examine the effects of forest fragmentation on the structure and composition of tree assemblages within three seasonal and aseasonal forest types of southern Brazil, including evergreen, Araucaria, and deciduous forests. We sampled three southernmost Atlantic Forest landscapes, including the largest continuous forest protected areas within each forest type. Tree assemblages in each forest type were sampled within 10 plots of 0.1 ha in both continuous forests and 10 adjacent forest fragments. All trees within each plot were assigned to trait categories describing their regeneration strategy, vertical stratification, seed-dispersal mode, seed size, and wood density. We detected differences among both forest types and landscape contexts in terms of overall tree species richness, and the density and species richness of different functional groups in terms of regeneration strategy, seed dispersal mode and woody density. Overall, evergreen forest fragments exhibited the largest deviations from continuous forest plots in assemblage structure. Evergreen, Araucaria and deciduous forests diverge in the functional composition of tree floras, particularly in relation to regeneration strategy and stress tolerance. By supporting a more diversified light-demanding and stress-tolerant flora with reduced richness and abundance of shade-tolerant, old-growth species, both deciduous and Araucaria forest tree assemblages are more intrinsically resilient to contemporary human-disturbances, including fragmentation-induced edge effects, in terms of species erosion and functional shifts. We suggest that these intrinsic differences in the direction and magnitude of responses to changes in landscape structure between forest types should guide a wide range of conservation strategies in restoring fragmented tropical forest landscapes worldwide

Genetic Characterization of Human T-Cell Lymphotropic Virus Type 1 in Mozambique: Transcontinental Lineages Drive the HTLV-1 Endemic

Human T-cell lymphotropic virus type 1 (HTLV-1) is the causative agent of Adult T-Cell Leukemia/Lymphoma (ATL), the Tropical Spastic Paraparesis/HTLV-1-associated Myelopathy (TSP/HAM) and other inflammatory diseases, including dermatitis, uveitis, and myositis. It is estimated that 2–8% of the infected persons will develop a HTLV-1-associated disease during their lifetimes, frequently TSP/HAM. Thus far, there is not a specific treatment to this progressive and chronic disease. HTLV-1 has means of three transmission: (i) from mother to child during prolonged breastfeeding, (ii) between sexual partners and (iii) through blood transfusion. HTLV-1 has been characterized in 7 subtypes and the geographical distribution and the clinical impact of this infection is not well known, mainly in African population. HTLV-1 is endemic in sub-Saharan Africa. Mozambique is a country of southeastern Africa where TSP/HAM cases were reported. Recently, our group estimated the HTLV prevalence among Mozambican blood donors as 0.9%. In this work we performed a genetic analysis of HTLV-1 in blood donors and HIV/HTLV co-infected patients from Maputo, Mozambique. Our results showed the presence of three HTLV-1 clusters within the Cosmopolitan/Transcontinental subtype/subgroup. The differential rates of HIV-1/HTLV-1 co-infection in the three HTLV-1 clusters demonstrated the dynamic of the two viruses and the need for implementation of control measures focusing on both retroviruses

Non-linear effects of drought under shade: reconciling physiological and ecological models in plant communities

The combined effects of shade and drought on plant performance and the implications for species interactions are highly debated in plant ecology. Empirical evidence for positive and negative effects of shade on the performance of plants under dry conditions supports two contrasting theoretical models about the role of shade under dry conditions: the trade-off and the facilitation hypotheses. We performed a meta-analysis of field and greenhouse studies evaluating the effects of drought at two or more irradiance levels on nine response variables describing plant physiological condition, growth, and survival. We explored differences in plant response across plant functional types, ecosystem types and methodological approaches. The data were best fit using quadratic models indicating a humped-back shape response to drought along an irradiance gradient for survival, whole plant biomass, maximum photosynthetic capacity, stomatal conductance and maximal photochemical efficiency. Drought effects were ameliorated at intermediate irradiance, becoming more severe at higher or lower light levels. This general pattern was maintained when controlling for potential variations in the strength of the drought treatment among light levels. Our quantitative meta-analysis indicates that dense shade ameliorates drought especially among drought-intolerant and shade-tolerant species. Wet tropical species showed larger negative effects of drought with increasing irradiance than semiarid and cold temperate species. Non-linear responses to irradiance were stronger under field conditions than under controlled greenhouse conditions. Non-linear responses to drought along the irradiance gradient reconciliate opposing views in plant ecology, indicating that facilitation is more likely within certain range of environmental conditions, fading under deep shade, especially for drought-tolerant species

Review of the projected impacts of climate change on coastal fishes in southern Africa

The coastal zone represents one of the most economically and ecologically important ecosystems on the planet, none more so than in southern Africa. This manuscript examines the potential impacts of climate change on the coastal fishes in southern Africa and provides some of the first information for the Southern Hemisphere, outside of Australasia. It begins by describing the coastal zone in terms of its physical characteristics, climate, fish biodiversity and fisheries. The region is divided into seven biogeographical zones based on previous descriptions and interpretations by the authors. A global review of the impacts of climate change on coastal zones is then applied to make qualitative predictions on the likely impacts of climate change on migratory, resident, estuarine-dependent and catadromous fishes in each of these biogeographical zones. In many respects the southern African region represents a microcosm of climate change variability and of coastal habitats. Based on the broad range of climate change impacts and life history styles of coastal fishes, the predicted impacts on fishes will be diverse. If anything, this review reveals our lack of fundamental knowledge in this field, in particular in southern Africa. Several research priorities, including the need for process-based fundamental research programs are highlighted

Sustainability of the South African Livestock Sector towards 2050 Part 2: Challenges, changes and required implementations

Challenges facing the livestock sector towards 2050 and the changes and management considerations required to maintain sustainability are discussed. Major challenges are associated with climate change and the environmental impact of the sector. Southern Africa is predicted to become drier and the average temperature may rise by 1.5 ºC to 2 ºC. Livestock CH4 emissions are 1330 Gg/year, with enteric fermentation contributing 95%. For commercial production of beef and milk, CH4 estimates are at the upper half of life cycle assessments of 14 - 32 kg CO2 e/kg beef and 0.84 - 1.4 kg CO2 e/kg milk recorded for developed countries. The water footprint depends on production system and efficiency. Global and South African water use estimates for red meat production vary from 80 to 540 L/kg meat. In dairy plants the water usage to process the same product may vary by more than 100%, suggesting scope for improvement. Although animal welfare in South Africa is supported by the Livestock Welfare Coordinating Committee and adherence codes, humane treatment of animals is more difficult to maintain in intensively-housed production systems. Livestock production in communal and small scale sectors requires rapid commercialisation to relieve poverty and contribute to gross domestic product. This requires partnerships, major inputs and paradigm shifts. Input costs including labour increase faster than commodity prices, the concern with labour costs being the impact on employment rates. Efficiency of production should be on par with competitors if the livestock sector is to compete on domestic and export markets. The poultry industry is on par, but rising feed costs, disease and subsidized imports are major concerns. Efficiency in the other industries as measured by off-take percentage is generally lower than competitors, a major reason being lower reproductive rates. In this context, the amount of feed, water and CH4/kg beef can be reduced by more than 20% if calving rate increases by 20 percentage points. Effective management of rangeland is critical, even more so because of climate change. Livestock production is only  marginally competitive and therefore vulnerable to deregulation and trade liberalization. To increase competitiveness exports should increase markedly. For participation in world trade, controlled and notifiable diseases remain a risk. Associated risks are zoonosis and microbial resistance to antibiotics. Stock theft and predation are major concerns. Farmers should employ bio-security measures to ensure the supply of safe products to the consumer. Government and the livestock industries will have to show a clear and strong commitment to address the challenges and opportunities to ensure sustainability of the livestock sector.Keywords: Challenges, environmental impact, animal welfare, health, commercialization, input costs, efficiency, markets, rangeland, theft, predation, consume

January and July climate simulations over the SADC region using the limited-area model DARLAM

High-resolution climate simulations of near-surface variables are presented for January and July over the Southern African Developing Countries (SADC) region using the CSIRO Division of Atmospheric Research Limited-Area Model (DARLAM) nested within a General Circulation Model (GCM). The model domain includes tropical (north and south of the equator) and subtropical (Southern Africa) regions. Objective measures of skill are used to assess the quality of model simulations, and the performance of the model is verified over various subregions of the model domain. South of the tropics, DARLAM fields are not only superior to those produced by the GCM, but also compare well with mesoscale observations. This is particularly true for the spatial distribution of rainfall and screen temperature simulations. DARLAM, however, severely over-estimates rainfall totals over regions of steep orography. WaterSA Vol.28(4) 2002: 361-37

Increased mortality of tropical tree seedlings during the extreme 2015–16 El Niño

As extreme climate events are predicted to become more frequent because of global climate change, understanding their impacts on natural systems is crucial. Tropical forests are vulnerable to droughts associated with extreme El Niño events. However, little is known about how tropical seedling communities respond to El Niño–related droughts, even though patterns of seedling survival shape future forest structure and diversity. Using long-term data from eight tropical moist forests spanning a rainfall gradient in central Panama, we show that community-wide seedling mortality increased by 11% during the extreme 2015–16 El Niño, with mortality increasing most in drought-sensitive species and in wetter forests. These results indicate that severe El Niño–related droughts influence understory dynamics in tropical forests, with effects varying both within and across sites. Our findings suggest that predicted increases in the frequency of extreme El Niño events will alter tropical plant communities through their effects on early life stages