Research Articles (Geography, Geoinformatics and Meteorology)

Permanent URI for this collectionhttp://hdl.handle.net/2263/1936

A collection containing some of the full text peer-reviewed/ refereed articles published by researchers from the Department of Geography

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Sustainable food systems through livestock–pasture integration
(MDPI, 2025-05) Rapiya, Monde; Mndela, Mthunzi; Ramoelo, Abel
The world’s population is projected to rise significantly, which poses challenges for global food security due to increased demand for food, especially from livestock products. As incomes grow in lower-income countries, there is a shift towards more diverse diets that include meat and dairy, stressing our agricultural systems. Livestock plays a crucial role in food production, contributing about 16% of dietary energy, and effective pasture management is vital for enhancing livestock productivity. This review explores how integrating pasture and livestock management can create sustainable food systems and improve nutrition and livelihoods. It assesses the economic viability of pasture-based livestock systems and examines how climate change affects both pasture productivity and livestock performance. The review also identifies innovative practices, such as improved grazing management and technological advancements, that can improve pasture health and livestock output. The findings underscore the importance of well-managed pastures, which can restore degraded lands, improve animal welfare, and support food security. It also highlights that adaptation strategies are necessary to address the challenges posed by climate change, ensuring that livestock systems remain sustainable. By focusing on innovative practices and better management, we can meet the growing demand for animal products while preserving ecosystems and promoting economic stability. Overall, this review emphasizes the need for a holistic understanding of how livestock and pasture management can work together to enhance food security in a changing world.
Towards building interventions in climate and health
(Springer, 2025) Ghosh, Arnab K.; Keenan, Olivia J.; Wright, Caradee Yael
Climate-amplified extreme weather events are on the rise. In the United States, 2023 represented the highest number of billion-dollar disasters according to the National Oceanic and Atmospheric Administration (NOAA). It is clear that the widespread impacts of anthropogenic climate change to the health of millions of Americans and those across the globe can no longer be ignored. Evidence that can be used to build, test, and adapt to climate-relevant interventions is urgently required.
Identifying globally relevant learnings from Africa’s challenges and solutions to climate change and air pollutionrelated health impacts : a data science scoping review protocol
(BMJ Publishing Group, 2024-05-20) Wright, Caradee Yael; Jaca, Anelisa; Kapwata, Thandi; Naidoo, Natasha; Awokola, Babatunde; Bainomugisha, Engineer; Berhane, Kiros; Blesic, Suzana; Kehbila, Anderson Gwanyebit; Naidoo, Rajen N.; Nemukula, Bono; Nyarko, Benjamin Kofi; Okekunle, Akinkunmi Paul; Oni, Tolu; Quansah, Reginald; Thaim, Sokhna; Zakari, Ibhrahim Sidi; Beyene, Negussie
INTRODUCTION : Leveraging data science could significantly advance the understanding of the health impacts of climate change and air pollution to meet health systems’ needs and improve public health in Africa. This scoping review will aim to identify and synthesise evidence on the use of data science as an intervention to address climate change and air pollution-related health challenges in Africa. METHODS AND ANALYSIS : The search strategy will be developed, and the search will be conducted in the Web of Science, Scopus, CAB Abstracts, MEDLINE and EMBASE electronic databases. We will also search the reference lists of eligible articles for additional records. We will screen titles, technical reports, abstracts and full texts and select studies reporting the use of data science in relation to the health effects and interventions associated with climate change and air pollution in Africa. ETHICS AND DISSEMINATION : There are no formal ethics requirements as we are not collecting primary data. Results, once published, will be disseminated via conferences and shared with policy-makers and public health, air pollution and climate change key stakeholders in Africa.
The heterogeneous effects of COVID-19 lockdowns on crime across the world
(BioMed Central, 2024-08-22) Trajtenberg, Nico; Fossati, S.; Diaz, Carlos; Nivette, A.E.; Aguilar, Raul; Ahven, Andri; Andrade, L.; Amram, Shai; Ariel, Barak; Arosemena Burbano, M.J.; Astolfi, Roberta; Baier, Dirk; Bark, Hyung-Min; Beijers, Joris E.H.; Bergman, Marcelo; Borges, D.; Breetzke, Gregory Dennis; Cano, I.; Concha Eastman, I.A.; Curtis‑Ham, Sophie; Davenport, Ryan; Droppelman, C.; Fleitas, Diego; Gerell, Manne; Jang, Kwang-Ho Jang; Kaariainen, Juha; Lappi‑Seppala, Tapio; Lim, Woon-Sik; Loureiro Revilla, R.; Mazerolle, Lorraine; Mendoza, C.; Mesko, Gorazd; Pereda, Noemi; Peres, Maria F.T.; Poblete-Cazenave , Ruben; Rojido, E.; Rose, Simon; Sanchez de Ribera, O.; Svensson, Robert; Van der Lippe, Tanja; Veldkamp, Joran; Vilalta Perdomo, C.J.; Zahnow, R.; Eisner, Manuel P.; greg.breetzke@up.ac.za
There is a vast literature evaluating the empirical association between stay-at-home policies and crime during the COVID-19 pandemic. However, these academic efforts have primarily focused on the effects within specific cities or regions rather than adopting a cross-national comparative approach. Moreover, this body of literature not only generally lacks causal estimates but also has overlooked possible heterogeneities across different levels of stringency in mobility restrictions. This paper exploits the spatial and temporal variation of government responses to the pandemic in 45 cities across five continents to identify the causal impact of strict lockdown policies on the number of offenses reported to local police. We find that cities that implemented strict lockdowns experienced larger declines in some crime types (robbery, burglary, vehicle theft) but not others (assault, theft, homicide). This decline in crime rates attributed to more stringent policy responses represents only a small proportion of the effects documented in the literature.
Roles of host and environment in shift of primary anthrax host species in Kruger National Park
(Public Library of Science, 2024-12-06) Ochai, Sunday Ochonu; Snyman, Lourens F.; Dolfi, Amelie C.; Ramoelo, Abel; Reilly, Brian K.; Botha, Judith M.; Dekker, Edgar H.; Van Schalkwyk, Ockert Louis; Kamath, Pauline L.; Archer, Emma Rosa Mary; Turner, Wendy C.; Van Heerden, Henriette
Environmental and climatic factors, as well as host demographics and behaviour, significantly influence the exposure of herbivorous mammalian hosts to pathogens such as Bacillus anthracis, the causative agent of anthrax. Until the early 1990s in Kruger National Park (KNP), kudu (Tragelaphus strepsiceros) was the host species most affected by anthrax, with outbreaks occurring predominantly in the dry season, particularly during drought cycles. However, the most affected host species has shifted to impala (Aepyceros melampus), with more frequent anthrax outbreaks during the wet season. This study investigates the roles of environmental variation and other host species in this shift. Temporal trends in environmental variables such as precipitation, soil moisture, temperature, and normalised difference vegetation index (NDVI) were analyzed in relation to anthrax occurrence (presence/ absence and counts). Additionally, correlations between host species' densities and anthrax mortalities over time were examined. Anthrax cases in 1990 were concentrated in the central and northern regions of KNP (excluding Pafuri), primarily affected kudus; while subsequent mortalities affected mostly impala and were restricted to the far north, in Pafuri. Significant correlations were found between kudu anthrax mortality and a decrease in NDVI, average temperature, SPI-6 and SPI-12 (Standardised Precipitation Index in various time intervals. Conversely, anthrax occurrence in impalas was associated with a decline in SPI-3, and temperature rise, with increased mortality during the rainy season. Elephant density correlated negatively with kudu mortality, but a positive correlation with both impala mortality and impala density. The study concludes that environmental variables and species' densities may alter the diversity and frequency of hosts exposed to B. anthracis. Climate extremes and alterations therein may exacerbate anthrax severity by modifying species susceptibility and their probability of exposure over time.
Impacts of heat exposure in utero on long-term health and social outcomes : a systematic review
(BMC, 2024-05-04) Brink, Nicholas; Lakhoo, Darshnika P.; Solarin, Ijeoma; Maimela, Gloria; Von Dadelszen, Peter; Norris, Shane; Chersich, Matthew F.; Chikandiwa, Admire; Nakstad, Britt; Wright, Caradee Yael; Harden, Lois; Roos, Nathalie; Luchters, Stanley; Part, Cherie; Areal, Ashtyn; Haghighi, Marjan Mosalam; Manyuchi, Albert; Boeckmann, Melanie; Pham, Minh Duc; Hetem, Robyn; Durusu, Dilara
BACKGROUND : Climate change, particularly global warming, is amongst the greatest threats to human health. While short-term effects of heat exposure in pregnancy, such as preterm birth, are well documented, long-term effects have received less attention. This review aims to systematically assess evidence on the long-term impacts on the foetus of heat exposure in utero. METHODS : A search was conducted in August 2019 and updated in April 2023 in MEDLINE(PubMed). We included studies on the relationship of environmental heat exposure during pregnancy and any long-term outcomes. Risk of bias was assessed using tools developed by the Joanna-Briggs Institute, and the evidence was appraised using the GRADE approach. Synthesis without Meta-Analysis (SWiM) guidelines were used. RESULTS : Eighteen thousand six hundred twenty one records were screened, with 29 studies included across six outcome groups. Studies were mostly conducted in high-income countries (n = 16/25), in cooler climates. All studies were observational, with 17 cohort, 5 case-control and 8 cross-sectional studies. The timeline of the data is from 1913 to 2019, and individuals ranged in age from neonates to adults, and the elderly. Increasing heat exposure during pregnancy was associated with decreased earnings and lower educational attainment (n = 4/6), as well as worsened cardiovascular (n = 3/6), respiratory (n = 3/3), psychiatric (n = 7/12) and anthropometric (n = 2/2) outcomes, possibly culminating in increased overall mortality (n = 2/3). The effect on female infants was greater than on males in 8 of 9 studies differentiating by sex. The quality of evidence was low in respiratory and longevity outcome groups to very low in all others. CONCLUSIONS : Increasing heat exposure was associated with a multitude of detrimental outcomes across diverse body systems. The biological pathways involved are yet to be elucidated, but could include epigenetic and developmental perturbations, through interactions with the placenta and inflammation. This highlights the need for further research into the long-term effects of heat exposure, biological pathways, and possible adaptation strategies in studies, particularly in neglected regions. Heat exposure in-utero has the potential to compound existing health and social inequalities. Poor study design of the included studies constrains the conclusions of this review, with heterogenous exposure measures and outcomes rendering comparisons across contexts/studies difficult. TRIAL REGISTRATION : PROSPERO CRD 42019140136.
Attributing impacts of LULCC on the boundary layer climate of South Africa’s eastern escarpment
(Springer, 2024-09) Mohomi, Tumelo; Mbatha, Nkanyiso B.; Boshoff, Danie S.; Mbokodo, Innocent L.; Ndarana, Thando; Bopape, Mary-Jane M.; Chikoore, Hector
Land surface characteristics may influence the planetary boundary layer atmosphere and climate through exchanges of moisture, energy, and momentum near the surface. We attributed the impact of multitemporal landsat-derived land use/land cover change (LULCC) on temperature and precipitation variability in eastern South Africa using reanalysis data and satellite-derived estimates from 1979 to 2020. Landsat images were classified into different land cover classes using a machine learning random forest pixel-based supervised algorithm within the cloud-based Google Earth Engine. Time series analysis was employed to analyze cycles and trends in LULCC and hydrometeorological variables, whilst the variable importance model determined the most sensitive variable. The impacts of LULCC on the boundary layer climate were attributed via multiple linear regression. An uninterrupted rapid expansion of urban areas was observed, resulting in the transformation of grasslands, water bodies, forests, and croplands. Statistically significant changes in moisture and energy fluxes, and hydrometeorological variables were observed across the study period. Latent heat flux (LHF), as well as rainfall decreased, while maximum temperature, sensible heat, and potential evapotranspiration (PET) increased significantly. We found that LULCC is significantly impacting the boundary layer climate, with urban and bare land, grasslands, forests, and croplands influencing temperature positively while negatively influencing rainfall. Rainfall was most sensitive to changes in LHF, whilst the key driver of temperature variability was PET. Our results reinforce the significance of LULCC and associated feedbacks to understanding boundary layer processes, climate variability, and change.
The health impacts of air pollution in the context of changing climate in Africa : a narrative review with recommendations for action
(Ubiquity Press, 2024-12-05) Atuyambe, Lynn; Arku, Raphael E.; Naidoo, Natasha; Kapwata, Thandi; Asante, Kwaku Poku; Cissé, Guéladio; Wright, Caradee Yael; Berhane, Kiros
INTRODUCTION : Despite the broad improvement in air quality, air pollution remains a major leading global risk factor for ill health and deaths each year. Air pollution has a significant impact on both health and economic growth in Africa. This paper reviews the health impacts of air pollution and the benefits of air pollution mitigation and prevention on climate change. METHODS : We conducted a narrative review and synthesized current literature on the health impact of air pollution in the context of changing climate in Africa. RESULTS : Particulate matter (PM2.5) concentrations in Africa pose significant health risks due to various sources, including household fuels and industrial emissions. Limited air quality monitoring hampers accurate assessment and public health planning. Africa’s rapid urbanization exacerbates air pollution, impacting vulnerable populations disproportionately. Renewable energy adoption and improved monitoring infrastructure are crucial for mitigating air pollution’s economic and health impacts. Recommendations include adopting air quality standards, identifying pollution sources, and prioritizing interventions for vulnerable groups. Integrating renewable energy into development plans is essential for sustainable growth. African leaders must prioritize environmental policies to safeguard public health amid ongoing industrialization. CONCLUSIONS : Air pollution prevention remains a vital concern that requires leaders to engage stakeholders, and other opinion leaders in society. African leaders should proactively explore new avenues to integrate non-polluting renewable energy sources such as solar power, wind and hydropower into their national development plans.
Assessment of the inland wetland ecosystem types in South Africa : threats and protection
(Taylor and Francis, 2025) Van Deventer, Heidi; Nel, Jeanne L.
Ecosystem threat status (ETS) and ecosystem protection levels (EPLs) are headline indicators that can assess freshwater ecosystems at a country-wide scale. A spatial layer of freshwater, inland wetland ecosystem types of South Africa was combined with a range of spatial data sets to model their ecological condition. The ETS and EPL of each ecosystem type were determined using the area of that type in good ecological condition relative to a biodiversity target, which represented 20% of the total area of that ecosystem type. Thresholds were applied to distinguish four ETS categories ranging from Least Concern to Critically Endangered, and four EPL categories ranging from Not Protected to Well Protected. A total of 79% of the 135 of South African inland wetland ecosystem types were found to be threatened, of which 83 (62% of the number of types) are Critically Endangered, 12 (9%) are Endangered, 12 (9%) are Vulnerable and 28 (21%) of Least Concern. Of the 135 inland wetland types, 61% were Not Protected, with 6% being Well Protected, 3% Moderately Protected, and 30% Poorly Protected. Protected and Ramsar sites hosted only 7% of the total area of inland wetlands, which means that the Aichi Biodiversity Target 11 for 2020 (17%) was not met.
Conserving cross-realm coastal biodiversity when real-world planning and implementation processes split the land and sea
(Elsevier, 2025-04) Harris, Linda R.; Van Niekerk, Lara; Holness, Stephen D.; Sink, Kerry J.; Skowno, Andrew L.; Dayaram, Anisha; Van Deventer, Heidi; Job, Nancy; Lamberth, Stephen J.; Adams, Janine B.; Raw, Jacqueline L.; Riddin, Tarn; Mackay, C. Fiona; Perschke, Myriam J.
Conservation planning and implementation are typically applied in land and sea areas separately, placing already impacted coastal biodiversity – which spans the divide – at risk of being inadequately managed and conserved. In South Africa, we tested how well existing land-based and marine biodiversity priority areas cover coastal priorities that we identified cross-realm using Marxan with >1000 biodiversity features. Existing priorities covered 83% of coastal priorities, indicating good but incomplete coverage. Proportionately, the seashore (foredunes, shores) and estuaries had greatest selection as coastal priorities, confirming their important biodiversity value. Finally, we developed a map of Critical Biodiversity Areas for the South African seashore and estuaries, with management recommendations. To include coastal biodiversity in real-world planning, we propose: co-developing data and targets for cross-realm features; identifying broad coastal priorities that can be used in land-based and marine plans; and developing dedicated seashore and estuary priorities to seamlessly align land-based and marine prioritisation maps.
Namib desert dust affects phytoplankton biomass in the Benguela upwelling region : insights from first mesocosm study
(Elsevier, 2025-02) Belelie, Monray D.; Burger, Roelof P.; Von Holdt, Johanna R.C.; Garland, Rebecca M.; Liswaniso, Gadaffi M.; Thomalla, Sandy J.; Piketh, Stuart J.
Please read abstract in the article.
Exploring the use of data in a digital twin for the marine and coastal environment
(MDPI, 2025-03) Haupt, Shelley; Sibolla, Bolelang H.; Molapo, Raymond; Mdakane, Lizwe; Fourie, Nicolene
The ocean plays a vital role in our society and represents a constantly changing landscape that is not well understood and therefore needs continuous monitoring and research. Sustainable monitoring is essential to assess both the current and future state of our oceans. However, conventional monitoring faces significant challenges, including issues of accessibility, and spatial and temporal constraints. The development of digital twins of the ocean (DTO) offers an emerging technology that could revolutionise our understanding of marine and coastal environments. Current DTO have shown effectiveness in monitoring marine and coastal environments in the European context. However, there is a need for a DTO for the Southern African and Western Indian Ocean regions that addresses specific concerns that are relevant to these regions. Successful development of a DTO depends on the availability of high-quality data. Therefore, various data inputs are necessary to build an accurate digital twin. This paper explores the data that can be utilised in a DTO, detailing how different ocean variables are collected and integrated into the digital twin. As a first step towards the development of a DTO in these regions, the paper proposes a data management plan and its implementation in the development of DTO. The data management plan is based on the phases of data in a geospatial data life cycle. Challenges regarding the management of data in this DTO and possible solutions are presented in the conclusion.
Assessing the economic viability of sustainable pasture and rangeland management practices : a review
(MDPI, 2025-04) Rapiya, Monde; Mndela, Mthunzi;; Truter, Wayne; Ramoelo, Abel
The livestock sector is crucial for global food security and economic development, particularly in developing nations, as it supports the livelihoods of approximately 1.3 billion people. However, with the global population expected to reach 9.2 billion by 2050, the sector must address increasing demand for livestock products while ensuring environmental sustainability. This study used the available literature to evaluate the economic viability of sustainable pasture and rangeland management practices to enhance livestock production. The key findings demonstrate that strategies such as rotational grazing and nitrogen fertilization can decrease winter feed costs by up to 40% while simultaneously improving pasture productivity and animal weight gains. Initial investments in these improved forage practices offer high internal rates of return, indicating their profitability. To guide sustainable pasture production and rangeland management, we propose a conceptual framework that balances cultivated pastures and natural rangelands. This framework assesses critical factors, including input costs, expected outputs (enhanced biodiversity and livestock production), and interventions to mitigate land degradation. For successful adoption of these practices, targeted policies are essential. Governments should develop financial support mechanisms for smallholder farmers, improve transportation infrastructure for efficient feed logistics, and provide technical assistance to educate producers on sustainable practices. Engaging stakeholders to align policies with local needs is also vital. By implementing these strategic interventions, the resilience of livestock systems can be strengthened, contributing to long-term sustainability and supporting food security and rural community well-being.
A power-cardioid candidate for wind direction modelling motivated by two South African case studies
(Springer, 2025-04) Van Wyk-de Ridder, Delene; Rad, Najmeh Nakhaei; Arashi, Mohammad; Ferreira, Johan; Bekker, Andriette, 1958-; johan.ferreira@up.ac.za
Wind energy claims a positive image globally; therefore, accurate modelling of wind direction at generation sites accurately can enhance the potential of this green energy source. The uncertain nature of wind direction can be modelled through probability distributions; in this paper, we propose a flexible yet simple distribution, namely the Power-Cardioid distribution, as an alternative and implementable candidate to model wind direction. After discussing some characteristics, the performance of the Power-Cardioid distribution is evaluated via a simulation study and applied to datasets of two wind farms in South Africa. The numerical results demonstrate that this distribution is a promising and exciting new candidate compared to well-known models within circular statistics.
Cross-realm biodiversity profile of the South African coastal zone
(Taylor and Francis, 2025) Harris, L.R.; Adams, J.B.; Dayaram, A.; Dunga, L.V.; Job, N.; Kirkman, S.P.; Lamberth, S.J.; Pfaff, M.C.; Raw, J.L.; Rishworth, G.M.; Robbins, A.; Sink, K.J.; Skowno, A.L.; Van Deventer, Heidi; Van Niekerk, L.
South Africa’s coast is 3 113 km long and includes microtidal shores that experience semi-diurnal tides and mostly high wave energy. From west to east, the cool Benguela Current and the warm Agulhas Current drive steep gradients in climate and environmental conditions, resulting in diverse coastal ecosystem types. Here, we review the biodiversity of South Africa’s coastal zone, focusing on the constituent ecosystem types from the terrestrial, freshwater, estuarine and marine realms, and provide a brief overview of cross-realm biodiversity patterns. We also give guidance on coastal boundaries to improve standardisation in this complex area to support assessment, planning and management. The ecologically determined coastal zone currently comprises 193 ecosystem types: 83 vegetation types (e.g. seashore vegetation, strandveld, duneveld, coastal forest); 22 estuary and 3 micro-estuary ecosystem types; and 85 marine ecosystem types (e.g. shores, islands, reefs, kelp forests, bays), with planned inclusion of freshwater types (e.g. coastal lakes, forested wetlands, dune slacks) in the future. Species richness is generally highest along the south and east coasts, with the highest levels of endemism mostly reported for the south coast. The South African coast is a national asset that warrants careful management for long-term sustainability to safeguard its unique biodiversity and many associated benefits for current and future generations.
Advancing action on the UN sustainable development goals
(Public Library of Science, 2024-01-04) Archer, Emma Rosa Mary; Males, Jamie
The UN Sustainable Development Goals (SDGs) are a set of objectives that were agreed by the global community in 2015 as a “shared blueprint for peace and prosperity for people and the planet, now and into the future” [1]. Climate action is directly embodied in one of the seventeen goals (SDG 13), in recognition of the extreme risks to humanity posed by the impacts of climate change. However, as highlighted in a recent report by the World Meteorological Organization [2], the intensifying effects of climate change are rapidly undermining progress on almost all the SDGs. These interactions look set to become even more important as it appears increasingly likely that we will exceed 1.5 C of warming.
Influences of climate variability on land use and land cover change in rural South Africa
(MDPI, 2024-04) Mogonong, Buster Percy; Twine, Wayne; Feig, Gregor Timothy; Van der Merwe, Helga; Fisher, J.T. (Jolene)
Changes in land use and land cover over space and time are an indication of biophysical, socio-economic, and political dynamics. In rural communities, land-based livelihood strategies such as agriculture are crucial for sustaining livelihoods in terms of food provision and as a source of local employment and income. In recent years, African studies have documented an overall decline in the extent of small-scale crop farming, with many crop fields left abandoned. This study uses rural areas in three former apartheid homelands in South Africa as a case study to quantify patterns and trends in the overall land cover change and small-scale agricultural lands related to changes in climate over a 38-year period. Random forest classification was applied on the Landsat imagery to detect land use and land cover change, achieving an overall accuracy of above 80%. Rainfall and temperature anomalies, as well as the Standardized Precipitation Evapotranspiration Index (SPEI) were used as climate proxies to assess the influence of climate variability on crop farming, as the systems investigated rely completely on rainfall. Agricultural land declined from 107.5 km2 to 49.5 km2 in Umhlabuyalingana; 54 km2 to 1.6 km2 in Joe Morolong; and 254.6 km2 to 7.4 km2 in Mangaung between 1984 and 2022. Declines in cropland cover, precipitation, and the SPEI were highly correlated. We argue that climatic variability influences crop farming activities; however, this could be one factor in a suite of drivers that interact together to influence the cropping practices in rural areas.
Evaluation of selected Sentinel-2 remotely sensed vegetation indices and MODIS GPP in representing productivity in semi-arid South African ecosystems
(Wiley, 2024-04) Maluleke, Amukelani; Feig, Gregor Timothy; Brummer, Christian; Rybchak, Oksana; Midgley, Guy
The ability to validate satellite observations with ground‐based data sets is vital for the spatiotemporal assessment of productivity trends in semi‐arid ecosystems. Modeling ecosystem scale parameters such as gross primary production (GPP) with the combination of satellite and ground‐based data however requires a comprehensive understanding of the associated drivers of how the carbon balance of these ecosystems is impacted under climate change. We used GPP estimates from the partitioning of net ecosystem measurements (net ecosystem exchange) from three Eddy Covariance (EC) flux tower sites and applied linear regressions to evaluate the ability of Sentinel‐2 vegetation indices (VIs) retrieved from Google Earth Engine to estimate GPP in semi‐arid ecosystems. The Sentinel‐2 normalized difference vegetation index (NDVI), enhanced vegetation index (EVI) and the land surface water index (LSWI) were each assessed separately, and also in combination with selected meteorological variables (incoming radiation, soil water content, air temperature, vapor pressure deficit) using a bi‐directional stepwise linear regression to test whether this can improve GPP estimates. The performance of the MOD17AH2 8‐day GPP was also tested across the sites. NDVI, EVI and LSWI were able to track the phase and amplitude patterns of EC estimated gross primary production (GPPEC) across all sites, albeit with phase delays observed especially at the Benfontein Savanna site (Ben_Sav). In all cases, the VI estimates improved with the addition of meteorological variables except for LSWI at Middleburg Karoo (Mid_Kar). The least improvement in R2 was observed in all EVI‐based estimates —indicating the suitability of EVI as a single VI to estimate GPP. Our results suggest that while productivity assessments using a single VI may be more favorable, the inclusion of meteorological variables can be applied to improve single VIs estimates to accurately detect and characterize changes in GPP. In addition, we found that standard MODIS products better represent the phase than amplitude of productivity in semi‐arid ecosystems, explaining between 68% and 83% of GPP variability.
The impact of rolling blackouts on environmental health in South Africa
(EHP Publishing, 2024-12-10) Wright, Caradee Yael; Mathee, Angela; Kapwata, Thandi; Laban, Tracey; Mahlangeni, Nomfundo; Shezi, Busisiwe; Nkambule, Sizwe; Webster, Candice; Naidoo, Natasha; Street, Renee
BACKGROUND : Rolling blackouts (planned power outages) are common in low- and middle-income countries, including South Africa. Recently, South Africa has experienced longer and more frequent rolling blackouts owing to its reliance on an aging electricity grid, among other challenges. During rolling blackouts, parts of the electricity grid are shut down, and the loss of power in homes, businesses, and industries across vast areas leads to a breakdown of key amenities required for environmental health. OBJECTIVES : This commentary contextualizes the existing consequences and potential implications of rolling blackouts for environmental health in South Africa. DISCUSSION : We examined key areas where rolling blackouts affect environmental health, including water and sanitation, air quality, food safety, and socioeconomic challenges. Power outages have led to contamination of freshwater bodies with raw sewage due to resultant interruptions of wastewater treatment works. The use of generators and burning of dirty fuels during blackouts have added to outdoor and household air pollution. Rolling blackouts also expose people to unsafe food. Finally, we discuss some ways forward and the benefits of using renewable energy sources. A critical evaluation of these impacts underscores the urgent need for more sustainable energy solutions that safeguard environmental health in South Africa.
Leveraging historic streamflow and weather data with deep learning for enhanced streamflow predictions
(IWA Publishing, 2024-04-01) Schutte, Christiaan E.; Van der Laan, Michael; Van der Merwe, Barend Jacobus
Streamflow information is crucial for effectively managing water resources. The declining number of active gauging stations in many rivers is a global concern, necessitating the need for reliable streamflow estimates. Deep learning techniques offer potential solutions, but their application in southern Africa remains largely underexplored. To fill this gap, this study evaluated the predictive performance of gated recurrent unit (GRU) and long short-term memory (LSTM) networks using two headwater catchments of the Steelpoort River, South Africa, as case studies. The model inputs included rainfall, maximum, and minimum temperature, as well as past streamflow, which was utilized in an autoregressive sense. The inclusion of streamflow in this way allowed for the incorporation of simulated streamflow values into the look-back window for predicting the streamflow of the testing set. Two modifications were required to the GRU and LSTM architectures to ensure physically consistent predictions, including a change in the activation function of the GRU/LSTM cells in the final hidden layer, and a non-negative constraint that was used in the dense layer. Models trained using commercial weather station data produced reliable streamflow estimates, while moderately accurate predictions were obtained using freely available gridded weather data.

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