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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Human health risk assessment of PM2.5, NO2, and SO2 and its impact on mortality in Nkangala and Gert Sibande, South Africa
(Ubiquity Press, 2025-08) Millar, Danielle Ann; Kapwata, Thandi; Howard, Marcus A.; Oosthuizen, Rietha; Naidoo, Natasha; Wright, Caradee Yael
Please read abstract in the article.
Monitoring coastal estuarine habitats for biodiversity along the temperate bioregion of South Africa
(Wiley, 2025-10) Campbell, Anthony; Adam, Elhadi; Adams, Janine B.; Barrenblitt, Abigail; Fatoyinbo, Temilola; Jensen, Daniel; Naidoo, Laven; Riddin, Taryn; Simard, Marc; Smith, Kyle; Thakali, Pati; Van Deventer, Heidi; Van Niekerk, Lara; Stovall, Atticus
Coastal wetlands provide critical ecosystem services, including the enhancement of biodiversity, carbon sequestration, and flood protection. Although these ecosystems have been mapped for country-level biodiversity typing, improved extent mapping is necessary to account for estuarine dynamics and improved reporting to the Kunming-Montreal Global Biodiversity Framework (GBF) by 2030. We achieved an overall coastal wetland accuracy of 90.7% (95% confidence interval: 90.2%–91.4%) utilizing a dense time series of very high spatial resolution (3 m) PlanetScope satellite imagery to map coastal wetlands with a combination of Random Forest to develop training data, U-Net convolutional neural networks, and a final decision tree to determine discrete ecosystem extents. Across the 84 mapped estuaries totaling 67,452 ha and 2,135 images, we mapped 9,131.1 ± 1,596.9 ha (13.5% of total estuarine functional zone extent) of salt marsh & reed beds and 1,718.6 ± 234.3 ha (2.5%) of Submerged Aquatic Vegetation (SAV). In addition to our earth observation analysis, we calculated tidal amplitudes and water level trends for 20 water level gauges across the region. We found tidal amplitude was a significant driver of salt marsh extent, explaining 33.6% of the variation (F (1,19) = 9.62, p = 0.005). We demonstrate a repeatable methodology for improved mapping of ecosystem zonation and utilize water level data to explore potential drivers of ecosystem distribution. Our method could be incorporated into a robust earth observation approach for reporting progress toward the goals of the/reporting to the GBF and Sustainable Development Goals (SDGs). PLAIN LANGUAGE SUMMARY Coastal wetlands provide many benefits to humans, including as habitat for a variety of species, accumulation of carbon in their soils, and protection from flooding and storm events. Global and regional maps of these ecosystems exist, but they lack precision in their identification of ecosystem zones. Improved maps could be used for improved reporting to international agreements and inform coastal management. We mapped three coastal wetland habitats to a high degree of accuracy (90.7%) utilizing a time series of commercial satellite data and machine learning algorithms. Across the 84 mapped estuaries totaling 67,452 ha, we mapped 9131.1 ± 1596.9 ha (13.5% of total estuarine functional zone extent) of salt marsh & reed beds and 1718.6 ± 234.3 ha (2.5%) of Submerged Aquatic Vegetation (SAV). We conducted additional analysis on how tidal amplitude, water level, and impervious surface influence the distribution of habitats in the region, finding that higher tidal amplitudes correlated with more salt marsh extent. Our methodology is repeatable and could improve the monitoring of these ecosystems in South Africa. KEY POINTS • We mapped coastal wetland habitats (salt marsh, reeds and sedges, and submerged aquatic vegetation) with a U-Net approach at >90% accuracy • We identified tidal amplitude as a major driver of salt marsh habitat, explaining 33.6% of the variation (F (1,19) = 9.62, p = 0.005). • Salt marsh was only 19.4% of coastal wetland extent, 40% of this extent was found within Knysna Estuary and Langebaan Lagoon.
Globale biodiversiteitsraamwerk vir varswatervleilande van Suid-Afrika : voorlopige berekening van die vordering om die restourasiemikpunt van doelwit 2 te bereik
(Suid-Afrikaanse Akademie vir Wetenskap en Kuns, 2025-07) Van Deventer, Heidi
AFRIKAANS : Die Nasionale Biodiversiteitsanalise van 2018 het bevind dat vleilande (riviermondings en varswatervleilande) die mees bedreigde van al die ekostelsels in Suid-Afrika is. Teen 2030 moet Suid-Afrika aan die Verenigde Nasies se Globale Biodiversiteitsraamwerk (GBR) rapporteer of Doelwit 2 bereik is, naamlik om 30% van gedegradeerde stelsels in die proses van herstel te hê. Hierdie studie het beoog om die voorlopige omvang as persentasie van varswatervleilande wat aan ekologiese ingrypings onderworpe was in verhouding tot die totale omvang van gedegradeerde varswatervleilande in Suid-Afrika te bereken. Ons het ook die persentasieomvang in verhouding tot eienaarskap van die gedegradeerde varswatervleilande en dié wat onder ekologiese restourasie is, bepaal. Die Werk vir Vleilandeprogram en die Werk vir Waterprogram se beskikbare data is ingesamel en met die Nasionale Vleilandkaart weergawe 6, gekombineer om die persentasies te bereken. Die meerderheid van Suid-Afrika se varswatervleilande (51%) is gemodelleer om degradasie te bepaal, met >2.0 miljoen hektaar van die 4 miljoen hektaar Suid-Afrikaanse vleilande wat impakte toon ten opsigte van veranderinge aan die hidrologiese siklus, waterkwaliteitsimpakte, fragmentasie en verlies van habitatte, voorkoms van indringerspesies en klimaatverandering, of ‘n kombinasie van hierdie impakte. Die 30% van Doelwit 2 beteken dus dat amper 613 136 ha van varswatervleilande teen 2030 onder ekologiese herstel moet wees. Ekologiese herstelprogramme het tot dusver slegs ongeveer 203 283 ha (10%) van Doelwit 2 bereik. Die meerderheid (82,8%) van vleilande is op privaat grond geleë, waarvan meer as die helfte gedegradeer is. Baie van die impakte op vleilande, asook die restourasieinisiatiewe wat deur die privaat sektor of individue uitgevoer word, word nie in hierdie berekening weerspieël nie. Monitering en kwantifisering van alle varswaterhabitatte is dus noodsaaklik om Doelwit 2 van die GBR teen 2030 te bereik. ENGLISH : The National Biodiversity Assessment of 2018 listed wetlands (estuaries and freshwater ecosystems) as the most threatened ecosystem of South Africa. By 2030, South Africa must report to the United Nations’ Global Biodiversity Framework (GBF) to which degree we have reached Target 2 that aims to have 30% of the extent of degraded ecosystems under restoration. This study aimed to calculate the preliminary extent as a percentage of wetlands that have been under ecological restoration interventions, relative to the total extent of degraded freshwater wetlands of South Africa. We also assessed the percentage of extent relative to ownership of the degraded wetlands and those that are under ecological restoration. Data released by the Working for Wetlands and Working for Water programmes were combined with the National Wetland Map version 6 as well as information on land ownership and protection level status of the country. The majority of the freshwater wetlands (51%) were modelled as degraded, with > 2 million ha of the 4 million ha of wetlands showed impacts resulting from various pressures, including changes to the hydrological cycle, water quality, fragmentation and degradation of habitats, climate change, or a combination of these pressures. The 30% GBF Target 2 requires that almost 613 136 ha of freshwater wetlands should be under restoration by 2030. The government’s two restoration programmes have reached only 203 283 ha (10%) of the desired target. The majority (82,8%) of freshwater wetlands is located on private land, of which the majority is degraded. Many of the impacts and none of the restoration interventions undertaken by the private sector or individuals are reflected. Monitoring and quantification of all freshwater habitats are therefore needed to attain the 30% extent target of the GBF.
Remote sensing monitoring of soil moisture for South African wetlands
(Water Research Commission, 2025-04) Van Deventer, Heidi; Naidoo, Laven; Le Roux, Jason; Blaauw, Ciara; Tema, Hebert
Surface soil moisture is an essential climate variable (ECV; https://gcos.wmo.int/en/essential-climate-variables/soilmoisture) which is monitored to inform our understanding of changes in the atmosphere and earth. Soil moisture is also an important indicator, in addition to vegetation and soil types, of the presence of a wetland.
African political ecologies
(Annual Reviews, 2025-10) Ramutsindela, Maano F.; Mba, Chika C.; Mushonga, Tafadzwa; Aremu, Adeyemi Oladapo; Mutune, Jane Mutheu; Matose, Frank; Dzingirai, Vupenyu; Muthama Muasya, A.; Dorvlo, Selorm Y.; Odhiambo, E.G.
This review locates African political ecologies at the intersection of the broader fields of political ecology and African studies. It focuses on African ecological thought and practices in relation to environmental challenges in Africa. Methodologically, it eschews the sectoral approach to the study of African environments by drawing together three interrelated themes of African epistemologies, African agency, and socioecological debt. It treats these themes as the bedrock of African political ecologies that are crucial for engaging and resolving socioecological challenges on the continent and for governing the African commons. These foundational themes offer avenues for appreciating African epistemologies, experiences, and actions as well as the possibilities for context-specific environmental justice within the broader frame of reparation. The review concludes by delineating the scope and agenda for the African political ecologies crucial for broadening political ecological research and African studies.
Soft computing for the posterior of a matrix t graphical network
(Elsevier, 2025-05) Pillay, Jason; Bekker, Andriette, 1958-; Ferreira, Johannes Theodorus; Arashi, Mohammad; andriette.bekker@up.ac.za
Modeling noisy data in a network context remains an unavoidable obstacle; fortunately, random matrix theory may comprehensively describe network environments. Noisy data necessitates the probabilistic characterization of these networks using matrix variate models. Denoising network data using a Bayesian approach is not common in surveyed literature. Therefore, this paper adopts the Bayesian viewpoint and introduces a new version of the matrix variate t graphical network. This model's prior beliefs rely on the matrix variate gamma distribution to handle the noise process flexibly; from a statistical learning viewpoint, such a theoretical consideration benefits the comprehension of structures and processes that cause network-based noise in data as part of machine learning and offers real-world interpretation. A proposed Gibbs algorithm is provided for computing and approximating the resulting posterior probability distribution of interest to assess the considered model's network centrality measures. Experiments with synthetic and real-world stock price data are performed to validate the proposed algorithm's capabilities and show that this model has wider flexibility than the model proposed by [13]. HIGHLIGHTS • Expanding the framework for denoising financial data inside the realm of graphical network theory, where the assumption of normality in the model is inadequate to account for the variation. • Introduction of the matrix variate gamma and inverse matrix variate gamma as priors for the covariance matrices; the univariate scale parameter β may be fixed or subject to a prior. • Following Bayesian inference with more flexible priors, there is an improvement based on relevant accuracy measures. • Experimental results indicate that our proposed framework and results outperform those of [13].
The potential of Sentinel-1 for monitoring forage productivity in rangeland ecosystems : a review
(Elsevier, 2026-02) Rapiya, Monde; Ngcoliso, Nasiphi; Qabaqaba, Mcebisi; Truter, Wayne Frederick; Ramoelo, Abel; u16400829@tuks.co.za
Rangelands are vital ecosystems that support forage production essential for livestock and biodiversity conservation, yet they face increasing degradation driven by anthropogenic pressures and climate variability. Remote sensing technologies offer scalable and non-destructive means to monitor forage productivity, with optical sensors limited by cloud cover and dense vegetation saturation. Synthetic Aperture Radar (SAR), particularly from the Sentinel-1 constellation, provides all-weather, high-resolution data capable of capturing structural and moisture-related vegetation attributes. This review evaluates the potential of Sentinel-1 SAR data for assessing and monitoring forage productivity in rangeland ecosystems. It highlights recent applications demonstrating Sentinel-1's effectiveness in forage productivity estimation and its integration with optical sensors like Sentinel-2 to enhance monitoring accuracy. Despite its advantages, challenges such as spatial resolution constraints, ecological sensitivity, and complex data processing impede full operational deployment. Future directions emphasize advanced data fusion techniques, machine learning approaches, and enhanced preprocessing algorithms to optimize Sentinel-1's utility. Integrating SAR with optical datasets promises to facilitate scalable, cost-effective, and reliable rangeland management strategies, supporting sustainable forage utilization and ecosystem resilience. Therefore, governments, the private sector, and NGOs should invest in Earth Observation infrastructure and capacity-building to translate remote sensing into actionable policies that promote sustainable rangeland management, climate change adaptation, and food security. HIGHLIGHTS • Sentinel-1 SAR offers all-weather, high-resolution rangeland monitoring. • Combines with optical sensors to estimate vegetation structure and biomass. • Data fusion and advanced algorithms boost accuracy and usability. • Enables large-scale, cost-effective forage and ecosystem health assessments.
Temporal variations in the short-term effects of ambient air pollution on cardiovascular and respiratory mortality : a pooled analysis of 380 urban areas over a 22-year period
(Elsevier, 2024-09) Schwarz, Maximilian; Peters, Annette; Stafoggia, Massimo; De’Donato, Francesca; Sera, Francesco; Bell, Michelle L; Guo, Yuming; Honda, Yasushi; Huber, Veronika; Jaakkola, Jouni J.K.; Urban, Aleš; Vicedo-Cabrera, Ana Maria; Masselot, Pierre; Lavigne, Eric; Achilleos, Souzana; Kyselý, Jan; Samoli, Evangelia; Hashizume, Masahiro; Sheng Ng, Chris Fook; Das Neves Pereira da Silva, Susana; Madureira, Joana; Garland, Rebecca M.; Tobias, Aurelio; Armstrong, Ben; Schwartz, Joel; Gasparrini, Antonio; Schneider, Alexandra; Breitner, Susanne; Kan, Haidong; Osorio, Samuel; Orru, Hans; Indermitte, Ene; Maasikmets, Marek; Ryti, Niilo; Pascal, Mathilde; Katsouyanni, Klea; Analitis, Antonis; Entezari, Alireza; Mayvaneh, Fatemeh; Kim, Yoonhee; Alahmad, Barrak; Zanobetti, Antonella; Diaz, Magali Hurtado; Arellano, Eunice Elizabeth Félix; Rao, Shilpa; Palomares, Alfonso Diz-Lois; Scovronick, Noah; Acquaotta, Fiorella; Kim, Ho; Lee, Whanhee; Íñiguez, Carmen; Forsberg, Bertil; Ragettli, Martina S.; Guo, Yue Leon; Pan, Shih-Chun; Li, Shanshan
BACKGROUND : Ambient air pollution, including particulate matter (such as PM10 and PM2·5) and nitrogen dioxide (NO2), has been linked to increases in mortality. Whether populations’ vulnerability to these pollutants has changed over time is unclear, and studies on this topic do not include multicountry analysis. We evaluated whether changes in exposure to air pollutants were associated with changes in mortality effect estimates over time. METHODS : We extracted cause-specific mortality and air pollution data collected between 1995 and 2016 from the Multi-Country Multi-City (MCC) Collaborative Research Network database. We applied a two-stage approach to analyse the short-term effects of NO2, PM10, and PM2·5 on cause-specific mortality using city-specific time series regression analyses and multilevel random-effects meta-analysis. We assessed changes over time using a longitudinal meta-regression with time as a linear fixed term and explored potential sources of heterogeneity and two-pollutant models. FINDINGS : Over 21·6 million cardiovascular and 7·7 million respiratory deaths in 380 cities across 24 countries over the study period were included in the analysis. All three air pollutants showed decreasing concentrations over time. The pooled results suggested no significant temporal change in the effect estimates per unit exposure of PM10, PM2·5, or NO2 and mortality. However, the risk of cardiovascular mortality increased from 0·37% (95% CI –0·05 to 0·80) in 1998 to 0·85% (0·55 to 1·16) in 2012 with a 10 μg/m3 increase in PM2·5. Two-pollutant models generally showed similar results to single-pollutant models for PM fractions and indicated temporal differences for NO2. INTERPRETATION : Although air pollution levels decreased during the study period, the effect sizes per unit increase in air pollution concentration have not changed. This observation might be due to the composition, toxicity, and sources of air pollution, as well as other factors, such as socioeconomic determinants or changes in population distribution and susceptibility.
Simulation of the African ITCZ during austral summer seasons and ENSO phases : application of an RCM derived from stretched grid ESM
(Frontiers Media, 2025-07) Ramotubei, Teke Solomon; Landman, Willem Adolf; Mateyisi, Mohau J.; Nangombe, Shingirai S.; Beraki, Asmerom Fissehatsion
INTRODUCTION : Climate predictability across timescales in a changing climate presents a unique opportunity and challenges for state-of-the-art climate models. The use of regional climate models (RCMs) forced with interactively coupled Earth System Models (ESMs) for the sub-seasonal, seasonal, and decadal predictions is an actively growing research area. METHODS : The study explores a stretched-grid RCM constrained with an ESM which integrates a climate change signature. Spectral relaxation paradigm is applied to limit the climate drift within the range of the multi-model sea-surface temperature (SST) and sea-ice concentration (SIC) variability. The model retroactive ensemble simulations for November initialization are evaluated on the seasonal migration of the ITCZ during El-Niño and La-Niña phases, exploring both the spatial and zonal positions. The model is also evaluated on the ITCZ process’ characteristics that include the Hadley cell (HC), stream function and the subtropical jet stream (STJ) using quantitative methods. RESULTS : The RCM and the driving ESM demonstrate skillful performance in identifying the seasonal trajectory of both the spatial and zonal migration of the ITCZ during El-Niño and La-Niña. Moreover, the RCM also demonstrates a good skill in determining both the descending edge of the HC and the STJ with the highest mean percentage error of 16.3 and 7.5% for the HC and STJ latitudes, respectively. CONCLUSIONS : The November initialization of the RCM skillfully simulates the seasonal migration of the ITCZ (and related characteristics) aligned to the observations and reanalysis datasets. Notwithstanding, the RCM manifests a tendency of more dynamic error growth relative to its driving ESM as the lead time increases. Furthermore, the RCM is also out of phase with a southerly shift of the stream function compared to the 500 hPa reanalysis stream function. The modeling framework offers process oriented and teleconnection studies. It also provides great potential for climate applications with suitable bias corrections techniques, albeit the source and mechanism of its dynamic error growth deserve further investigation.
Multisystemic resilience and its impact on youth mental health : reflections on co-designing a multi-disciplinary, participatory study
(Frontiers Media, 2025-03) Theron, Linda C.; Bergamini, Matteo; Chambers, Cassey; Choi, Karmel; Fawole, Olufunmilayo I.; Fyneface, Fyneface Dumnamene; Höltge, Jan; Kapwata, Thandi; Levine, Diane T.; Mai Bornu, Zainab; Makape, Makananelo; Matross, Celeste; McGrath, Brian; Olaniyan, Olanrewaju; Stekel, Dov J.; Hey, Josh Vande; Wright, Caradee Yael; Zion, Ameh Abba; Ungar, Michael; linda.theron@up.ac.za
Youth depression is a global emergency. Redressing this emergency requires a sophisticated understanding of the multisystemic risks and biopsychosocial, economic, and environmental resources associated with young people's experiences of no/limited versus severe depression. Too often, however, personal risks and a focus on individual-level protective resources dominate accounts of young people's trajectories towards depression. Further, studies of depression in high-income countries (i.e., “western”) typically inform these accounts. This article corrects these oversights. It reports on the methodology of the Wellcome-funded R-NEET study: a multidisciplinary, multisystemic, mixed method longitudinal study of resilience among African youth whose status as “not in education, employment or training” (NEET) makes them disproportionately vulnerable to depression. Co-designed by academics, community-based service providers and youth in South Africa and Nigeria, with partnerships in the United Kingdom, Canada and the United States, the R-NEET study is identifying the physiological, psychological, social, economic, institutional, and environmental risks and resources associated with distinct trajectories of depression. Using the methodology of the R-NEET study as exemplar, this article advances an argument for understanding resilience as a contextually and culturally rooted capacity that draws on the multiple, co-occurring systems that young people depend upon to support their wellbeing. Acknowledging and harnessing the multiple systems implicated in resilience is critical to researchers and mental health providers who seek to support young people to thrive, and to young people themselves when protecting or promoting their mental wellbeing.
All-cause, cardiovascular, and respiratory mortality and wildfire-related ozone : a multicountry two-stage time series analysis
(Elsevier, 2024-07) Chen, Gongbo; Guo, Yuming; Yue, Xu; Xu, Rongbin; Yu, Wenhua; Ye, Tingting; Tong, Shilu; Gasparrini, Antonio; Bell, Michelle L.; Armstrong, Ben; Schwartz, Joel; Jaakkola, Jouni J.K.; Lavigne, Eric; Saldiva, Paulo Hilario Nascimento; Kan, Haidong; Royé, Dominic; Urban, Aleš; Vicedo-Cabrera, Ana Maria; Tobias, Aurelio; Forsberg, Bertil; Sera, Francesco; Lei, Yadong; Abramson, Michael J; Li, Shanshan; Abrutzky, Rosana; Coêlho, Micheline de Sousa Zanotti Stagliorio; Garcia, Samuel David Osorio; Correa, Patricia Matus; Ortega, Nicolás Valdés; Kyselý, Jan; Orru, Hans; Maasikmets, Marek; Ryti, Niilo R.I.; Pascal, Mathilde; Schneider, Alexandra; Breitner, Susanne; Katsouyanni, Klea; Samoli, Evangelia; Mayvaneh, Fatemeh; Entezari, Alireza; Goodman, Patrick; De’Donato, Francesca; Stafoggia, Massimo; Seposo, Xerxes; Hashizume, Masahiro; Honda, Yasushi; Hurtado-Díaz, Magali; Valencia, César De la Cruz; Overcenco, Ala; Ameling, Caroline; Houthuijs, Danny; Rao, Shilpa; Carrasco-Escobar, Gabriel; Madureira, Joana; Nunes, Baltazar; Holobaca, Iulian-Horia; Garland, Rebecca M.; Kim, Ho; Lee, Whanhee; Íñiguez, Carmen; Åström, Christofer; Ragettli, Martina S; Guo, Yue Leon; Pan, Shih-Chun; Zeka, Ariana; Alahmad, Barrak; Zanobetti, Antonella; Scovronick, Noah; Colistro, Valentina; Dang, Tran Ngoc; Dung, Do Van
BACKGROUND : Wildfire activity is an important source of tropospheric ozone (O3) pollution. However, no study to date has systematically examined the associations of wildfire-related O3 exposure with mortality globally. METHODS : We did a multi-country two-stage time series analysis. From the Multi-City Multi-Country (MCC) Collaborative Research Network, data on daily all-cause, cardiovascular, and respiratory deaths were obtained from 749 locations in 43 countries or areas, representing overlapping periods from Jan 1, 2000, to Dec 31, 2016. We estimated the daily concentration of wildfire-related O3 in study locations using a chemical transport model, and then calibrated and downscaled O3 estimates to a resolution of 0·25° × 0·25° (approximately 28 km² at the equator). Using a random-effects meta-analysis, we examined the associations of short-term wildfire-related O3 exposure (lag period of 0–2 days) with daily mortality, first at the location level and then pooled at the country, regional, and global levels. Annual excess mortality fraction in each location attributable to wildfire-related O3 was calculated with pooled effect estimates and used to obtain excess mortality fractions at country, regional, and global levels. FINDINGS : Between 2000 and 2016, the highest maximum daily wildfire-related O3 concentrations (≥30 μg/m³) were observed in locations in South America, central America, and southeastern Asia, and the country of South Africa. Across all locations, an increase of 1 μg/m³ in the mean daily concentration of wildfire-related O3 during lag 0–2 days was associated with increases of 0·55% (95% CI 0·29 to 0·80) in daily all-cause mortality, 0·44% (–0·10 to 0·99) in daily cardiovascular mortality, and 0·82% (0·18 to 1·47) in daily respiratory mortality. The associations of daily mortality rates with wildfire-related O3 exposure showed substantial geographical heterogeneity at the country and regional levels. Across all locations, estimated annual excess mortality fractions of 0·58% (95% CI 0·31 to 0·85; 31 606 deaths [95% CI 17 038 to 46 027]) for all-cause mortality, 0·41% (–0·10 to 0·91; 5249 [–1244 to 11 620]) for cardiovascular mortality, and 0·86% (0·18 to 1·51; 4657 [999 to 8206]) for respiratory mortality were attributable to short-term exposure to wildfire-related O3. INTERPRETATION : In this study, we observed an increase in all-cause and respiratory mortality associated with short-term wildfire-related O3 exposure. Effective risk and smoke management strategies should be implemented to protect the public from the impacts of wildfires.
Road-associated variation in insect abundance differs between three common orders
(Springer, 2025-04) Sempe, Nhlanhla Pheletso Suzan; Sole, Catherine L.; Haussmann, Natalie S.; natalie.haussmann@up.ac.za
The ecological impacts of roads are well-researched for many vertebrates, but studies are relatively lacking with regards to invertebrates. Here, changes in the abundance of ground-dwelling species of the three most common insect orders, Hymenoptera (specifically ants), Hemiptera (true bugs) and Coleoptera (beetles), with distance from a gravel road in a grassland system in South Africa, are documented. Insects were collected by means of pitfall traps (n = 164) installed at 2, 5, 10 and 20 m perpendicular to a gravel road, and abundances of these three orders were compared statistically between the four distances. Whereas no significant differences in the numbers of Hymenoptera and Coleoptera were observed with distance from road, the abundance of Hemiptera was greater closer to the road. Our results show that quieter, low-traffic roads can affect the distribution of insect species at finer spatial scales.
Rossby wave breaking morphologies on the Southern Hemisphere dynamical tropopause
(American Meteorological Society, 2025-09) Barnes, Michael A.; Reeder, Michael J.; Ndarana, Thando
Rossby waves are fundamental meteorological structures in the extratropics of both hemispheres. Several extremes and weather regimes have been linked to the amplification and breaking of Rossby waves propagating along the extratropical waveguide. The morphology and evolution of Rossby wave breaking (RWB) on the Southern Hemisphere dynamical tropopause is studied here through an objective classification algorithm. Although the well-known classifications of RWB morphologies (LC1, LC2, P1, and P2) work well, the objective algorithm identifies important distinctions between RWB events with higher and lower amplitude structures and more meridional and zonal orientations. The different morphologies reflect the differences in the structure of the Rossby wave packets, the degree of phase locking with the low levels, the strength of the diabatic processes, and the amplitude of the nonlinearities in the flow. Anticyclonic RWB morphologies are associated with the decay of a Rossby wave packet, often producing a cyclonic–anticyclonic potential vorticity (PV) dipole in its wake. The cyclonic PV cutoff in this PV debris field can be stirred back into the extratropical waveguide resulting in a cyclonically overturned PV contour. Unlike anticyclonic RWB morphologies, cyclonic RWB morphologies in the Southern Hemisphere upper troposphere are associated with Rossby wave packet generation and downstream development. SIGNIFICANCE STATEMENT : This work aims to determine how well the well-known and much-used two- and four-type classifications of Rossby wave breaking (RWB) represent the full range of morphologies and analyze the differences in their evolution. An objective clustering technique identifies important distinctions between high- and low-amplitude patterns and more meridional and zonal orientations that the two- (anticyclonic, cyclonic) and four- (P1, P2, LC1, and LC2) type classifications do not. Anticyclonic RWB leads to the decay of a Rossby wave packet, whereas cyclonic RWB generates another Rossby wave packet and downstream development. This fundamental difference in the evolution, together with differences in the physical processes shaping these morphologies, deepens our understanding of RWB in the Southern Hemisphere upper troposphere.
A new look at the dirichlet distribution : robustness, clustering, and both together
(Springer, 2025-03) Tomarchio, Salvatore D.; Punzo, Antonio; Ferreira, Johannes Theodorus; Bekker, Andriette, 1958-
Compositional data have peculiar characteristics that pose significant challenges to traditional statistical methods and models. Within this framework, we use a convenient mode parametrized Dirichlet distribution across multiple fields of statistics. In particular, we propose finite mixtures of unimodal Dirichlet (UD) distributions for model-based clustering and classification. Then, we introduce the contaminated UD (CUD) distribution, a heavy-tailed generalization of the UD distribution that allows for a more flexible tail behavior in the presence of atypical observations. Thirdly, we propose finite mixtures of CUD distributions to jointly account for the presence of clusters and atypical points in the data. Parameter estimation is carried out by directly maximizing the maximum likelihood or by using an expectation-maximization (EM) algorithm. Two analyses are conducted on simulated data to illustrate the effects of atypical observations on parameter estimation and data classification, and how our proposals address both aspects. Furthermore, two real datasets are investigated and the results obtained via our models are discussed.
Ambrosia (ragweed) pollen - a growing aeroallergen of concern in South Africa
(Elsevier, 2024-12) Gharbi, Dorra; Berman, Dilys; Neumann, Frank H.; Hill, Trevor; Sidla, Siyavuya; Cillers, Sarel S.; Staats, Jurgens; Esterhuizen, Nanike; Ajikah, Linus; Moseri, Moteng E.; Quick, Lynne J.; Hilmer, Erin; Van Aardt, Andri; John, Juanette; Garland, Rebecca M.; Finch, Jemma; Hoek, Werner; Bamford, Marion; Seedat, Riaz Y.; Manjra, Ahmed I.; Peter, Jonny
BACKGROUND : Ragweed is an invasive, highly allergenic weed predicted to expand its habitat with warming global temperatures. Several Ambrosia species have been identified in South Africa for well over a century; however, its presence remained undetected by allergists and aerobiologists until the development of an extensive aerospora monitoring system across South African urban areas since 2019. This paper presents the inventory of preliminary investigation of the Ambrosia airborne pollen and the taxonomic identification of ragweed species. METHODS : Burkard volumetric spore traps for collecting pollen samples are set up in 9 South African cities (Johannesburg, Cape Town, Pretoria, Kimberley, Durban, Potchefstroom, Ermelo, Bloemfontein, and Gqeberha). Light microscopic identification was combined with environmental DNA metabarcoding analysis to confirm the species level of airborne Ambrosia at selected monitoring stations. Ragweed sensitisation was examined in Cape Town between February 2019 and February 2024, using Allergy Xplorer (ALEX2) multicomponent allergen array. RESULTS : Ambrosia pollen was detected in 5 aerobiological monitoring stations over the sampling period (Durban, Kimberley, Pretoria, Potchefstroom, Johannesburg). Periods of 4 consistent pollination years were observed in Kimberley (min: 1; max: 16 p.g/m3) and Durban (min: 26; max: 66 p.g/m3). In Pretoria, ragweed pollen was detected for 2 years (2020–2021; 2022–2023) with average total annuals (5-17 p.g/m3). A peak flowering period between March and April was observed in Potchefstroom, and several ragweed pollen peaks were present between the end of December and the beginning of May in Durban. The highest number of Ambrosia pollen grains was recorded in Potchefstroom, with 308 grains, and a maximum peak of 47 p.g/m3. eDNA metabarcoding confirmed the presence of Ambrosia artemisiifolia and A.trifida species. The overall prevalence of Ambrosia-sensitisation amongst 673 tests (age range 7–72 years) was 8.2% (55/673), with no significant difference in sensitisation patterns between age groups. CONCLUSION : Our study confirms the need to monitor the spread of ragweed, and an increasing awareness of Ambrosia as an allergen of concern in Southern Africa. Extension of aerobiological networks and testing for Ambrosia sensitisation across urban and rural sites will be required.
Factors that affect the resilience of young adults to depression : a systematic review
(Elsevier, 2025-05) Theron, Linda C.; Stekel, Dov J.; Holtge, Jan; Fawole, Olufunmilayo, I.; Levine, Diane; Mai-Bornu, Zainab; Maksudi, Kassa; Olaniyan, Olanrewaju; Wright, Caradee Yael; Ungar, Michael; linda.theron@up.ac.za
Depression among young people (aged 18–29 years) transitioning to adulthood is becoming more widespread. Knowing which factors in which systems co-enable resilience to depression is crucial, but there is no comprehensive synthesis of the physiological, psychological, social, economic, institutional, cultural, and environmental system factors associated with no or minimal emerging adult depression, or combinations of these factors. We have therefore conducted a preregistered systematic review (Prospero, CRD42023440153). We searched eight databases for observational studies reporting factors associated with depression symptomology that is mild, minimal, or absent among emerging adults with exposure to risk factors for depression; independently screened titles, abstracts, and full texts; extracted data; and assessed study quality. From 1824 unique citations, we included 139 papers (N=17721; in study populations that are majority female, cisgender, and in North America) and conducted a multisystemic resilience-informed narrative synthesis and quantitative summary. Personal (eg, psychological resilience and positive cognition) or social factors (eg, social support and family support) were frequently linked to reduced depression symptomology, followed by combinations of these. Economic, institutional, cultural, and environmental factors, or combinations of factors from three or more systems, were rarely reported. Low-income and middle-income countries, in which most young people live, were under-represented, which suggests inadequate understanding of emerging adult resilience to depression. Future studies should include more diverse populations and redress the tendency to reduce resilience to depression to a psychological or limited social phenomenon.
Skin cancer prevention and sunscreens
(BMJ Publishing Group, 2025-07) Nicholson, Anna; Abbott, Rachel; Wright, Caradee Yael; Kamali, Perdy; Sinclair, Craig
A parent visits their general practitioner with their 1 year old child, who is due to receive several vaccinations. During the appointment, the parent asks whether it is OK to start using infant sunscreen formulations, as they have heard there is a risk that sunscreens can be unsafe for infants, and that they can cause skin reactions. You observe that the infant has fair skin. The parent notes their child has sensitive skin, which is easily irritated, and asks for your recommendation. WHAT YOU NEED TO KNOW • The global burden of disease from melanoma is high and increasing; it occurs predominantly as a result of exposure to ultraviolet (UV) radiation (from sunlight or sunbeds) most commonly in people with fair, sun sensitive skin. • The World Health Organization recommends sun protection measures when the UV index is forecast to reach 3 and above. • Regular use of sunscreen can prevent melanoma and squamous cell carcinoma; however, the effectiveness of sunscreen is dependent on the amount applied, coverage of exposed skin, and reapplication. • Opportunistic behavioural counselling from healthcare professionals can increase sun protection behaviours and is recommended for parents of young children, adolescents, and groups at high risk. • Tailor sun protection recommendations to individual risk factors, considering skin pigmentation, concurrent risk of vitamin D deficiency, immune system status, and UV radiation exposure.
Camera trap-based estimates reveal spatial variability in African clawless otter population densities and behaviour
(Cambridge University Press, 2025) Lewis, Candice B.; Majelantle, Tshepiso Lesedi; Haussmann, Natalie S.; Mcintyre, Trevor
Estimating the population size of shy and elusive species is challenging but necessary to inform appropriate conservation actions for threatened or declining species. Using camera-trap surveys conducted during 2017–2021, we estimated and compared African clawless otter Aonyx capensis population densities and activity times in six conserved areas in southern Africa. We used two different models to estimate densities: random encounter models and camera-trap distance sampling. Our results highlight a general pattern of higher estimated densities and narrower confidence intervals using random encounter models compared to camera-trap distance sampling. We found substantial variation in densities between study areas, with random encounter model estimates ranging between 0.9 and 4.2 otters/km2. Our camera-trap distance sampling estimates supported the relative density estimates obtained from random encounter models but were generally lower and more variable, ranging from 0.8 to 4.0 otters/km2. We found significant differences in otter activity patterns, with populations either being nocturnal, mostly nocturnal or cathemeral. As all study areas experience little human disturbance, our results suggest that there are large natural variations in otter densities and activity patterns between regions. When densities are converted to metrics that are comparable to previous studies, our estimates suggest that African clawless otter population numbers are generally lower than previously reported. This highlights a need for broader spatial coverage of otter population assessments and future studies to assess potential environmental drivers of spatial, and potentially temporal, variation in population numbers and activity patterns.
SCALE-up - a new framework to assess the effectiveness of climate change adaptation interventions for human health and health systems
(BioMed Central, 2025-07) Wright, Caradee Yael; Naidoo, Natasha; Anand, Nalini; Kapwata, Thandi; Webster, Candice
Climate change is a grave threat to human health and wellbeing. Adaptation is one mechanism (the other is mitigation) by which we can intervene to increase adaptive capacity and preparedness to protect people. Adaptation interventions (evidence-based adjustment of programs/practices that lead to improved response and resilience to climate change) are being conducted around the world. However, existing conceptual frameworks to assess the effectiveness of these interventions, especially with respect to improving health outcomes and systems are not readily applied in areas where these are needed. This is applicable to both interventions intended to improve health as well as those without a health-focus but which may have health co-benefits. To address this gap, we conducted a multi-vocal review comprised of a scoping review and key informant interviews, which informed the development of an initial assessment framework. We included 21 academic articles and 12 reports (from the grey literature) for data collation and synthesis. Of the 21 articles analyzed, only seven presented primary evidence of health improvement outcomes, such as reduction in neo-natal care unit admissions was partially attributed to moving the maternity ward to the cooler, lower floor of the hospital. From the 10 interviewees, we learnt that most existing tools to assess the effectiveness of adaptation are for country or regional (several countries sharing borders within a large section of a continent) scales (e.g., Notre Dame Global Adaptation Initiative Index) and none focused specifically on health / health co-benefits. From these learnings together with a guiding concept, we crafted the first iteration of an assessment framework, SCALE-up, comprising six steps that prompt a researcher to consider the effectiveness of their adaptation intervention at a project-scale, including from a health benefit perspective. We apply the framework in four scenarios: hot days-heat; floods; droughts; and vector-borne diseases, to illustrate how the framework may help guide the researcher to think about effectiveness from project proposal stage. The next steps are to implement and pilot the framework in the four proposed scenarios and refine the framework.
Sustainability of the linkages between water-energy-food resources based on structural equation modeling under changing climate : a case study of Narok County (Kenya) and Vhembe district municipality (South Africa)
(MDPI, 2024-11-07) Zwane, Nosipho Ntombani; Botai, Joel Ongego; Botai, Christina M.; Mabhaudhi, Tafadzwanashe
Due to the current and predicted increase in the global demand for water–energy–food (WEF) resources, as well as the inevitable linkages between the WEF sectors and sustainable development, the WEF nexus is rapidly being recognized as a method to effectively manage sustainable development. Many African countries still face challenges in terms of the demand for and accessibility of WEF resources. For this reason, a comparative study of two sites (Narok County and Vhembe District Municipality), which exhibit similar socio-economic, environmental, and technological circumstances, was undertaken. In the present study, we considered 218 questionnaire responses, which we analyzed using partial least squares structural equation modeling (SEM) based on the WEF nexus constructs. This study is anchored on the null hypothesis (H0), whereby no interdependencies exist between the state of the climate and WEF resources, as constrained by sustainable development options. The results show that the proposed hypothesis does not hold, but rather, an alternative hypothesis (Ha)—there exist linkages between climate change and WEF resources—holds. This is demonstrated by the descriptive statistics indicating p values < 0.05 for both the t-test and the Bartlett test. Furthermore, analysis from the multi-regression, particularly for the model where we combined the sites, showed p values < 0.05 and higher adjusted r-squared values, which denoted a better fit. The communities in both study sites agree that the regions have experienced a scarcity of WEF resources due to climate change. The results show that climate change is an intrinsic part of the developmental options for the sustainable livelihood of both study sites, which aligns with the 2030 UN agenda on sustainable development goals targets. Moreover, the sustainable management of natural resources that are people- and planet-centric is crucial to climate change adaptation and mitigation, social justice, equity, and inclusion. The SEM results showed with significant confidence that the water, energy, and food sectors are closely interconnected; however, their impact on climate and sustainability is significantly different. Food has a direct positive impact on climate and sustainability, while both water and energy have an indirect negative impact. Moreover, the climate construct indicated a significant direct link to sustainability for all the relationships explored. This is particularly true because, in most underdeveloped countries, sustainable development and societal wellbeing heavily rely on goods and services derived from natural resources and the environment. This study contributes to the nexus modeling research field by introducing SEM as an innovative methodology over a single equation modeling framework in analyzing variables that have complex interrelationships, facilitating advanced WEF nexus resource governance.

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