Research Articles (Earth Sciences)

Permanent URI for this collectionhttps://hdl.handle.net/10566/273

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A deep learning framework for monotonic and physics-compliant CO2 trapping index forecasting
(Elsevier Ltd, 2026) Afolayan, Blessing Ayotomiwa; Opuwari, Mimonitu; Amaechi, Paschal Ogechukwu
The permanence and security of geological CO2 storage, a critical climate change mitigation strategy, hinges on a thorough understanding of subsurface trapping mechanisms. Predicting trapping efficiency traditionally relies on computationally-intensive numerical simulations, especially for complex, heterogeneous reservoirs. While data-driven deep learning models offer accelerated computation, they often act as “black boxes” with poor interpretability and no inherent adherence to physical laws. To address this, we present a physics-incorporated Deep Operator Network (DeepONet) for predicting two key density-driven trapping indexes: the Residual Trapping Index (RTI) and Solubility Trapping Index (STI). Our architecture enforces physical realism by encoding the laws of mass conservation and temporal monotonicity directly into a composite loss function and through architecturally guaranteed constraints, supported by advanced regularisation techniques. The model was trained and tested on a comprehensive dataset of over 11,000 samples compiled from global studies. Results demonstrated high predictive precision, with mean absolute errors of 0.0042 (RTI) and 0.0022 (STI), and R2 scores of 0.994 and 0.982, respectively. Crucially, the model maintained a 0% violation rate of the fundamental physical constraint (RTI+STI≤1) and preserved the expected monotonic behaviour of trapping over time. The close clustering of predicted and actual values, along with residuals centred around zero, confirms the model's robustness, reliability, and strong generalisation capability for predicting CO2 trapping across diverse geological conditions.
Soil organic carbon, weed suppression and fruit yield in response to cover crop species and termination method in citrus orchard (eureka lemon)
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Silwana, Sibongiseni; Jovanovic, Nebo; Mulidzi, Azwimbavhi Reckson
Cover crops are increasingly used in citrus production systems to improve soil health, reduce weed pressure and enhance fruit yield and quality. While the benefits of integrating cover crops into orchard management have been widely reported in several countries, information on their use under South African citrus-growing conditions remains limited. Therefore, this study was undertaken to investigate the influence of different cover crop species on soil organic carbon, weed biomass and citrus fruit yield under two cover crop termination practices, namely slashing and non-slashing. The cover crop treatments consisted of vetch, medics, oats and an untreated control without cover crops. The experiment was established as a split-plot arrangement within a randomized complete block design with six replications. Cover crop species constituted the main plot factor, while termination method was assigned to sub-plots. Soil was sampled before planting cover crops and one year after planting cover crops. Cover crop and weed dry weight samples were collected during the termination stage and fruit weight measurements were taken at harvest. Legume cover crops significantly increased Soil Organic Carbon (SOC) in the 0–30 cm soil depth, with vetch recording the highest SOC (0.6–0.8%), representing an increase of approximately 0.14% compared with oats. No significant SOC differences were observed at the 30–60 cm depth. Weed biomass declined markedly over time, from more than 1.4 t ha−1 in 2021/22 to less than 0.6 t ha−1 in 2022/23. Oats provided the greatest weed suppression, reducing weed dry weight to approximately 0.10 t ha−1 in 2022/23, whereas the control treatment consistently recorded the highest weed biomass. Cover crop biomass was highest under oats in 2021/22 (1.50 t ha−1), while excessive rainfall in 2022/23 reduced biomass production across treatments. Termination methods did not significantly influence weed biomass or cover crop biomass. Citrus fruit yield was not significantly affected by either cover crop species or termination method during the short-term study period. The findings indicate that legume cover crops improve SOC, while oats are more effective for weed suppression in lemon orchards. However, longer-term studies are needed to determine whether these soil and weed management benefits translate into increased citrus productivity.
Seasonal and interannual surface water variability in the Okavango river basin using multi-satellite data and machine learning
(Academic Press, 2027) Sigopi, Maria; Moropane, Lebogang M; Dube, Timothy; Shoko, Cletah
Surface water resources in arid regions are increasingly vulnerable to climate variability and growing demand, which calls for accurate, timely, and spatially explicitly monitoring approaches. This study developed a machine learning-based framework for quantifying seasonal and interannual surface water dynamics through multi-sensor fusion approach by combining radar and optical data. Sentinel-1 synthetic aperture radar (SAR), Sentinel-2 multispectral imagery, and Landsat-8 surface reflectance data were processed within the Google Earth Engine (GEE) platform for the period 2015-2021. The study used Random Forest (RF) and Gradient Tree Boosting (GTB) classifier, achieving a remarkable overall classification accuracy from Sentinel-1/2 (OA = 99.34-99.92%; Kappa = 0.8862-0.9983) and Landsat-8 (OA = 99.33-99.76%; Kappa = 0.9859-0.9949). Moreover, positive correlations were observed among water indices, particularly Modified Normalized Difference Water Index (MNDWI) and Normalized Difference Water Index (NDWI), whereas SAR backscatter variables (VV_median and VH_median) indicated a positive correlation with vegetation indices such as Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI). Meanwhile, Shapley Additive Explanations (SHAP) revealed that the MNDWI, NDWI, and SAR backscatter metrics were the most influential predictors of surface water occurrence, followed by vegetation indices and lastly single bands (B2-B8). Seasonal analyses presented greater surface water variability in October and November compared to drier months of May to September. Interannual variability analysis was conducted, indicating maximum surface water extent in 2016 (28,869 km2), and minimum in 2019 (9743 km2). Meanwhile, descriptive analysis with hydroclimatic variables showed that variations in precipitation and evapotranspiration (ET) corresponded with observed spatiotemporal patterns of surface water extent except in 2017. Overall, the proposed framework offers a scalable approach for monitoring surface water variability in data-scarce arid regions, supporting water resource management, drought monitoring, and climate adaptation.
Using systems thinking causal loop modelling to analyze the water resources system in Rietspruit sub-basin, South Africa
(Springer Science and Business Media Deutschland GmbH, 2026) Banda, Vincent Dzulani; Kanyerere, Thokozani; Dzwairo, Rimuka Bloodless
A qualitative system dynamics modelling framework was applied in this study to analyze the main driving forces and their feedback interactions influencing water resources management in the Rietspruit sub-basin, South Africa. The dynamics of the water resource system were analyzed using the Vensim™ PLE modelling platform and its archetypes of causal loop diagram, reinforcing and balancing loops. The model visually displayed the causal links of different processes influencing the water resource system and their feedback loops. Special focus was to ascertain and analyze the reinforcing feedback loops within a typical urbanized watershed, with the aim of depicting constraints that could influence sustainable water resource management and adaptation thereof. The causal loop model synthesized that, based on evidence from scientific literature and policy documents, the main driving forces towards the water resource challenges in the study area are associated with rising temperature, degraded water infrastructure and institutional and socioeconomic processes. The study, through the presented conceptual model, offered leverage points and potential pathways for sustaining both water quantity and quality, including infrastructure investment, sustainable revenue generation, decentralized groundwater use and public awareness and participation. The analysis in this study provided a conceptual framework for understanding of interactions of elements within the different systems influencing water resources in the Rietspruit sub-basin. This could be key for ensuring effective and sustainable management of the resource in the context of changing climate and socioeconomic developments.
A theoretical approach to the remediation of saline streamflow conditions downstream of the Nwanedi catchment reservoir
(Nature Research, 2026) Gumbo, Anesu Dion; Kapangaziwiri, Evison; Mugari, Ephias
The Nwanedi River Catchment in Limpopo Province, South Africa, experiences seasonal salinity accumulation that constrains downstream water use and undermines agricultural productivity. This study develops a hydrology-based framework to define environmental flow requirements (EFRs) to mitigate salinity through flow-driven dilution and flushing. A desktop methodology integrating the Revised Desktop Reserve Model (RDRM), GIS-based catchment characterisation, stakeholder insights, and empirical water quality analysis was implemented. Results reveal a distinct downstream increase in salinity, with electrical conductivity (EC) reaching approximately 146.8 mS/m during the dry season. Modelled EFRs indicate that, under Environmental Management Class D, minimum low-flow allocations correspond to 18.7% and 21.0% of mean annual runoff for sub-catchments A80H and A80J, respectively. Monthly dry-season flow releases range between 0.35 and 1.05 Mm3, while maintaining an average residual volume of approximately 1 Mm3 to support agricultural demand. These environmental flows are derived from naturalised flow regimes and are assumed to re-establish the critical hydrological conditions necessary to dilute and mobilise saline baseflows. The findings, therefore, do not quantify direct reductions in salinity but demonstrate that maintaining these flow thresholds can recreate the hydraulic conditions required for salt flushing, particularly in downstream reaches where salinity accumulation is most pronounced. This study provides a preliminary, process-based foundation for developing adaptive water allocation protocols. It establishes a testable framework for future cause-and-effect analyses, in which controlled dam releases and systematic water-quality monitoring can be used to quantify the extent to which EFRs reduce salinity in semi-arid, data-scarce catchments.
A model for sustainable development of geoparks in Northeastern Nigeria and other underrepresented regions in Africa
(Springer Nature, 2026) Omosanya, Kamaldeen O. L.; Dada, Silas S.; Oha, Ifeanyi A.
Geoheritage-rich regions of Africa remain underrepresented in UNESCO Global Geopark planning despite their scientific, educational, and livelihood potential. To help address this gap, this study develops a reproducible geoheritage inventory and prioritization framework for Northeastern Nigeria. We present the first integrated, quantitative geoheritage inventory of 24 priority geosites in Northeastern Nigeria. Here, we combine (i) a 12-criterion numerical evaluation (1–5 scale) spanning scientific significance, educational and tourism potential, and conservation readiness, with (ii) SWOT analysis and (iii) the Abiotic–Biotic–Cultural (ABC) framework to capture governance and development constraints. Our ranking results identify four Tier-1, geopark-ready localities, which are Yankari Wikki Warm Springs, Mambilla Plateau, Kaltungo Horst, and the Lamurde geothermal system that jointly concentrate high geodiversity, interpretive value, and immediate conservation–tourism use. A further set of Tier-2 sites (e.g., Lake Chad, Biu Plateau/crater lakes, and the Gombe Inlier) show strong regional significance but require targeted upgrades in access, interpretation, and visitor management. Across the portfolio, the dominant limiting factors are weak geoheritage visibility, uneven protection status, and gaps in on-site interpretation, despite consistently high scientific value. We therefore propose a five-year phased geopark development roadmap anchored in policy alignment, community co-management, and inter-agency partnerships. Importantly, this study provides a transferable model for accelerating geopark planning in underrepresented regions of the Global South by translating geosite rankings into an actionable implementation pathway.
3D modeling and carbon dioxide storage capacity estimation of the non-hydrocarbon Santa reservoir, onshore Zululand Basin, South Africa
(Springer Nature, 2026) Valentin, Awa; Opuwari, Mimonitu; Titinchi, Salam
Carbon dioxide (CO2) storage in geologic formations is a highly effective and promising strategy for significantly reducing CO2 emissions into the atmosphere. This study focuses on assessing the volume of CO2 that can be stored in a non-hydrocarbon reservoir located in the onshore Zululand Basin, South Africa. We utilised well logs and seismic data employing geostatistical methods to develop three-dimensional(3D) models. The petrophysical modeling has demonstrated favourable reservoir properties, indicating adequate porosity and permeability essential for effective CO2 storage. By applying the compressibility method, we estimated the CO2 storage capacity of the reservoir. The reservoir is predominantly composed of sandstone, exhibiting a mean effective porosity of 20% and a permeability value of 100 to 1000 mD. Three distinct facies were identified within the reservoir: sandstone, siltstone, and shale. In the northwestern, central, and southern areas of the reservoir, porosity and permeability are lower due to the presence of shale and siltstone. Our analysis of the shale volume model demonstrates a strong dominance in sandstone, with water saturation values of 10% and 20%. This makes the reservoir an ideal candidate for CO2 storage, due to its favourable petrophysical characteristics. The static storage capacity assessment indicates that the reservoir can store up to 0.54 million tons (Mt) and 0.1 Mt of CO2. Sensitivity analyses revealed that as water saturation increases, storage capacity decreases and declines with an increase in storage capability.
Contrasting storage security in closed and open aquifers: numerical modeling of CO2 sequestration in the Bredasdorp Basin, South Africa
(Elsevier Ltd, 2026) Opuwari, Mimonitu; Afolayan, Blessing Ayotomiwa; Mackay, Eric
Geological carbon storage is a critical pathway for reducing anthropogenic carbon dioxide (CO2) emissions and achieving energy sustainability, particularly in fossil fuel-dependent nations like South Africa. This study presents a numerical simulation of CO2 storage in a saline aquifer within Bredasdorp Basin, offshore South Africa. Using a compositional reservoir simulator, we compared two end-member boundary scenarios, a closed aquifer (no fluid exchange) and an open aquifer (fully permeable lateral boundaries), under identical injection conditions (762,000 m3/day for 20 years, followed by 20 years of post-injection monitoring). Results reveal that boundary conditions fundamentally control storage performance. In the closed aquifer, rapid pressure buildup (a 115% increase to 56,100 kPa) restricted the CO2 plume to the wellbore vicinity, suppressed dissolution, and left 73.9% of the injected CO2 in a mobile supercritical state after 40 years, posing significant geomechanical and containment risks. In contrast, the open aquifer maintained near-hydrostatic pressure (24,900 kPa), enabling extensive lateral plume migration (2-3 times greater lateral extent) and enhancing dissolution; by 2070, only 57.9% of the injected CO2 remained mobile, with 35.7% dissolved in brine. The contrasting density anomalies (∼25 kg/m3 in the closed system versus ∼13 kg/m3 in the open system) imply divergent potentials for long-term convective mixing and mineral trapping. These findings demonstrate that open, hydraulically connected aquifers offer faster progression to secure storage but require larger monitoring footprints, while closed aquifers concentrate the plume but demand rigorous pressure management. This work provides a foundational framework for site-specific carbon storage assessments in South Africa's offshore basins.
Petrophysics‑based machine learning assessment of siliciclastic reservoir sediments for CO2 storage in the Bredasdorp Basin, Offshore, South Africa
(Springer Science and Business Media Deutschland GmbH, 2026) Olayinka Yinka Ayodeji; Opuwari Mimonitu; Eruteya Ovie Emmanuel
Carbon capture and storage (CCS) is a significant mitigation approach for decreasing carbon emissions, particularly in coal-dominated energy systems like South Africa, where coal combustion accounts for around 80% of national CO2 emissions. The availability of credible datasets for subsurface characterisation, on the other hand, poses a significant problem for geological carbon storage. In other words, even with suitable geology, a lack of high-quality, comprehensive, and accessible subsurface data significantly limits the chance of identifying and quantifying viable storage locations, as well as predicting the long-term behaviour of stored CO2. Therefore, this study aims to evaluate the CO2 storage potential of a depleted oil reservoir in the Bredasdorp Basin of South Africa. We used an integrated approach (petrophysics, machine learning, and petrography). This was achieved by adopting a robust methodological workflow that incorporated reports from thorough sedimentary petrography of thin-sectioned cored samples, coupled with wireline logs, which were subjected to petrophysical analysis using a combination of standard empirical relationships, six (6) different machine learning techniques, and core petrophysical analysis. As a result, the sandstones in the reservoir's cored intervals (sand AF) in both wells are compositionally and texturally quite similar and homogenous. The average volume of shale measured in the reservoir reveals that the sand is clean, with secondary porosity discovered in all of the porous sandstone samples following the breakdown of a precursor carbonate cement. When compared to empirical methodologies, the introduction of XG-Boost and Neural Network improved reservoir poroperm predictions, which were then calibrated using core data. As a result, the average porosity values of 15% and 16%, along with the reservoir permeability values of 193 mD and 160 mD, respectively, across the two wells indicate a good estimation of the CO2 storage potential, significantly enhancing the performance of formation evaluation. The average fluid (water) saturation of the reservoir across both wells yields good values suitable for CO2 injection, and the absence of reactive clays in the reservoir sheds light on sand AF's potential as a safe CO2 sink in South Africa's Bredasdorp Basin. The findings from this work have shown that it is critical for South Africa to tap into its geologic CO2 storage potential in hydrocarbon reservoirs, as it would be challenging to swiftly phase out fossil fuel energy sources in the near future and avoid an energy shortage crisis. Hence, the implementation of sustainable solutions is pertinent in order to mitigate climate change.
Integrated characterisation of groundwater-ecosystems-surface water interactions in the Tuli-Karoo transboundary aquifer
(Elsevier B.V., 2026) Majola , Kwazikwakhe; Xu, Yongxin; Kanyerere, Thokozani
groundwater-supported ecosystems’ incorporation in resource management. This phenomenon is underresearched in data-scarce southern Africa, especially in transboundary aquifer settings. To investigate this interrelationship, this study was initiated in the semi-arid South African portion of the Tuli-Karoo transboundary aquifer, shared with Botswana and Zimbabwe. Water Table Fluctuation (WTF) and Chloride Mass Balance (CMB) methods were employed for recharge; Environmental isotopes (δ 2H, δ18O, and 3H) analysis for recharge mechanism; and baseflow algorithms for groundwater contribution to baseflow. The estimated alluvial aquifer average recharge ranges from 17.3 to 43.9 mm/a (5 – 12.9% of MAP), while for the sandstone aquifer it ranges from 0.4 to 8.2 mm/a (0.12 – 2.5% of MAP). Local precipitation is the source of post-evaporation recharge. Isotope analysis indicated bi-directional groundwater-surface water interactions. Baseflow average is 3.4 m3/s with a low baseflow index of 7.6%. On average, groundwater contributes 0.39 m3/s and 0.22 m3/s during wet and dry periods, respectively. Additionally, groundwater levels were observed to be declining gradually, which could negatively impact groundwater component of baseflow, and riparian and wetland vegetation. It can be concluded that rainfall seasonal fluctuations control groundwater-ecosystems-surface water interactions. These aquifer-specific findings are crucial for comprehensive implementation of integrated water resource management that is inclusive of associated ecosystems and their protection.
Inter-annual flood mapping using a cloud computing platform and multi-source spatial data
(Taylor and Francis Ltd., 2026) Manyaka, Naledi; Gxokwe, Siyamthanda; Shoko, Cletah
Flooding is one of the devastating natural disasters globally, with developing areas vulnerable due to insufficient data availability. This study develops an inter-annual flood extent mapping framework using Google Earth Engine Platform and multi-source spatial datasets to assess flood patterns and evaluate land-use impacts over 2020–2024. Sentinel-1 SAR data were used for mapping flood extent through threshold-based change detection, while Sentinel-2 data with random forest algorithms enabled land use classification. Results indicate substantial inter-annual variations in flood extent, fluctuating between 30,823 ha (2024) and 488,070 ha (2021), showing strong correlation with regional rainfall patterns. Cropland areas experienced flooding of up to 39,363 ha in 2023, while built-up areas recorded approximately 80,711 ha of inundation in 2021. The derived rainfall thresholds provide foundations for early warning systems. This scalable methodology contributes to enhanced flood risk management and climate resilience, informing policy development for achieving sustainable development goals in flood-prone regions.
Mesoscale eddies in the Southern Ocean influence foraging trip behaviour of multiple penguin species
(Elsevier Ltd, 2026) Wilson, Joshua C.; Trathan, Philip N.; Venables, Hugh J.; Ainley, David G.; Auger, Matthis
Mesoscale eddies are rotating vortices of water that perturb the local physical, chemical, and biological environment. In the Southern Ocean, penguins inhabit regions characterised by intense eddy activity, which can offer foraging opportunities. To better understand relationships between penguins and eddies, we collated tracking data for five species (emperor, king, chinstrap, Adélie, and macaroni penguins), totalling 3189 individuals from 59 colonies. Data were subset by colony and breeding stage to create 74 case studies. We then fitted Hidden Markov Models to penguin tracks to identify Area-Restricted-Search (ARS) behaviour (a proxy for foraging) and used Generalised Additive Mixed Models to relate behaviour to the presence of eddies. In 28 case studies, penguins displayed a pronounced increase in ARS within specific parts of eddies. All five species exhibited an association between ARS and eddies in several case studies, though substantial regional differences in association strength were observed. In life history periods when penguins experienced central place constraints, ARS was more frequently associated with eddies. By studying five extensive case studies in greater detail, we found that eddies possibly influenced trip trajectories by aggregating prey at submesoscale filaments around their peripheries, by interacting with the distribution of sea ice, and potentially by transporting key prey species in their interiors. In these case studies, eddy maturity, amplitude, and intensity also differed between eddies collocated with ARS and the background eddy field. When eddy abundance varied, foraging trip durations also varied, though with opposing trends depending on the colony and breeding stage. Eddy activity is projected to increase in the Southern Ocean, which in isolation would have mixed impacts on penguins, though the negative impacts of broad-scale changes in prey availability and sea ice concentration are likely to outweigh any impacts of changing eddy fields.
A new macroflora from the Turonian–Coniacian Moreno Hill Formation, New Mexico, USA
(Elsevier Masson s.r.l., 2026) Cilliers, Charl D.; Contreras, Dori L.; Tucker, Ryan T.; Roychoudhury, Alakendra N.; Zanno, Lindsay E.
The Moreno Hill Formation of the Salt Lake Coal Field (New Mexico, USA) preserves terrigenous sediments deposited from ∼90.9 until after 88.6 Ma, a critical window of climatic recovery following the ∼94.5 Ma peak of the Cretaceous Thermal Maximum. Recent fieldwork uncovered new macrofloral assemblages: a lower member flora derived from a paralic delta plain, with carbonaceous, pedogenetically altered floodplain sediments indicating often waterlogged conditions, and an upper member flora uncovered from slightly drier, more distal floodplain sediments. We report 18 distinct foliar morphotypes from the study of 116 leaf specimens. Dicot angiosperms are the most diverse in both assemblages, including platanoids, Saliciphyllum, and Cinnamomoides. While only two dicot morphotypes are shared between the lower and upper assemblages, two conifers (Brachyphyllum and taxodiaceous Cupressaceae indet.) are found in both. The fossils at both sites were collected from overbank deposits and lack evidence for significant transport; thus, we infer that the floodplains adjacent to channels during this interval were occupied by a mixed angiosperm-conifer woodland ecosystem. Although the two assemblages are separated by ∼1.5 to 2 million years, they reflect similar floodplain woodlands on a changing landscape in which the Western Interior Seaway was regressing and the local conditions drying. Sedimentological, leaf physiognomic, and wood growth-ring data collectively support persistent warm, yet gradually more seasonal conditions after the thermal maximum. This first report of Moreno Hill Formation leaf macrofossils establishes a regional Turonian–Coniacian palaeobotanical baseline for future studies of vegetation and ecosystem change in the southern Western Interior.
Spectral assessment of nutrient limitation in the savanna landscape: selection of spectral indices towards Sentinel-2 upscaling
(Frontiers Media SA, 2026) Ngcoliso, Nasiphi; Gxokwe, Siyamthanda; Ramoelo, Abel; Tsele, Philemon; Qabaqaba, Mcebisi
Nutrient limitations can significantly impact the ecosystem services provided by the savanna biome, potentially leading to degradation and reduced grazing capacity if not detected in time. A key indicator of growth-limiting nutrients is the Nitrogen to Phosphorus (N:P) ratio. However, grass foliar phosphorus content has rarely been studied in African savannas, especially using remote sensing approaches. As a result, there is limited information on the spatial distribution of nutrient limitations in these ecosystems. This study aimed to develop a Sentinel-2-based machine learning regression model to predict and map the distribution of the N:P ratio in the northern region of Kruger National Park (KNP), South Africa, which is dominated by the savanna rangeland biome. Fieldwork was conducted between 15 March and 30 April 2008 to collect grass samples and spectral data using an Analytical Spectral Device (ASD). The hyperspectral field data were then resampled to match the multispectral configuration of Sentinel-2 imagery. A Random Forest Regression (RFR) technique was applied to the simulated Sentinel-2 datasets to develop predictive models of the N:P ratio. Model accuracy was evaluated using the Root Mean Square Error (RMSE) Relative Root Mean Square Error (RRMSE), Percent Bias (PBIAS), and the coefficient of determination (R2). The results showed that vegetation indices (VIs), particularly the Normalized Difference Red Edge (NDRE) derived from Sentinel-2 bands B8 and B5, was optimal for estimating N:P ratio. This index explained over 80% of the N:P variability, with the lowest PBIAS of 0.02%. The best-performing model was used to map nutrient limitations across the study area using Sentinel-2 imagery. The spatial analysis indicated consistent nitrogen limitation and co-limitation across the investigated regions, with no evidence of phosphorus limitation. The high-accuracy models demonstrate the effectiveness of Sentinel-2 imagery for estimating nutrient limitations in heterogeneous savanna landscapes. This study offers a cost-effective, scalable tool for decision-makers involved in the management, sustainability, and restoration of the savanna biome. Future research should consider incorporating textural and environmental variables to enhance model performance and understanding of nutrient dynamics.
GIS-based assessment of sika deer (cervus nippon) habitat suitability and human conflict risk using integrated analytical hierarchy process-multi-criteria decision analysis
(Elsevier B.V., 2026) Dube, Timothy; Pandit, Santa; Oki, Kazuo
This study employed geospatial techniques to determine habitat suitability for sika deer ( Cervus nippon ) and evaluated the risk of human-deer conflict (HDC) in the Hatase district of Taki Town, Japan. The assessment of deer habitat appropriateness and HDC risk involved a structured four-step approach: criterion selection, decision hierarchy development, expert ranking collection, and Analytical Hierarchy Process (AHP) for variable weight assignment. Habitat suitability was categorized into land factors (elevation, slope, land use, and agricultural land area) and environmental factors (proximity to rivers, total wetness index (TWI), land surface temperature (LST), normalized difference vegetation index (NDVI), and precipitation). The risk of HDC was assessed using proximity (distance to deer occurrence, forests, fences, roads, and croplands) and exposure metrics (habitat suitability, population density, and settlement density). Insights were derived from ten experts in diverse fields. The results revealed that environmental factors played a more significant role than land-based parameters in determining habitat suitability for the species. Among these, NDVI was the most influential factor, followed by precipitation and land use. The risk assessment identified habitat suitability as the primary driver of HDC potential, with settlement and population density as notable secondary contributors. In the risk matrix, the exposure metrics substantially outweighed the proximity metrics. Spatial analysis of habitat suitability revealed a heterogeneous distribution, with moderate suitability covering approximately 45 % of the study area. The HDC risk assessment further highlighted conflict hotspots in the northern and eastern regions, where optimal deer habitats overlap with human settlements. The integration of these analyses provides a robust spatial framework for targeted conservation planning and the development of conflict mitigation strategies. These findings enhance our understanding of sika deer ecology within human-modified landscapes and provide practical guidance for wildlife management, particularly in regions experiencing intensified human–wildlife interactions due to evolving socioecological conditions.
Multidisciplinary assessment of geoheritage and geotourism for economic development: a case study of Oyo State, Southwestern Nigeria
(Springer, 2026) Bankole, Ayomipo O.; Omosanya, Kamaldeen Olakunle L.; Mosuro, Ganiyu Omotola; Sheriff, Shadrach; Maigana, Maryam Sani; Bunyaminu, Isah; Oseni, Ridwan D.; Lawal, Temitope K.; Amosun, Aishat O.; Odugbesan, Joseph A.; Akinsipe, Aramide B.; Ajumobi, Olashile B.; Anthony, Oyindamola B.
Geoheritage resources in Nigeria remain underdocumented in ways that link their scientific significance with their cultural meanings and practical tourism potential. This study presents an integrated assessment of selected geosites in Oyo State, southwestern Nigeria, to evaluate their geoheritage significance and geotourism prospects within a sustainable regional development framework. The study combines geological field mapping, drone-assisted visual documentation, GIS-based terrain analysis, community-based interviews, numerical geosite evaluation, and application of the Geosite Assessment Model (GAM). Our geological observations reveal diverse lithological and structural features, including granitic terrains, pegmatitic intrusions, and migmatitic outcrops that contribute to the scientific value of the sites. Terrain analysis further highlights strong spatial contrasts across the study area, with rugged upland landscapes in the north and gentler lowlands in the south. Community interviews show that several geosites also function as cultural landscapes rooted in local memory, spirituality, and identity. The integrated assessment shows clear differences among sites in terms of scientific value, scenic appeal, accessibility, functional attributes, and tourism readiness. Ado Awaye Hill emerged as one of the strongest multifunctional geosites, while Asejire Dam showed relatively favorable supporting amenities. In contrast, several other sites are still constrained by weak infrastructure, limited accessibility, and insufficient tourism services. Overall, our results indicate that the geosites of Oyo State have substantial geoheritage and geotourism potential, but their contribution to regional development will depend on improved conservation planning, community participation, and targeted investment in visitor infrastructure. Importantly, our study provides a transferable framework for geoheritage assessment in data-scarce regions of sub-Saharan Africa.
Water level identification through the trade-off between the standards of drought defense and flood control for a reservoir in flood season
(Elsevier B.V., 2026) Niu, Zhilin; Liu, Dedi; Ren, Jinqiu; Zhang, Lisheng; Rao, Guanghui
Study Region: Songhuaba Reservoir, Yunnan Province, China Study Focus: As extreme droughts become increasingly frequent and widespread, the inherent conflict between drought defense and flood control presents a critical challenge for reservoir management, particularly during the flood season. To determine an optimal water level that balances the conflict for a reservoir in its flood season, a trade-off framework is developed to quantify drought defense and flood control standards and then the Technique for Order Preference by Similarity to Ideal Solution (i.e., TOPSIS) is applied to select the optimal water level. New hydrological insights for the region: Taking Songhuaba Reservoir in Yunnan, China, as a case study, the framework reveals a pronounced nonlinear trade-off relationship between drought defense and flood control standards. The flood control standard exhibits a steeper gradient when the drought defense standard is more stringent, indicating higher sensitivity under severe drought conditions. The optimal water level is identified as 1970.0 m, corresponding to a drought defense standard of 6.39% and a flood control standard of 0.87%, and indicates a compromise between the flood control and drought defense two objectives in the flood season. A weight analysis further reveals that the optimal water level adjusts stepwise with the varying criterion weights. The proposed framework for identifying an optimal water level can balance the conflicting drought defense and flood control and will help reservoir management in flood season.
Performance evaluation of solar-powered groundwater pumping systems in rural communities of greater Giyani municipality, Limpopo, South Africa
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Jovanovic, Nebojsa; Shika, Seemole S.; Mashabatu, Munashe
Large portions of rural population in South Africa lack access to basic water and sanitation. This advocates for urgent interventions in support of water supply. This study assessed the performance of solar-powered groundwater pumping systems established at nine pilot sites in rural areas of Greater Giyani Municipality (Limpopo, South Africa). Performance assessment indicators, namely weather, groundwater abstraction, power supply, water supply, water quality, number of beneficiaries and farm productivity, were monitored (2023–2024). Increased groundwater abstraction reduced groundwater levels by 0.4–11 m, depending on the monitored borehole. This was replenished by above-average rainfall in 2023 (≈650 mm). Power supply and pump discharge rates were stable with generally low fluctuations at recommended pumping rates (0.5–2.0 L s−1). Groundwater quality was generally fit to marginal for irrigation and drinking. High levels of NO3− and total organic carbon, especially in the proximity of villages, mandated the installation of mini water treatment plants for drinking water. The implementation of solar-powered groundwater pumping schemes was generally successful, with more than 5000 villagers benefiting directly from the interventions, whilst smallholder farms turned into commercial and financially viable enterprises. Long-term monitoring of bio-physical and socio-economic drivers is essential to ensure long-term sustainability of the solar-powered groundwater pumping systems.
Provenance of the late Ediacaran minas de Corrales formation, Nico Pérez terrane, Uruguay: paleogeographic implications
(Frontiers Media SA, 2026) Frei, Dirk; Abre, Paulina; Blanco, Gonzalo
The Nico Pérez Terrane, located in the eastern margin of the Río de la Plata Craton, played a critical role in the assembly of SW Gondwana. The Isla Cristalina de Rivera basement klippe represents the northernmost exposures of the Nico Pérez Terrane in Uruguay, where the metavolcanic-sedimentary Minas de Corrales Formation represents the only preserved Ediacaran supracrustal cover. The provenance analyses of this key succession have unraveled the crustal signature and ages of its sources, providing constraints on the paleogeography and tectonic evolution of the Arachania subduction-related orogeny that developed along the eastern margin of the Río de la Plata Craton. We compare it to other coeval extensional basins in a back-arc position regarding Arachania linked to the opening of the Brazilides Ocean. Detrital mineral quantification and whole-rock geochemistry of the Minas de Corrales Formation indicate that the bulk of the detritus was rapidly sourced from basement rocks, with a composition similar to average unrecycled upper continental crust, with influences of a less differentiated component. Nd isotopes further suggest a Mesoproterozoic mantle extraction age for the juvenile component of the metavolcanic sandstones. Detrital zircon patterns of all studied samples point to diverse source rock ages: one metasandstone displays a dominance (95%) of Siderian–Rhyacian ages, whereas the other shows a concentration of Tonian to Cryogenian ages (89%); the metavolcanic sandstones yield main populations of Rhyacian, Calymmian, and Ectasian ages. All provenance indicators suggest that the Ediacaran Mina de Corrales Formation was fed from Paleoproterozoic and Neoproterozoic basement sources that likely comprised the rift-shoulders and nearby areas; these sources are traced to the Taquarembó, Tijucas, São Gabriel, and Nico Pérez Terranes. The Minas de Corrales Formation was deposited in an extensional basin emplaced on the eastern margin of the Río de la Plata Craton that developed during the opening of the Brazilides Ocean.
Columnanidus calitzdorpensis ichnogen. ichnosp. nov: a new middle pleistocene subterranean termite trace fossil from South Africa
(John Wiley and Sons Ltd, 2026) Abrahams, Miengah; Muir, Robert A; Genise, Jorge F; Almond, John E; Hadebe, Gcinamahlubi; Hellstrom, John C; Jacobs, Rabia; Harris, Chris
Termites are landscape geo-engineers whose nesting activities substantially modify the physical and chemical properties of soils. Fossilised termite nests commonly constitute the only identifiable evidence of ancient termite activity and represent valuable trace fossil archives for reconstructing past environments. Here, we describe a new ichnogenus and ichnospecies, Columnanidus calitzdorpensis ichnogen. ichnosp. nov., from Quaternary alluvial deposits near Calitzdorp, South Africa. The subterranean nests are subcylindrical structures, reaching ~1 m in height and ~65 cm in diameter, and are characterised by a ~12 cm wide, shelved nest wall surrounding an empty central cavity. Within the nest wall, the gallery and chamber morphology and abundance vary between the inner and outer zones. The nests are preserved as calcretised features, composed of inter-laminations of clastic sediment and pedogenic carbonate precipitate. U-series dating of the carbonate laminations yields robust age peaks at 401 ± 46 ka and 323 ± 12 ka, indicating a Middle Pleistocene minimum age for nest formation. These ages coincide with intervals favourable for pedogenic carbonate development under semi-arid to arid climatic conditions. Hardpan calcretes capping the nests suggest prolonged periods of semi-arid conditions and sustained pedogenic stability during the Middle Pleistocene in the Calitzdorp region.

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