Research Articles (Earth Sciences)

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

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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.
1D basin modelling of upper jurassic to upper cretaceous source rocks in the Southern Pletmos Sub-Basin, Outeniqua Basin, offshore South Africa
(John Wiley and Sons Inc, 2026) Agbor, Fritz Ako; Mhlambi, Sanelisiwe; Donker, Jan van Bever
The Pletmos sub-basin in the Outeniqua Basin, offshore South Africa, is divided by the Superior, Pletmos and Plettenberg faults into northern and southern depocentres. In this study, geological and organic geochemical data together with 1D basin modelling were used to investigate the burial, thermal and maturation histories, and the timing of hydrocarbon generation and expulsion of clay-rich source rocks in the southern depocentre. The modelled source rocks were of Kimmeridgian, Valanginian, Hauterivian, Aptian and Turonian ages. Source rock burial histories at the Ga-A4, Ga-E1, Ga-E2, Ga-H1, Ga-Q1 and Ga-Q2 wells in the Ga-A gas field were reconstructed with subsequent modelling of source rock thermal and maturation histories. The models were calibrated using vitrinite reflectance data from six offshore wells and constrained by palaeotemperature, heat flow and kinetic parameters. The modelling results indicate three principal phases of hydrocarbon generation (132–89, 89–45 and 45 Ma to present day), with a critical moment occurring at approximately 23 Ma during the Oligocene. The deepest syn-rift Kimmeridgian and Valanginian source rocks reached late-mature to over-mature conditions and are interpreted as the principal contributors to hydrocarbon charge in the basin. These results indicate that the petroleum system in the southern Pletmos sub-basin is predominantly gas-prone to gas-dominant, reflecting the advanced maturity of the deeper syn-rift source intervals and highlighting the continued exploration potential of deeply buried petroleum systems in the Outeniqua Basin
Occupational health and safety hazards associated with informal solid waste scavenging at Richmond sanitary landfill, Bulawayo, Zimbabwe
(Springer International Publishing, 2026) Musasa, Tatenda; Muringaniza, Kudakwashe C. R.; Simakani, Ashley
Solid waste scavenging has historically been a challenge in most developing countries. This study assesses occupational health and safety (OHS) hazards associated with informal solid waste scavenging at Richmond Sanitary Landfill (RSL) in Bulawayo city, Zimbabwe. The case study research design was used combining qualitative and quantitative methods. Data was collected from secondary sources as well as primary sources using questionnaires, interviews, and observations. The participants were sampled using snowball and purposive sampling methods. A total of 90 questionnaires were administered to representatives of selected households involved in scavenging at RSL from which inferences were made. The data was analysed using the Statistical Package for Social Sciences (SPSS). Occupational health and safety hazards at RSL were dominated by ergonomics hazards emanating from manual lifting and awkward postures (86%), dust (79%), leachate ponds (50%), noise (58%), sharp objects (43%), chemical contaminated waste (21%) and pathogen infested waste (17%) all of which have potential to cause injuries and illnesses. OHS hazards were identified as a risk factor and a Chi square test of the association between occupational hazards and injuries encountered (p = 0.00) was done. The Municipality of Bulawayo did not have a documented number of scavengers working at their landfill, or an OSH program. To address OHS issues, there is need for the Municipality to adopt an OSH policy. Training of scavengers and waste pickers is recommended to make them competent in identifying health and safety hazards, effective use of personal protective clothing and enabling them to uphold best safety and health practices.
Spatiotemporal analysis and future projections of co and o3 concentrations in Gauteng province using sentinel-5p and cmip6 models
(Elsevier B.V., 2026) Maphanga, Thabang; Muneri, Aluwani Innocent; Madonsela, Benett Siyabonga
This study is among the first to integrate high-resolution Sentinel-5P TROPOMI observations, ground-based SAAQIS measurements, and CMIP6 climate model outputs to generate long-term air quality projections for Gauteng Province. Gauteng, South Africa's economic hub, continues to experience severe air quality pressures driven by rapid urbanization, industrial emissions, and traffic density. However, long-term, multi-source projections for key pollutants such as carbon monoxide (CO) and ozone (O3) remain limited for the region. The objectives of this research were to: (1) characterize the spatiotemporal distribution of CO and O3 across Gauteng during the 2019–2020 baseline period using Sentinel-5P data (2) evaluate and validate CMIP6 climate model outputs against both satellite observations and SAAQIS ground-based measurements and (3) develop deterministic decadal projections for CO and O3 for the year 2030 under the SSP2-4.5 scenario. Model validation showed that CMIP6 outputs systematically underestimated pollutant levels, with consistently negative mean bias errors for CO (≈−101 ppb) and O3 (≈−18 ppb). Despite these biases, spatial correlations with observed concentrations were moderate to strong (r > 0.6). Under the SSP2-4.5 pathway, projections indicate a substantial decrease and increase in pollutants by 2030, with CO showing an increase (+4 to +7) on the other ha nd O3 showing the most pronounced decline (−7 to −95), likely driven by reductions in precursor emissions and associated chemical feedback. Spatial patterns suggest that existing pollution hotspots will shift eastward, away from the Johannesburg–Pretoria urban core. Overall, the findings demonstrate the value of an integrated satellite-ground-modelling approach for regional air quality assessment. While the magnitude of projected changes should be interpreted with caution due to model resolution and inherent uncertainties, the study provides critical evidence to support future policy development and long-term air quality management in Gauteng Province
Fault seal analysis for geological carbon dioxide storage in the pletmos basin, offshore South Africa
(Taylor & Francis Group, 2025) Amponsah-Dacosta Maxwell; Opuwari Mimonitu; Titinchi Salam
Sedimentary basins are considered to be potential carbon sinks and could provide a significant solution to decarbonising the global economy. In the highly faulted Pletmos Basin located offshore South Africa, there is potential for CO2 storage that draws attention to analysing the behaviour of faults as seals or pathways for CO2 migration. Faults were examined based on 3D seismic imagery using shale volume (Vshale) logs from well data. We employed well juxtaposition analysis using triangle-type diagrams and Shale Gouge Ratio (SGR) algorithms to predict their sealing potential. The sealing classification was based on results from SGR calculations. SGR between 0 and 0.2 represented “not sealing,” 0.2–0.4 represented “moderately sealing” and 0.5–1.0 represented “highly sealing.” From the seal classification, faults F-2, F-3, F-7 and the Superior Fault were moderately sealing faults, and fault F-11’s SGR (0.5) with limited sand-sand juxtapositions was classified as highly sealing. The SGR for the respective faults exceeded the 0.2 threshold, indicating their potential to act as seals for CO2 migration. The findings are expected to provide valuable knowledge that could enhance the overall understanding of the feasibility of geological CO2 storage in South Africa.
Tracing Groundwater Recharge Sources and Controls on Groundwater Quality in a Delineated Aquifer to Support Groundwater Allocation, De Aar, Northern Cape, South Africa
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Baloyi, Lucky; Mqhayi, Sikelela; Kanyerere, Thokozani
Groundwater-dependent communities such as De Aar require a better understanding of groundwater systems to ensure sustainable allocation. This study aims to trace recharge sources in unconfined and confined aquifers and identify processes controlling groundwater quality using hydrogeochemistry and environmental tracers. It argues that aquifer delineation and hydraulic parameters alone cannot fully identify recharge sources or geochemical processes; integrating them with hydrogeochemistry and environmental tracers provides stronger evidence to support groundwater allocation. To validate the argument, the study integrated hydrogeochemical analysis, stable isotopes, tritium, radon-222, and statistical methods supported by depth-specific groundwater sampling. The results, interpreted using Piper and Gibbs diagrams, PHREEQC modelling, and scatter plots, show that groundwater evolution is mainly controlled by rock–water interaction, ion exchange, evaporation, and mixing processes. Ca–HCO3 water indicates recent recharge, while Na–Cl water reflects evaporation effects in both unconfined and confined aquifers, with halite dissolution contributing to Na and Cl enrichment. Isotope results indicate that unconfined aquifer water is isotopically enriched and linked to recent recharge, whereas confined aquifer and spring waters are depleted, suggesting recharge from higher elevations through fractured zones. Tritium dating reveals young (<30 years), intermediate (30–50 years), and old groundwater (60–109 years), while radon results indicate active groundwater flow path, particularly along fractures. These findings demonstrate that groundwater recharge is derived from both local meteoric sources and regional contributions, resulting in predominantly fresh groundwater; however, localized quality concerns should be considered for improved water allocation.
Assessing water resources service value through simulation of a water supply–hydropower generation–ecosystem photosynthesis nexus system
(Elsevier B.V., 2026) Liu, Dedi; Yue, Feng; Liang, Hanxu
Water resources generate service values through water supply (S), hydropower generation (H), and ecosystem photosynthesis (E), forming a SHE nexus system that supports sustainable water resource management under the impacts of both climate change and human activities. However, these service values are often assessed in isolation, overlooking the complex interactions within the SHE nexus system and hindering the water resource management. To address this issue, we have coupled an ecohydrological model, reservoir operation rules, and a value assessment model to simulate the intricate dynamic and quantify the service values within the SHE nexus. The couple model is applied to the Han River Basin (HRB), which serves as the critical source region for the Middle Route of the South-to-North Water Diversion Project (MRSNWDP) in China. The results reveal significant trade-offs among these service values: water supply is the most prominent in low-elevation croplands, hydropower dominates high-elevation grasslands, and ecosystem photosynthesis peaks in mid-elevation forests. The synchronous variations in these service values are primarily driven by climate factors (∼ 60%) in the upper HRB, whereas hydrological processes dominate in the middle and lower reaches. Increased precipitation promotes hydropower generation and photosynthesis capacity. Reservoir operations improve water resource service values via increased streamflow; however, the MRSNWDP suppresses these gains wet seasons by reducing available flow for power and ecosystems. Therefore, our proposed model quantifies water resource service values to support integrated land–water management and water diversion operations.
Analysis of synthetic oviabsorption associated with galaxy groups in simba and tng50 simulations
(American Astronomical Society, 2026) Singh, Tanmay; Borthakur, Sanchayeeta; Nelson, Dylan; Dav́e, Romeel; McCabe, Tyler J.
We compare O vi absorption in synthetic spectra from galaxy groups in the SIMBA and TNG50 cosmological hydrodynamic simulations against those observed from the Cosmic Origins Spectrograph (COS)-IGrM survey. We select 14 galaxy groups from each simulation with (Formula presented) 12.89≤log(Mhalo/M⊙)≤13.61, closely matching COS-IGrM, and create 90,000 synthetic spectra per group. We demonstrate the utility of synthetic absorption spectroscopy when comparing simulations with QSO absorption-based observations. We investigate absorber properties such as radial distributions and kinematics with respect to the group and nearest galaxy. The O vi covering fractions (fOVI) in TNG50 (20.62% ± 2.56%) and SIMBA (5.98% ± 0.82%) are both systematically lower than COS-IGrM (44% ± 5%). A kinematic analysis reveals that the vast majority (∼95%) of absorbers in both of the simulations are gravitationally bound. In TNG50, strong absorbers ( (Formula presented) logNOV I>15 ) are located near star-forming galaxies ( (Formula presented) logsSFR>−11 ) within ∼200 kpc, suggesting a physical connection to stellar feedback, whereas SIMBA shows no comparable trend. Furthermore, in TNG50, the occurrence of O vi absorbers at small impact parameters increases with the stellar mass of the nearest galaxy, but shows no dependence on the total stellar mass of the group. In contrast, SIMBA shows no clear correlation with the nearest galaxy’s stellar mass, although groups with higher total stellar mass exhibit a higher detection rate at larger impact parameters. Differences observed in simulations may arise from feedback models and resolution effects. Finally, we show absorber analysis methodology is an important factor when comparing simulations with absorption spectroscopy observations.
Spectral assessment of senescent sourveld and sweetveld grass quality using continuum-removed absorption features from EnMAP spaceborne imaging spectrometer
(Elsevier B.V, 2026) Masenyama, Anita; Mutanga, Onisimo; Dube, Timothy; Sibanda, Mbulisi
Sourveld and sweetveld grasses exhibit interesting nutritional quality dynamics at the senescent stage, which have not been investigated from a remote sensing perspective. This study presents the first spatially explicit method(s) for estimating biochemical constituents of senescent grass across sour and sweet veld types using the spaceborne Hyperspectral Imager (HSI) on board the Environmental Mapping and Analysis Programme (EnMAP). Specifically, this study assessed the effectiveness of applying continuum removal to absorption features in data acquired from the EnMAP HSI. We also identified the key wavelengths relevant for senescent grass quality estimation in the different velds. Grass quality was quantified using three foliar biochemical indicators: nitrogen (N), acid detergent fibre (ADF) and acid detergent lignin (ADL). Data analysis was conducted using the random forest (RF) model and five broad continuum-removed absorption features which have been found to relate to foliar biochemicals in dry vegetation spectra. The study first evaluated the performance of four metrics derived from continuum-removed spectra, namely the continuum-removed derivative reflectance (CRDR), band depth (BD), band depth ratios (BDR) and the normalized band depth index (NBDI). The CRDR combined with RF regression was then used to identify key wavelengths from the absorption features for predicting senescent grass canopy N, ADF, and ADL across both veld types. Using the testing datasets, the selected wavebands yielded strong predictive performance for senescent sourveld, with R2 values of 0.72, 0.71, and 0.69, RMSEs of 0.08, 6.96, and 3.68, and RMSE% (of mean) of 13.77, 12.64, and 16.38 for N, ADF, and ADL, respectively. Statistical agreement was highest in sweetveld grasses, yielding R2 values of 0.73, 0.78, 0.82, corresponding RMSEs of 0.13, 5.82, and 2.01 while the RMSE% (of mean) were 10.95, 11.81 and 11.26 for N, ADF, and ADL, respectively. Overall, the R550.69 – 741.83 absorption feature had the highest number of optimal wavelengths in estimating canopy N across both velds. Moreso, optimal wavebands for estimating fibre concentration of senescent grass were derived more from the SWIR with the R2224.58 – 2376.95 absorption feature, yielding higher estimation accuracies. CRDR exhibited promising results, as it identified wavelengths causally linked to N, ADF and ADL in senescent vegetation. This work underscores the potential of spaceborne hyperspectral data with continuum removal on known absorption features for regional estimation of senescent grass quality.
The analysis ready multispectral data and machine learning algorithms for mapping groundwater-dependent invasive alien plants in Heuningnes Catchment, South Africa
(Taylor and Francis Ltd., 2026) Moropane, Mmasechaba L.; Dube, Timothy; Shoko, Cletah; Masocha, Mhosisi
Field monitoring of groundwater-dependent invasive alien plants (GDIAPs), though accurate, is spatially limited and prone to misclassification bias. Satellite imagery and machine learning algorithms (MLAs) offer scalable alternatives, yet their effectiveness in mapping GDIAPs remains underexplored. This study assessed Sentinel-2 and Landsat-8 data using five MLAs with pixel- and object-based approaches to delineate GDIAPs within groundwater-dependent ecosystems (GDEs) of the Heuningnes Catchment. Pixel-based random forest (RF) achieved the highest overall accuracies (98% with Sentinel-2, 94% with Landsat-8), while object-based gradient tree boosting (GTB) using Sentinel-2 achieved 85%, outperforming RF (82%). The class-specific F1-scores for GDIAPs and native plants exceeded 90% when pixel-based RF classifications were used. The Sentinel-2 pixel-based RF results indicated that GDIAPs dominated 26.8 km² (60%) of GDEs in 2022, compared to 13.6 km² (31%) of GDEs occupied by native fynbos. These findings demonstrate the value of satellite-based machine learning for monitoring GDIAPs and supporting invasive species management, ecosystem protection, and water resource planning.
Urban expansion and ecological implications in Table Bay nature Reserve: a multi-temporal remote sensing study
(Multidisciplinary Digital Publishing Institute (MDPI), 2026) Maphanga, Thabang; Koloko, Mosa; Madonsela, Benett Siyabonga
Urban expansion presents significant challenges and opportunities for ecological conservation in developing countries, particularly in regions such as the Table Bay Nature Reserve in Cape Town, South Africa, where urban development interfaces with sensitive ecosystems. This article examines the complex dynamics between urban growth and ecological implications in this unique landscape, employing multi-temporal remote sensing techniques to analyze changes over time. By investigating the historical trajectory of urbanization in Table Bay, alongside its impacts on biodiversity and ecosystem services, we aim to underscore the urgent need for sustainable urban planning and conservation strategies. To analyze land use/land cover (LULC) dynamics over a 24-year period, this study leveraged a time series of satellite imagery processed within the Google Earth Engine (GEE) platform. Data can be accessed using their respective collection IDs within the GEE platform. The use of remote sensing tools aligns with Sustainable Development Goal (SDG) 15, which focuses on the protection, restoration, and sustainable use of terrestrial ecosystems. Urban encroachment analysis indicates that approximately 0.324 km2 of built-up area expanded directly within the reserve boundary, highlighting a measurable degree of infringement into protected zones. The dominance of built-up and bare land classes highlights the early encroachment of urban infrastructure and anthropogenic disturbance, setting the stage for subsequent land cover transformations observed in later years (2012 and 2024). These findings demonstrate a persistent trend of urban encroachment and ecological alteration within the Table Bay Nature Reserve. With the increase in global population levels, urban expansion into protected conservation areas has become a critical environmental concern, threatening biodiversity globally. This challenge is particularly acute in developing countries as seen in regions like the Table Bay Nature Reserve in Cape Town, South Africa, where urban development is interfaced with sensitive ecosystems.
The multiplier effect and systemic patterns of urban reclaimed water utilization
(KeAi Communications Co., 2026) Ma, Nian; Xu, Yongxin
The multiplier effect describes how an initial change in a variable leads to a larger overall impact through interconnected processes. The utilization of reclaimed water offers a promising solution to water scarcity while preserving fresh water for diverse applications. Integrating reclaimed water into urban water systems alters both the balance and composition of water resources and affects system efficiency. However, there is currently no unified method for evaluating the efficiency of reclaimed water utilization (RWU). This paper introduces the concept of the multiplier effect to establish a comprehensive evaluation framework. The mechanism of the multiplier effect is dissected, an accounting methodology for the reclaimed water utilization multiplier (RWUM) developed. We also further identify various RWU patterns and their impacts on the multiplier estimation. By examining case studies in Singapore and Chongqing, the paper explores how to increase the RWUM with the multiplier accounting. We found that the multiplier effect enhances the optimal utilization of available water resources, thereby improving both the effectiveness and efficiency of urban water systems. Improving each component's performance increases RWUM and boosts overall water system efficiency. Selecting an appropriate systemic pattern significantly enhances the efficiency of reclaimed water use. Increasing reclaimed water use rates, refining its application patterns, and improving urban water cycle operations significantly boost RWU efficiency and urban water system performance. The methodology for RWUM evaluation provides a comprehensive and standardized framework for assessing the utilization efficiency of urban reclaimed water, yielding comparable results. This framework can guide the planning and management of urban reclaimed water systems and is applicable to various global water systems for cities alike.

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