Research Articles (Earth Sciences)

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

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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.
Sociotechnical analyses of households’ comprehension of land use and land cover change in the Eastern Cape province of South Africa
(Springer Nature, 2026) Ndhleve, Simbarashe; Kabiti, Hlekani Muchazotida; Ayisi, Kingsley Kwabena; Zhou, Leocadia; Nakin, Motebang Dominic Vincent; Dube, Timothy I.
Communal land systems are undergoing degradation, and this has implications for food and water security. This study examines land use and land cover changes in communal land system of Mthatha river catchment, South Africa, by using a juxtaposition of GIS and Remote Sensing imageries and ethnography aimed at understanding how custodians of this land system comprehend LULC changes in their localities. The article examines the extent of divergence and/or convergence of inhabitants’ perceived LULC changes and GIS and Remote Sensing imageries of their area. A semi structured questionnaire was used to collect perceptions data from 183 randomly selected households within the catchment. Mitigation and adaptation strategies were also identified in the paper. Findings revealed that most participants (90%) correctly perceived an increase in built up areas, decreases in cultivated land (77%), water bodies (56%), plantations (72%), grasslands (52%) and natural forests (59%). Bare lands were perceived to be decreasing (72%) in contrast to an observed 11% increase through satellite imagery. Lack of consensus between perceived changes and findings from satellite images indicates gaps in existing knowledge about LULC. These divergence and convergence of understanding between the technical outputs of GIS and Remote Sensing and local communities’ knowledge, perceptions and practical experiences can be useful in managing LULC changes in context specific ways. How individuals perceive the problem determines the level of commitment to solving it. The findings of this study are important for policymakers and scientific communities as they create the important base for dialogue with communities.
Trimester-specific exposure to multiple heat indicators and adverse birth outcomes across four European countries
(Academic Press Inc., 2026) Jackson, Debra; Bao, Mian; Nobile, Federica
The health of pregnant women and their fetuses is increasingly challenged by abnormal heat events. Few studies have disentangled the trimester-specific effects of heat exposure during pregnancy on perinatal outcomes and examined potential differences across multiple heat indicators. This study included singleton births from multiple national and region registries across Europe: Sweden (2014-2019), Belgium (2012-2022), Italy (Lazio Region) (2001-2019), and Greece (1999-2021). We obtained 2-m air temperature, Universal Thermal Climate Index (UTCI), Wet Bulb Globe Temperature (WBGT), and Heat Index data from the ERA5 reanalysis dataset. Our study outcomes were preterm birth (PTB), stillbirth (SB), small for gestational age (SGA), and large for gestational age (LGA). Cox proportional hazard models, with gestational age as the underlying time scale, were applied to evaluate trimester-specific associations between multiple heat indicators and adverse birth outcomes. Country-specific estimates were then combined through meta-analyses. In total, 4,924,422 mother-child pairs were included in the analysis. An increase in mean temperature from the 75th to the 99th percentile in the third trimester was associated with PTB (HR = 1.51, 95% CI: 1.34-1.71), SB (HR = 1.54, 95% CI: 1.44-1.65), SGA (HR = 1.16, 95% CI: 1.11-1.20), and LGA (HR = 1.12, 95% CI: 1.07-1.17). Comparable associations were observed across heat indicators and countries for each trimester. Our findings suggest that the third trimester is a critical exposure window of vulnerability for heat during pregnancy. The comparable effect estimates among heat indicators highlight the usefulness of mean air temperature in Europe.
Groundwater responses to decadal rainfall variability in semi-arid South Africa
(Elsevier B.V., 2026-04) Kanyerere, Thokozani; Bjerre, Elisa; Jessen, Søren
This study examines groundwater responses to climate trends and variability in semi-arid South Africa (SA). Groundwater is a vital water resource in the semi-arid regions of Africa, which are characterized by low, erratic rainfall and intermittent streamflow. In these regions, water scarcity is intensifying due to rising irrigation demands, urbanization, and climate change. Semi-arid SA experiences significant rainfall variability at inter-annual and decadal timescales. However, groundwater responses to SA’s climate remains underexplored, partly due to limited observational data. This study analyses long-term trends and variability in rainfall, temperature, and groundwater levels in the Hout/Sand River catchment from 1940 to 2022 using climate and groundwater indices. Groundwater response to rainfall variability is assessed through correlations between the Standardized Precipitation Index (SPI) and the Standardized Groundwater Index (SGI) across annual to decadal timescales. Results indicate no significant trends in total annual rainfall, but rainfall patterns intensified manifested as higher daily rainfall intensity, longer dry periods, and shorter wet periods. The highest SGI-SPI correlation occurs at 7- and 8-year accumulation periods (r = 0.80), which indicates a dependence of groundwater levels on antecedent rainfall consistent with the region’s decadal climate variability of dry and wet epochs. The study adds to our conceptual understanding of groundwater responses to large-scale climatic patterns, which is essential for assessing future water availability under climate change.
A multiple spatial scales water use simulation for capturing its spatial heterogeneity through cellular automata model
(Copernicus Publications, 2025) Zhang, Jiayu; Liu, Dedi; Wang, Jiaoyang; Yue, Feng; Liang, Hanxu; Peng, Zhengbo; Guan, Wei
Reliable water use simulation is essential for sustainable water resource planning, especially under intensifying pressures from climate change, population growth, and socio-economic transitions. While previous studies have extensively explored water availability as supply side modeling across multiple spatial scales for its spatial heterogeneity, the water demand side remains relatively underdeveloped – often constrained by fixed spatial scales and coarse statistical data that assume spatial homogeneity. This mismatch between supply side and demand side limits the ability of existing models to accurately represent spatial heterogeneity in water use and brings uncertainty into water resource allocation strategies. To address this mismatch, we propose a novel multi-scale water use simulation framework by integrating cellular automata (CA) model with Generalized Likelihood Uncertainty Estimation (GLUE). The CA model captures the spatial heterogeneity of water use through the grid-based update rules. Two update rules are adopted – probability rule (i.e., capturing stochastic transitions via distribution fitting) and linear rule (i.e., modeling neighborhood-weighted evolution). To evaluate the impacts of spatial scale on water use heterogeneity, simulations are conducted at three spatial scales: 1 km, appropriate scale, and prefecture scale across 341 prefectures in China. Results show that both the update rule and spatial scale significantly affect spatial heterogeneity and uncertainty of water use. The probability rule can capture the broader variability but results in higher Root Mean Squared Error (RMSE) and Relative Error (RE) while the linear rule brings more stable performance with lower errors. While the 1 km scale increases uncertainty due to sensitivity to local fluctuations, and the prefecture scale suppresses spatial details, the appropriate scale offers the best trade-off between stability and spatial heterogeneity. The uncertainty quantified by GLUE, expresses as confidence intervals, varies across prefectures and spatial scales. Overall, the proposed framework offers a flexible tool for multi-scale water use simulation and highlights the critical role of spatial heterogeneity, thereby supporting adaptive water resource planning and management.
Utilizing Aquifer Hydraulic Parameters to Assess Local and Regional Recharge Potentials for Enhancing Water Allocations in Groundwater-Dependent Areas in De Aar, Northern Cape, South Africa
(MDPI, 2025) Baloyi, Lucky; Kanyerere, Thokozani; Muchingami, Innocent; Pienaar, Harrison; Igwebuike, Ndubuisi; Mukhawana, Mxolisi B
The precise and accurate use of aquifer hydraulic parameters for assessing local and regional recharge potential for enhancing groundwater allocation planning is vital for many hydrogeological studies. The conventional approach for allocating groundwater presents a challenging scenario, as it remains uncertain whether the applied recharge estimate is local or regional recharge. The approach does not account for the extent of the aquifer recharge in terms of local and regional scale; instead, it assumes that recharge is distributed across the catchment. This study aimed to demonstrate the use of aquifer hydraulic parameters (transmissivity and storativity) to explain areas of potential recharge (local and regional) for enhancing groundwater allocation planning with a specific case study of De Aar, Northern Cape, South Africa. It argues that not integrating local and regional recharge potentials in planning for groundwater allocations can result in over- or under-allocation of groundwater resources to users. A constant discharge pumping test and recovery test matching the duration of pumping were conducted for data collection. The Flow Characteristics method was used as a diagnostic tool to understand the different aquifer flow regimes in the study area. To develop an integrated understanding of the groundwater system, a hydrogeological conceptual model was used to visualize areas with higher or lower recharge potential across local and regional scales. Results showed significant variability in transmissivity, ranging from 213 to 596 m2/d, and storativity, ranging from 0.0000297 to 0.000185. The transmissivity values suggest that groundwater moves faster; meanwhile, the storativity values suggest that the aquifer system has high water storage capacity. These results will assist water resource planners in making informed decisions on how to allocate groundwater to users. This study demonstrated that aquifer hydraulic parameters are a valuable tool for improving groundwater allocations, thereby highlighting the importance of considering areas for potential recharge, both local and regional, in planning groundwater allocation.
Household water insecurity severity across urban areas with varying aridity levels in sub-saharan Africa: examples from Namibia
(Elsevier B.V., 2026) Munyayi, Rennie; Swatuk, Larry A.; Mazvimavi, Dominic; Chiramba, Thomas; Mapani, Benjamin Siyowi E.
AbstractWater insecurity is shaped not only by water availability but also by governance and service systems, an issue that is increasingly pressing in cities. In the African policy context, the Africa Water Vision 2063 and Policy, positions water security and safe sanitation as central to achieving Agenda 2063. Framing household water insecurity through reliability and spatial equity, speaks directly to these continental aspirations. This study examines household water insecurity in three Namibian towns, (Ongwediva, Rundu, and Windhoek), which differ in their hydroclimatic conditions and water supply systems. Drawing on the 12-item Household Water Insecurity Experiences (HWISE) scale and supplementary survey data, we examine how the severity of household water insecurity varies across towns and across socio-spatial groups within each town. The findings show significant between- and within-town differences. Windhoek, the capital city and economic hub of the country, faces severe physical water scarcity. Respondents in Windhoek report lower water insecurity scores, which could be explained by the city’s long-standing investment in augmenting the water supply and consistent promotion of water demand management strategies. Rundu, the second-largest town, is located in a water-rich basin (the Okavango Basin) and has the highest household water insecurity scores. These findings could result from inadequate and ageing water infrastructure and institutional constraints that affect the continuity of supply. In Ongwediva, relatively high levels of service coverage do not fully protect households from insecurity, as the system remains vulnerable due to its dependence on a long-distance transboundary transfer corridor that is affected by other factors, such as power cuts. In town comparisons reveal that informal and higher-density suburbs tend to have higher insecurity scores than other residential areas. These findings suggest that household water security is rarely the result of hydrology alone. Infrastructure constraints, institutional capacity, and climate variability often intersect in ways that shape the reliability of water services.
3D seismic-based structural and slip tendency analysis of a depleted reservoir offshore South Africa: Implications for safe CO2 storage
(Elsevier Ltd, 2026) Mhlambi, Sanelisiwe; Emmanuel Eruteya, Ovie Emmanuel; Moscariello, Andréa
Carbon capture and storage (CCS) technology is increasingly recognised as a key enabler of a low-carbon energy future, with growing importance for reducing anthropogenic CO2 emissions in resource-rich countries such as South Africa. The long-term success of CCS depends on the availability of secure storage capacity and a robust geomechanical understanding of injection sites, particularly in structurally complex, depleted hydrocarbon reservoirs. This study presents one of the first reservoir-scale integrated deterministic and probabilistic assessments of fault slip potential (FSP) applied to a depleted offshore gas reservoir in the Bredasdorp Basin. A high-resolution 3D seismic dataset was interpreted to characterise the fault network and construct a structural framework comprising fifty (50) selected faults within a syn-rift sandstone reservoir. This framework underpins a combined deterministic geomechanical and probabilistic sensitivity-modelling workflow to evaluate fault reactivation risk during CO₂ injection, using a simplified radial pressure-diffusion formulation.Results show that faults proximal to injection wells exhibit elevated slip potential due to their orientation relative to the regional stress field and their spatial association with pressure build-up. Sensitivity analyses indicate that pore-pressure increase is the dominant control on slip potential, followed by fault friction coefficient (µ), fault strike, and stress-field uncertainty. Variations in permeability primarily affect the magnitude and persistence of pressure build-up, while variations in μ govern slip-onset thresholds. Faults within ∼5 km of injection wells are most susceptible to reactivation. Time-dependent modelling highlights elevated risk during late-stage injection and early post-injection pressure redistribution, underscoring the need for continuous monitoring and adaptive pressure management. Overall, the study provides a rigorous, fault-specific geomechanical framework for CCS operations, and emphasises the importance of explicitly incorporating uncertainty into CCS risk assessments.
Understanding the tradeoff between the flood risk and the hydropower benefit from the integrated flood control operation of a reservoir group and a flood detention basin
(Elsevier B.V., 2026) Mu, Zhenyu; Liu, Dedi; Wang, Zhenyu; Zhang, Yuling; Liu, Pan; Xiong, Lihua; Chen, Jie; Chen, Hua; Yin, Jiabo
To mitigate flood disasters and reduce their risks, a lot of reservoirs, as a reservoir group, and some flood detention basins (FDBs) have been constructed. As the flood control targets of the reservoir group and the FDB are often the same or are interrelated, it is necessary to integrate the reservoir group and FDB operation instead of operating them independently. Hydropower benefit is one of the functions of the reservoir group besides its flood control. There should be a tradeoff between the flood risk and the hydropower benefit from the integrated flood control operation of a reservoir group and FDB. A framework is proposed to determine and understand the tradeoff for enhancing decision-making in flood control. It has been applied in a case study of the Jingjiang FDB and a mixed reservoir group (Three Gorges, Shuibuya, and Geheyan) in the Changjiang River Basin. It has been found that the integrated operation of Jingjiang FDB can enhance the exchange between extreme flood risk and hydropower benefit, while this exchange is weakened for the non-extreme flood conditions due to the operational inflexibility of Jingjiang FDB. The safety flow at the downstream protection target has a significant impact on the tradeoff under non-extreme flood conditions but only a slight impact under extreme flood scenarios. The damage coefficient exerts a significant and consistent influence on the tradeoff across both extreme and non-extreme flood conditions. It is critical to determine the damage coefficient and the safety flow for improving the performance of the flood control operation. The proposed framework not only determines the tradeoff between flood risk and hydropower benefit but also helps facilitate the integrated flood control operation of a reservoir group and FDB.
Mapping persistent oil spill risk in the Niger Delta using sentinel-1 SAR and environmental exposure indicators
(Elsevier Ltd, 2026) Oseni, Ridwan; Omosanya, Kamaldeen Olakunle; Mosuro, Ganiyu Omotola; Saka, Hawa Oluwatosin; Oludipe, Victoria; Oshomoji, Adeoye Olugbemi
Oil spills remain a major source of marine and coastal pollution in hydrocarbon-producing regions, where repeated releases can lead to long-term contamination of wetlands, waterways, and adjacent communities. Although satellite remote sensing has improved the detection of oil spills, translating these observations into assessments of cumulative environmental and human exposure is still challenging, particularly in complex deltaic systems. Here, we present a spatially explicit framework for assessing persistent oil spill exposure in the Niger Delta by integrating Sentinel-1 synthetic aperture radar (SAR) observations with ecological, infrastructural, terrain, and demographic data. Rather than focusing on individual spill events, we quantify chronic exposure patterns by finding recurring oil spill signatures and combining them within a multi-criteria risk model. Our results reveal persistent contamination hotspots strongly associated with dense oil infrastructure, low-lying wetlands, flat terrain, and high population density, collectively affecting approximately 9400 km2 over the past decade. Spill exposure extends beyond reported incident locations and includes both protected and upland areas, showing widespread vulnerability across the delta. These findings show that long-term pollution risk in the Niger Delta is governed by cumulative exposure and landscape controls rather than isolated spill events alone. The proposed framework provides a transferable approach for monitoring, assessing, and managing chronic oil pollution in coastal and deltaic environments worldwide.
Decorum in nature: impala (Aepyceros melampus melampus) dung middens follow spatial point patterns in Mukuvisi Woodland, Zimbabwe
(Taylor and Francis Ltd., 2025) Tagwireyi, Paradzayi; Muhoyi, Hardlife; Ndaimani, Henry; Mpakairi, Kudzai Shaun
Guided by the Optimum Foraging Theory,the Avoidance Concept, and assuming that the impala Aepyceros melampus melampus defecate purposevely at dung middens, we hypothesized that the impala’s dung midden locations do not: (1) follow complete spatial randomness; (2) cluster along park tracks; and (3) cluster along the waterways. Using geolocation data for all impala dung middens in the Mukuvisi Woodland, Zmbabwe, the G(r) function revealed a clustered pattern at 0–100 m. Additionally, the 2nd Order Gcross function showed evidence of spatial aggregation of dung middens to within 25 m of park tracks, but no evidence of spatial aggregation between impala dung middens and waterways. Our findings give insight into possible evolutionary decorum for optimum olfaction, energy-saving, disease,pest avoidance, and contamination avoidance.
Assessing drivers of vegetation fire occurrence in Zimbabwe - Insights from Maxent modelling and historical data analysis
(Elsevier B.V, 2025) Mupfiga, Upenyu; Mutanga, Onisimo; Dube, Timothy
Vegetation fires are known to profoundly impact ecosystem structure and composition, posing threats to ecosystem stability and human safety. In Zimbabwe, uncontrolled fires have been recurrent, yet a rigorous analysis of the key drivers is still lacking. Previous studies in Zimbabwe have predominantly focused on spatio-temporal dynamics of the occurrence of vegetation fire, leaving a gap in understanding the underlying drivers. Accurate prediction of fire occurrence and identification of the major driversis imperative foreffective fire management strategies. The study employs the Maxent model, a machine-learning approach, to analyze historical MODIS fire data alongside bioclimatic, topographic, anthropogenic, and vegetation variables, to assess the likelihood of fire occurrence in Zimbabwe. The research also aims to elucidate the major factors that influence fire occurrence within the region. The independent contributions of predictor variables to the model’s goodness of fit are evaluated using a jackknife test, while model accuracy is assessed using the AUC (area under the receiver operating characteristic curve). Results indicate that elevation, precipitation seasonality, temperature annual range and human footprint emerge as the major factors influencing fire occurrence in Zimbabwe. The model demonstrates an acceptable accuracy, with an average AUC of 0.77. This study underscores the utility of the Maxent model in elucidating the contributions of various environmental factors to vegetation fire occurrence. Moreover, the ability of the model to predict the probability of fire occurrence offers valuable insights for fire managers, facilitating the assessment of the spatial vulnerability of vegetation to fire occurrence. Overall, this research contributes to an improved understanding of the drivers of vegetation fires in Zimbabwe and provides a practical tool for enhancing fire management efforts in the region and beyond.
Understanding the tradeoff between the flood risk and the hydropower benefit from the integrated flood control operation of a reservoir group and a flood detention basin
(Elsevier B.V, 2026) Mu, Zhenyu; Liu, Dedi; Wang, Zhenyu; Zhang, Yuling; Liu, Pan; Xiong, Lihua; Chen, Jie; Chen, Hua; Yin, Jiabo
To mitigate flood disasters and reduce their risks, a lot of reservoirs, as a reservoir group, and some flood detention basins (FDBs) have been constructed. As the flood control targets of the reservoir group and the FDB are often the same or are interrelated, it is necessary to integrate the reservoir group and FDB operation instead of operating them independently. Hydropower benefit is one of the functions of the reservoir group besides its flood control. There should be a tradeoff between the flood risk and the hydropower benefit from the integrated flood control operation of a reservoir group and FDB. A framework is proposed to determine and understand the tradeoff for enhancing decision-making in flood control. It has been applied in a case study of the Jingjiang FDB and a mixed reservoir group (Three Gorges, Shuibuya, and Geheyan) in the Changjiang River Basin. It has been found that the integrated operation of Jingjiang FDB can enhance the exchange between extreme flood risk and hydropower benefit, while this exchange is weakened for the non-extreme flood conditions due to the operational inflexibility of Jingjiang FDB. The safety flow at the downstream protection target has a significant impact on the tradeoff under non-extreme flood conditions but only a slight impact under extreme flood scenarios. The damage coefficient exerts a significant and consistent influence on the tradeoff across both extreme and non-extreme flood conditions. It is critical to determine the damage coefficient and the safety flow for improving the performance of the flood control operation. The proposed framework not only determines the tradeoff between flood risk and hydropower benefit but also helps facilitate the integrated flood control operation of a reservoir group and FDB.
Regional variability in the Acheulian to Middle Stone Age transition in southern Africa
(Nature Research, 2026) Muir,Robert. A; Blackwood A.F; Wilkins J.
Homo sapiens emerged in Africa around 300 − 200 thousand years ago (ka). Although the earliest H. sapiens fossils are associated with the Middle Stone Age (MSA), lithic technologies considered diagnostic of the MSA have been found alongside Acheulian technology in eastern Africa and the interior of southern Africa by ~ 500 − 400 ka, suggesting a deep evolutionary history of our species in these regions. The southern coastal plain of South Africa, geographically separated from the interior by the Cape Fold Belt and Great Escarpment, has one of the best documented records of the MSA in Africa; however, only a single site is older than 125 ka and little is known about the origins of the MSA in this region. Here, we report a stratified sequence of Acheulian to MSA lithic assemblages from the open-air site of Amanzi Springs covering the period between ~ 379 to 95 ka. We show that the MSA emerged around 230 ± 18 ka, significantly earlier than previously documented along the southern coast. The pattern of technological change also differs to the interior, with no diagnostic MSA elements found in the late Acheulian, although persistent methods of flake production indicate a gradual transition and continuity into the MSA. The relatively late emergence of the MSA along the southern coast highlights the variable and complex nature of demographic and behavioural change during this period, with regionally distinct technological trajectories extending into the Middle Pleistocene in southern Africa.
Sociotechnical analyses of households’ comprehension of land use and land cover change in the Eastern Cape province of South Africa
(Springer Nature, 2026) Ndhleve, Simbarashe; Kabiti, Hlekani Muchazotida; Ayisi, Kingsley Kwabena; Zhou, Leocadia; Nakin, Motebang Dominic Vincent; Dube, Timothy
Communal land systems are undergoing degradation, and this has implications for food and water security. This study examines land use and land cover changes in communal land system of Mthatha river catchment, South Africa, by using a juxtaposition of GIS and Remote Sensing imageries and ethnography aimed at understanding how custodians of this land system comprehend LULC changes in their localities. The article examines the extent of divergence and/or convergence of inhabitants’ perceived LULC changes and GIS and Remote Sensing imageries of their area. A semi structured questionnaire was used to collect perceptions data from 183 randomly selected households within the catchment. Mitigation and adaptation strategies were also identified in the paper. Findings revealed that most participants (90%) correctly perceived an increase in built up areas, decreases in cultivated land (77%), water bodies (56%), plantations (72%), grasslands (52%) and natural forests (59%). Bare lands were perceived to be decreasing (72%) in contrast to an observed 11% increase through satellite imagery. Lack of consensus between perceived changes and findings from satellite images indicates gaps in existing knowledge about LULC. These divergence and convergence of understanding between the technical outputs of GIS and Remote Sensing and local communities’ knowledge, perceptions and practical experiences can be useful in managing LULC changes in context specific ways. How individuals perceive the problem determines the level of commitment to solving it. The findings of this study are important for policymakers and scientific communities as they create the important base for dialogue with communities.
Quantifying land use and land cover influences on surface water quality through Sentinel-2 observations in the Letaba catchment, South Africa
(Elsevier B.V., 2026) Dube, Timothy; Mashala, Makgabo Johanna; Ayisi, Kingsley Kwabena
This study evaluates the association between land use and land cover (LULC) and surface water quality in the Letaba Catchment, South Africa, by integrating in-situ physicochemical measurements with Sentinel-2 Multispectral Instrument (MSI) data. Water quality parameters including temperature, pH, dissolved oxygen (DO), electrical conductivity (EC), total dissolved solids (TDS), and salinity (SAL) were measured using a multi-parameter probe. Sentinel-2 spectral bands and derived water indices were analysed using Pearson's and Spearman's correlation coefficients and stepwise multiple linear regression. Statistically significant relationship (p < 0.05) was observed in the visible and red-edge bands with EC and TDS exhibiting strong predictive performance (R2 = 0.84 and 0.87, respectively). Models for DO, SAL, temperature, and pH showed more variable performance, reflecting parameter-specific optical sensitivities. Weak model performance for pH is attributed to its limited spectral expression in the visible-near infrared (VNIR) region. Overall, the results indicate that LULC patterns are significantly associated with spatial variations in water quality, particularly in areas dominated by built up and plantation land uses. The study demonstrates the utility and limitations of Sentinel 2 data for catchment scale water quality monitoring in semi-arid environments.
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.

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