School of Animal, Plant and Environmental Sciences (ETDs)

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Sex and age related distinctions in the feeding ecology of the African elephant
(2010-01-29T08:19:33Z) Greyling, Michelle Deborah
The influence of plant phenolic compounds on the host range of Coniatus tamarisci Fabr. (Coleoptera: Curculionidae): a potential biological control agent of invasive Tamarix L. (Caryophyllales: Tamaricaceae) Taxa in South Africa
(University of the Witwatersrand, Johannesburg, 2022) Hatile, Sivenathi Luvolwethu; Byrne, Marcus; Mayonde, Samalesu
Tamarix L. (Caryophyllales: Tamaricaceae) are halophyte species that are native to Eurasia, North Africa, and southwestern Africa. These phreatophyte trees or shrubs have become prominent and widespread invaders in North America, South America, Australia, and South Africa. In South Africa, the Alien and Invasive Species regulations of the National Environmental Management: Biodiversity Act 2014 (NEM:BA) has classified invasive Tamarix as category 1b invader, which require control. Thus, three potential biological control agents have undergone laboratory-based host-specificity trials for the long-term sustainable control of Tamarix. The first two of these biocontrol agents, Diorhabda carinulata (Desbrochers.) (Coleoptera: Chrysomelidae) and Trabutina mannipara (Hemprich & Ehrenberg) (Hemiptera: Pseudococcidae), both failed the laboratory-based host-specificity trials because they completed their life cycle on the indigenous T. usneoides E. Mey ex Bunge. Previously, potential biocontrol agents were selected based on their native distribution and the phylogenetic relatedness of the invasive weed to indigenous nontarget species. However, it has recently been suggested that secondary metabolites also play a major role in insect host selection, and thus should be considered to improve the selection criteria of potential biocontrol agents. The current study is based on the third biocontrol agent that recently underwent laboratory based host-specificity trials in South Africa, Coniatus tamarisci (Fabr.) (Coleoptera: Curculionidae). This was in conjunction with an analysis of the potential influence Tamarix phenolic compounds have on insect host selection. The results show that although C. tamarisci could complete its’ life cycle on T. usneoides, the weevil had a low affiliation/risk associated with the indigenous Tamarix taxon. This advocates for the conduction of open field host-specificity trials, which will allow for a better understanding of C. tamarisci behaviour in a natural setting. Regarding phenolic compounds, three phenolic acids have been identified as being significantly prominent in T. usneoides compared to the invasive Tamarix taxa present in South Africa. These are gallic acid, dehydrodigallic acid, and syringic acid. These compounds are associated with protection from plant herbivory, which could explain the behaviour of C. tamarisci when exposed to and reared on T. usneoides.
Tolerance, uptake, and translocation of platinum (Pt), nickel (Ni), and cobalt (Co) by Tamarix usneoides E. Mey. ex Bunge
(University of the Witwatersrand, Johannesburg, 2022) Mader, Anthony E.; Weiersbye, Isabel M.; Mycock David J.
The intensification of platinum (Pt), cobalt (Co) and nickel (Ni) mining and processing results in the release of salts and metals into the environment. This calls for the identification of halophytes with an ability to tolerate and desalinate metal-contaminated sites while simultaneously allocating metals (Pt, Ni, and Co) into harvestable biomass. Tamarix usneoides E. Mey ex Bunge is an indigenous exo-recretohalophyte that has been used for erosion control and for the desalination and allocation of metals from gold and uranium mine tailings and land contaminated by metallurgical effluent. The aim of this study was to investigate the uptake, translocation, and tolerance of Pt, Ni, and Co by T. usneoides from liquid medium (in vitro) and soil contaminated by base metal refinery effluent spillages and previous overspray from the enhanced evaporation spray system (in situ). More specifically, the in situ study investigated the utility of mature T. usneoides trees in the desalination of soil contaminated by previous metallurgical spillages and overspray emissions through the extraction of sulphur and metals Pt, Ni, and Co into harvestable biomass. Four T. usneoides trees were categorised into different size classes based on tree measurements and allometric equations. Seven soil pits (four “planted” and three “unplanted” – control) were excavated and opposite faces of the soil profile were sampled at 20 different intervals (0 – 340 cm). Soil samples were freeze-dried and analysed for total element concentrations. Root systems were harvested by excavating soil pits (maximum depth of 3.5 meters) using a mechanical excavator. Trees were harvested and immediately separated into above (leaves, twigs, wood, and flowers) and belowground (coarse and fine roots) plant organs. Tree biomass was further separated into different above (outer bark, inner bark, and sapwood and heartwood) and belowground (epidermis, cortex, and stele) tissue types. Plant material was rinsed three times in tap water to remove unbound residual metals and residual substrate from root and shoot surfaces. It must be noted that the determined metal concentrations are a combined measure of metals adsorbed on the root surface, assimilated in planta, and excreted on the plant surface from the foliar salt glands. Metals were allocated in trees (across plant organs and tissue types) in the order: Ni (59.46 ± 4.67 mg/kg) > Co (2.65 ± 0.34 mg/kg) > Pt (50 ± 6 µg/kg) whereas sulphur (S) was hyperaccumulated in tree leaves [39 900 ± 861 mg/kg (3.9% ± 0.7 %)]. Platinum was bioaccumulated [bioconcentration factor (BCF) > 1.5] and translocated [translocation factor (TF) > 1] in the leafy shoots of one individual tree, Ni in one (BCF = 1.03), and Co in another replicate (BCF = 1.02). Soil chemical properties (pH, electrical conductivity, and redox potential) differed between planted and unplanted pits whereby pH and EC were lower in planted pits [pH 6.0; EC = 3 499 µS/cm (34.99 mM NaCl)] compared with unplanted [pH 7.6; EC = 9 644 µS/cm (96.44 mM NaCl)] (ANOVA, p < 0.01). The lower EC, along with S hyperaccumulation (BCF > 20; TF > 1), supports the potential use of T. usneoides for phytoextraction of S and Ni in shoot tissues and Co and Pt in roots. At a spacing of 1333 trees / ha, T. usneoides trees could remove an estimated 2.23 ± 0.30 mg Pt/ha, 3.02 ± 0.83 kg Ni/ha, 1.28 ± 0.90 kg Co/ha, and 1.28 ± 0.09 tons S/ha, excluding excreted salts. Excreted salts were visible but could not be quantified without confounding surface dust contamination. The first in vitro study determined factors influencing the rhizogenesis of T. usneoides in order to develop a mass propagation protocol. Explant establishment in vitro was influenced by various donor plant factors, viz. growing conditions (contaminated < non-contaminated; Kruskal-Wallis (KW), p < 0.05), physiological age (younger > older donor plants; ANOVA, p < 0.05), genotype (KW, p < 0.001), season of culturing (higher establishment in winter; KW, p < 0.05), length of explant (40 mm > 25 mm; KW, p < 0.05), and volume of growth vial (50 mL > 15 mL; KW, p < 0.05) but not pH, chronological age, strength of plant growth medium, or auxin pulse treatments. This study indicates that propagation protocols can be developed by controlling factors influencing explant establishment. A standardised and rapid in vitro protocol was developed for the mass propagation of T. usneoides explants. This in vitro protocol was used for the metal uptake studies whereby established explants were exposed to 25 % Murashige and Skoog standard plant growth medium supplemented with Pt, Co, or Ni (as sulphate complexes) at 0, 25, 50, or 100 mg/L at pH 5.5 or 7.5 over a 14-day exposure period. On completion of the metal exposure period, plantlets were harvested, separated into roots and shoots, freeze-dried, and analysed for metal concentrations. Higher metal concentrations (Ni > Co >> Pt) were accumulated in roots (combined measure of metals adsorbed on the root surface and assimilated in planta) compared with shoots whereby BCF > 1 (excluding Pt) and TF < 1. Metal BCF (Ni > Co >> Pt; KW, p < 0.05) and TF (Co > Ni >> Pt; KW, p < 0.05) increased in a dose-dependent fashion and were not influenced by pH level. Cobalt and Ni (≤ 50 mg/L) uptake dynamics did not v differ suggesting similar uptake dynamics, when treated separately. Platinum (defined in this study as Pt > 1 – 4 mg/kg), Ni (> 1 000 mg/kg), and Co (> 300 mg/kg) were hyperaccumulated in roots (“rhizo-hyperaccumulation”) across treatments with possible Co-hyperaccumulation in shoots by two genotypes. Genotype influenced Co allocation in shoots but not Ni or Pt. Tolerance indices did not differ [Co (97 %) > Pt (82 %) > Ni (77 %)] between pH, metal, treatment concentration, or the interplay between these factors. Metal treatments did not impact measured morphological parameters (excluding Ni treatments which promoted shoot length increment) (KW, p < 0.05). Plantlet survival differed between pH and metals [Pt (90 %) > Ni (81 %) > Co (62 %)] (KW, p < 0.05). Variability in Co accumulation capacity between genotypes indicated that selective breeding, using the developed in vitro mass propagation protocol, for improved rhizofiltration and phytoextraction traits is feasible. Results demonstrate that T. usneoides has the potential for recovery of Ni and Co (and Pt to a lesser degree) from effluents, exhibiting a tolerance to Ni, Co, and Pt at 1, 10, and 10,000 times the average soil crustal abundance, respectively, under moderately acidic (pH 5.5) and alkaline (pH 7.5) conditions and across a wide metal concentration range. Results from the in situ study indicate that 9- year-old T. usneoides trees can be used for the decontamination of sulphate-contaminated soils under study site conditions which are more conducive to the survival of glycophytes. Tamarix usneoides is thus able to assimilate, translocate, and tolerate Ni, Co, and Pt (to a lesser degree) when exposed to metals across a wide pH and metal concentration range, under different (in situ and in vitro) experimental conditions. This opens the possibility for the species to be used in a range of phytotechnologies.
The reproductive system of Campuloclinium macrocephalum and its implications for biocontrol implementation
(University of the Witwatersrand, Johannesburg, 2022) Moodley, Saness; Glennon, Kelsey; Goodman-Cron, Glynis
Invasive species are a threat to biodiversity therefore it is imperative to determine the factors that facilitate the invasion potential of a species. Campuloclinium macrocephalum Less. (DC), the ‘pompom weed’, is an alien invasive species in South Africa and is currently threatening the persistence of the grassland, wetland, and savanna biomes. The species is also significantly contributing to a decline in plant diversity by outcompeting native vegetation in these areas. Various integrated approaches using combinations of chemical, mechanical and biocontrol management programs have been developed to manage the spread of the species in its invaded range, however the species has still been able to persist. The persistence of the species was hypothesised to be a consequence of the co-occurrence of apomixis and polyploidy, however despite the identification of triploid and tetraploid cytotypes in South African populations of the pompom weed, the reproductive strategy of the species has not yet been determined. The aim of this study was therefore to infer whether populations of C. macrocephalum (pompom weed) reproduces via vector-mediated crosses, self-pollination or apomixis (either facultative or obligate) and examine the relationship of the mode of reproduction with ploidy level. Male fertility was also assessed to ascertain if interploidy gene flow was possible. The collated information was then used to infer the potential impact of reproductive strategies and polyploidy on biocontrol. All examined populations were shown to have high mean pollen viability percentages of 90% and 98% with no significant differences in pollen viability amongst the four populations. The high pollen viability percentages were supported by prolific pollen grain germination on the stigmatic surfaces (margins of style at base of style branches) and the sides of the style. This suggested that the pollen grains can fertilize and interploidy mating is likely possible in South African populations of the pompom weed. It is plausible that the high pollen viability is enabling triploids to act as a ‘triploid bridge’. However, the high pollen viability was confounded by the pollen tube analyses revealing that pollen tube growth is being arrested on the stigmatic surface suggesting that overall male fertility is low. The arrested pollen tube growth is typically associated with a ‘triploid block’. Nevertheless, the production of viable gametes can reduce the triploid block and facilitate gene flow between populations. The predominant mode of reproduction was determined by assessing the contribution of insects to pollen transfer, pollinator exclusion experiments, germination trials, pollen tube growth to the ovules and genetic analyses. We found that the African Monarch butterfly (Danaus chrysippus) and the honeybee (Apis mellifera) contributed most to pollen transfer in comparison to the other insects visiting C. macrocephalum. A pollinator exclusion experiment showed that the pompom weed can set seed in the absence of pollinators, albeit at lower quantities than in the open treatments. Nevertheless, germination percentages showed that reproductive success was similar between open and bagged treatments in each population. The Modderfontein population showed lower reproductive success and seedling establishment in comparison to the other populations, presumably due to the severity of the biocontrol infestation on this population. Genetic analyses revealed low genetic variation within and amongst populations. Pollen tube analyses showed no pollen tube growth to the ovules in all samples, which suggests that seed set is independent of fertilization. The lack of pollen tube growth is a strong indicator of obligate autonomous apomixis which is further corroborated by the low genetic differentiation between maternal plants and their respective offspring. The co-occurrence of apomixis and polyploidy made it difficult to discern which factor contributes more to the invasiveness of the species, however, we hypothesise that autonomous apomixis provides the pompom weed with the competitive advantage to persist in its invaded range. However, further studies on the reproductive strategies of tetraploid cytotypes are needed to confirm this hypothesis. The low genetic variation suggests that all populations should be equally susceptible to biocontrol agents, however that this may be affected by other factors such as environmental conditions or phenotypic plasticity. Phenotype plasticity refers to a single genotype producing different phenotypes in response to environmental conditions. This could reduce the efficacy of biocontrol agents as they may exhibit differential responses on different phenotypes
The reporting of the sustainability goals and the Sustainable Development Goals (SDGs) in the context of the private sector in South Africa
(University of the Witwatersrand, Johannesburg, 2022) Mosi, Tumelo
Sustainability challenges continue to mount and the fate of this planet lies in a precarious position. In response, the United Nations has introduced a global agreement known as the Sustainable Development Goals (SDGs). These are 17 goals underpinned by 169 targets for addressing social, economic and environmental issues on a global scale. The SDGs seek to do so by unlocking the potential that lies within the private sector and more. The aim of my research was to assess the sustainability goals disclosed by the top 25 Johannesburg Stock Exchange (JSE) listed companies against that of five other countries in 2017. Furthermore, I compared the environmental SDG disclosure of five companies from the metals and mining sector as well as the consumer products sector respectively, within the same period. The sample was selected from the original sample of the top 25 JSE listed companies. Comparisons were done by analysing sustainability/annual/integrated reports of the top 25 JSE listed companies. The results for the sample showed South Africa to be lagging behind the other countries with regards to disclosing sustainability goals in the corporate sustainability reporting for 2017. From 2017 to 2019, the number of reports addressing environmental SDGs from the selected sectors showed an increase. Furthermore, the study companies from the metal and mining sector performed better than those from the consumer products sector with regards to environmental SDG disclosure. However, the environmental SDG score of the study companies from the consumer products sector increased relatively more within the three years of assessment (2017-2019). Variation was also found between the study companies from the two sectors with regards to preference for specific environmental SDGs which included Responsible Consumption and Production (SDG 12), Climate Action (SDG 13), Life Below Water (SDG 14) and Life on Land (SDG 15). Moreover, the iii interviews conducted with the relevant participants revealed that SDG awareness has improved overtime, however internalisation of the SDGs remains the biggest challenge.
Eco-art for a transformative climate culture
(University of the Witwatersrand, Johannesburg, 2022) Warrington-Coetzee, Hannelie; Voge, Coleen; Manderson, Lenore
Human”‘development” since the industrial revolution has unequivocally attributed to a code red of climate disasters, according to the recent IPCC Sixth Assessment Report of the Intergovernmental Panel on Climate Change report (IPCC, 2022a). To selectively unlearn or de-grow the unsustainable industrial culture crisis, humanity needs seriously to consider and act to transform (e.g., through ecocitizenship) in support of governments, scientists, and other civic actions in our journey to sustainable futures. Using a transdisciplinary praxis approach, artists can provide various forms of transformative possibilities, including transgressive interventions at a grassroots level, deliberately designed to provoke and inspire change. This research interrogates how eco-art deeply engages audiences to identify the key characteristics of such potentially radically transformative artworks. Humans have a narrowing window to transform our relationship to the Earth’s resources and reverse or slow temperature rise. The ‘near term’ (2022 – 2030) will determine and define the extent of various climate transformation pathways (IPCC, 2022, p. 7). Relational eco-art creates spaces for meaningful dialogue to design opportunities for transcendence to ecological citizenship. Art also holds a potential revolutionary connection tool that can unite science and society in incidences of immersion and change to spur further creations and change. These works, which visually articulate diverse types of knowledge, are described in the literature as situated in the fecund middle, a hidden third zone in which components are rhizomatically connected. Here I use fecundity to refer to intellectual productivity. The study aimed to establish which characteristics in eco-art can contribute significantly more to sustainable eco-cultural development and what form and opportunities such transformative interventions manifest. The ways in which artists position their work to contribute to cultural climate change adaptation is interrogated in transdisciplinary praxis. In doing so, I interrogate previously published work of a select group of artists. This is not an inquiry into the methodology of transdisciplinary research, but, drawing on the artists’ praxis, I argue and expand on how the value of collaboration of scholars and artists working in these liminal spaces can reach new audiences. Two datasets are interrogated to analyse the approaches in art related to the environment, one eco-art characteristic derived from the author’s public art praxis, and the second, a broader interrogation of 50 international eco-artworks. By comparing and contrasting the two datasets, characteristics of intentionality, often built into the artworks, were identified. Six key characteristics were isolated, described and further interrogated to discover how they may create opportunities for society to build and foster potential cultural climate change solutions
A comparative analysis of mining environmental management programme reports following a change to the one environmental system
(University of the Witwatersrand, Johannesburg, 2022) Mathe, Lebogang; Watson, I.
The mining fraternity has recently seen a shift in terms of environmental requirements under the ambit of the Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) to the National Environmental Management Act 107 of 1998 (NEMA). The objective was to ensure a streamlined environmental compliance and to put emphasis on integrated environmental management. The One Environmental System (OES) was introduced which denotes that all environmental related projects or activities, including mining, are regulated through an ambit of one system. NEMA is recognised as an overarching law which provides for co-operative environmental governance; therefore, all environmental related activities are regulated under its ambit and EIA regulations. In this research report, the Environmental Management Programme (EMP) reports and Environmental Authorisations that were issued under the MPRDA and the 2014 NEMA regulations respectively, were analysed using the respective regulations to compare the environmental management measures outlined in the reports to achieve better environmental results. The aim of the research was to assess whether the Environmental Authorisations granted in terms of NEMA reflect better environmental results as compared to those issued under the MPRDA. Better environmental results mean improved management plans with clearer assessment of impacts, more detailed mitigation measures with specific, achievable, relevant and time bound actions that do not pose harmful effects on the environment and communities. A mixed method of analysis was implemented which included a review and comparison of legislation, evaluation and scoring of 20 EMPs (10 submitted under MPRDA and 10 submitted under NEMA) and interviews with key informants, namely competent authorities and the Environmental Assessment Practitioners (EAPs) were conducted to support the findings of the reports. In conclusion, the reports analysed presented a significant improvement and better environmental results under NEMA. The interviews conducted with authorities and the EAPs have also substantiated the observations made in terms of Environmental Management Programme reports and Environmental Authorisations submitted. The findings indicated that there were similarities in the MPRDA and NEMA regulations as 4 | P a g e regards some environmental requirements. However, the MPRDA lacked to outline a detailed description of environmental requirements needed to manage environmental impacts. Thus, applicants provided limited information in terms of the management of impacts. NEMA has provided additional requirements, including baseline environmental information, specialist reports and public participation amongst others; these contributed to improved environmental results. The study revealed that the reports submitted under NEMA provided better environmental management measures as compared to the reports submitted under MPRDA.
The Assessment of the Current Geographical Information System (GIS) initiatives in the public enterprises of Swaziland
(University of the Witwatersrand, Johannesburg, 2022) Khumalo, Malungisa Blessing; Adam, Elhadi
There is a growing use of geographic information systems (GIS) within the public sector in many countries. GIS require considerable financial resources and investment in information and communication technology (ICT) and human resources, which are primarily financed by public funds. The growth in adoption is partly influenced by the promising potential of GIS that has been widely discussed in the literature on GIS. The usefulness and application of GIS in aiding decision making and in public policy formulation and implementation have also been widely discussed in the literature on GIS. To examine the effectiveness of GIS in public policy, one has to develop a mechanism for measuring the success achieved by the implementation of GIS in decision making. However, the methodologies for the evaluation of the use of GIS in the public sector are mainly lacking. The aims of this research were to evaluate the effective use of GIS in the public sector in Swaziland. Three organisations were selected, namely the Swaziland Posts and Telecommunications (SPTC), Swaziland Water Services Corporation (SWSC) and Swaziland National Housing Board (SNHB). Like in most developing countries, the lack of GIS evaluation to improve implementation is a challenge for these organisations. The current GIS applications at SPTC, SWSC and SNHB were evaluated using maturity, value and GIS product assessments. Four methods of analysis were used for data analysis: GIS maturity calculation; relative frequency of maturity calculation; gap analysis; and GIS value assessment. The results found that the SPTC, SWSC and SNHB were all in the exploitation stage of maturity. The overall relative frequency of maturity in the dimensions is the following: 35% of indicators are in the exploration stage; 56% are in the exploitation stage; and 9% are in the enterprise stage. The gap analysis shows that the organisations are in the exploitation stage of maturity. Cost prevention, coordination, employee satisfaction, better data management, time saving and better quality of information were regarded as the main ways in which GIS add value to organisations. The GIS product assessment results show that the overall compliance rate with the cartographic standards is 57.09%.
Water quality assessment at Vaalkop Dam in North-West Province using multispectral remote sensing data
(University of the Witwatersrand, Johannesburg, 2022) Mthimkulu, Lindy Ndzumbululo; Adam, Elhadi
Water is a life-sustaining resource for all organisms. As much as nature share the value of water with human being it cannot supersede how human have become dependent on water for drinking, sanitation, farming, mining, and other industrial purposes such as power generation. Water is perceived as a vital component in the fight against poverty, the foundation of any successfully growing and developed country is also measured on water and sanitation provision (Basson et al., 1997). The water law in South Africa stresses that essential human and ecological necessities must be given (DWAF, 1998) and that the misuse of water from all perspectives should be feasible (New, 2002).
Extreme weather events and human health in South Africa: implications for climate services
(University of the Witwatersrand, Johannesburg, 2022) Manyuchi, Albert Edgar; Erasmus, Barend; Wright, Caradee; Vogel, Coleen
Extreme weather events (EWEs), defined as ‘weather events that are rare at a particular place and time of the year’, have increasingly been affecting many countries worldwide (IPCC 2014). The increased occurrence and intensity of EWEs, among other factors, has increased public interest and demand for climate information. More detail is needed on EWEs and how they can be more effectively coupled to climate services in Africa. This study brings a compendium of empirical evidence, conceptual clarity and transdisciplinary approaches to policymakers, researchers and practitioners dealing with these crucial issues. The main aim of this study is to explore the human health effects of EWEs, particularly heat and the delivery of climate services for health in Africa. Through a systematic review, the study examines the potential impacts of heat on human health in Africa. Using a case study approach heathealth effects are evaluated including the status of climate services in the Agincourt subdistrict of South Africa. A novel systems theory-based conceptual framework and an inclusive analytical framework are employed to explore climate services delivery within the context of climate change adaptation. The study produces two main findings. First, EWEs particularly heat, potentially affects human health in Africa by changing mortality and morbidity patterns. In the Agincourt sub-district in particular, heat may be associated with adverse health effects on vulnerable populations, including inter alia the elderly, children and outdoor workers. Despite this, Africa-specific heat-health interventions and policy suggestions are scarce. Second, climate services are generally in embryonic stages of development and climate services for health in Agincourt subdistrict are non-existent. Within the South African context, the main barriers to delivery of climate services for health are paucity of interagency coordination and gaps in meteorological data. One of the key conclusions of the study is that African countries can promote development of climate services to adapt to EWEs such as heat. Heat, and heatwaves, for example, are already affecting populations, and are projected to increase in frequency and intensity with concomitant adverse effects on health outcomes on vulnerable population groups. The three key recommendations from this study are as follows. First, African policymakers and practitioners must avoid a reductionist approach to analysis of EWEs, especially heat impacts and start viewing these as harmful to human health. Therefore, governments must prioritise interventions, create institutions and formulate policy measures to deal with the health effects of heat within their national adaptations plans. Second, African countries must prioritise policy mixes that promote climate services in general and climate services for health in particular. And finally, further policy-science research that generates empirical evidence for African policymakers and practitioners engaged in international negotiations and programmes for climate change adaptation and climate services should be encouraged.
The impact of fly ash on the growth rate of maize (Zea mays L.) and the potential for fly ash to be used commercially in agriculture
(University of the Witwatersrand, Johannesburg, 2022) Riba, Mpho Mahlatse; Scholes, Mary
South Africa’s coal-fired power plants (CFPPs) produce about 34.4 million tons of fly ash (FA) per annum, as a by-product of the coal combustion process, which is stockpiled adjacent to these CFPPs. This FA contains traces of heavy metals (HMs), as a result it is a potential environmental hazard. The purpose of this study was, therefore, to establish the effects of (‘FA’) on the growth of maize (Zea mays L.), as well as its potential commercial use in agriculture due to its nutrient content, instead of maintaining the status quo. Another aim of the study was also to determine the phytoextraction abilities of the HMs (Mn, Cr, Ba and Mo) from contaminated soils by the maize plants. The study was conducted by planting maize seeds in five soil substrates with 0 %, 20 %, 40 %, 55 % and 60 % FA treatment, on mass basis. The ANOVA indicated that there were significant differences when comparing most of the mean stem length, number of leaves, root length and the mean mass of total plant dry biomass, across all the FA treatments, after 122 days of growth. The mean stem lengths after 122 days of growth were 86.67  20.55 cm, 148.33  13.87 cm, 154.17  18.10 cm, 121.17  14.99 cm and 149.50  24.20 cm for maize plants grown in 0 % , 20 %, 40 %, 55 % and 60 % FA treatments, respectively. The mean number of leaves were 12  1.87, 16  2.34, 18  2.83, 12  1.87 and 14  1.79 across all treatments, respectively. The key finding was that the growth of these plants improved with the amount of FA in the soil, with the plants that were grown in the 40 % FA treatment yielding the best results. The same observation was made with the root length and the mean masses of total plant biomass (roots, stems and leaves). Another important finding was that the accumulation of the HMs (Mn and Cr) in the plants increased, across the FA treatments, while their concentrations in the soil decreased across the FA treatments. The accumulation of Ba and Mo in the plants also increased, across the FA treatments, while Ba remained slightly constant and Mo increased in the soil. This indicated that the maize plants can potentially remediate Mn and Cr contaminated soils, through phytoextration, but are retained in the root system.
Evaluating the Effectiveness of Green Drop Audit Criterion in Relation to Its Link to Enforcement Protocol in South Africa
(University of the Witwatersrand, Johannesburg, 2022-08) Tshongweni, Olwethu Lenox; Tutu, Hlanganani; Richards, Heidi L.
The Green and Blue Drop programs are incentive-based regulatory systems based on the Department of Water and Sanitation's (DWS) realization that rewarding positive behaviour is more efficient and effective than penalizing undesirable behaviour. The Green Drop was developed for the Wastewater Quality Management Regulation certification program. In contrast, the Blue Drop was developed for the certification program for the Drinking Water Quality Management Regulation (Burgess, 2021). Most municipalities have accepted them and have raised awareness about the need for better efficiency in the wastewater sector. The Sand River, in Polokwane wastewater treatment works (WWTWs), was chosen as the research area for this study. This particular river was selected based on the premise of continuous non-compliance of the wastewater treatment plant and the resulting pressure it puts on the Sand River by compromising its quality, with the DWS not having a successful way of regulating and enforcing the water user to abide by the rules of the license that has been issued. This study aims to evaluate the effectiveness of the Green Drop Program audits and assessments about their link to the regulatory system within the DWS. Additionally, a risk assessment and cumulative risk rating are used to assess wastewater discharge into the Sand River in the Limpopo Province. Based on the observation made during the study, it appears that within the DWS organizational arrangements, the lack of coordination among the sectors (compliance monitoring, water quality management, the green drop program, and enforcement), lack of accountability, and the regulatory requirement of cooperation within DWS sectors have hindered implementation. Some of the non-compliance factors may be due to the misuse of funds meant for infrastructure development and difficulties relating to capacity, procurement, and management of the WWTWs. Moreover, DWS's absence of interactive data management systems and business processes contributes to non-compliance. The Polokwane WWTW, directly linked to the Sand River, is overloaded and needs to comply with the Water Use Licence (WUL) conditions. For example, the 21 August 2022, this facility was found to be non-compliant by 69.01%, collectively with administration and technical conditions of the WUL issued to the facility (DWS, 2022c). In addition, this investigation discovered that the Polokwane facility, which has been operating outside of regulations for the past four years, therefore, as calculated in equation 7 could be responsible for 72.3% of the hazards to people's health, the quality of the river's water, and the aquatic ecosystem life in the Sand River in a single month. As much as some municipalities do not perform according to the desired standards, there have been a few noticeable, well-performing ones reported in the green drop report released in 2022. These include Langebaan WWTW (90%), Riebeek Valley WWTW (97%), Gansevallei WWTW (84%), and Wellington WWTW (95%), and this illustrates that the Green Drop Certification is achievable if the municipalities follow and adhere to the Water Use Authorization (WUA) issued them (DWS, 2022b). The DWS must integrate the internal structures or link sectors responsible for monitoring and regulating municipal water service facilities and incentivize performing facilities to improve their performance. Additionally, facilities with minor compliance issues, such as water quality, must be referred to the Water Quality Management (WQM) unit for further investigation and recommendations. However, those non-compliances of authorized wastewater treatment facilities that require regulatory attention must be referred to the compliance monitoring sector through the system for compliance monitoring. Lastly, those facilities that are not authorized must be directed to enforcement for further action. Therefore, using the Integrated Regulatory Information System (IRIS) as the umbrella body for both database and work-based information has an imperative role that can curb some of the issues faced by the DWS. Standard operating procedures (SOPs) should guide all interactions between these systems.
Understanding disturbance, vegetation density, seed banks and pollination for the conservation of Protea curvata
(University of the Witwatersrand, Johannesburg, 2023) Mabuza, Precious Gugulethu Babalwa; Balkwil, Kevin
Background Aims: Protea curvata (Proteaceae) is a threatened species endemic to Mpumalanga, South Africa. Previous records of the species showed discrepancies in location data and information on population demographics was sparse. At the time of the study (2018), the last IUCN assessment of P. curvata was 20 years ago and one subpopulation of the species was reported to have a low number of mature individuals. In 2017, a census of another subpopulation indicated that the mature individuals were the most abundant cohort and there was no recruitment of P. curvata seedlings. Thus, there was uncertainty regarding how population size, population demographics and threats faced by the species may have changed over the last 20 years. The study aimed to update the IUCN status of P. curvata and to assess factors relating to P. curvata recruitment, namely the breeding biology of the species and the woody species composition on P. curvata sites. Methods: A census was conducted on P. curvata sites. Census data and site composition was compared between sites with contrasting management. Soil samples were collected from six sites. Pollination modes in P. curvata were investigated by manually pollinating inflorescences that were covered at bud phase to exclude animal pollinators. Five treatments were tested: autogamous selfing, tree geitonogamous selfing, inflorescences geitonogamous selfing, natural outcrossing and pollen supplemented outcrossing. Seeds from each treatment were weighed and tested for viability using TTZ staining. Animal pollinators were observed in the field and through camera traps positioned in front of non-covered inflorescences. Key Results: Five subpopulations were identified. P. curvata recruitment was low in two subpopulations and absent in three subpopulations. When comparing the site with the lowest recruitment (Site A) to the site with the highest recruitment (Site C), woody cover and tree density was higher on the site with low recruitment – indicating bush encroachment. This was attributed primarily to long intervals between fires at Site A. Site A showed a concerning net decline in subpopulation size (3% loss per year). Despite having more P. curvata juveniles, Subpopulation C showed a similar rate of decline (2% loss per year). The species was identified as endangered; with severe hailstorms and delayed, intense fires posing the major threats. Hailstorms compounded fire-induced damage on P. curvata bark. Flowering declined significantly after a hailstorm. (x̄pre-hail = 10.94 inflorescences per tree, x̄post-hail = 4.28 inflorescences per tree, p-value = 0.0031). During pollination experiments, Protea curvata was able to self-pollinate. However, seed mass and viability were significantly higher in outcrossed treatments. Viability in naturally outcrossed treatments (x̄=42.7%) was similar to pollen-supplemented outcrossed treatments (x̄=32.1%), but significantly higher than treatments of autogamous selfing (x̄=21.95%), geitonogamous selfing within inflorescences (x̄=27.1%) and geitonogamous selfing within trees (x̄=26.2%) [C.I= 95%; d.f.= 4, 95; Fcalc= 4.5; p = 0.0021]. Colletid bees and Apid bees contributed to P. curvata pollination via geitonogamy and early removal of self-pollen from stigmas. Birds were the most frequent visitors of P. curvata and were the most effective pollinators due to their prominent role in natural outcrossing. Bats infrequently visited inflorescences but may possibly complement outcrossing since they make contact with stigmas and do not spend their visit time restricted to one inflorescence or tree. P. curvata was non-serotinous and possessed a short-lived, soil seed bank. Across all sites, the average viability of seeds in the soil was well below that of freshly collected seeds from pollination experiments (4–9% for soil seed bank; 22.0–42.6% for fresh seeds). Seed bank size was surprisingly low in subpopulations with high flowering. Conclusions: Reducing seed loss after release from the canopy appeared to be more important than high flowering for maintaining a large seed bank. Therefore mild, frequent fires will be essential for reducing bush encroachment, making way for seed deposition and encouraging seedling survival
Seasonal abundance and diversity of mites in Coffea arabica L. at Beaver Creek Coffee Estate, South Africa
(University of the Witwatersrand, Johannesburg, 2023) Chikomo, Nontobeko Natasha; Situngu, Sivuyisiwe
The presence of multiple species of mites inside the leaf domatia of Coffea arabica is well documented by various studies. This study examined the influence of seasonal changes on the abundance and diversity of mites in the leaf domatia of Coffea arabica. The study furthermore documented the species of predatory mites that were associated with coffee. The results of the study showed that there was a significant variation in the abundance of mites due to changes in season. Mite counts were significantly higher in spring followed by autumn and lowest in summer. There was no correlation between the number of mites and temperature and relative humidity. Therefore, this study could not establish what drives the seasonal changes in the mite populations and we postulate that this was because we did not measure the microclimate of the individual trees we sampled. This would have given us more accurate data on the temperature and relative humidity experienced by these mites. The Shannon-Weiner Diversity Index was found to be highest in summer and lowest in winter. The Phytoseiidae, Tydeidae, Stigmaeidae, and Tenuipalpidae were found to be the predominant families in this study. This study is one of the few studies in South Africa to directly investigate the effects of seasonal changes in mite abundance, and could potentially open avenues for further research, particularly on what seasonal parameters drive the mite population changes. We recommend that future studies use Ibuttons to get a true measure of the climatic variables that are experienced by the mites sampled at a tree level
Characterisation of Drought Using Hydrological and Meteorological Indices: A Case Study of Bethlehem, South Africa
(University of the Witwatersrand, Johannesburg, 2023) Tshabalala, Khanyisile; Evans, Mary; Masindi, Khuliso
The study aims to assess the severity and evolution of drought/s in Bethlehem using the hydrological: Streamflow Drought Index (SDI), Reconnaissance Drought Index (RDI), Effective Reconnaissance Drought Index (eRDI) and meteorological: Standardised Precipitation Index (SPI), Agricultural Standardised Precipitation Index (aSPI), and Precipitation Deciles (PD) indices. These indices were computed using the Drought Indices Calculator (DrinC). The RDI, eRDI, aSPI, and SPI identified three drought events between 1980 and 2017. The PD on the other hand, identified particular years between 1980 and 2017 that received below-normal to much below- normal precipitation. Further, the years identified to have received below normal to much below normal precipitation fell between the drought periods identified by the other indices, such as the 1980 – 1990 drought identified by the SPI, RDI, aSPI, and eRDI; the PD identified 1982, 198, 1985, and 1986 as specific years the received significantly low precipitation within the decade long drought. Of critical note is the absence of the SDI results, stream levels data was not available at the time the results presented in this report were computed. The unavailability of SDI values did not compromise or negatively affect the results presented in this study as the computed indices had a strong correlation, implying the reliability of the results presented in this report
The effects of elevated carbon dioxide on the secondary metabolites and biological activities in Moringa oleifera Lam. and Moringa peregrina Forssk
(University of the Witwatersrand, Johannesburg, 2023) Moloi, Thato; Dukhan, Shalini; Ramalepe, Phillemon; Risenga, Ida
Climate is crucial for the distribution and survival of medicinal plants as it can influence phytochemicals and regulatory hormones that are responsible for the normal growth and development, as well as their interactions with the environment. Thus, it is important to understand how climate change will impact these crucial plant compounds and hormones that play a significant role in the plant’s survival and development. With the increasing CO2 in the atmosphere, it is expected that climate change effects will be devastating to the world and Southern Africa. The present study intended to achieve two aims, the first being to investigate the impacts of elevated CO2 (eCO2) on the secondary metabolites and biological activities of two important Moringa species, Moringa oleifera Lam. (M. oleifera) and Moringa peregrina - (Forssk.) Fiori (M. peregrina). The second aim was to investigate how the use of M. oleifera leaf extract (MLE) based and commercial (PhytoStim®) biostimulants influence the productivity as well as the adaptability of M. oleifera and M. peregrina under elevated eCO2. The first set of three-month-old potted plant samples were exposed to 400 ppm (control), 600 ppm and 800 ppm for three months, respectively. The second set of plants were placed in the greenhouse and sprayed (foliar application) with 200 mL of M. oleifera leaf extract (MLE) and 200 mL commercial biostimulant PhytoStim® every second week for three months, respectively. The control samples were unsprayed. The third set of plants were exposed 600 ppm and 800 ppm (separately) and simultaneously sprayed with 200 mL of M oleifera leaf extract (MLE) and 200 mL commercial PhytoStim® (separately) every second week for three months to assess the influence of biostimulants on the adaptability of the Moringa species under eCO2. The control samples under 400 ppm were unsprayed. In this study, 80% methanolic extracts from all the above mentioned treatments of M. oleifera and M. peregrina were screened for 17 secondary metabolite groups (tannins, saponins, flavonoids, quinones, phenols, terpenoids, cardiac glycosides, coumarins, steroids, phlobatannins, anthracyanine, volatile oils, phytosterols, triterpenoids, proteins and amino acid, glycosides, carbohydrates) using qualitative methods. Quantitative analyses were performed to determine the total phenolic content (TPC), total flavonoid content (TFC), total tannin content (TTC) and total proanthocyanidin content (TPAC). The antioxidant assays were performed to determine the reducing, scavenging and chelating abilities against DPPH, H2O2 and metal (Iron) chelating. The antimicrobial activities against gram negative Escherichia coli and gram-positive Staphylococcus aureus, Streptomyces albulus were assessed by using the agar well diffusion assay. In the control samples, out of 17 screened secondary metabolites, four (phytosterols, volatile oils, anthocyanin and phlobatannins) were not detected in both species’ extracts. On average, M. peregrina showed higher total content of tannins, phenolics, flavonoids and proanthocyanidins. M. peregrina showed stronger antioxidant activity against iron chelating and H2O2, whilst M. oleifera showed stronger antioxidant activity against DPPH. Both M. oleifera and M. peregrina extracts displayed an acceptable bacterial growth inhibition capability (ZOI ≥10 mm) with only S. albulus being resistant to the control of M. oleifera. Qualitative phytochemical analysis indicated the presence of secondary metabolites such as tannins, saponins, flavonoids under 600 ppm and a slight decline under 800 ppm in both species. The quantitative analysis indicated an increase in the total content of phenols, flavonoids (flavanols), tannins, and proanthocyanidins. An increase in CO2 resulted in an increase in the activity of antioxidants and antibacterial for both species. On average, Moringa peregrina showed higher accumulation of secondary metabolites, higher antioxidant and antibacterial activities in comparison to Moringa oleifera. The foliar application of MLE and PhytoStim® showed an increase in some secondary metabolites and decrease in metabolites such as tannins and phenols in M. oleifera. The application of biostimulants (MLE and PhytoStim®) also resulted in an increase in TPC, TTC and TPAC in M. peregrina, with a decline in total contents of these compounds in M. oleifera. However, the decline did not negatively impact both species' pharmacological abilities (antioxidant and antimicrobial activities), as they exhibited stronger antioxidant and antimicrobial activities when compared to the untreated plants (control samples). The use of the above mentioned plant based biostimulants resulted in an enhanced adaptability as indicated by the increase in the accumulation of selected screened secondary metabolites plant samples that exhibited signs of stress. The higher accumulation of secondary metabolites was observed under 600 ppm, in combination with PhytoStim® for either species. The combined CO2 and biostimulant treatments improved the total phenolic content (TPC) of both M. oleifera and M. peregrina significantly, with M. oleifera showing higher TPC content when compared to M. peregrina. On average, both M. oleifera and M. peregrina exhibited lower total flavonoid content (TFC), total tannin content (TTC) and total proanthocyanidins (TPAC), with M. oleifera showing higher contents of the above-mentioned phytochemicals in comparison to M. peregrina. The study also highlighted a decline in biological activities for all treatments, with the controls showing higher biological activities for both species. In the three antioxidant assays conducted, the leaf extracts of the controls had significant lower IC50 values for DPPH and H2O2, when compared to the stressed M. oleifera and M. peregrina. Antimicrobial assays also showed no significant difference in the bacterial inhibition capabilities of M. peregrina and M. oleifera under 600 ppm and 800 ppm with either biostimulant application. M. peregrina and M. oleifera controls showed high ZOI for the selected bacterium. The study has demostrated that biostimulants (MLE and PhytoStim®) enhanced the adaptability of both species under potential stress coursed by eCO2. The present study has demonstrated that the exposure to elevated CO2 could alter the accumulation and biological processes (such as antioxidant activity and antimicrobial activity) in both M. oleifera and M. peregrina. Moringa peregrina exhibited more tolerance to elevated CO2 when compared to Moringa oleifera and showed higher antioxidant and antimicrobial activity which might be attributed to the stronger presence of phytochemicals such as flavonoids, phenols and tannins. The data also suggests that both Moringa oleifera and M. peregrina can adapt to high levels of CO2 concentrations (~600 ppm), however, as medicinal plants, it might be difficult to sustain the acclimatisation and tolerance due to membrane oxidation and DNA damage. Therefore, foliar application of the biostimulants could enhance the adaptability and productivity of both species under high levels of CO2. This study may contribute towards better planning on conservation efforts to improve the chances of survival of the Moringa oleifera and M. peregrina and could aid with food security.
The effects of resource variability on the demographic rates of black and white rhinoceroses
(University of the Witwatersrand, Johannesburg, 2023) Ndlovu, Latoya; Marshal, Jason
Given the importance of rhino survival and reproduction to conservation goals, the aim of the study was to investigate the effects of resource variability on the demographic rates of black (Diceros bicornis) and white (Ceratotherium simum) rhinos at Lapalala Wilderness. I used historical rhino-monitoring, rainfall and vegetation greenness data to investigate the vital rates of two rhino populations. I investigated population demographics (mainly density, growth rates, age and sex structure) and survival using stratified Cox models. Black and white rhino density peaked at 0.06 rhinos/km2 and 0.2 rhinos/km2 , respectively during the study period and was below the estimated maximum density for suitable rhino reserves. Average growth rate for the black rhinos was 4.784%, which was almost half of the white rhino’s rate of 8.861%. The survival of both species was stage-specific, and rainfall effects were similar for both species and age groups as low amounts of rainfall, which likely represent decreased forage availability, were associated with increased mortality risk. Decreasing greenness was also associated with increased mortality except with white rhino calves, where mortality increased with greenness. I suggest that this case might have been caused by their nutritional requirements: most grasses lose nutritional value as the season progresses (i.e., represented as increases in greenness values and so reduced access to high quality forage might affect mom’s body condition and her ability to produce nutritious milk, consequently resulting in increased mortality rates of calves. I also investigated the reproductive phenology (mainly conception and birth timing, age at primiparity and inter calving intervals) and birth sex ratios in relation to sex allocation theories. White rhinos conceived and calved at an earlier age compared to the black rhinos; mean age at primiparity for white and black rhinos was 9.448 years (8.467, 10.43) and 11.724 years (10.52, 12.927), respectively. Conceptions for both species peaked during the wet season and were associated with periods of high forage availability; however, births were asynchronous and occurred throughout the year. Effects of rainfall and greenness on age at first conception differed between species; the odds of having their first calf increased with rainfall, EVI and NDVI for white rhinos but decreased with EVI and NDVI for the black rhinos. Increases in wet-season integrated greenness during conception periods might indicate a shorter period of access to high quality forage for the black rhinos. Age at primiparity increased with density for both species because population density increases competition for resources, potentially making it difficult for females to accumulate the body mass and energy reserves needed to reproduce. Inter-calving intervals increased with rainfall, supporting the idea that excessive amounts of rainfall might result in lower forage quality, which then affects maternal body condition. In conclusion, vital rates of black and white rhinos are associated with resource availability as a function of environmental stochasticity and density, which in turn affects productivity and performance as climate change results in more variable conditions.
The past, present and future of cactus invasions in South Africa in response to rising atmospheric CO2 and climate change
(University of the Witwatersrand, Johannesburg, 2023) Venter, Nicolaas; Byrne, Marcus
Cactaceae originate from the Americas and over the past 250 years have been introduced into South Africa and elsewhere for agricultural and horticultural purposes. Numerous species, including useful taxa, have become important invasive weeds that have serious socio-economic and environmental impacts. Fortunately, management strategies, in particular biological control, have been successful in controlling certain species. However, with rising atmospheric CO2 invasive cacti are likely to pose a renewed threat, whereby evidence shows that cactus species are responsive to CO2 fertilisation, which is likely to increase their vigour, mainly through improved water use efficiency (WUE). Additionally, studies show that plant quality declines with increasing CO2 which in general has negative effects on their arthropod herbivores. This study sought to determine the effect of CO2 on two functionally different invasive cactus species and how they may respond to predicted increases in atmospheric CO2. Opuntia stricta (a succulent shrub) is an obligate CAM photosynthetic species that invades grasslands and savannas across semi-arid to subtropical environments whereas Pereskia aculeata (a scrambling woody vine with well-developed leaves) is a CAM-cycling photosynthetic species that invades forest type habits across subtropical environments. Plants were grown at three CO2 concentrations that represented pre-industrial (sub-ambient - 250 ppm), current (ambient - 400 ppm) and future (elevated - 600 ppm) atmospheric CO2 conditions. Plants were also subject to suboptimal and optimal watering treatments for the duration of the experiments to determine the ameliorative effect of CO2 on productivity in response soil moisture deficits. In addition, an experiment was conducted on O. stricta to test the effects of the three CO2 concentrations on plant quality and the subsequent effect on the fitness and efficacy of its insect biological control agent, Dactylopius opuntiae. Growth and productivity of O. stricta and P. aculeata responded positively to increasing CO2, however the responses varied with CO2 concentration. Increasing atmospheric CO2 concentration from date of introduction to present possibly facilitated O. stricta invasion whereas this was less likely for P. aculeata. In both species WUE increased with increasing CO2. Under suboptimal watering, there was partial amelioration of productivity at 600 ppm CO2, but the plant traits that benefitted varied according to species. Plant quality declined for both species, most notably cladode nitrogen (N) content decreased, and carbon/nitrogen ratios (C/N) increased. When D. opuntiae were exposed to O. stricta grown at elevated CO2 (only tested on well-watered plants), D. opuntiae fitness was reduced which in turn reduced the rates of plant mortality due to the insect damage. Using the WUE results from O. stricta, a mechanistic species distribution model (SDM) created here predicted greater increases in its potential distribution in South Africa under climate change relative to the SDM that did not include WUE as a predictor variable. This suggests that improved WUE under future CO2 concentrations can offset the effect of declining rainfall in certain regions of South Africa. Overall, these results suggest that O. stricta and P. aculeata will show more vigorous growth and are also likely to expand their ranges into regions where rainfall currently limits their distribution. This expanded distribution may be further facilitated by reduced biocontrol agent efficacy as host plant quality declines. These findings suggest that management of these two species and other invasive cacti is likely to become more challenging with increasing atmospheric CO2 and climate change.
Assessment of the Environmental Authorisation Processes and Mining Right Applications for Improved Environmental Outcomes
(University of the Witwatersrand, Johannesburg, 2023) Antoniades, Maria; Watson, Ingrid
This study investigates alignment of South African mining right and environmental authorisation application processes to determine their adequacy in catering for optimised early mine planning seeking to achieve enhanced environmental outcomes. First the legislative requirements for mining right and environmental authorisation applications are evaluated. Results are critically analysed, including an assessment of process alignments and disjunctions. Secondly, integration of the application study processes in practice are investigated. The practical implications of the application requirements are qualitatively examined through key informant and case study analysis. It is shown that integrated planning is not a legislated requirement nor readily adopted by proponents. Environmental planning conforms to technical outputs as tick-box exercises rather than being iterative and co-operative. Workstreams misalignments result in poor planning to the detriment of environmental outcomes. Finally, a practical guidance is presented for early integrated study processes aimed at meaningful project design through parallel planning to optimise environmental results.
Factors affecting mammal utilisation of non-wildlife railway underpasses within the Greater Kruger, South Africa
(University of the Witwatersrand, Johannesburg, 2023) de Villiers, Hannah; Parrini, Francesca; Teren, Gabriella
Railways are an integral component of sustainable transport systems, but cause significant impacts to biodiversity, primarily through wildlife-train collisions and the habitat fragmentation created in the landscape. Crossing structures (CSs) for wildlife are the key mitigation measure for these adverse impacts, which will be critical throughout Africa, where 55,000 km of new railway lines are predicted to cut through hundreds of protected areas. For the first time in southern Africa, mammal usage of railway underpasses that were not designed to facilitate wildlife movement was studied using camera traps in the Greater Kruger National Park, South Africa. This study demonstrates that 70% of the terrestrial medium and large mammals species present in the area used at least one non-wildlife CS during the study period, with a total of 1,823 usage events by 33 species. Twelve medium to large African mammal species used underpasses regularly, improving the permeability of the railway line for these species. A viaduct design was characterised by almost four times the usage rate of a typical box culvert and was used by twice as many species, including megaherbivores and mesoherbivores, whereas box culverts supported a smaller number of species, of which the majority were predators. Species most affected by rail collisions in the study area were mostly herbivorous and seldom used non-wildlife underpasses. These results indicate that a railway line with only drainage culverts and the occasional viaduct is not effective in providing adequate safe crossing structures for megaherbivores and ungulate mesoherbivores. Contrary to expectations, vegetation and environmental factors influenced mammal usage of box culverts more than structural dimensions. Ensuring that there is high visibility through the structure, with less herbaceous cover and more woody cover outside of entrances, is likely to enhance culvert usage by most trophic groups. In a savanna context where faunal diversity is high and no single species is a target for mitigation, a range of underpass designs including larger viaducts, located in different types of vegetation cover, thereby combining the range of requirements of different guilds, is recommended.

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