Browsing by Author "Trisos, Christopher"

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    Climate change risk to southern African native wild food plants
    (2021) Wessels, Carina; Trisos, Christopher
    Climate change is a threat to food security. A substantial body of research supports this conclusion for climate change threats to plants with agricultural value, as well as wild-harvested food from animals, such as fish. However, much less is known about climate change threats to wild-harvested food plants despite these species meeting important dietary needs for a large number of households in developing countries, especially when crops fail or during other times of hardship. My study was the first to look at climate change risk to a broad group of wild edible plants and focussed on the wild food plants (WFPs) of southern Africa. The aims of my study were to determine where WFPs occur in southern Africa; whether these WFPs will be threatened by climate change; and how climate change risk for WFPs intersects with climate change risk to staple crops. Species distribution models were used to obtain the historical geographic range of 1190 WFP species and to make projections of range change for 2070 under both low (Representative Concentration Pathway (RCP) 2.6) and high (RCP 8.5) greenhouse gas emissions scenarios. I also mapped percentage change between historical and future yields for maize and sorghum to identify regions where both crops and WFPs, or just one of these are at risk from climate change. WFP species richness in southern Africa generally increases from west to east across the region, with the Eastern Cape, Kwazulu-Natal and Mpumalanga provinces of South Africa having the highest WFP species richness. It is projected that for RCP 2.6, 40% of WFP species will experience a decrease in range extent within southern Africa, increasing to 66% of WFP species for RCP 8.5. For RCP 2.6, the loss of suitable climatic conditions is projected to decrease local WFP species richness most in the north-eastern parts of southern Africa, while increases in WFP species richness are projected in the south and east of South Africa. For RCP 8.5, decreases of more than 200 species are projected for multiple regions in north-eastern South Africa, and local WFP species losses of more than 50% are projected for most of Botswana. Despite these decreases, WFPs could still play an important role in food security during times of low agricultural yield as a result of changing climate conditions, especially in low-income, rural communities that are reliant on smallholder farming. For instance, in parts of the Eastern Cape province of South Africa and northern Namibia, WFP species richness is projected to increase while maize and sorghum yield are projected to decrease. People may be more able to rely on WFPs as a nutritional safety net in these regions into the future. This safety net, however, may be lost in large regions of South Africa's North West and Free State provinces, on the north-eastern border between South Africa and Botswana, as well as parts of northern Namibia, where declines in both crop yield and WFP species richness are projected. This research could prove valuable for climate change adaptation planning, especially in more vulnerable rural regions of southern Africa. Furthermore, by integrating traditional knowledge of WFPs into food security risk assessments and response options, it could provide a more inclusive range of food supply options people can use in order to mitigate risk. However, in order to ensure future food security, more research is needed on WFP uses, nutritional value, responses to climate change, and suitability for cultivation. Still, by looking beyond the farm level and conventional crops to the exceptional diversity of WFPs people obtain from their environment, my research has made a first step towards understanding the linkages between WFPs, agriculture, food security, and climate change.
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    The evolution of annuality in association with a shift to more arid environments in the daisy genera Ifloga and Tricogyne
    (2007) Trisos, Christopher; Bergh, Nicola G; Verboom, George Anthony
    An annual life history is often viewed as a model adaptation to arid environments. Annuality is predicted to have evolved in response to low adult survival and high seedling survival. In this study I evaluated the idea that increases in aridity should be associated with the evolution of an annual life history. I also investigated the correlated evolution of annuality and growth form. Ancestral character states for life history characters and climate variables were mapped onto a molecular phylogeny (obtained using plastid trnL-trnF and psbA-trnH and nuclear ETS sequences) of the genera Trichogyne and Ifloga (Asteraceae). Bayesian methods were used for phylogeny inference and maximum likelihood methods for ancestral state reconstructions. Only two phylogenetically independent contrasts were obtained and so the association between changes from annuality to perenniality and increases in aridity along branches of the tree were recorded and evaluated using Fisher's exact test. In order to account for ancestral character state reconstruction uncertainty, four different possible scenarios suggested by the maximum likelihood methods for the evolution of annuality were examined. This is the first molecular phylogeny of the group. Bayesian analysis of the sequence data places the Trichogyne+ Ifloga clade within the Gnaphileae. The genus Ifloga is shown to be paraphyletic. Trichogyne ambigua, as currently described, is polyphyletic and may contain two species. The origin of the Trichogyne+ Ifloga clade is within southern Africa and a northwards migration via the arid corridor is suggested to explain the disjunct distribution of the two Northern Hemisphere species. There is an association between the duration of the moisture growing season and the evolution of annuality. This is consistent with the idea that annuality is favoured by long drought periods making perennation difficult. The evolution of annuality was correlated with a non-woody, tufted, growth form. Amphi-basicarpy was discovered for T. polycnemoides, making it only the second known example of this reproductive strategy within Asteraceae.
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    Mobilising biodiversity data gathered during environmental impact assessments in South Africa
    (2024) Van Eeden, Dona; Trisos, Christopher; Cowan, Oliver
    The purpose of this study is to identify the barriers to sharing data on species of conservation concern (SCC) in South Africa that are collected during environmental impacts assessments (EIAs) and to propose potential solutions to overcome these barriers. This was done by i) reviewing literature related to this topic, ii) determining the actors responsible for sharing the data collected during EIAs, iii) identifying the technical and non-technical barriers that these actors face when considering the sharing of these data, and iv) exploring solutions to overcoming these barriers while considering the different actors and regulations that impact the data-sharing process. A mixed methods approach was used to accomplish these objectives, including a review of the available literature, preliminary interviews, surveys, and key-informant interviews. Preliminary interviews identified that the experts hired to conduct biodiversity surveys during EIAs play the most important role in sharing data gathered on SCC. Consequently, surveys were sent to 75 biodiversity specialists, containing questions focused on species of conservation concern (SCC) data sharing practices and barriers to data sharing, which led to a 58,7% response rate (44 responses). A thematic analysis of the qualitative results showed the key themes that should be focused on for targeted interventions to overcome barriers to sharing data. Key themes included challenges related to time constraints and workload, data ownership, data quality and accuracy, fear of data misuse and challenges in adopting new technologies for data sharing. Key-informant interviews were conducted with 20 EIA stakeholders across South Africa— including environmental impact assessment practitioners (EAPs), biodiversity specialists, government authorities, and individuals from non-governmental organisations (NGOs) — to elaborate on these themes and to identify possible solutions to encourage more data-sharing from biodiversity professionals in the EIA process. Findings from the key-informant interviews suggest that it is important to build trust among the EIA stakeholders, to establish collaborative networks within the EIA stakeholder ecosystem for data sharing, to improve the communication and dissemination of protocol updates, clarify where to show proof of sharing data, enhance support for specialists and EAPs, strengthen the roles of the Department of Forestry, Fisheries and the Environment (DFFE) and the South African Council for Natural Scientific Professions (SACNASP), and provide continuous capacity building and training on new tools and technologies for data capture and sharing for specialists and EAPs.
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    Potential key drivers of thicket expansion in savanna
    (2007) Trisos, Christopher; Bond, William J
    The invasion of grasslands by woody plants and their increase in savannas is a global phenomenon. There has been a lot of work on the ecology of savanna trees, but very little on the drivers of the increase of non-savanna (forest and thicket) vegetation within savannas. The swit9h from savanna to closed canopy thicket represents a biome switch for the system and is therefore of concern to land and conservation managers. Data on height growth, root suckering and fire damage were collected for two thicket forming species. A simulation model was developed to evaluate the effect of different biotic and abiotic factors on the spread of a thickerclump in savanna in the Hluhluwe Game Reserve, South Africa. The amount of damage from fire suffered by a thicket clump is increased by higher fire intensity and decreased by larger clump area or greater pre-burn mean clump height. A sensitivity analysis indicated that increased height and area growth rates and decreased fire frequency allows thicket expansion to occur and that data on these is essential for predicting the expansion of thicket clumps. Predictions from the model suggest that a thicket clump's situation within the landscape is important and that spatial modelling, incorporating fire spread and fire refugia such as river banks is necessary to further improve understanding of thicket expansion.
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    The role of indigenous and local knowledge on climate adaptation for smallholder farmers in Chiredzi, Zimbabwe
    (2024) Zvobgo, Luckson; Johnston, Peter; Trisos, Christopher; Simpson, Nicholas
    Increasing smallholder farmers' resilience to the impacts of climate change requires informed decision-making that utilises locally validated information sources, including Indigenous knowledge (IK) and local knowledge (LK). Smallholder farmers across multiple regions of the world rely on IK and LK forecasts for climate decision making. This knowledge provides a rich foundation for locally led adaptation by smallholder farmers because of its contextual embeddedness within microclimatic conditions. Recent peer-reviewed literature on IK and LK in Africa was analysed to assess the role of IK and LK in adaptation in the water sector, showing that adaptation responses with IK and LK had higher evidence of risk reduction, but only 10% of African governments included IK and LK in adaptation planning in their intended Nationally Determined Contributions. A cross-sectional survey was used to establish the role of IK and LK in adaptation for smallholder farmers in the Chiredzi District, Zimbabwe. Data were collected from 210 smallholder farmers between 2021-2022, through face-to-face interviews. The analysis of observed climate data for Chiredzi between 1972-2022 corroborated the survey data. A framework was developed and applied to assess smallholder farmers' vulnerability in relation to their use of IK and LK. The results demonstrate that IK and LK are important in reducing the vulnerability of smallholder farmers by increasing the implementation of crop adaptation responses. These include the use of indigenous, drought-resistant seed crop varieties and using IK and LK weather and seasonal climate forecasts for informed decision making on appropriate crop varieties and timing of planting to reduce crop exposure to climate risk. Farmers using IK and LK forecasts implemented adaptation responses three times more than those relying on other sources of climate forecasts. Twenty-three decision types from the IK and LK forecasts that contributed to on-farm adaptation responses were identified, including crop variety selection (e.g., drought-resistant crops), cropping area management (e.g., water conservation measures), and agricultural calendar planning and management (e.g., zero tillage, dry planting, or irrigation). A further framework was developed and applied to assess the effectiveness of IK- and LK informed adaptation responses. IK and LK adaptation responses showed limited, positive, and promising signs of effectiveness. Eight (44%) of the 18 responses showed high and medium evidence of effectiveness in reducing climate risk by reducing exposure and vulnerability components of climate risk. The IK and LK seasonal forecasts were most reliable for near- term forecasts. These findings led to the development of a conceptual framework that facilitates the inclusion of IK and LK in planned adaptation. This study broadens the understanding of how IK and LK contribute to the adaptation cycle of the global goal on adaptation of the 2015 Paris Agreement, demonstrating the value of IK and LK to the global climate agenda. The findings of this study are important for interventions that target increasing effectiveness of adaptation responses, thereby reducing smallholder farmers' vulnerability and exposure to climate change. Greater recognition of and attention to IK and LK is needed across national climate adaptation planning in Nationally Determined Contributions and National Adaptation Plans for its potential to be realised