Department of Agricultural Economics

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Browsing Department of Agricultural Economics by browse.metadata.advisor "Blignaut, James Nelson"

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    Sustainable land use planning in the aftermath of the clearing of alien invasive plant species : a system dynamics modelling approach
    (Stellenbosch : Stellenbosch University, 2018-12) Mudavanhu, Shepherd; Vink, Nick; Blignaut, James Nelson; Stellenbosch University. Faculty of Economic and Management Sciences. Dept. of Agricultural Economics.
    ENGLISH SUMMARY : Biological invasions caused by invasive alien plant species (IAPs) pose diverse direct and indirect impacts on economic, social and environmental systems globally. The net impacts can be beneficial or harmful, although in most cases the negative impacts outweigh the beneficial effects. IAPs pose a significant threat to various systems through for example loss of biodiversity, excessive consumption of water, reduction in stream flow, health hazards to both animals and humans, increased fire risks and encroachment into agricultural lands and native ecosystems. Despite these negative impacts, IAPs to a limited extent also offer benefits to society, amongst them carbon sequestration, raw materials for manufacturing of value added products as well as habitat services for fauna. Given the predominant negative effects, however, the government of South Africa, through the Working for Water Programme (WfW), funded the clearing of IAPs mainly through labour intensive manual, mechanical and chemical means, as well as biological control using pathogens and insects as the control agents. Despite the aforementioned clearing efforts, IAPs have continued to spread exponentially, warranting more funding to finance the clearing operations targeting both new invasions and follow up clearing. In addition, the failure to contain invasions by IAPs has also led to sub-optimisation of agricultural land, which is attributed to a deficiency of land use planning frameworks and the ineffectiveness of laws governing agricultural land use in South Africa. As disclosed in this study, most of the research conducted to date has focussed mainly on control, distribution mapping, impact assessments and evaluation and to a lesser extent, partial cost benefit analyses of controlling IAPs. Given the complexities involved in the science of IAPs and land use planning decisions, the linear approach used in most studies has not been successful in fully capturing all the system elements, dynamics, causal and effect relationships thereof in order to understand the impacts of IAPs on the whole system. These complexities are further exacerbated by differences in land tenure systems. In order to understand the implications of the various land use options on land restored through clearing IAPs, within different contexts and tenure systems, it is imperative to undertake a non-linear analysis that captures the aforementioned complexities. This study identified the key decision-rules that should guide decision making in selecting the best land use and management options under diverse contexts, within the aforementioned complex and dynamic system. This was done using a system dynamics modelling approach and a multiple criteria decision analysis. The, focus was put on four study sites in the Western Cape and Northern Cape provinces of South Africa. Three system dynamics models and one multiple criteria decision analysis (MCDA) model were developed for: (i) understanding the integrated (i.e. both private and externality) benefits and costs associated with restoration of natural capital1 through the clearing of IAPs; (ii) exploring and identifying the land use capability of the land restored through clearing of IAPs and the alternative best use land types based on multiple criteria decision analysis; (iii) investigating the potential economic, social and environmental sustainability of the returns emanating from the land use types and value added industries implemented inter alia the valuation of ecosystem goods and services; (iv) assessing the economic feasibility of prospective land use types and value added products (VAPs) that can be pursued in the areas were clearing of IAPs has taken place in South Africa (with a specific focus on four sites in SA) (v) determining the opportunity cost of unrestored land cleared from invasive alien plant species in South Africa (vi) formulating scenarios under which the land use types, VAPs and management options considered will be tested using the system dynamics modelling approach in order to see the respective impacts thereof; and for (vii)understanding the policy shortcomings, options, and implications with respect to restoration of natural capital and land use types in South Africa. Validation tests of system dynamics models were also done. These included structure verification, parameter verification, dimensional consistency and extreme conditions tests which were undertaken to check for the structural validity. In addition, a behavioural validity test was conducted using multivariate sensitivity analysis to test the sensitivity of the Net Present value to the discount rate. As for the MCDA model, a parametric sensitivity analysis was conducted to test the sensitivity of the results to a change in the model parameters in order to build confidence in the analysis.Lastly, while efforts were made to capture all the economic, social and environmental aspects of IAPs management and land use planning decisions, not all core aspects were considered due to unavailability of data, methodological limitations and other unanticipated modelling complications. The limitations of the study were made explicit while concluding remarks and recommendations were made.