Sustainable land use planning in the aftermath of the clearing of alien invasive plant species : a system dynamics modelling approach

Thesis (DCom)--Stellenbosch University, 2018.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.AFRIKAANSE OPSOMMING : Die biologiese indring veroorsaak deur uitheemse indringer plante (UIP) skep ʼn verskeidenheid van direkte en indirekte ekonomiese, sosiale, en omgewingsimpakte op verskeie stelsels regoor die wêreld. Die netto uitwerking van hierdie indringing kan óf positief óf negatief wees, maar oor die algemeen oorheers die negatiewe die positiewe gevolge. UIP is ʼn noemenswaardige bedreiging vir verskeie sisteme deur byvoorbeeld ʼn verlies aan biodiversiteit, die oormatige verbruik van water, die verlies aan water vloei in ʼn rivier, gesondheidsrisiko’s vir beide mens en dier, toenemende brandgevare en die indringing van landbougrond en inheemse ekosisteme. Ten spyte van hierdie negatiewe gevolge, het UIP ook beperkte positiewe gevolge, soos, onder andere, die absorpsie van koolsuurgasse, die verskaffing van ru-materiaal vir die vervaardigingsindustrie, sowel as habitat vir fauna. Gegewe die oorweldigende negatiewe gevolge van UIP, befonds die Suid-Afrikaanse regering, deur die Werk-vir-Water (WvW) program die skoonmaak en beheer van UIP, meestal by wyse van arbeidsintensiewe, meganiese en chemiese metodes, maar ook by wyse van biologiese beheer deur van patogene en insekte gebruik te maak. Ten spyte van hierdie beheermaatreëls, versprei UIP eksponensieel en dit regverdig meer befondsing om die beheermaatreëls te finansier ten einde beide huidige en nuwe indringing die hoof te kan bied sowel as opvolg aksies te kan uitvoer. Die onvermoë om UIP te beheer het ook gelei tot die sub-optimale gebruik van landbougrond. Dit is toe te skryf aan die gebrek aan grondgebruik beplanningsraamwerke en die oneffektiwiteit van die grondgebruik wetgewing in die landbou sektor in Suid-Afrika. Soos onthul word in hierdie studie, die meeste van die navorsing tot op hede het gefokus op die beheer van, die kartering van verspreiding, impak analise en die evaluasie daarvan, en tot ʼn mindere mate die koste-voordeel analise van die beheer van UIP. Gegewe die kompleksiteit betrokke in die wetenskap van UIP en grondgebruiksbeplanning besluitneming, was die liniêre benadering wat gebruik is in die meeste studies onvoldoende om al die elemente van die dinamiese sisteem, sowel as die oorsaaklikheid en die oorsaak en gevolg verhoudings van UIP, na wese weer te gee of te verstaan. Hierdie kompleksiteit word verder verdiep deur die verskille in grondeienaarskapstelsels wat bestaan. Ten einde beter begrip te hê vir die impak van die verskeidenheid grondgebruik opsies van gerestoureerde grond nadat UIP verwyder is, binne ʼn verskeidenheid van kontekste en grondeienaarskapstelsels, is dit belangrik om ʼn nie-lineêre analise te onderneem wat poog om die voorafgenoemde kompleksiteite weer te gee. Hierdie studie identifiseer die kern veranderlikes wat besluitneming behoort te rig ten einde die beste grondbestuursopsies te kies – en dit binne die genoemde komplekse agtergrond. Dit was gedoen deur van ʼn sisteem dinamiese model en ʼn veelvoudige kriteria analities-besluitnemings model gebruik te maak. Vier studie areas in die Wes en Noord Kaap provinsies van Suid-Afrika was gekies vir hierdie studie. Drie sisteem dinamiese modelle en een veelvoudige kriteria analities-besluitnemings model is ontwikkel ten einde: i) ʼn begrip te ontwikkel vir die geïntegreerde voordele en kostes verbonde aan die restourasie van natuurlike kapitaal2 deur die beheer van UIP; ii) die ondersoek na en identifisering van die grondgebruik vermoë na restourasie by wyse van die beheer van UIP en die soeke na die beste grondgebruik gebaseer op ʼn veelvoudige kriteria analities-besluitnemings model; iii) die ondersoek van die potensiële volhoubaarheid op grond van ekonomiese, sosiale en omgewingsoorwegings voortvloeiend die voordele van die verskillende grondgebruiksmoontlikhede en addisionele waardetoevoeding en die toename in die waarde van die ekosisteem; iv) die evaluering van die ekonomiese lewensvatbaarheid van die voornemende grondgebruik opsie en die waardetoevoeging by wyse van produkte wat ondersoek kan word in areas waar UIP verwyder is in Suid-Afrika (met spesifieke verwysing na die vier studie areas); v) die beraming van die geleentheidskoste van ongerestoureerde grond; vi) die formulering van scenario’s waaronder die grondbestuur tipes, die waardetoegevoegde produkte, en die bestuuropsies getoets word by wyse van ʼn sisteem dinamiese model ten einde vas te stel wat die onderskeie gevolge daarvan is, en vii) om insig te verkry in die beleidstekortkominge, en die opsies en implikasies daarvan met betrekking op die restourasie van natuurlike kapitaal en die verskillende grondgebruik tipes in Suid-Afrika. Die sisteem dinamiese model is ook onderwerp aan stawingstoetse. Hierdie sluit onder andere strukturele stawing, parameter stawing, toetse insake dimensionele konsekwentheid en ekstreme voorwaardes ten einde die strukturele stawing. Gedragstoetse is ook onderneem deur meervoudige veranderlike sensitiwiteitsanalise ten einde die sensitiwiteit van die netto huidige waarde vir die diskontokoers te bepaal. Wat die veelvoudige kriteria analities-besluitnemings model betref, ʼn sensitiwiteitstoets insake verskeie parameters is onderneem ten einde die sensitiwiteit van die resultate ten opsigte van ʼn verandering in die model parameters vas te stel om sodoende vertroue in die model en die analise te bou. Laastens, terwyl ʼn verskeidenheid van pogings aangewend is om al die ekonomiese, sosiale en omgewings impakte van die bestuur en grondgebruiksbesluitneming van UIP vas te vang, kon nie alle impakte geïnkorporeer word nie as gevolg van ʼn gebrek aan data, metodologiese beperkings, en onverwagte modellerings aspekte. Die beperkings van die studie word pertinent uitgewys binne die konteks van die slot opmerkings en aanbevelings