Land cover change and its effect on landscape function in the Koue Bokkeveld

Vos, Elizmay (2014-12)

Thesis (MSc)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: Natural vegetation and wetlands in regions of the Western Cape are being replaced by agricultural development. Previous studies on one such region - the Koue Bokkeveld, a high mountainous region at the source of three major drainage basins, demarcated for study purposes to cover nearly 2500 km2, have failed to provide a comprehensive overview of such change and its landscape outcomes. This research aimed to detect, capture, record and classify the spatial nature, extent and change dynamics of various landscape elements and functions due to change in the land cover of this region. It assembled a comprehensive spatial database by digitising existing maps, aerial photograph mosaics and satellite imagery. Land cover maps were created for three historical and land cover change analyses were performed for the interim periods. Morphological landscape images were derived from a DEM and used to explain and interpret the location of land cover types and trends in change patterns. The effects on three landscape functions were determined, namely modelled run-off production, biodiversity deduced from landscape pattern structure and SANBI ratings, and carbon storage potential based on published figures. The research found that the regional landscape has undergone substantive land cover change , since the reference state. Increased intensity and productivity of agriculture and its related infrastructure increased its coverage to nearly 45 000 ha or 20 % of the total area. Perennial agriculture (nearly 10 000 ha of orchards and plantations) and annual (intensive vegetable growing and diminishing cereal crops) agriculture, accompanied by improved enabling infrastructure, such as irrigation technology (large storage dams, pipelines, micro delivery modes), transportation, roads, product cooling and packing plants, have extensively replaced natural vegetation. Located in valley bottoms and along toe-slope locations, where they compete for space directly with expanding and constantly intensifying agricultural activities, wetlands, shale fynbos and renosterveld face complete replacement. Land use and land cover changes have profoundly affected landscape functioning. Modelled rainfall run-off has increased (2% overall) in most subregions, opening possibilities for sedimentation and erosion. A high degree of fragmentation of the vulnerable and affected vegetation types threatens biodiversity. Increased carbon storage in perennial agriculture offers a benefit of change, as opposed to the negative outcomes on biodiversity of change in the Koue Bokkeveld. The research recommends improved institutional provision of the data required for system and regional modelling of processes like run-off in developing communities and for meeting the requirements of more sophisticated and accurate landscape models. Improved availability and appropriateness of GIT software solutions to conduct regional research and the use of more economical open software for GIS applications are to be encouraged. Ongoing and improved management and control are advocated for the expanding and intensified agriculture in a sensitive fynbos setting and for the maintenance of healthy landscape functioning. Concerning the discipline of geography, the exploitation of landscape functioning as a transdisciplinary focus inherent to a new regional geography is encouraged to arrest disciplinary drift. Specifically, future research should intensify the examination of the linkages between land use, land cover, change and ecological landscape functioning.

AFRIKAANSE OPSOMMING: Natuurlike plantegroei en vleilande in substreke van die Wes-Kaap word voortdurend vervang deur landbou-ontwikkeling. Vorige studies oor een so 'n streek - die Koue Bokkeveld, 'n hoogliggende bergagtige streek op die oorsprong van drie groot dreineerbekkens, wat afgebaken vir studie-doeleindes byna 2500 km2 dek  bied geen omvattende oorsig van sodanige verandering en die landskapsuitkomste daarvan nie. Hierdie navorsing was daarop gemik om die ruimtelike aard, omvang en veranderingsdinamika van verskillende landskapselemente en -funksies as gevolg van die verandering van grondbedekking van hierdie streek na te spoor, op te teken en te klassifiseer. 'n Omvattende ruimtelike databasis is saamgestel uit versyferde bestaande kaarte, lugfoto-mosaïeke en satellietbeelde. Grondbedekkingskaarte vir drie historiese tydsnitte is geskep en verandering oor die tussentydse periode is ontleed. Morfologiese landskapselemente is uit 'n DEM onttrek en gebruik om die patroon van grondbedekking en tendense in veranderingspatrone te verklaar en te verduidelik. Die nagevolge op drie landskapsfunksies, naamlik reënval-afloop produksie, biodiversiteit soos afgelei van die landskap se patroonstruktuur en SANBI graderings, en koolstof-opgaringspotensiaal gebaseer op gepubliseerde syfers, is bepaal. Die navorsing het bevind dat die streekslandskap sedert die vroegste verwysingstaat wesenlike grondbedekkingsverandering ondergaan het. Verhoogde intensiteit en produktiwiteit van die landbou en sy verwante infrastruktuur het die dekking daarvan vergroot tot byna 45 000 ha of 20% van die totale oppervlakte. Permanente (nagenoeg 10 000 ha boorde en plantasies) en jaarlikse (intensiewe groente en dalende graangewas verbouing) landbou, saam met verbeterde infrastruktuur, soos besproeiingstegnologie (groot opgaardamme, pypleidings, mikroleweringstoerusting), vervoer, paaie, produkverkoeling en -verpakkingsgeriewe, het natuurlike plantegroei grootskaals vervang. Geleë in valleivloere en aanliggende heuwelhange, waar hulle direk om ruimte meeding met die uitbreidende en voortdurend intensiferende landbou-aktiwiteite, is vleilande, skalie-fynbos en renosterveld onderhewig aan volledige vervanging. Grondgebruik- en bedekkingsverandering raak landskapsfunksionering wesenlik. Gemodelleerde reënvalafloop het toegeneem (2% in totaal) in die meeste substreke en vergroot so die moontlikhede vir sedimentasie en erosie. ‘n Hoë vlak van landskapsfragmentasie in die kwesbare en geaffekteerde plantegroeitipes bedreig biodiversiteit. Verhoogde koolstofopgaring in meerjarige landbougewasse impliseer wel 'n positiewe opbrengs van grondbedekkingsverandering, in teenstelling tot die negatiewe biodiversiteitsuitkomste van verandering in die Koue Bokkeveld. Die navorsing beveel aan dat institusionele voorsiening van data wat benodig word vir stelsel- en prosesmodellering (bv. reënvalafloop) in ontwikkelende gemeenskappe, en die vereistes van meer gesofistikeerde en akkurate landskapsmodelle, verbeter word. Die beskikbaarheid en geskiktheid van GIT sagteware-oplossings vir streeksnavorsing, en die gebruik van meer ekonomiese oop-programmatuur vir GIS-toepassings, word aangemoedig. Vir praktiese doeleindes word deurlopend-verbeterde bestuur en beheer oor die uitbreiding en intensifering van van landbou in 'n sensitiewe fynbosomgewing en die instandhouding van gesonde landskapsfunksionering bepleit. Met betrekking tot die dissipline van geografie, moedig die navorsing die ontginning van die landskap se funksionering as 'n transdissiplinêre fokus inherent aan 'n nuwe tipe streeksgeografie aan, om dissiplinêre uiteenloping te stuit. Toekomstige navorsing kan spesifiek die ondersoek van die skakels tussen grondgebruik, grondbedekking, verandering en ekologiese landskapsfunksionering verskerp.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/95941
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