Land-cover change in the Berg River catchment : implications for biodiversity conservation

Stuckenberg, Tristan (2012-12)

Thesis

ENGLISH ABSTRACT: Biodiversity refers to the variety of life on earth at all scales of observation. Its persistence underlies ecological and evolutionary processes and is pivotal for the sustenance and future development of human societies through the provision of ecosystem services. Especially since the industrial revolution, anthropogenic land-cover change has placed ever-increasing strain on natural systems through the destruction and degradation of habitat. The Cape Floristic Region (CFR) is a global biodiversity hot spot which contains some of the highest levels of floristic diversity and endemism on the planet. Since European settlement large swathes of this region have been transformed to facilitate socio-economic development, placing tremendous pressure on indigenous biodiversity. Due to the intimate relationship that exists between land cover and biodiversity it is possible to draw inferences on the current state of the biodiversity of an area, assess the pressures that will likely face it in the future and plan accordingly based on an analysis of land-cover change. As a means of assessing the state of biodiversity in the CFR, this thesis has developed a series of three land-cover maps for the Berg River catchment in the Western Cape province for 1986/1987, 1999/2000 and 2007 using Landsat TM and ETM+ data. Areas of natural vegetation were delineated on the land-cover maps using an object-orientated nearest neighbour supervised classification. Remnants of natural vegetation were classified according to potential vegetation boundaries described by Mucina and Rutherford’s map of the vegetation of South Africa, Lesotho and Swaziland. Contrary to initial expectations, the area occupied by natural vegetation had increased by 14%. However, considerable variation was recorded between vegetation types with certain types exhibiting marked increases in extent while others had been encroached by expanding cultivated and urban areas. An assessment of the accuracy of the 2007 land-cover map showed that significant swathes of natural vegetation were infested with alien invasive species or dominated by particularly resilient species which are not as severely affected by anthropogenic activities as other species. It is concluded that the methodology employed in this study provides a scoping mechanism by which more intensive research may be directed toward areas exhibiting significant land-cover change.

AFRIKAANSE OPSOMMING: Biodiversiteit verwys na die verskeidenheid lewe op aarde op alle waarnemingsvlakke. Die volhouding daarvan onderlê ekologiese en ewolusionêre prosesse en die verskaffing van ekosisteemdienste is deurslaggewend vir die onderhoud en toekomstige ontwikkeling van menslike samelewings deur. Veral sedert die industriële rewolusie het veranderinge in antropologiese gronddekking toenemende druk op natuurlike sisteme geplaas, grootliks deur die vernietiging en ontaarding van habitatte. Die Kaapse Floristiese Streek (KFS) met van die hoogste vlakke van floristiese diversiteit en endemisiteit op aarde, is ‘n brandpunt van wêreldwye biodiversiteit. Sedert die vestiging van Europese setlaars is uitgebreide dele van hierdie streek omskep om sosio-ekonomiese ontwikkeling te bevorder, wat geweldige druk op inheemse biodiversiteit geplaas het. Te wyte aan die intieme verhouding wat tussen gronddekking en biodiversiteit bestaan, is dit moontlik om deur middel van ‘n ontleding van gronddekkingsveranderinge afleidings te maak rakende die huidige stand van biodiversiteit in ‘n streek. Sodoende kan bepaal word watter druk ʼn streek moontlik in die toekoms sal moet weerstaan. Vooruitbeplanning kan dienooreenkomstig gedoen word. Ten einde die stand van biodiversiteit in die KFS te beraam, het hierdie tesis ‘n reeks van drie gronddekkingskaarte (1986/1987, 1999/2000 en 2007) vir die Bergrivier-opvangsgebied in die Wes-Kaapprovinsie met behulp van Landsat TM en ETM+ data ontwikkel. Areas met natuurlike plantegroei is met behulp van ‘n voorwerp-georiënteerde naaste-buurman klassifikasie afgebaken. Oorblyfsels van natuurlike plantegroei is volgens potensiële plantegroeigrense, soos beskryf deur Mucina en Rutherford se kaart van die plantegroei van Suid-Afrika, Lesotho en Swaziland, geklassifiseer. In teenstelling met aanvanklike verwagtinge, het die area wat deur natuurlike plantegroei bedek word met 14% toegeneem. Tog is aansienlike variasie tussen plantegroeitipes opgemerk, met sekere soorte wat opvallende omvangstoename toon, terwyl ander plantegroeitipes deur landbou en stedelike groei vervang is. ‘n Beraming van die akkuraatheid van die 2007-gronddekkingkaart toon dat noemenswaardige stroke natuurlike plantegroei deur uitheemse indringerspesies besmet word of deur uiters weerstandige spesies, wat nie so ernstig as ander spesies deur antropologiese aktiwiteite beïnvloed word nie, gedomineer word. Die gevolgtrekking is dat die metodologie wat in hierdie studie gebruik is ‘n meganisme verskaf waardeur meer intensiewe navorsing op areas wat aansienlike verandering in gronddekking ten toon stel, gerig kan word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/71641
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