Alien invasive species pose a great threat to ecosystems and human communities (Richardson & van Wilgen 2004; Hobbs & Humphries 1995). On private lands, there is a need to find institutional, administrative and scientific responses to the alien plant problem that operate beyond the scale imposed by property boundaries (Slocombe 1998; Grumbine 1994). One such response is the development and support of institutions, such as the St Francis Conservancy, that foster cross-boundary management of landscapes (Hurley et al. 2002). This study seeks to promote collective decision-making and collaborative management by private landowners through the development of a resource allocation system for the control of alien invasive plants on the St Francis Conservancy. The conservancy is located in the south-eastern lowlands of the Cape Floristic Region, between the villages of Cape St Francis and Oyster Bay, and is comprised of the properties of multiple landowners. Mutliple Criteria Decision Analysis (MCDA) and Geographical Information Systems (GIS) techniques were integrated to provide a spatially explicit resource allocation system that considered environmental, social and economic concerns. The MCDA technique selected for use was the Analytical Hierarchy Process (AHP). This technique has a record of providing robust, defensible decisions and enabled the resource allocation decision-problem to be decomposed into a hierarchy of objectives, criteria and indicators. Stakeholders participated in the development of the resource allocation system, especially through providing input into the determination of the relative importance of criteria and indicators through the assignment of weights. Various weighting scenarios were presented and these were interpreted into an ii implementation plan. The costs and effort required to clear alien plants were estimated, and obstacles facing the implementation of the plan were identified.

Thesis (MScConsEcol (Conservation Ecology and Entomology))--Stellenbosch University, 2008. / In the Mediterranean climate regions of the world, agricultural practices have caused considerable landscape transformation and lead to introduction of alien species that now dominate secondary succession on abandoned agricultural fields. Various restoration attempts have been made to reduce alien plant species cover, and to enhance the re-establishment and cover of native plant species. However, results and successes were mostly short-term due to re-growth and persistence of the weedy alien species, which has been suggested to be caused by land use history, especially the nutrient enrichment of soil, and particularly phosphorus and nitrogen. This study investigated different soil properties (pH, electrical conductivity (EC), soil moisture, as well as available phosphorus (P) and total nitrogen (N)) on 10 and 20 year old abandoned fields, as a function of depth in three habitats (ridge (old cultivated area), ditch (old drainage line) and slope (intermediate zone between ridge and ditch)) on the old fields. The relationship between these soil properties and the vegetation occurring on the two old fields was established. At the same time, restoration treatments (autumn burn, combination of autumn burn and herbicide, herbicide application alone, as well as spring burn) were conducted to reduce the cover and abundance of non-native plant species and Cynodon dactylon, and to enhance cover of native species. Results from the study show that levels of all investigated soil properties were higher on the younger field. The highest difference was observed in EC and pH. Seasonal differences in both soil properties could also be observed. A principal component analysis indicated that the dynamic of all soil properties shaped the vegetation type on old fields, with the main soil properties being dependent on land-use history and time since abandonment. This study suggests that EC and pH could be part of parameters that drive the persistence of undesirable species persistence on old fields and inhibit native plant species instead.

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Invasive alien trees, especially Acacia species, are a great threat to biodiversity in South African rivers. The national Working for Water Programme is addressing the alien problem by removing alien trees from river margins. The concern is that this may be creating even further disturbance by affecting water quality and habitats. In particular, how is this affecting rare and endemic species? Benthic macro invertebrates and aerial odonates were assessed along five Western Cape rivers in alien-invaded, cleared and natural sites between December and March. The aim was to assess the effect of both alien invasion and alien clearing on aquatic invertebrates. Odonata, being easily sampled, were also assessed as they are severely affected by the lack of understorey plants in shaded, alien-invaded sites. Odonata and benthic macroinvertebrates were treated as two separate studies and no attempt was made to correlate the results obtained from both studies. SASS5, a qualitative, rapid bioassessment technique, based on the sensitivity of the families present, was used as a measure of river health and, indirectly, of water quality. SASS indicated a decline in water quality conditions after alien clearing, a likely response to the greater insolation as well as erosion of cleared banks, resulting in elevated temperatures and suspended solids and lowered oxygen levels. Community responses to alien disturbance and other environmental factors were analysed using PRIMER and CANOCO software. Assemblages of Odonata were found to provide a rapid, cost-effective means of assessment and monitoring. Potential indicator and detector species were also identified using the lndicator Value method. Assemblage patterns of aquatic invertebrates, however, were dominated by between-river and seasonal effects. Therefore, while SASS detected overall changes in river health, without identifying the cause, potential aquatic detector taxa were identified that may be useful for linking general disturbance to alien invasion or clearing. All indicator and detector taxa identified in both studies can be used for long-term monitoring and for identifying biodiverse areas for clearing or protection. In both studies, sensitive, endemic taxa were lost after clearing, being replaced by more tolerant, widespread taxa. Recovery of the biota appears to follow the recovery succession of the vegetation, with most sensitive or endemic taxa only appearing after the recovery of indigenous plants. A number of recommendations are made regarding the restoration of both water quality (particularly with respect to shade and soil erosion) and biotope availability (particularly in terms of the recultivation of indigenous plants) in order to achieve biodiversity objectives. The role of catchment management, prioritisation procedures and long-term monitoring are also discussed. / AFRIKAANSE OPSOMMING: Uitheemse, indringerbome, veral Acacia spesies, is 'n groot bedreiging vir biodiversiteit in Suid- Afrikaanse riviere. Die nasionale Werk vir Water-projek spreek hierdie probleem aan deur uitheemse bome van rivieroewers te verwyder. Die kommer is dat water kwaliteit en habitatte sodoende verder versteur kan word. Byvoorbeeld, hoe word endemiese en bedreigde spesies geraak? Akwatiese makroinvertebrate en volwasse Odonata in vyf Wes-Kaapse riviere is tussen Desember en Maart bestudeer en gemonster in natuurlike gebiede, in gebiede waar indringerbome teenwoordig is, en in gebiede waar hulle verwyder is. Die doel was om die effek van indringerverwante impakte op akwatiese invertebrate vas te stel. Odonata is ook bestudeer omdat hulle maklik gemonster kan word en omdat hulle ernstig geraak word deur indringers. Die uitheemse plantegroei oorskadu die oewers en verhoed die groei van inheemse oewerplante. Die bentiese makro-invertebrate en Odonata is as twee aparte studies behandel en geen poging is gemaak om die resultate van die twee te vergelyk nie. SASSS, 'n kwalitatiewe, bioasseseringsmetode wat op die sensitiwiteit van die aanwesige families baseer word, is gebruik om waterkwaliteit op 'n indirekte manier te bepaal. SASS het aangedui dat daar 'n afname in waterkwaliteit is nadat indringerplante verwyder is. Dit is moontlik as 'n gevolg van groter blootstelling aan sonskyn en erosie van rivieroewers wat veroorsaak dat temperature en die hoeveelheid gesuspendeerde materiaal verhoog word, en dat suurstof konsentrasies verminder word. Die gevolge van indringerplante en ander omgewingsfaktore op akwatiese gemeenskappe is met PRlMER en CANOCO sagteware ontleed. Groepering van Odonata kan gebruik word om op 'n maklike en koste-effektiewe manier om die impak van indringerplante en hul verwydering te bepaal en te monitor. Aanwyserspesies is ook deur middel van die 'Indicator Value' metode geïdentifiseer. Die verspreidingspatrone van invertebraatspesies word deur geografiese en seisoenale effekte oorheers. Dus, terwyl SASS veranderinge in waterkwaliteit kan aantoon, sonder om die oorsaak daarvan te identifiseer, kan aanwyserspesies gebruik word om meer spesifieke impakte deur indringerplantegroei, of indringerverwydering, te bepaal en te monitor. Hulle kan ook gebruik word om gebiede met hoë biodiversiteit vir bewaring of indringerverwydering te identifiseer. Beide studies dui aan dat sensitiewe en endemiese taksa na indringerverwydering verlore gaan, en vervang word met meer geharde, wydverspreide taksa. Herstel van die biota volg op die herstel van die plant gemeenskappe, en die mees sensitiewe of endemiese taksa herstel eers nadat die inheemse plantegroei herstel het. 'n Aantal aanbevelings in verband met die restorasie van waterkwaliteit (veral in terme van die hoeveelheid skaduwee en erosie) en die beskikbaarheid van biotope (veral in terme van inheemse plante) om biodiversiteitsdoelwitte te bereik word gemaak. Die rol van opvanggebied bestuur, voorrang prosedures en lang termyn monitering word ook bespreek.

There is little understanding of the implementation efficiency and effectiveness of restoring plant invaded landscapes within operational contexts. South Africa's Working for Water (WfW) programme is arguably the most ambitious alien plant control programme in the world, yet little is known about its cost-effectiveness and the challenges it faces in linking poverty and environmental objectives. My first aim was to assess the cost-effectiveness of invasive plant removal, and the factors that underpin its effectiveness over large spatial and temporal scales. The second aim was to compare the accuracy of evidence-based findings with managers' experience-based beliefs, and to assess whether managers are willing to change their beliefs after being exposed to it. The third aim was to assess the costs and benefits of removal versus removal followed by active native re-vegetation. My final aim is to assess the challenges and lessons learnt by managers linking ecological restoration with poverty alleviation objectives, specifically within the public works model. My study area was focused primarily on two WfW river catchment projects in the western region of the Eastern Cape province. I adopted an interdisciplinary approach drawing from a range of methods such as observational studies, statistical modelling and interviews with managers. The key findings were that control efforts in the two catchment projects are largely inadequate owing to many sites being re-invaded and not enough resources being allocated to the catchments. It would take between 54 and 695 years to clear the respective catchments. In terms of cost-effectiveness, my results exceeded previous estimates by 1.5 to 8.6 times for each catchment project. After being exposed to the evidence-based findings, the managers did not change their beliefs when it came to forecasting the future effectiveness. I found that active native re-vegetation after removal of invasive plants is very costly and that priority should be given to understanding the effectiveness of the removal treatments on native species recovery. The managers cited significant challenges in effectively and efficiently meeting the programmes dual objectives. Based on a broader review of the public works literature I recommend WfW re-examine the type of public works they currently use.