The increased movement of plants around the world is a serious and impactful environmental consequence of increased human dominance globally. Some of these plants will become established in new areas, some will proliferate, and some will become invasive causing environmental and socio-economic damage. Environmental processes contribute to plants becoming introduced, established and invasive. However, humans have an increasingly important role in all stages of the invasion process. In particular, the social processes that shape decision making, such as knowledge, risk perceptions, values and attitudes, can influence people’s behaviour that might lead to increased or decreased spread of invasive non-native plants (INNP). The social processes contributing to individual decision-making can be particularly influential in domestic gardens as it is the individual(s) responsible for that garden that decides how it is managed. Furthermore, the socio-economic impacts of INNP can be particularly acute in domestic gardens. In addition to the direct impacts of INNP in domestic gardens, an increase of their abundance therein could be detrimental to the health and well-being benefits gardens can provide, such as increased connectedness to nature. Invasion ecology is a rapidly growing area of research, however, key gaps in knowledge remain. In particular, little research has been done on INNP in domestic gardens and the perceptions of risk people have about the impacts they can have therein. This thesis applies an interdisciplinary approach to address these gaps. Japanese knotweed Fallopia japonica, is used as a case study throughout as it exemplifies many of the environmental and socio-economic impacts of INNP, many of which are particularly acute in domestic gardens. Identifying the processes contributing to the spread of INNP will help develop mitigation strategies to reduce their spread and therefore impact - this is the focus of chapters two to six. Chapter two explores the predictors of presence and abundance of Japanese knotweed at a 1km resolution within Cornwall, UK, finding that building density is the strongest predictor, followed by biophysical variables (minimum and maximum monthly temperature), and then socio-economic status of the residents within the 1km grid-cell. Chapter three considers one social process that might be contributing to the spread of INNP - the movement of propagules within soil. One of the key results of this chapter is that the abundance of invasive and naturalised species was significantly higher in garden than in housing development samples. This suggests that informal movement of soil between gardens poses a greater risk of spreading invasive plants than do commercial sources. Chapter three highlights the importance of high levels of identification skills of INNP to reduce their spread, however no previous research has tested INNP identification levels amongst the public. Chapter four explores this idea, finding that less than 20% of the public could identify Japanese knotweed. Even if people can identify INNP, if it is present in their garden they may not know how to manage it correctly and details of the impacts it can have therein. Chapter five analyses internet-based information about the management advice and impacts of INNP, determines the authors of this discourse, and considers whether and how this could be confusing to those responsible for managing domestic gardens. Analysis identified extensive variation in document structure, topics discussed, references and links to other sources, and language style; sometimes this variation was between and sometimes within author categories. A key conclusion from chapter five is that some internet-based information sources might potentially contribute to amplification (or attenuation) of risk perceptions, that could in turn lead to inappropriate management actions, resulting in increased spread of INNP. Chapter six uses a survey approach to explore risk perceptions of INNP in domestic gardens further. The results suggest differences in perceived risk of Japanese knotweed depends on people’s occupation, their direct experience of the species in a domestic context, their geographical proximity to the risk, their age and level of education. Greater understanding of the impacts INNP can have within domestic gardens will help assess the level of risk, plan mitigation strategies and design risk communication. This is the focus of chapter seven, which focuses on the economic impacts within domestic gardens. Results indicate that the magnitude and frequency of the risks Japanese knotweed poses in domestic gardens are much lower than anticipated based on media coverage, and compared with public perception. The results of this thesis have several important implications: (1) To mitigate potential inaccurate perceptions of INNP, governmental authorities need to provide clear and accurate communication about the impacts of INNP and how best to manage them. (2) When resources are limited, identifying the areas of society where knowledge is lowest or perceptions most inaccurate can help awareness and educational campaigns to be more impactful, thus reducing spread and impacts of INNP. (3) Implementation of the recommendations to reduce the spread and impacts of INNP within domestic gardens given within this thesis could contribute towards preserving the health and well-being benefits gardens can provide. Overall this thesis demonstrates further evidence of the need to consider the human causes and solutions to INNP and the need for knowledge on this topic to be applied by a diverse range of stakeholders.

Urban environments are typically host to a high level of biodiversity which is important for the provision of ecosystem services, and for facilitating contact between humans and nature. However, accelerating urbanisation precipitates considerable declines in the number of species which inhabit these environments as a greater number of homes and roads are constructed to accommodate a growing global human population. Domestic gardens afford an important opportunity to combat these declines, owing to their capacity to support a high level of biodiversity and the substantial land area which they cover. However, the fine spatial scale of individual isolated domestic gardens constrains their ability to increase biodiversity at larger spatial scales. Consequently, managing domestic gardens collectively, by conjoining multiple neighbouring domestic gardens and managing them as a single larger habitat, has been proposed as a promising approach to increase biodiversity at these scales. Importantly however, the practical implementation of this approach necessitates neighbouring householders to collaboratively undertake biodiversity favourable garden management and to conjoin their domestic gardens. Crucially, this management is performed by householders discretionarily and can be influenced by demographic, perceptual, environmental, and socio-economic factors. Furthermore, householder attitudes towards conjoining domestic gardens may also influence the practicality of this approach. Therefore, this research explores what impact the extent to which householders undertake biodiversity favourable garden management has on the practicality of the collective management approach and how this is influenced by the aforementioned factors. In addition, it explores how this practicality is influenced by householder attitudes to conjoining domestic gardens. Lastly, it investigates how the collaborative undertaking of biodiversity favourable garden management by neighbouring householders could be encouraged, taking into consideration the constraints associated with current projects which promote such management. A survey was used to explore the prevalence of biodiversity favourable garden management, the influences on this management, and attitudes towards conjoining domestic gardens. This was conducted with an online semi-structured questionnaire which was distributed to householders using the social-networking site, Facebook. In addition, a bio-indicator approach was used to analyse the impact of general domestic garden management on biodiversity and birds were selected as a bio-indicator. Accordingly, respondents to the survey were also required to identify which bird species visit their domestic gardens. Seventeen elite interviews were also conducted with representatives from a range of organisations operating domestic garden projects, participants in such projects, and academics with expertise in domestic garden management, in order to explore the constraints associated with current domestic garden projects. The survey yielded 276 responses and provided support to the practicality of the collective management approach. In particular, it indicated that householders commonly undertake biodiversity favourable garden management, by predominantly providing food for birds and planting vegetation, and 60% of householders are willing to conjoin domestic gardens. However, the survey also highlighted that biodiversity favourable garden management is impeded by a number of factors. These included small domestic gardens, which particularly limit vegetation planting, and can be commonplace in urban environments. In addition, householders commonly nullify the benefits afforded by undertaking this management by covering domestic gardens with hard surface and lawns, which eliminate space for vegetation. Moreover, strong desires to retain ownership and privacy of domestic gardens precipitate the unwillingness of a significant proportion of householders to conjoin domestic gardens. This therefore challenges the practicality of the collective management approach. The results from the elite interviews indicated that householders lack commitment to current domestic garden projects, which are constrained by difficulties acquiring sufficient funding. These issues could also be pertinent to approaches which are developed to encourage the collaborative undertaking of biodiversity favourable garden management, further rendering the collective management approach impractical. The practicality of the collective management approach could be enhanced by modifying the design of new housing in a manner which is favourable to biodiversity and which ensures a minimal domestic garden size. In addition, including domestic gardens in green infrastructure strategies could further enhance this practicality. Furthermore, amending planning policy to regulate the covering of domestic gardens with hard surface and lawns more stringently could reduce the prevalence of these features. Householder commitment to approaches which encourage the collaborative undertaking of biodiversity favourable garden management could be promoted by providing feedback regarding the contribution this makes to increasing biodiversity at large spatial scales. Moreover, greater funding for these approaches could be acquired by also focusing on promoting the provision of ecosystem services. Finally, householder collaboration could be encouraged by accommodating desires for ownership and privatisation of domestic gardens. This could be respectively achieved by permitting flexibility regarding the biodiversity favourable garden management undertaken and separating conjoined domestic gardens with hedgerows.

Urbanization is seen as a threat to biodiversity within urban ecosystems, which are largely reliant on humans for their composition. Two types of extremes exist in the spectrum of urban domestic gardens; on one end, the typical urban garden which is planted by landscapers at the time the house is built and is generally left unchanged, and, at the other, a "wild" landscape planted entirely with native plants which provides habitat for native fauna and pollinators. This study assesses the plant choices made by members of organized gardening groups-the Denton County Master Gardeners (DCMG), the Elm Fork Master Naturalists (EFMN), the Trinity Forks Native Plant Society (TFNPS), and Keep Denton Beautiful (KDB)-and toward which extreme these choices put these gardens on the psectrum. TFNPS and EFMN both fall closer to the wild garden extreme, with TFNPS the closest to a "wild garden." DCMG was almost directly between the two extremes, but fell closer to the typical urban garden. By looking at how these groups manage their gardens, we begin to understand the ways in which gardeners can mitigate and soften the harsh changes between wild landscapes and urban environments. Collaboration between groups could have the potential to encourage more people to use native plants which provide habitat for native fauna and pollinators if those in the typical urban garden spectrum could find in the "wild" gardens of those on the opposite end of the spectrum.

Globally urbanization has increased to such an extent that more than half of the human population currently resides in cities. In the years to come, urban expansion will especially take place in developing countries through efforts to improve economic growth and poverty alleviation. This may have a negative effect on native biodiversity within and surrounding urban environments. However, residential areas with a high proportion of gardens form a significantly large part of urban environments and these domestic gardens contribute to the maintenance and preservation of biodiversity in cities. Although the preservation of biodiversity in these gardens is important in the overall conservation of urban green spaces, little is known about how these gardens can possibly contribute to conservation purposes in urban areas. Bearing in mind that anthropogenic activities are possible drivers of urban biodiversity, it is vital to quantify socio-economic aspects within urban ecological research. In developing countries, such as South Africa, the inclusion of socio-economic aspects are especially important because there is a wider gap between poor and wealthy households. There are also a larger number of people that are dependent on their gardens for subsistence purposes, such as vegetable gardening. In the Municipal Area of Tlokwe, South Africa, there exists a definite socio-economic gradient from the poorer western to the more affluent eastern part of the city. Five socio-economic status (SES) classes, primarily based on % unemployment, were used in this study. The ultimate aim of this study was therefore to determine the plant- and arthropod diversity within urban domestic gardens along a socio-economic gradient. Vegetable gardens within domestic gardens were selected to quantify plant- and arthropod biodiversity. Biodiversity of adjacent lawns were also sampled for comparative purposes. The study also attempted to determine to what extent socio-economic aspects of city residents may be possible drivers of biodiversity within the gardens. Various other factors that might have an effect on the plant and/or arthropod diversity were included such as soil characteristics, specific management factors of the gardens and other land-uses surrounding domestic gardens. Arthropod diversity was surveyd by means of pitfall traps and suction sampling in eight 0.25 m2 squares along an 8 m transect in each representative garden. Arthropods were identified up to morphospecies level. Vegetation was surveyed along the same transect and total species composition was determined. Plants were identified up to species level. The plant and arthropod surveys were conducted in both the vegetable gardens and lawns of all SES classes. For the soil samples a 1:2.5 water analysis was conducted. A social survey was conducted in all representative gardens by means of a questionnaire and a SPOT 5 satellite imagery was used to determine the land-use types in the areas surrounding the participating gardens. All the above mentioned factors were compared between the different SES classes. Diversity indices for the arthropods, multivariate statistical analyses and ANOVA analyses were applied to test for meaningful variables between socio-economic status classes as well as vegetable gardens and lawns. From the results it was evident that the more affluent SES classes had significantly higher arthropod diversity values, whilst the lower income classes had higher plant diversity. The factor analysis between the plants and arthropods with the surrounding land-uses revealed two significant factors. Firstly, arthropod diversity was influenced by domestic gardens in the surrounding landscape and there was a positive correlation between these two variables. This indicates that a high percentage of surrounding domestic gardens were possible drivers of arthropod diversity. No correlations were evident between plant and arthropod diversity. Secondly, the other significant factor showed that one SES class had a significantly higher percentage of woodlands and grasslands as opposed to two of the other classes that had a significantly higher percentage of built structures within the surrounding area. Differences were also apparent between the SES classes concerning management regimes, financial stability and level of education. The two more affluent SES classes had obtained a higher level of education and income and had management practices that were uncommon in the three poorer SES classes. This study proposes that domestic gardens are a means to conserve biodiversity in cities. Vegetable gardens in domestic gardens will also be able to harbour a larger diversity of plants and arthropods than the lawns. The socio-economic status of residents also had a significant effect on biodiversity and therefore it should be included in studies on urban domestic gardens. This study also provides additional knowledge to the fundamentals of the field of urban ecology and the importance of using domestic gardens as an urban green space for conservation purposes. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

Globally urbanization has increased to such an extent that more than half of the human population currently resides in cities. In the years to come, urban expansion will especially take place in developing countries through efforts to improve economic growth and poverty alleviation. This may have a negative effect on native biodiversity within and surrounding urban environments. However, residential areas with a high proportion of gardens form a significantly large part of urban environments and these domestic gardens contribute to the maintenance and preservation of biodiversity in cities. Although the preservation of biodiversity in these gardens is important in the overall conservation of urban green spaces, little is known about how these gardens can possibly contribute to conservation purposes in urban areas. Bearing in mind that anthropogenic activities are possible drivers of urban biodiversity, it is vital to quantify socio-economic aspects within urban ecological research. In developing countries, such as South Africa, the inclusion of socio-economic aspects are especially important because there is a wider gap between poor and wealthy households. There are also a larger number of people that are dependent on their gardens for subsistence purposes, such as vegetable gardening. In the Municipal Area of Tlokwe, South Africa, there exists a definite socio-economic gradient from the poorer western to the more affluent eastern part of the city. Five socio-economic status (SES) classes, primarily based on % unemployment, were used in this study. The ultimate aim of this study was therefore to determine the plant- and arthropod diversity within urban domestic gardens along a socio-economic gradient. Vegetable gardens within domestic gardens were selected to quantify plant- and arthropod biodiversity. Biodiversity of adjacent lawns were also sampled for comparative purposes. The study also attempted to determine to what extent socio-economic aspects of city residents may be possible drivers of biodiversity within the gardens. Various other factors that might have an effect on the plant and/or arthropod diversity were included such as soil characteristics, specific management factors of the gardens and other land-uses surrounding domestic gardens. Arthropod diversity was surveyd by means of pitfall traps and suction sampling in eight 0.25 m2 squares along an 8 m transect in each representative garden. Arthropods were identified up to morphospecies level. Vegetation was surveyed along the same transect and total species composition was determined. Plants were identified up to species level. The plant and arthropod surveys were conducted in both the vegetable gardens and lawns of all SES classes. For the soil samples a 1:2.5 water analysis was conducted. A social survey was conducted in all representative gardens by means of a questionnaire and a SPOT 5 satellite imagery was used to determine the land-use types in the areas surrounding the participating gardens. All the above mentioned factors were compared between the different SES classes. Diversity indices for the arthropods, multivariate statistical analyses and ANOVA analyses were applied to test for meaningful variables between socio-economic status classes as well as vegetable gardens and lawns. From the results it was evident that the more affluent SES classes had significantly higher arthropod diversity values, whilst the lower income classes had higher plant diversity. The factor analysis between the plants and arthropods with the surrounding land-uses revealed two significant factors. Firstly, arthropod diversity was influenced by domestic gardens in the surrounding landscape and there was a positive correlation between these two variables. This indicates that a high percentage of surrounding domestic gardens were possible drivers of arthropod diversity. No correlations were evident between plant and arthropod diversity. Secondly, the other significant factor showed that one SES class had a significantly higher percentage of woodlands and grasslands as opposed to two of the other classes that had a significantly higher percentage of built structures within the surrounding area. Differences were also apparent between the SES classes concerning management regimes, financial stability and level of education. The two more affluent SES classes had obtained a higher level of education and income and had management practices that were uncommon in the three poorer SES classes. This study proposes that domestic gardens are a means to conserve biodiversity in cities. Vegetable gardens in domestic gardens will also be able to harbour a larger diversity of plants and arthropods than the lawns. The socio-economic status of residents also had a significant effect on biodiversity and therefore it should be included in studies on urban domestic gardens. This study also provides additional knowledge to the fundamentals of the field of urban ecology and the importance of using domestic gardens as an urban green space for conservation purposes. / Thesis (Master of Environmental Sciences)--North-West University, Potchefstroom Campus, 2013

Urbanisation has increased tremendously over the last 60 years so that more than 50 per cent of the world population now live in cities. This is especially true for in developed countries, but it is expected that developing countries will take the lead in future urban population growth. This increasing trend of urbanisation has severe consequences for the environment, as it fragments and changes natural areas and alter environmental conditions. This has compelled scientists from many different disciplines to focus on the inclusion of humans into ecology as a driving force of change to create a better understanding of urban ecosystems. The diversity of fauna and flora in the urban environment provides a myriad of ecosystem goods (such as food and fuel) and services (e.g. cleaning the air and reducing noise levels). Apart from these tangible benefits, urban green space also provides recreational, educational and social benefits to urban inhabitants. A surprisingly substantial proportion (21‒36 %) of the total urban green space that produces these ecosystem goods and services is located in private yards. This portrays the importance of the flora of this land-use type, but very little is known about garden flora and its potential for conservation. The determinants of diversity and species richness in gardens were found to be different than for semi-natural ecosystems, because of the high anthropogenic influence. One of these is the socio-economic status of the inhabitants. People with higher socio-economic status were found to harbour more diverse species assemblages in their gardens than those of lower socio-economic status. This phenomenon was termed the “luxury concept”. In the Tlokwe City Municipality (TCM), the legacy effects of apartheid created a steep socio-economic gradient as a result of the inequitable distribution of economic, natural and social resources. The aims of this study were to gain information on the flora that is present in the domestic gardens of the TCM and to determine if socio-economic status (SES), a management index (MI) and demographic factors influences the distribution of plant species between these gardens. A total of 835 plant species were recorded from 100 domestic gardens and the majority were of alien origin. This large number of species included some Red Data species, invasive alien species and also many utilitarian species. This portrays gardens as important ex situ conservation habitats, but simultaneously it could also threaten the integrity of our natural ecosystems through the distribution of alien invasive species. The gamma, alpha and beta diversity were determined across five SES classes to describe the patterns of domestic garden plant species diversity in the TCM. In accordance with other studies, correlations showed that the SES of the inhabitants affected the plant species distribution in the study area. This was especially true for the distribution of alien species that are cultivated for their ornamental value. More species were found in areas of high SES than those of lower SES. The other aspect that influenced the distribution of plant species in these gardens were the MI, although this was to a lesser extent than the effect of SES. The confirmation of differences along the SES gradient could be utilised by urban planners and policy makers to correct this imbalance through the provision of urban green spaces where it is needed most. / Thesis (M. Environmental Sciences and Management)--North-West University, Potchefstroom Campus, 2011.

Urbanisation has increased tremendously over the last 60 years so that more than 50 per cent of the world population now live in cities. This is especially true for in developed countries, but it is expected that developing countries will take the lead in future urban population growth. This increasing trend of urbanisation has severe consequences for the environment, as it fragments and changes natural areas and alter environmental conditions. This has compelled scientists from many different disciplines to focus on the inclusion of humans into ecology as a driving force of change to create a better understanding of urban ecosystems. The diversity of fauna and flora in the urban environment provides a myriad of ecosystem goods (such as food and fuel) and services (e.g. cleaning the air and reducing noise levels). Apart from these tangible benefits, urban green space also provides recreational, educational and social benefits to urban inhabitants. A surprisingly substantial proportion (21‒36 %) of the total urban green space that produces these ecosystem goods and services is located in private yards. This portrays the importance of the flora of this land-use type, but very little is known about garden flora and its potential for conservation. The determinants of diversity and species richness in gardens were found to be different than for semi-natural ecosystems, because of the high anthropogenic influence. One of these is the socio-economic status of the inhabitants. People with higher socio-economic status were found to harbour more diverse species assemblages in their gardens than those of lower socio-economic status. This phenomenon was termed the “luxury concept”. In the Tlokwe City Municipality (TCM), the legacy effects of apartheid created a steep socio-economic gradient as a result of the inequitable distribution of economic, natural and social resources. The aims of this study were to gain information on the flora that is present in the domestic gardens of the TCM and to determine if socio-economic status (SES), a management index (MI) and demographic factors influences the distribution of plant species between these gardens. A total of 835 plant species were recorded from 100 domestic gardens and the majority were of alien origin. This large number of species included some Red Data species, invasive alien species and also many utilitarian species. This portrays gardens as important ex situ conservation habitats, but simultaneously it could also threaten the integrity of our natural ecosystems through the distribution of alien invasive species. The gamma, alpha and beta diversity were determined across five SES classes to describe the patterns of domestic garden plant species diversity in the TCM. In accordance with other studies, correlations showed that the SES of the inhabitants affected the plant species distribution in the study area. This was especially true for the distribution of alien species that are cultivated for their ornamental value. More species were found in areas of high SES than those of lower SES. The other aspect that influenced the distribution of plant species in these gardens were the MI, although this was to a lesser extent than the effect of SES. The confirmation of differences along the SES gradient could be utilised by urban planners and policy makers to correct this imbalance through the provision of urban green spaces where it is needed most. / Thesis (M. Environmental Sciences and Management)--North-West University, Potchefstroom Campus, 2011.