Comparison of the urban domestic garden flora along a socio–economic gradient in the Tlokwe City Municipality

Abstract

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.