Managing domestic gardens collectively to promote urban biodiversity

Posted by Lee Dixon

Lee was a Research Masters student in our group before moving to University of Manchester to take up a ‘President Doctoral Scholarship’ to study urban biodiversity. Here he talks about his PhD work. 

Urban biodiversity

Cities frequently consist of a highly diverse mosaic of habitats which are subject to varying degrees of human intervention and manipulation. These habitats range from semi-natural habitats such as urban parks to totally artificial habitats such as industrial parks. As a result, cities have the capacity to hold a large number of ecological niches which in turn can support a surprising number of species. This biodiversity is vital for the sustained provision of ecosystem services, most notably those provided by pollination, but is also important for the health benefits that contact with nature has for humans.

Gardens are important habitat for Bumblebees (Bombus spp) currently declining in Europe and elsewhere as a result of urbanisation and climate change (Photo: Aconcagua).

To maintain high urban biodiversity and associated ecosystem service and health provision, it is important that growth in the world’s cities, land use changes, habitat fragmentation, and other by-products of human living such as pollution, do not result in loss of important species or communities. A key resource for urban wildlife is the domestic garden and their value is at the heart of my PhD. Urban gardens, although individually small in size, cover considerable areas of cities and have the capacity to hold a high level of biodiversity. As a result, domestic gardens taken as a collective entity may reasonably be described as a major nature reserve within cities. However, their value is contingent on the decisions made by householders about the composition of their own garden. 

Greater than 25% of the UK's national population of the Red Listed Song Thrush (Turdus philomelos) are held in domestic gardens (Photo: Tony Mills).

The habitat garden approach

The collective management of domestic gardens whereby multiple domestic gardens are managed in aggregation as a single habitat as opposed to individually (the habitat garden approach) has recently been proposed as a promising means to maintain or boost urban biodiversity. The approach is based on the 'species-area relationship', which describes the typical increase in number of species contained in larger and larger areas.It stands to reason that a collection of gardens all managed sympathetically for wildlife, as a single unit, may be better than individual gardens acting ‘unilaterally’.

South Manchester gardens make up a significant proportion of the urban landscape. Here is Stu's garden and the not-quite-as-nice gardens of his neighbours (Image: Google Maps).

There are, of course, social scientific factors which may influence the level of biodiversity within domestic gardens which are managed collectively as a single habitat. These include differences in how householders perceive the purposes of domestic gardens and different forms of garden wildlife, and the different garden management practices which they may implement in their gardens. These perceptions and management practices, if unfavourable to urban biodiversity, may nullify the potential benefits that this approach may bring to urban biodiversity and, as such, may form a constraining factor in its implementation in residential areas of cities. Moreover, it is unclear how institutions may promote householder perceptions and garden management practices which are favourable to urban biodiversity in order to maximise the potential benefits that the collective management of domestic gardens may bring for urban biodiversity.

'Privatisation' of domestic gardens such as the erection of fences and walls keep gardens relatively small in size and act as barriers to species' movement - in turn reducing the potential benefits that the habitat garden approach may bring to urban biodiversity (Photo: Lee Dixon).

The PhD

This research will explore what effect these householder perceptions and garden management practices may have on the potential benefits that the collective management of domestic gardens may bring for urban biodiversity and, with this taken into consideration, the feasibility of its implementation in cities. The research will also explore what incentives and approaches institutions could employ to promote householder perceptions and garden management practices which are favourable to urban biodiversity, and how these institutions may facilitate householder collaboration in the collective management of domestic gardens.

The specific objectives are

1.    To explore how householders perceive the purposes of domestic gardens, and garden wildlife

2.    To analyse how householder garden management practices may affect the biodiversity of domestic gardens

3.    To explore what incentives and approaches institutions could employ to promote biodiversity favourable householder perceptions and garden management practices

4.    To investigate if the collective management of domestic gardens is an appropriate approach to promoting urban biodiversity