Assessing the contribution of domestic gardens to urban ecosystem services
Green spaces are essential to the healthy functioning of our cities. Providing us with many benefits, they help to cool the air, improve air and water quality, absorb water, support wildlife, and provide a setting for recreational activities. Domestic gardens also have a vital role to play, making up a significant portion of the land area in cities, they can be important patches of green space that provide connectivity between larger green spaces such as parks and recreation grounds.
While individually, a domestic garden may appear insignificant, collectively domestic gardens contribute a large proportion of greenspace within the urban matrix, which becomes especially important at the city scale. In spite of this, the quantity and quality of green infrastructure provision by domestic gardens is not well-evidenced. This has implications for the future resilience of an urban environment and the health and well-being of its citizens. Current data over-estimates the amount of vegetation within private gardens, which leads to subsequent inaccuracies in environmental model outputs (e.g. surface water runoff in an extreme rainfall event), and in the identification and prioritisation of areas of GI need, inhibiting effective action on-the-ground. Furthermore, the general public are often unaware of the environmental value of their own private garden and how they can improve it.
The My Back Yard project developed a new understanding of the benefits that gardens provide to residents in Manchester. The research sought to provide evidence on the amount of green space in gardens, how it is spatially distributed across the city, and how this affects the associated benefits that green space provides. An Action Plan was then co-developed with partner organisations, with the aim to increase green space and enhance wildlife in gardens across Manchester.
Whilst the project focussed on the Manchester City Council area as a case study, diminishing green space in gardens is a pertinent issue within all urban areas, and the event provides transferable messages and learning that is relevant beyond Manchester.
There were four consecutive stages in the project approach:
1. The first stage involved an online survey to gather information from Manchester residents on how much green space exists in their gardens. Information on how people value their gardens was also collected. Over 1,000 people took part in the survey.
2. The information gathered from the online survey was validated against detailed aerial images. Furthermore, aerial images were used to extend and complement the survey information. This process resulted in a robust estimate of the amount of green space in gardens.
3. The amount of green spaces in gardens was used in models that estimate the natural processes that take place within gardens. The natural processes investigated were cooling the city, and absorbing rainfall. These estimates indicated benefits relating to reduced risks from heat waves and flooding.
4. This new information was incorporated into an action plan to improve the benefits provided by gardens. Four project partners took part in three rounds of discussions, negotiations, and consensus building. These resulted in a co-developed action plan, which can be downloaded below.
Domestic gardens cover a significant proportion of the total area of Manchester, with around one fifth of Manchester’s land area being gardens. The average proportion of domestic gardens to total ward area is 22-26%. This ranges between 0.5% (City Centre) to 47% across Manchester’s wards.
The findings of the My Back Yard project demonstrate that gardens are not completely green infrastructure (green and blue space). This affects the total estimate of green and blue space cover across Manchester, which is now estimated at 49%. The previous estimate of GI across Manchester that assumed gardens were completely green and blue space was 58%.
Less green space in domestic gardens means that the potential benefits they provide to people (ecosystem services) are reduced.
Dr Gina Cavan (Project Investigator, PI) & Dr Konstantinos Tzoulas (Co-Investigator), Manchester Metropolitan University; and, Dr Claire Smith (Co-Investigator), University of Leicester. Fraser Baker (Research Assistant, Manchester Metropolitan University).
Partner organisations: Manchester City Council, Manchester City of Trees, Southway Housing Trust, Lancashire Wildlife Trust, The Mersey Forest.
- Baker, F, Smith, C and Cavan, G (2018) A Combined Approach to Classifying Land Surface Cover of Urban Domestic Gardens Using Citizen Science Data and High Resolution Image Analysis. Remote Sensing. 10(4), pp.537-537
- Cavan, G., Baker, F., Tzoulas, K., Smith, C.L. (2022) ‘Manchester : the role of urban domestic gardens in climate adaptation and resilience.’ In Ren, C., McGregor, G. (ed.) Urban Climate Science for Planning Healthy Cities. Springer Nature Switzerland, pp. 99-118.
- My Back Yard: An Action Plan to increase green space and enhance wildlife in domestic gardens across Manchester
- Dr Konstantinos Tzoulas
- Dr Claire Smith, University of Leicester
- Fraser Baker
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