Infilling practices and environmental impacts on domestic gardens
by Anna Ojala
This ongoing research further examines the infill process in the Helsinki Metropolitan Area, focusing on detached house areas and their gardens and yards. In the first phase of this study it was discovered that there was no previous information available on the extent or distribution of domestic gardens in the HMA. Thus, the aim of this research is to quantify the recent garden cover changes in a case study area in Vantaa. The results are being compared to previous work done in Helsinki. In addition, the relevant planning policies and documents of these cities are analysed. Finally, the role of private green spaces as habitat providers for urban fauna and flora is reviewed from the literature.
The infill process is studied from city planning documents from two case study areas: Ylästö in Vantaa and Paloheinä in Helsinki. In the first phase of the study, the present garden and yard areas in Paloheinä were measured and mapped using GIS –methods. The same methods are used in this study in order to measure the scale of the changes to the garden areas in Ylästö during 1998-2009.
The research questions to be addressed here are:
- How much have the garden and yard areas diminished due to infilling practices in the case study area in 1998–2009?
- What kind of detailed city plans do the case study areas have? Have the planning regulations changed over time? If so, do they consider ecological values such as maintaining the existing vegetation?
At this point, preliminary results from the ongoing are available. It seems that, in general, the infill development has been a lot less intensive in the plots of Ylästö than of Paloheinä. One reason for this is the differences of their housing and planning histories. It seems that there were very different objectives in the two case areas: In Paloheinä the infill was considered so important that the rather dramatic change of the character of the area was accepted with e.g. row house construction, whereas in Ylästö the identity of the area with detached houses was preserved.
Many studies have documented that domestic gardens provide a number of ecological, environmental and sociocultural benefits. The research work done in the UK, highlights the potential role of domestic gardens in maintaining urban biodiversity. However, private gardens can also have unwanted impacts on biodiversity, as they may, for instance, provide sources for non-native and invasive species. In a research done in Espoo 2011 it was discovered that gardens and yards were most common habitat type for studied harmful invasive species. The results of this survey indicate that a more detailed investigation of the gardens would be beneficial for the city of Espoo.