Ojala et al. 2017 Impacts of Residential Infilling on Private Gardens in the Helsinki Metropolitan Area1 Anna Ojala, Jari Niemelä, Vesa Yli-Pelkonen Accepted final draft version Reference: Ojala, A, Niemelä, J., Yli-Pelkonen, V. (2017) Impacts of residential infilling on private gardens in the Helsinki Metropolitan Area. In: Clark, P., Niemi, M., Nolin, C. (eds.) Green Landscapes in the European City, 1750-2010. Routledge Studies in Modern European History, Routledge, London and New York, pp. 71-86. Disclaimer: The PDF document is a copy of the final version of this manuscript that was subsequently accepted for publication in the book. It has not been subject to any additional copy editing or publisher-specific formatting. It thus looks different from the final published version. Residential areas in Finland are largely comprised of low-rise housing areas with detached and semi-detached houses. At present, there are over 68,000 detached and semi-detached houses with associated gardens and yards in the Helsinki Metropolitan Area (Table 1). Private gardens can have multiple roles in urban areas as they are special and valuable environments for people and wildlife.2 They are unique and heterogeneous environments, where the management choices of individual 1 We thank Prof. Peter Clark for numerous useful comments, the city planners and other persons who provided information on the topic, Timo Cantell and Minna Pitkäniemi from the City of Helsinki Urban facts for the SeutuCD'10 data, Pirjo Ilosalo and Timo Lehtola from the City Survey Department of the City of Vantaa for the aerial photographs and cadastral boundary maps of Ylästö, and Timo Kallaluoto and Juhani Nieminen from the Planning Department of the City of Vantaa for the detailed plans of Ylästö. 2 C. Smith, D. Dawson, J. Archer, M. Davies, M. Frith, E. Hughes and P. Massini, ‘From green to grey; observed changes in garden vegetation structure in London, 1998-2008’, London Wildlife Trust, Greenspace Information for Greater London and Greater London Authority (London, 2011), <https://www.rbkc.gov.uk/pdf/Garden%20Research%20Full%20report.pdf > (accessed July 2015); see also reviews: M.A. Goddard, A.J. Dougill and T.G. Benton, ‘Scaling up from gardens: Biodiversity conservation in urban environments’, Trends in Ecology and Evolution, 25 (2010), 90-98 and R.W.F Cameron, T. Blanuša, J.E. Taylor, A. Salisbury, A.J. Halstead, B. Henricot and K. Thompson, ‘The domestic garden – Its contribution to urban green infrastructure’, Urban Forestry & Urban Greening, 11 (2012), 129-137. 1 Ojala et al. 2017 gardeners are important, particularly when considering the possibilities of these habitats to maintain and enhance urban biodiversity and to provide ecosystem services for urban inhabitants.3 Table 1. The number of residential buildings in the Helsinki Metropolitan Area, which includes the cities of Helsinki, Espoo, Vantaa and Kauniainen (31.12.2013). Detached and semi- Row and terraced Blocks of flats detached houses houses Helsinki 20072 4244 10262 Espoo 26371 3735 2735 Vantaa 21120 2869 2326 Kauniainen 1076 146 99 Helsinki Metropolitan Area 68639 10994 15422 Source: Statistics Finland, Helsingin seudun aluesarjat, ‘Rakennukset käyttötarkoituksen ja rakentamisvuoden mukaan 31.12.2013’, <http://www.aluesarjat.fi/> (Accessed July 2015). Prior to this study, there was no information available on the extent and distribution of domestic gardens in residential areas of the Helsinki Metropolitan Area. As the cities in the area have not been monitoring the state of private green areas, such as domestic gardens, there are no detailed registers or statistics of these green areas. In addition, there is a considerable lack of ecological research done on private garden environments in Finland. However, increasing attention is being paid to the urban garden environments in many European cities and research done in the United Kingdom in particular highlights the potential of such habitats in supporting urban and wider region wildlife. 4 Although subject to high levels of management activities, gardens may provide beneficial resources for urban fauna: a diversity of vegetation covers and structures as well as additional water elements, such as ponds, that could function as habitats for aquatic and other water-dependent species.5 The abundance of trees and shrubs in gardens can be essential for insect and bird species diversity.6 Gardens provide breeding 3 Goddard et al., ‘Scaling up from gardens’; J. Tratalos, A.F. Richard, P.H. Warren, R.G. Davies and K.J. Gaston, ‘Urban form, biodiversity potential and ecosystem services’, Landscape and Urban Planning, 83 (2007), 308-317. 4 Goddard et al., ‘Scaling up from gardens’; Smith et al., ‘From green to grey’; D.E. Chamberlain, M.P. Toms, R. Cleary-McHarg and A.N. Banks, ‘House sparrow (Passer domesticus) habitat use in urbanized landscapes’, Journal of Ornithology, 148 (2007), 453–462; J.-A. Carrier and T.J.C. Beebee, ‘Recent, substantial, and unexplained declines of the common toad Bufo bufo in lowland England’, Biological Conservation, 111 (2003), 395–399; R.L. Bland, J. Tully and J.J.D. Greenwood, ‘Birds breeding in British gardens: an underestimated population?’, Bird Study, 51:2 (2004), 97- 106. 5 A. Loram, P. Warren, K. Thompson and K.J. Gaston, ‘Urban domestic gardens: The effects of human interventions on garden composition’, Environmental Management, 48 (2011), 808–824; A. Loram, K. Thompson, P.H. Warren and K.J. Gaston, ‘Urban domestic gardens (XII): The richness and composition of the flora in five UK cities’, Journal of Vegetation Science, 19 (2008), 321-330. 6 Y. Paker, Y. Yom-Tov, T. Alon-Mozes and A. Barnea, ‘The effect of plant species richness and urban garden structure on bird species richness, diversity and community structure’, Landscape and Urban Planning, 122 (2014), 2 Ojala et al. 2017 environments for birds and habitats for several other species, including frogs, hedgehogs, rabbits, foxes, bats and grey squirrels.7 Furthermore, urban domestic gardens are important nesting and feeding habitats for bumblebees,8 which are thereby favoured as useful pollinators. Gardens thus have a significant role in maintaining biodiversity in urban environments.9 Urban gardeners may also use active management methods such as wildlife gardening to enhance local biodiversity.10 Urban gardens, including allotment gardens and private domestic gardens, can also provide a variety of ecosystem services for the benefit of urban inhabitants,11 as summarised in Table 2. Table 2. Potential ecosystem services provided by domestic gardens. Provisioning services Cultural services Regulating services Supporting services Food Aesthetic values Regulation of microclimate Habitat for fauna and flora Ornamental resources Inspiration Erosion regulation Pollination Fire wood Nature education Noise reduction Seed dispersal Recreation Pest regulation Water cycling Social relations Air pollution mitigation Soil formation Source: Modified from J. Colding, J. Lundberg and C. Folke, ‘Incorporating green-area user groups in urban ecosystem management’, Ambio 35 (2006), 237-244. Although there have been very few ecological surveys done in Finland on private gardens,12 in one rare study the garden floras of 41 private gardens in the city of Helsinki were inventoried.13 The main finding of this study was similar to that of studies done in Britain: while many of the garden 186-195; R.M. Smith, P.H. Warren, K. Thompson and K.J. Gaston, ‘Urban domestic gardens (VI): Environmental correlates of invertebrate species richness’, Biodiversity and Conservation, 15 (2006), 2415-2438; R.M. Smith, K.J. Gaston, P.H. Warren and K. Thompson, ‘Urban domestic gardens (VIII): Environmental correlates of invertebrate abundance’, Biodiversity and Conservation, 15 (2006), 2515-2545. 7 Carrier and Beebee, ‘Recent, substantial, and unexplained declines’; P.J. Baker and S. Harris, ‘Urban mammals: what does the future hold? An analysis of the factors affecting patterns of use of residential gardens in Great Britain, Mammal Review, 37:4 (2007), 297-315. 8 J.L. Osborne, A.P. Martin, C.R. Shortall, A.D. Todd, D. Goulson, M.E. Knight, R.J. Hale and R.A. Sanderson, ‘Quantifying and comparing bumblebee nest densities in gardens and countryside habitats’, Journal of Applied Ecology, 45 (2008), 784-792. 9 e.g., Goddard et al., ‘Scaling up from gardens’; G. Galluzzi, P. Eyzaguirre and V. Negri, ‘Home gardens: neglected hotspots of agro-biodiversity and cultural diversity’, Biodiversity and Conservation, 19 (2010), 3635-3654. 10 Loram et al., ’Urban domestic gardens’; Z.G. Davies, R.A. Fuller, A. Loram, K.N. Irvine, V. Sims and K.J. Gaston,’A national scale inventory of resource provision for biodiversity within domestic gardens’, Biological Conservation, 142 (2009), 761-771. 11 J.H. Breuste and M. Artmann, ‘Allotment gardens contribute to urban ecosystem services: Case study Salzburg, Austria’, Journal of Urban Planning and Development, A5014005 (2014); J. Colding, J. Lundberg and C. Folke, ‘Incorporating green-area user groups in urban ecosystem management’, Ambio 35 (2006), 237-244. 12 But see e.g., N. Nieminen, ’Lilacs, phloxes and irises –The ornamental garden flora in Puu-Käpylä”, M.Sc. thesis, Faculty of Agriculture and Forestry, University of Helsinki (Helsinki, 2010) (in Finnish with short summary in English), a historical perspective to ornamental flora. 13 P. Piirainen, ‘Kasvikartoituksen satoa’, in L. Eerikäinen et al. (eds), Vihreä kylä – monta tarinaa. Kanta-Helsingin omakotiyhdistyksen historiikki 1987-2007 (Helsinki, 2007), pp. 254-262. 3 Ojala et al. 2017 plants may be introduced species, the gardens show high levels of floristic diversity.14 Furthermore, private gardens in Helsinki and Vantaa provide habitats for strictly protected species such as flying squirrels and certain types of bat.15 Although private gardens may be rich in species,16 they cannot replace natural habitats. However, they can complement such habitats and provide resources (for example, foraging, overwintering and nesting sites) that benefit urban fauna.17 In particular, species with good dispersal abilities or high mobility, such as birds and flying insects, are most likely users of garden environments.