Trees in Towns: Factors Affecting the Distribution of Trees in High Density Residential Areas of Greater Manchester A thesis submitted to the University of Manchester for the degree of Ph.D. in the Faculty of Humanities 2010 Justine Michelle Hall School of Environment and Development Planning and Landscape Department Table of Contents Contents Page Table of Contents 2 List of Figures 7 List of Tables 10 Abstract 13 Declaration 14 Copyright Statement 14 Acknowledgements 15 Chapter 1 – Introduction 17 1.1 Aims and Objectives of the Thesis 19 Chapter 2 – Trees in the Urban Environment 22 2.1 Introduction 22 2.2 The Benefits of Trees in Urban Areas 23 2.2.1 Trees and Air Quality 23 2.2.2 Trees and Water 26 2.2.3 Trees and the Urban Heat Island Effect 27 2.2.4 Trees and Human Physical and Psychological Health 30 2.3 Factors Affecting the Distribution of Urban Trees 36 2.3.1 Socioeconomic Factors Affecting the Distribution of Urban Trees in the USA 37 2.3.2 Socioeconomic Factors Affecting the Distribution of Urban Trees in the UK 39 2.3.3 The Effects of Housing Density and Land Use on the Distribution of Urban Trees 40 2.3.4 The Effects of Housing Layout on the Distribution of Urban Trees 43 2.3.5 Attitudes and Awareness of Residents about Urban Trees 51 2.4 Potential Factors for Protecting and Increasing Urban Tree Cover 55 2.4.1 Effects of Municipal Regulations 55 2.4.2 Effects of Community Greening Schemes 58 2.4.3 Potential Effects of the Loss of Greenspace in Residential Areas 59 2 2.5 Conclusions 60 Chapter 3 – Research Methodology 62 3.1 The Research Context 62 3.1.1 A Conceptual Framework for the Research 63 3.2 Justification of the case study approach 65 3.3 Case Study Selection 66 3.4 Justification and Overview of the Methods Used in the Thesis 70 3.4.1 Objective One 70 3.4.2 Objective Two 73 3.4.3 Objective Three 74 3.4.4 Objective Four 76 3.5 Conclusion 78 Chapter 4 – An Exploration of Tree Cover and its Location in Differing Housing Types 79 4.1 Introduction 79 4.2 Methods 81 4.2.1 Determination and Delineation of Housing Morphology Types 81 4.2.2 Categorising Surface Covers and Land Uses 88 4.2.3 Position of Trees 93 4.3 Results 94 4.3.1 Housing Morphology 94 4.3.2 Surface Cover and Land Use Analysis 95 4.3.3 Comparative Data 110 4.3.4 Locations of trees 114 4.4 Discussion 115 4.4.1 Distribution and amount of housing types across the study area 115 4.4.2 Influences on tree cover in housing types 116 4.5 Summary and Conclusions 118 Chapter 5 – Increasing Tree Cover and its Effects on Maximum Surface Temperatures and Rainfall Runoff 119 5.1 Introduction 119 5.2 Methods 119 5.2.1 Determination of Potential Increases in Tree Cover 120 5.2.2 Calculating Increase in Tree Cover 122 5.2.3 The Energy Balance Model 122 5.2.4 Surface Runoff Model – Background 127 3 5.3 Results 130 5.3.1 Increases in Tree Cover 130 5.3.2 Location of Potential Trees 131 5.3.3 Energy Exchange Model for Surface Temperature Calculations 133 Temperature Projections with Current and Increased Tree Cover 134 5.3.4 Rainfall Runoff Calculations 146 5.4 Discussion 149 5.4.1 Increases in Tree Cover 149 5.4.2 Location of Potential Trees 149 5.4.3 Maximum surface temperatures 150 5.4.4 Surface Runoff 150 5.5 Summary and Conclusions 151 Chapter 6 – Residents’ Attitudes Towards Trees in Differing Types of High Density Residential Streets 152 6.1 Introduction 152 6.2 Methods 154 6.2.1 Identifying the survey objectives 154 6.2.2 Selecting the sampling frame 154 6.2.3 Determining the sampling method 156 6.2.4 Developing the questionnaire 157 6.2.5 Surveying residents 157 6.2.6 Analysis of Data 158 6.3 Results 159 6.3.1 Response Rates 159 6.3.2 Trees and Everyday Life Questions 161 6.3.3 Positive Statements About Trees 162 6.3.4 Negative Statements About Trees 164 6.3.5 Length of Stay in Current Home 166 6.3.6 Respondents’ Views About Their Street 166 6.3.7 Trees and House Prices and Future Homes 168 6.3.8 Street Specific Questions 169 6.3.9 Socioeconomic data 173 6.3.10 Crosstabulations 176 6.4 Discussion 182 6.4.1 Response Rates 182 6.4.2 The Importance of Trees to Everyday Life 182 6.4.3 Positive Statements about Trees 183 6.4.4 Negative Statements About Trees 185 6.4.5 Length of Stay in Current Home 187 6.4.6 Respondents’ Views About Their Street 187 6.4.7 Trees and House Prices and Future Homes 188 6.4.8 Street Specific Questions 189 6.5 Comparisons of UK data and US data 190 4 6.6 Summary and Conclusions 195 Chapter 7 – Barriers and Opportunities to Increasing Tree Cover 197 7.1 Introduction 197 7.1.1 The Legal and Planning Context for Urban Trees 198 7.2 Practitioner Workshop 201 7.2.1 Methods 201 7.2.2 Results 205 7.2.3 Discussion 211 7.3 Increasing Tree Cover in High Density Housing – Examples 212 7.3.1 Case Study Area Selection 212 7.3.2 Methods 215 7.3.3 Results 215 7.3.4 Discussion 218 7.4 Factors Affecting Red Rose Forest Green Streets Project Uptake 221 7.4.1 Methods 221 7.4.2 Results 221 7.4.3 Summary 223 7.5 Factors Affecting Use of Trees and Greenspace in Regeneration Schemes 224 7.5.1 Methods 224 7.5.2 Chimney Pot Park 224 7.5.3 Grove Village 226 7.5.4 The Use of Greenery in Developments 228 7.5.5 Discussion 228 7.6 Summary and Conclusions 230 Chapter 8 – Discussion 232 8.1 Introduction 232 8.2 Factors Affecting the Distribution of Urban Trees 232 8.2.1 Socioeconomic Factors Affecting the Distribution of Urban Trees 232 8.2.2 The Effects of Housing Layout on the Distribution of Urban Trees 233 8.2.3 Attitudes and Awareness of Residents about Urban Trees 234 8.3 The Benefits of Trees in Urban Areas 238 8.3.1 Increasing Tree Cover and Maximum Surface Temperatures 238 8.3.2 Trees and Rainfall Runoff 239 8.4 Potential Factors for Protecting and Increasing Urban Tree Cover 239 8.4.1 Existing and Potential Tree Cover in Different Housing Types 239 8.4.2 Effects of Municipal Regulations 242 8.4.3 Effects of Municipal Practice 244 8.4.4 Raising Money for Tree Planting and Maintenance 245 5 8.4.5 Saving Money in Arboricultural Departments 247 8.4.6 Encouraging Community Involvement in Tree Based Activities 248 8.4.7 Community Greening Projects 249 8.4.8 Comparison of Differing Approaches to Increasing Tree Cover 250 8.5 Conclusions 250 Chapter 9 – Conclusions 253 9.1 Summary of Main Research Findings 253 9.1.1 Revisiting the Conceptual Framework 253 9.2 Recommendations of the Research 258 9.2.1 National Government 258 9.2.2 Local Government 259 9.2.3 Developers 262 9.2.4 Residents 263 9.2.5 Community Greening Projects 264 9.3 Limitations of the Research Methodology 264 9.4 Recommendations for Further Work 265 References 266 Appendix 1. Cover Letter and Questionnaire Exploring Residents’ Attitudes Towards Trees 280 Appendix 2. ‘Barriers and Opportunities for Increasing Tree Cover within Urban Areas’: Summary of Practitioner Workshop Held On Monday 22 nd February 2010, at the University of Manchester 289 Word count: 77,116 6 List of Figures Figure 2.1 . Two examples of ‘byelaw’ terraces in Manchester, UK, built pre-1919. (Source: 1:10,000 OS map, within a GIS). 44 Figure 2.2 . A street map of an area of Letchworth Garden City, Bedfordshire, UK. Note the much lower density and lack of straight roads and crossroad junctions compared to Figure 2.1. (Source: 1:10,000 OS map, within a GIS). 45 Figure 2.3 . A block of flats within a high density housing area in Gorton, Manchester. Note the small patch of grass to the left which is the only vegetated area around the flats. The trees are part of a separate development. 48 Figure 2.4 . An example of 1960s housing in Gorton, Manchester, which is only accessible on foot. There is no road access to the rear of the properties either. 49 Figure 3.1 . A conceptual framework outlining potential influences on tree distribution in high density housing areas. Thick arrows indicate relationship described in the literature, thin arrows indicate hypothesised relationships. 64 Figure 3.2 . The location of Greater Manchester within the north west of England, UK, and the study area (white) within Greater Manchester. 69 Figure 4.1 (1). Clockwise from top left –Pre 1919 terraced housing with a front yard; Pre 1919 terraced housing with a front and back garden; Pre 1919 semi-detached housing; 1919-1959 terraced housing; 1960s terraced housing with a driveway; 1960s terraced housing with a walkway; 1919-1959 semi-detached housing; Pre 1919 terraced housing opening directly onto the road. 85 Figure 4.1 (2). Top – Post 1960s terraced housing. Right- Post 1950s semi-detached housing. Bottom – Post 1960s Court/Square housing.