THE ANIMAL BIODIVERSITY OF GREEN WALLS IN THE URBAN ENVIRONMENT Caroline Chiquet July 2014 A thesis submitted to Staffordshire University in the subject of Ecology for the Degree of Doctor of Philosophy by Supervised Research Caroline Chiquet. PhD Thesis. Urban animal biodiversity and green walls Caroline Chiquet. PhD Thesis. Urban animal biodiversity and green walls i “If you are not a little bit afraid every day, you are not trying hard enough.” (Anonymous) “Follow passion first and foremost. Do valuable things that have little or nothing to do with your PhD. Be utterly busy with everything awesome and worthwhile.” (Bradley L. Garrett) Caroline Chiquet. PhD Thesis. Urban animal biodiversity and green walls ii ABSTRACT Over the last few decades, a substantial body of literature has highlighted the importance of the natural environment for human well-being and health. In the urban environment where, space is particularly costly, the abundance of plants can be increased by growing them vertically as ‘green walls’, rather than horizontally. Although green walls ecology is a rapidly growing science, large gaps remain in our knowledge as only few studies have investigated their ecosystem services, focusing mainly on their thermal values. This doctoral research is one of the first attempts to establish the value of varying vertical greening systems for animal biodiversity. To identify the animal populations of green walls, surveys were carried out on bird, snail, spider and insect communities in green façades and living walls of Stoke- on-Trent, Birmingham and London, UK. The study then focused on the effects of varying characteristics of green walls (e.g. vegetation surface area, plant density and richness, botanical composition, type of foliage) on these communities and also investigated if the local environment (e.g. pedestrian and vehicle traffic volumes, abundance of nearby vegetation) influenced the use of green walls by animals. The results showed that animal groups respond differently to the characteristics of green walls and the surrounding features. Importantly, the design and the maintenance interventions of green walls influence their use by animals and, as such, it is possible to modify these environments to make them more attractive to certain animal communities. Whether growing on independent self-supporting structures, or directly on or in buildings, plants can use largely underexploited vertical space allowing an additional type of ecosystem to be incorporated into the urban environment. Caroline Chiquet. PhD Thesis. Urban animal biodiversity and green walls iii AKNOWLEDGEMENTS I would like to express my gratitude to all those who helped me during my PhD study. Many people have made invaluable contributions, both directly and indirectly to my research. My deepest gratitude goes first and foremost to Professor John Dover, my supervisor, for his continuous encouragement and guidance. His enlightening instruction and constant patience stimulated me and taught me considerably during these years of research. I would also like to express my gratitude to Dr. Paul Mitchell, second supervisor, for the demanding identification of spiders and his valuable suggestions, and to Dr. Dave Skingsley for the crucial identification of snails. The whole project was made possible thanks to the funding received from the Research Excellence Framework. I am most grateful to the landowners, the manufacturers and installers, for the access to the walls, the help received, and for their enthusiasm for the study. I own my sincere gratitude to Dr Roger Dennis for his help on the multi-variate analysis of the data and the time he granted me for the explanations. I owe my sincere gratitude to Rosie Duncan, Dr. Sam Harrison and Charlotte Orphanou who have put up with me in the office, always available to answer my questions, to give valuable advices in the English writing and to help me with the English vocabulary and grammar. I also thank all my colleagues for their availability and their help. Christine Dover and Sam deserve thanks for proofreading the manuscript, sometimes within a quite short time scale :-). Rosie Duncan gave important support in the making of the maps in Appendix 6 to 8, thanks! My brother Vincent and my husband Cedric helped me with some of the fieldwork sessions, being enthusiastically the ‘pack horses’ and for that I am most grateful. I am also most grateful to the owners, who gave access to their property and land so that the green façades and living walls could be studied, and for their enthusiasm for the study. Assistance provided by the manufacturers was also greatly appreciated. I would not have followed the path of research without my parents’ enthusiasm and encouragement for continuously questioning things; I am immensely in debt towards them. Thanks for my constant support of my somewhat never ending education; I hope I made you proud. Last but not least, my thanks would go to Cedric, for his whole-hearted support, his love and his patience all through these years, since ‘Math sup/spé Bio’ to this PhD. Your turn now! . Caroline Chiquet. PhD Thesis. Urban animal biodiversity and green walls iv TABLE OF CONTENT Abstract................................................................................................................................iii Aknowledgements ...............................................................................................................iv Table of Content .................................................................................................................. v List of Figures......................................................................................................................xi List of Tables ..................................................................................................................... xiv List of Abbreviations ........................................................................................................ xvii List of Symbols ............................................................................................................. 17xvii Thesis methodology and chapter organisation ................................................................ 1 1. Thesis Outline .............................................................................................................. 3 1.1 Aims and objectives of the doctoral research ............................................................... 3 1.2 Planning ....................................................................................................................... 3 1.3 Justification of methods and pilot study ........................................................................ 4 1.4 Creation of a living wall on the University campus ........................................................ 4 2. Literature Review ......................................................................................................... 6 2.1 Green walls: a green infrastructure component ............................................................ 6 2.1.1 Green infrastructure definition and services ....................................................................... 6 2.1.2 The importance of green infrastructure ............................................................................... 8 2.2 The umbrella concept of green walls ...........................................................................10 2.2.1 Green walls, definitions and characteristics. Proposal for classification ........................... 10 2.2.2 Short history of green walls; ecology, research and utilisation ......................................... 14 2.2.3 Commercial systems in the Northern Hemisphere ........................................................... 16 2.3 The environmental values of green walls .....................................................................18 2.3.1 The specific use of hedges compared to other green walls ............................................. 18 2.3.2 Floral biodiversity of green walls ....................................................................................... 20 2.3.3 A building bioprotection cover or a biodeteriorative role? ................................................. 21 2.3.4 Urban heat island reduction, thermal mitigation and energy saving ................................. 22 2.3.5 Air quality improvement .................................................................................................... 25 2.3.6 Noise attenuation .............................................................................................................. 27 2.3.7 Stormwater management .................................................................................................. 28 2.3.8 Economic, social and health aspects ................................................................................ 29 2.4 Enhancing animal habitat in urban areas .....................................................................30 2.4.1 Theoretical context: different approaches for biodiversity conservation and landscape ecology .............................................................................................................................. 30 Caroline Chiquet. PhD Thesis. Urban animal biodiversity and green walls v 2.4.2 The importance of spatial context, heterogeneity and habitat concept in the study of green walls .................................................................................................................................