the animal biodiversity of green walls in the urban ... thesis.pdf · pdf file urban...

Caroline Chiquet. PhD Thesis. Urban animal biodiversity and green walls

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 i

Caroline Chiquet. PhD Thesis. Urban animal biodiversity and green walls ii

“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 iii

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 iv

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 v

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 .........................................................................