TOWARDS IMPROVED URBAN GREEN anthropocentric review and design guidelines Marina Zaldua SetiĂŠn
TOWARDS IMPROVED URBAN GREEN anthropocentric review and design guidelines Author: Marina Zaldua Setién Supervisor: Natalie Marie Gulsrud Master’s Thesis - MSc in Landscape Architecture University of Copenhagen
“Nature is not a place to visit. It is home� The Practice of the Wild, Gary Snyder (1990)
ABSTRACT This work seeks to discover the way to improve the qualitative status of urban nature in order to obtain enhanced benefits of it. However, as urban green is subject of social construction, the multiple ways in which human action impacts over nature’s success will have to be analysed. Nature in the cities is usually underestimated. In cities, incorrect decisions over design, species selection and management of urban green spaces are leading to the loss of benefits that nature is likely to provide freely. These advantages bring the environmental, social, cultural and economic benefits needed to make cities sustainable living places, thus their deficiency is now compromising the global economy and human health. This thesis has been structured into three main parts; The first one aims at reviewing
the existing scientific literature about the called “objective” benefits of nature. In this section, two approaches will be analysed to see not only nature’s contributions but the drawbacks. The second part will recall the subjectivity of humans, influencing over the theory through both how they perceive nature and the room they make for it. This will be specifically illustrated by two case studies in an international comparative. The third section delivers the results of the working process, where green legislation guidelines will be proposed. Based on worldwide practices, these are a way to improve the green benefits and refrain the inconveniences incurred. It is hoped that through the identification of the mistakes committed and the proposed guidelines, this study will stimulate urban green practitioners towards responsible solutions and improved nature’s benefits.
ACKNOWLEDGMENTS This work is the final product of the Master’s in Landscape Architecture at the University of Copenhagen, and has been prepared as a 30 ECTS-point thesis from the 30th November, 2018 to 31st May, 2019. The defence will have place the 28th of June, 2019. The result of this six month period is “Towards Improved Urban Green”, an anthropocentric review and design guidelines, aimed at stimulating practitioners over urban green towards responsible greening practices in order to enhance the benefits obtained by nature in the cities. In this section, I would like to express my gratitude to all the people that have followed me and my work throughout this time. First of all, to my supervisor Natalie Gulsrud, who’s continuous enthusiasm and trust on me from the first day have encouraged my words, resulting in the present work. I also acknowledge the periodic reviews and presentations shared with the student study board, their constructive comments,
valuable suggestions and discussions over skype. I specially recognise the assistance of Marcus Spaull, unconditional friend that has proof read these lines over and over again, correcting my english expressions. For this research, a small questionnaire was carried out. I would like to thank all the people that have helped me getting foreign perspectives and also to all those that have dedicated their time answering the survey on ‘nature perception’. All your insights were not only constructive for this work but building for myself. Above all, this thesis would not have been possible without the determined support of my parents, that have sponsored my decision of embarking this complementary twoyear education in Landscape Architecture. To my beloved Thomas, for being always there, despite the distance and finally to all my friends that have contributed through my studies, thank you.
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NOTE TO THE READER During my years studying and working as an architect, I perceived a constant lack of consideration for the design of the green spaces surrounding my buildings. The function of the built environment was always the first objective. The landscape at the service of the user; dense canopies for shading, deciduous trees to allow winter sun in, oversized tree planting to ‘dress up’ the project… If the vegetation’s function was not enough argument to justify a design decision, the next claim was the aesthetics. Considered as “landscaping creativeness” are; a fragrant blooming, colourful flowers, interesting foliage… This might be the reflection of the education that I received in Spain, a country that has commonly relied on the non-urban environment to provide us with nature. The green that is planned on our cities ends up being merely aesthetic (although sometimes inaesthetic) and potentially functional (although frequently dysfunctional). Nevertheless, I will not focus my critique on my home country, I will neither dare to compare cities and walk into the increasingly common competition of “who is greener”. Because I think this is not about quantity but about quality. In the context of landscape, Mies Van der Rohe’s famous line, “less is more” only works if the “less” is efficient. Until today, I have not proved the existence of any city completely uninhabited by green. Yet in Petra, the “rock-carved city” of Jordan, native fauna and flora inhabit the archaeological site. I venture myself when I affirm that there is nature in every city of the world, whether as parks, gardens or trees allées. Certainly, we need more nature than
cities but this is a quite romantic appraisal and rather far from reality. However, what we could really do is to improve the green surface that we now enjoy. Nowadays, the urban green is undervalued and few space is left for it in the city. My hypothesis is that the origin of this issue relies first on our nature perception. The lack of environmental examples in the daily city life, makes us slowly lose the basic awareness of ecological processes. The fact that we do not understand how nature works or how beneficial it can be, leads to an exclusion of the vegetation’s quantitative and qualitative needs in the urban regulations and design standards. As a result, the space given to green in the cities is often scarce and sometimes omitted. Moreover, how this green is managed is also a matter of analysis. Since nature in the cities is socially constructed, we are also in charge of the benefits it provides. Nature needs to be understood not as a complement to the built environment, neither as bare ornament subject to critics. Like the modern farmer has forgotten that cows are herbivores, we seem to have forgotten that humans need nature to live. My intention with this work is to render clear to the common reader the value of urban green, hidden behind the scientific theory of the benefits provided by nature. In order to support my critique I will bring real life examples, with the clear aim of opening the eyes of all those urban planners, architects, engineers, landscape architects, and decision makers in charge of making our cities better places to live.
TOWARDS IMPROVED URBAN GREEN Table of Contents
- INTRODUCTION _______________________________________________________ pg 15 - METHODS ____________________________________________________________ pg 17 - DEFINITIONS - What is “urban” ___________________________________________________ pg 21 - What is “green” ___________________________________________________ pg 23 - What is “urban green” ______________________________________________ pg 25 - FIRST PART: THE THEORY OF URBAN NATURE - The interest of urban nature _________________________________________ pg 30 - The objective value of urban nature ___________________________________ pg 31 - Ecosystem services ________________________________________ pg 31 - Nature’s contribution to people ________________________________ pg 35 - Nature’s contribution to the city ________________________________ pg 37 - Urban nature’s drawbacks ___________________________________ pg 43 - SECOND PART: HUMAN IMPACT OVER THE THEORY - The subjectivity of nature’s value _____________________________________ pg 51 - Nature perception __________________________________________ pg 53 - Cities as nature’s context ___________________________________________ pg 59 - Human actions over urban green ______________________________ pg 60 - Relating human actions to nature’s contributions __________________ pg 64 - Study cases _____________________________________________________ pg 67 - San Sebastian, Spain _______________________________________ pg 69 - Alto de Errondo street _________________________________ pg 71 - Urbieta street _______________________________________ pg 73 - Errondo street _______________________________________ pg 75 - Dr. Marañón alley ____________________________________ pg 77 - Pau, France _______________________________________________ pg 79 - Auchan parking _____________________________________ pg 81 - Tourasse boulevard __________________________________ pg 83 - Edouard VII avenue __________________________________ pg 85 - Alsace Lorraine boulevard _____________________________ pg 87 - THIRD PART: TOWARDS IIMPROVED GREEN - Result of the international comparison ________________________________ pg 95 - Proposal ________________________________________________________ pg 97 - Discussion _____________________________________________________ pg 100 - Conclusion _____________________________________________________ pg 101 - REFERENCES - Text references __________________________________________________ pg 107 - Image and table references ________________________________________ pg 110
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INTRODUCTION We currently live in the Anthropocene, an era where humans are the dominant geological force and at the same time we have entered an Urban Age. Over half of humanity now lives in towns and cities and this fraction is still predicted to increase endlessly (United Nations, 2019). The rate of urban growth is unprecedented. The Earth System has become urbanized in the sense that decisions by the majority of the human population now living in cities affects the resilience of the entire planet (Seto et al., 2011).
environmental, social, cultural and economic benefits, better known as ‘ecosystem services’ or ‘nature’s contribution to people’. Nature in the cities is a social phenomena, created by a combination of environmental conditions, socioeconomics, demographics and politics (Etingoff, 2015). This mainly anthropocentric approach makes humans responsible for nature’s prosperity too, a subject that needs further consideration. The aim of this work is to study the multiple ways in which human action impacts on the success of green space and thus, how to maximise the benefits provided by urban nature.
The origins of every urban settlement are in the suppression of nature, and so the problems caused by urbanisation are great and varied. Phenomenon like the ‘urban heat island’ or the ‘urban rainfall effect’, are some of the consequences of the massive construction and paving of surfaces, which make cities progressively unsustainable and vulnerable. Likewise, cities have caused a distancing between humans and the natural environment, triggering different social and even biological problems. Nevertheless, it is not until recently that we have come to realise how relevant the nature is. Through the expanding body of scientific literature on the green resource, we should know by now the potential functions and best ways to plan, design and manage urban nature (Konijnendijk et al., 2005). Green spaces can improve the climatic conditions engendered in the city by enhancing urban temperature cooling through shade provision and leaf evapotranspiration, balancing precipitation, reducing wind speed, decreasing the storm water runoff, filtering air pollution... and at the same time bringing nature closer to humans.
For this purpose, it is important to recall the importance of urban green space through a theoretical review, to be able to link human influences to nature’s benefits and vice versa. In this way, the objective valuation of nature’s advantages will encounter the subjective character of the value of nature, which far from being generalised, has to be studied case-specifically. Nevertheless, there are multiple ways of estimating the benefits obtained from green space, among which the human intervention has rarely been closely contemplated. This study reveals that not only through our nature perception or understanding but the actions of design, species selection and management of urban green, we directly alter the provided services and generated disservices. As ecosystems underpin the global economy and human well-being (TEEB, 2009), the quality of green space is increasingly relevant, being ‘green’ is no longer enough. Green infrastructure must be as well planned and provided as the rest of urban services. Nature needs to be considered and responsible greening practices need to be embodied and incorporated in the decision making processes.
Nature is essential for any urban agglomeration. Green spaces assist many of the challenges caused by cites and at the same time provide urban dwellers with 15
METHODS The scope of this research is to present the multiple ways in which human action impacts on nature’s performance and thus, the ways towards enhancing the contributions of urban green. This is in fact applicable worldwide, to every city where urban green derives from a social construction. Therefore, the present analysis will not focus on a specific context or location, but on a situation that is likely to happen everywhere.
attachment that has triggered this research action. The close relation to both sites presents a further local perspective, where inaccessible assumptions to the foreign eye have been possible. Moreover, the illustrated cases are located in different countries, with different cultures, urban nature values and greening practices. Even though the objective is not a country comparison, inevitable similarities arise when looking at the human impact on nature’s prosperity, sign of the mistakes on the construction of urban green being committed worldwide, no matter the preexisting conditions.
In order to answer the research question, this work will be using case studies, where the result of human action over the green space has been empirically reported. These situations set the example of issues in design, species selection and management regarding urban green resources. Moreover, this analysis makes it possible to comprehend the consequences of human action over nature’s ability to provide contributions and incur drawbacks. This data would not have been possible to obtain from satellite or GIS systems, since they do not possess such an accurate definition and images tend to differ temporally from the present. The objective is not to count the green surface of the city but to report the quality (or lack of it) of urban nature through the benefits and disbenefits that are currently been provided.
The purpose of this comparative evaluation on the consequences of human action over the urban green, is to serve as a stimulation for practitioners to aim at responsible greening practices. By this means, not only nature could be managed, but the benefits provided can be maximised. Through the analysis of the mistakes we commit and the exploration of the existing solutions, we can look at the nature that surrounds us differently and consider not how many, but how do we want our surrounding nature to be. Greening the cities is primarily a responsibility of designers and decision makers. However, the way this nature is perceived and understood, is a responsibility of every citizen. For this reason, the language used throughout this analysis pursues to get both sides of the city, nature “builders” and users.
The presented examples are located in the European context for practical reasons. Two cities have been selected due to a personal
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DEFINITIONS
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WHAT IS ‘URBAN’ There is surely an instant image that pops into anyone’s mind when thinking of the answer to ‘what is urban’. We certainly visualise those seductive pictures of the skyscrapers in North American cities, reflecting on the water. Surely, we think likewise of enormous road crossings and huge railways navigating through the city. This is somewhat correct if we take the narrow definition given by the dictionary, who defines this adjective as “in, relating to, or characteristic of a town or city” (Oxford dictionary online, 2019). What they fail to define are the attributes of the urban environment to be considered a city. Therefore, the answer to where ‘urban’ begins and ends stays blurred.
and precipitation in and around urban areas (Seto and Shepherd, 2009). The most studied manifestation of urban modification of regional climate is the urban heat island. The conversion of vegetated surfaces to hard impermeable surfaces modifies the exchange of air, water and heat between the land surface and overlying atmosphere (Crutzen, 2004); this leads to the “urban heat island effect”, characterized by elevated temperatures in and near urban areas when compared to surrounding regions. There is mounting evidence that urbanization affects precipitation variability, a phenomenon described as an “urban rainfall effect” (Shem and Shepherd, 2009). In some parts of the world there is an observed increase in regional precipitation due to urbanization, while in other regions there is a measurable decline in precipitation. Lastly, in addition to the ‘urban heat island’ and ‘urban rainfall effects’, urbanization significantly affects the terrestrial carbon cycle (Elmqvist et al., 2013) which reduces the net primary productivity, understood as the rate of plant growth during a certain period of time.
There is no general agreement on a definition of the urban environment and considerable differences in classification of urban and rural areas exist among countries and continents. In Europe, the urban landscape is often defined as an area with human agglomerations and with more than 50% of the land covered by built surface and an overall population density of more than ten individuals per hectare (Elmqvist et al., 2013). In other contexts, population size, the density of economic activity or the form of governance structure are used to delineate what is a town, city or region, but there is significant variation in the criteria for defining what is urban.
Since the scale of the urban settlement relates to the degree of ecosystems affection, it makes no sense to define a precise dimension for the urban setting. In this work, what will be considered as urban will not depend upon the numbers of population density or built cover percentage. Instead, what is ‘urban’ will be delimited by the environmental challenges encountered. Thus in this case, even in a rural context, if there would be a highly built area suffering from any environmental disorder, it could be considered as an urban cluster and the origin of the issues analysed as in the city.
While everyone struggles to define exactly what is meant by a city, nobody negates the shifting patterns of world population, the overall growth of cities and the consequent damage to worldwide ecosystems. Landcover changes associated with urbanisation have considerable impacts on temperature
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WHAT IS ‘GREEN’ The definition of ‘green’ has also been largely debated.. If we take the color ‘green’ as the guideline for the definition, every vegetated space would be a green space. However the green colour can be found at different heights, as at ground level or in the tree canopies. Would a group of trees in a paved plaza be ‘green’ if there is no vegetation in the floor? Some authors define green spaces as a land consisting predominantly of unsealed, permeable or ‘soft’ surfaces, such as soil, grass, shrubs and trees (Dunnett et al., 2002). The emphasis is on the ‘predominant’ character because green may include buildings and hard surfaced areas. Nowadays, there is not even the need of a soft surface to display vegetation. Green can be contained in above ground planting pits and pots.
It seems to me that the green space is not defined by a colour code, but by the ability to provide benefits to all urban inhabitants. Thus there would not be better or worse green spaces, nor this will depend upon their dimension, there will simply be less or more benefit-providing green spaces. It is important to understand that green does not understand the limits of legally defined property boundaries. It can be found in private and public, accessible and inaccessible, managed or unmanaged spaces. Several authors have defined urban green space typologies, Green Surge (Braquinho et al. 2015) provides an extensive list of forty-four urban green spaces. Some examples are; tree allées, house gardens, urban parks, green verges, botanical gardens, cemeteries, community gardens, lakes, wetlands...
If we were to play the devil’s advocate, green space could also be the opposite to green, it could be grey. Open spaces are as much important as vegetated spaces. Among others, they provide urban decongestion, space for recreational activities and opportunities for huge social events and gatherings. Well-known examples are the Place Vendôme in Paris (France), or the Piazza di Campo in Siena (Italy). Both examples, completely unprovided of vegetation, provide in the other hand plenty of cultural, historical and aesthetic values.
While there is no global agreement on the definition of green, frequent contradictions arise between the professional and lay persons perspective. The concept of ‘green’ turns to be a very subjective concept, closely related to the understanding of ‘nature’, which will be explored later in this study. The idea behind this work is that every type of urban green has the potential to contribute in a different degree to the local scale environmental impacts of urbanisation and provide diverse benefits to urban dwellers. However,facing the myriad typologies and variability existing in green spaces, this work will only focus on the vegetated elements and spaces, what could be understood as purely ‘green’ colour. Surface permeability will be an added performance indicator in the analysis of the green space, as well as other important factors.
There is a last color that could be taken into consideration in the definition of green, the blue. In the form of natural lakes and rivers or man-made canals and fountains, water provides numerous benefits to the urban environment and dwellers. It can support urban biodiversity, contribute to the mitigation of the elevated temperatures and serve varied recreational purposes.
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WHAT IS ‘URBAN GREEN’ Since we moved from being a hunter-gatherer community to dwelling urban environments, we have been using the urban green in very different ways. The vegetation that had primarily served the provision of raw materials and was later planted for aesthetic purposes, now has ended up being used to mitigate the consequences caused by overproduction and overpopulation. As urban populations continue to grow, cities are constantly expanding and environmental damage is continuously being caused. In the urban context, one way to cope with these issues is by creating functional linkages between urban green spaces and the ecosystems provided by them. Healthy environments are the foundation for sustainable cities, influencing and affecting human well-being (TEEB, 2011).
or impedes the movement of organisms and processes. This last one is a product of both, structure and the response of organisms to it and it is species and landscape-specific. Distinguishing between these two types of connectivity is important because the first does not imply the success of the second, and vice versa. However, what we currently understand by landscape connectivity refers to the functional connectivity (Meiklejohn,2009). As a consequence of natural ecosystems working jointly, far more important than just greening the city, is to design an intertwined system of green and blue spaces through the urban fabric. The benefits provided by this interconnected network are increasingly recognised as having an essential role to play in maintaining human-nature interaction and in tackling various urban challenges like climate change. Green spaces can make substantial contributions to the sustainable urban development, such as improving public health, protecting biodiversity, enhancing social cohesion, supporting the economy, providing opportunities for recreation, and helping cities adapt to a changing climate (Green Surge, 2017). It is the ecological framework needed for environmental, social and economic sustainability and yet green spaces are under pressure in many cities due to rapid urban growth, redensification and infill development in cities.
Urban green infrastructure is understood as the strategic approach to develop an interconnected network of multifunctional green space that conserves natural ecosystem values and functions and provides associated benefits to human populations (Benedict and MacMahon, 2002). Being part of the urban network means that it has to be combined with other types of infrastructure, such as the roads system, water and energy supply and waste management, among others. For this structure to work successfully, there has to be not just an urban planning but a growth projection too, in order to avoid the obsolescence of the infrastructure.
Indeed, nature in the cities has always been constructed through the balance of biodiversity (the support) and culture (the circumstances). Therefore, the benefits provided are shaped by the decisions made by society through time and space. In this study, the role of humans creating functional green linkages will be analysed when measuring the ability of nature to provide benefits.
The connectivity within the landscape is the key factor for the correct functioning of urban green ecosystems. This connectivity can be broken into two different categories; structural connectivity, which refers to the physical relationship between landscape elements; and functional connectivity, that describes the degree to which the landscape facilitates 25
FIRST PART THE THEORY OF URBAN NATURE
In this first section, the theoretical framework of urban nature will be introduced; why do we need it, what do we need it for and who benefits from it. This information is given as a foundation for the next section, in which the research question will be uncovered lying between theory and practice. In order to assemble this database, the objective interest of urban nature will be explained through two methods and for two types of users; we, humans and our habitat, the city. Accordingly, urban nature’s benefits and disbenefits will be recalled.
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THE INTEREST OF URBAN NATURE In this research about how to maximise nature’s benefits, it is essential to analyse first the interest of nature, what do we obtain from it and why. Pavan Sukhdev affirms that “we cannot manage what we do not measure and we are not measuring either the value of nature’s benefits nor the costs of their loss” (The Guardian, 2010). Both, the objective and subjective value of nature are often unknown as they are highly variable (through time, scale or location) and difficult to assess through simple means. As a result, this complete review of the benefits supplied by urban green, should serve designers and decision makers to justify its integration in the city regulations and the suitable design and management.
and adults around the world have become increasingly disconnected from nature, with profound implications for human health and development; impacts on attention disorders, Vitamin D deficiency, myopia, obesity and the growing epidemics of both inactivity and loneliness. This called nature-deficitdisorder is largely developed by Richard Louv (2008), who reminds us how important is to recognise and quantify the many needs that green spaces provide in the urban context. Secondly, the city needs nature to assist mitigating the effects of massive urbanisation, reducing elevated temperatures, storm water runoff, providing open spaces for air renewal and decongestion, etc. Cities have shown an average greenhouse gas emission of 1,84 ton per capita (Folke et al., 1997). The current urban demand for functioning ecosystem is becoming the major driver behind global environmental change (Camill, 2010). Urban vegetation in woodlands, parks, gardens, and aligning streets and squares are the most important elements of green areas, yet their benefits are often overlooked and their proper care neglected (Konijnendijk et al., 2005).
In order to build this nature valuation study, the objective benefits obtained from nature will first be determined to be used as a baseline for the following section. The advantages that we extract from nature, also known as “goods or services”, are in fact mesurable, which makes them easier to understand and correlate to human actions. For instance, if we take apples as an objective benefit obtained from nature, removing the tree that produce them or simply not implementing this service in the city would be a direct human matter.
In the following section, the numerous nature benefits obtained by humans and specifically the ones provided by the urban green in the city environment are going to be described. This theoretical review will be used later in this study to evaluate gains and losses over nature’s contributions derived from human action.
There are two major advantages of urban nature; the first, humans need nature because we are biologically connected to it, not just because of the health outcomes but also for social reasons. In recent decades, children
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THE OBJECTIVE VALUE OF URBAN NATURE Behind the anthropocentric theory in which nature’s ecological processes are translated into benefits to humans, there are two approaches that will be presented. The first approach is the oldest of the two and was described by Costanza et al. (1997). Their analysis was latter officially established by the Millennium Ecosystem Assessment (2005) under the name of Ecosystem Services. In this case, nature’s benefits are distributed into four broad categories, based on scientific and economic analysis to estimate the monetary value of nature’s benefits.
categories. This new approach was a reaction to criticism of the Ecosystem Services perspective holding a predominantly stockand-flow frame of people-nature relationships, failing to engage with social sciences and humanities. This new method, although being rooted in the first, welcomes wider perspectives and viewpoints. What is specially interesting is that this method recognizes the central role of culture defining links between people and nature and is therefore less likely to be subsumed within a narrow economic approach as the mediating factor between people and nature. Nevertheless, both methods have been presented in this work to be able to see similarities within two different scientific approaches to the same theory.
The second theory provided by Diaz et al. (2018), named ‘Nature’s Contributions to People’, is a recent classification of nature’s benefits. These are roughly split into three
ECOSYSTEM SERVICES (Millennium Ecosystem Assessment, 2005)
services. It is also important to emphasise the interdependent nature of many ecosystem functions. For example, some of the net primary production in an ecosystem ends up as food, the consumption of which generates respiratory products necessary for primary production (Costanza et al., 1997).
Ecosystems are a way of describing nature’s function and they consist of independent components(plants, animals, microorganisms, water, air, etc.) as well as the interactions between these components. Ecosystem goods (such as food) and services (such as waste assimilation) represent the benefits that human populations derive, directly or indirectly from ecosystem functions. These material and non-material benefits derived from nature are known as ecosystem services. Ecosystem services and functions do not necessarily show a one-to-one correspondence. In some cases, a single ecosystem service is the product of two or more ecosystem functions whereas in other cases a single ecosystem function contributes to two or more ecosystem
The first general classification of ecosystem services, by Constanza el al. (1997), grouped services into four categories: regulating, habitat, production and information functions. Regulating functions included services related to maintaining earth’s life support system, such as, chemical composition of the atmosphere and biological diversity. Habitat functions described services that provide space and resources, such as 31
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recreation and tourism, while production functions included the provision of resources such as water and food. Finally, information functions referred to services such as cultural enrichment and education. This classification
was later rearranged to become the basis for the Millennium Ecosystem Assessment (2005) four categories of ecosystem services: provisioning, regulating, cultural and supporting services.
PROVISIONING SERVICES Photosynthesis and nutrient uptake by autotrophs converts energy, carbon dioxide, water and nutrients into a wide variety of carbohydrate structures which are then used by secondary producers to create an even larger variety of living biomass. This broad diversity in carbohydrate structures provides many ecosystem goods for human consumption, ranging from food and raw materials to energy resources and genetic material. REGULATING SERVICES This group of functions relate to the capacity of natural and semi-natural ecosystems to regulate essential ecological processes and life support systems through biogeochemical cycles and other biospheric processes. In addition to maintaining ecosystem (and biosphere) health, these regulation functions provide many services that have direct and indirect benefits to humans, such as clean air, water,soil, and biological control services. CULTURAL SERVICES Because most of human evolution took place within the context of undomesticated habitat, natural ecosystems provide an essential ‘reference function’ and contribute to the maintenance of human health by providing opportunities for reflection, spiritual enrichment, cognitive development, recreation and aesthetic experience. These services are tightly bound to human values and behaviour, as well as to human institutions and patterns of social, economic, and political organization. Thus perceptions of cultural services are more likely to differ among individuals and communities than, say, perceptions of the importance of food production. SUPPORTING SERVICES Natural ecosystems provide refuge and reproduction habitat to wild plants and animals and thereby contribute to the (in situ) conservation of biological and genetic diversity and evolutionary processes. Supporting services are those that are necessary for the production of all other ecosystem services. They differ from provisioning, regulating, and cultural services in that their impacts on people are either indirect or occur over a very long time, whereas changes in the other categories have relatively direct and short-term impacts on people. For example, humans do not directly use soil formation services, although changes in this would indirectly affect people through the impact on the provisioning service of food production.
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NATURE’S CONTRIBUTION TO PEOPLE (Diaz et al., 2018)
This perspective seeks a universally applicable classification of flows from nature to people. Living nature’s (diversity of organisms, ecosystems, and their associated ecological and evolutionary processes) contribution to people’s quality of life are both positive and negative. Beneficial contributions include, for example, food provision, water purification, and artistic inspiration. Whereas, detrimental
contributions include disease transmission and predation that damage people or their assets (Diaz et al., 2018). This theory, identifies twenty-eight categories and classifies them within three partially overlapping groups: regulating, material, and nonmaterial nature contributions, defined according to the type of contribution they make to people’s quality of life.
MATERIAL CONTRIBUTIONS Substances, objects, or other material elements from nature that directly sustain people’s physical existence and material assets. They are typically physically consumed in the process of being experienced, for example, when organisms are transformed into food, energy, or materials for ornamental purposes.. NONMATERIAL CONTRIBUTIONS Nature’s effects on subjective or psychological aspects underpinning people’s quality of life, both individually and collectively. Examples include forests and coral reefs providing opportunities for recreation and inspiration, or particular animals and plants being the basis of spiritual or socialcohesion experiences. REGULATING CONTRIBUTIONS Functional and structural aspects of organisms and ecosystems that modify environmental conditions experienced by people and/or regulate the generation of material and nonmaterial contributions. Regulating contributions frequently affect quality of life in indirect ways. For example, people directly enjoy useful or beautiful plants but only indirectly benefit from the soil organisms that are essential for the supply of nutrients to such plants. In this case, the culture permeates through and across all three broad groups rather than being confined to an isolated category (as the “cultural ecosystem services” category in the Millennium Ecosystem Assessment framework). In addition, the three broad groups, rather than being independent compartments, as typically framed within the ecosystem services approach, explicitly overlap.
The contributions’ classification is made for practical reporting reasons, acknowledging that many of the nature contribution categories do not fit squarely into a single group. For example, food is primarily a material contribution because calories and nutrients are essential for physical sustenance. However, food is full of symbolic meaning well beyond physical survival. Indeed, nonmaterial and material contributions are often interlinked in most, if not all, cultural contexts. 35
NATURE’S CONTRIBUTION TO THE CITY the local or global scale according to the scope of the problem they are connected to and the possibility of transferring the service from where it is produced to the city where humans benefit from it. Such a transfer can take place both by man-made transport and by natural means (through the atmosphere) (Bolund and Hunhammar, 1999). Easily transferred services with a global scope, like carbon sequestering, do not necessarily have to be produced close to the source of the problem. Services which are impossible to transfer must, however, be provided onsite or close to where they are consumed.
The presented theories might seem quite general regarding the urban context. Nowadays, most provisioning or material benefits that we extract from nature (such as wood or fuel) still derive from the rural environment. Cities have recently started to be given the chance to produce primary materials, such as;food or freshwater provision. Concerning the remaining nonmaterial and supporting services, comprehensive analysis of urban green spaces have shown that in both private and public land uses, gardens, cemeteries, old brown-fields and golf courses contribute significantly to ecosystem services provided by the urban landscape (Colding et al. 2006; Goddard et al. 2010).
Out of the non-tradable goods, six are considered to have a major importance in urban areas: air filtering (gas regulation), micro-climate regulation (temperature and wind reduction), noise reduction (disturbance regulation), rainwater drainage (water regulation), sewage treatment (waste treatment) and recreational, cultural and habitat values (Trowbridge and Bassuk, 2004; Bolund and Hunhammar, 1999).
Several of these benefits provided by ecosystems are not consumed by humans directly, but are needed to sustain the ecosystems themselves. Such indirect services include pollination of plants and nutrient cycling, among others, but their classification is not obvious. Another aspect of ecosystem services is that they have a different spatial cover. Services can be available on
AIR FILTERING (GAS REGULATION) Air pollution caused by transportation and heating of buildings, among other things, is a major environmental and public health problem in cities. Plants play an important role in reducing both particulate and gaseous pollution. Research has quantified this effect, which is just beginning to be studied in depth. Vegetation acts as a natural filter, removing not only particulate matter but also gaseous pollutants including carbon monoxide (CO) and sulfur dioxide (SO2) by absorbing them through leaves and other plant parts. Leaf filtering capacity increases with the surface, and therefore will be higher for trees than bushes or grassland. Due to the larger total surface area of needles, coniferous trees have a larger filtering capacity than trees with deciduous leaves. This capacity is also greater because the needles are not shed during the winter, when the air quality is usually worst. However, coniferous trees are sensitive to air pollution and deciduous trees are better at absorbing gases (Stolt, 1982). A mix of species therefore seems to be the best alternative. The remaining particulate matter that clings to trunks, twigs and leaves is usually washed into the soil by rainfall. 37
The location and structure of vegetation is important for the ability to filter the air. Bernatzky (1983) reports that up to 85% of air pollution in a park can be filtered out, and in a street with trees, up to 70%. According to some estimates (Tolly, 1988), 1 hectare of mixed forest can remove 15 tones of particulate pollution per year from the air. In general, vegetation is much better than water or open spaces for filtering the air. However, vegetation does not have the ability to absorb low levels of noxious fumes without related damage to the plant. MICRO-CLIMATE REGULATION (TEMPERATURE AND WIND REDUCTION) Local climate and even weather are affected by the city. In studies of US cities, some of these differences have been quantified, and expressed as changes compared with surrounding countryside: air temperature is 0.7°C higher measured as the annual mean, solar radiation is reduced by up to 20%, and wind speed is lowered by 10–30% (Haughton and Hunter, 1994). Facing the urban heat island, all natural ecosystems in urban areas can help to reduce air temperatures. The actual reduction in temperature may vary from a few degrees to more than -7ºC. Improved human comfort levels and a reduced need for air conditioning are the direct result of the knowledgeable placement of appropriate-sized vegetation in urban spaces, especially adjacent to buildings. A single large tree can transpire 450 liters of water per day. This consumes 278 kilowatt-hour of heat energy to drive the evaporation process. In this way city trees can lower summer temperatures of the city markedly (Hough, 1989). To have the greatest effect on cooling a building in the Northern Hemisphere, deciduous trees should be planted primarily on its west side and secondarily on its east side. The leaves will have their cooling effect in the summer heat but let most of the winter sun in after leaf-fall. Trees are most effective at shading people and buildings from the sun’s rays as well as reflecting radiation back into the atmosphere. Planting green to reduce wind speeds has long been practiced around the world. Research shows that semiporous windscreens that include trees and shrubs can have a profound windreducing effect. A barrier of approximately 35% transparent material (Trowbridge, Mudrak et al., 1988) can create a long calm zone that can improve human comfort levels by decreasing wind chilling. Reduced wind speeds can also improve human mobility, including walking and riding bicycles in places where wind tunneling impairs outdoor activities. NOISE REDUCTION (AND VISUAL BARRIER) Noise from traffic and other sources creates health problems for people in urban areas. On the noise impact, the distance to the acoustic source is one key factor, because the distance doubling decreases the equivalent level by 3 dB(A). Another key factor is the character of the in-between ground. A soft lawn, rather than a concrete pavement, decreases the level by another 3 dB(A) (SOU, 1993). Vegetation can contribute to the reduction, but at what level is uncertain. This is because the noise reduction depends greatly on the vegetation density and species selection, because the leaf surface and absorption index will varies. What we know is that few plants alone do a poor job of reducing noise. However, dense planting especially combined with landforms, can reduce noise significantly. 38
As cities become denser, reduction of noise pollution becomes a significant factor in increasing human well-being and reducing stress. Contemporary work has focused along busy highways near residential and commercial development where noise pollution creates the greatest negative impacts. Society is prepared to pay large sums for lowered noise levels . High cost technical solutions to decrease noise include, for example, 3–5-meter high walls that decrease the noise by 10–15 dB(A). However, the urban visual landscape would be destroyed if such walls were built everywhere. Another example of a technical solution are the insulated windows in houses, but they are only effective for indoors (Bolund and Hunhammar, 1999). Increasing the areas with soft ground and vegetation may decrease these noise levels. Vegetation can also contribute by shielding the visual intrusion of traffic and thus making it less disturbing. In this case, evergreen trees will be preferred, in order to have an all-year-long protection. RAINWATER DRAINAGE (AND REGULATION) The urban built-up infrastructure, with concrete and asphalt surfaces, results in alterations of water flow compared to an equivalent rural catchment. A higher proportion of rainfall becomes surface-water runoff which results in increased peak flood discharges and degraded water quality through the pick-up of urban street pollutants (Haughton and Hunter, 1994). Moreover, the impermeable surfaces and high extraction of water causes the groundwater level of many cities to decrease. Plants play a crucial role in trapping and slowing stormwater runoff as well as reducing soil erosion. The soft ground of vegetated areas allows water to seep through and the vegetation takes up water and releases it into the air through evapotranspiration. Incorporating plants can significantly reduce our reliance on stormwater abatement systems, improve natural water infiltration and reduce the velocity of water moving over a landscape. Allowing for water evaporation, evapotranspiration and infiltration as well as the replenishment of urban groundwater are universally critical aspects. Plants can provide the ability to reduce runoff on highly erodible soils as well as areas of steep topography. Plants with a highly fibrous root system that yield a more complete ground cover with their stems and leaves work best in this regard. In vegetated areas only 5–15% of the rainwater runs off the ground, with the rest evaporating or infiltrating the ground. In vegetationfree cities about 60% of the rain water is instead led off through storm water drains (Bernatzky, 1983). This will of course affect both the local climate and the groundwater levels. Valuation of this service depends on the local situation. Cities with a high risk of flooding will benefit more from green areas that take up water than do other cities. SEWAGE TREATMENT (AND WASTE) Sewage treatment costs cities large amounts of money, and the nutrients that are still released contribute to the eutrophication (the process by which a body of water becomes enriched in dissolved nutrients, resulting in the depletion of dissolved oxygen) of the water ecosystems. In many cities, large scale experiments are taking place where natural systems, mainly wetlands, are being used to treat sewage water. The wetland plants and animals can assimilate large amounts of the nutrients and slow down the flow of the sewage water, allowing particles to settle out on the bottom. Up to 96% of the nitrogen and 97% of the phosphorus can be 39
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retained in wetlands, and so far wetland restorations have largely been successful, increasing biodiversity and substantially lowering costs of sewage treatment (Ewel, 1997). The cost of nitrogen reduction through wetland restoration has been calculated to be almost five times cheaper than the cost in a sewage treatment plant (Gren, 1995). Other benefits of wetlands, such as the biomass production and biodiversity, have yet not been included in the valuation. RECREATIONAL, CULTURAL AND HABITAT VALUES (FOR HUMANS, FAUNA AND FLORA) The recreational aspects of all urban ecosystems, with possibilities to play and rest, are perhaps the highest valued ecosystem service in cities. All ecosystems also provide aesthetic and cultural values to the city and lend structure to the landscape. At the same time, they also provide habitat for urban flora and fauna, which can be accounted as added recreational values. Urban green spaces are the places where most of the city dwellers connect with the natural world actively pursuing these values. Green cities are always listed as desirable places to live, certainly because they provide a fundamental link to the natural world, marking seasonal changes and answering human need to be connected with nature. Green spaces are also psychologically very important. One example is a study on the response of persons put under stress in different environments (Ulrich et al., 1991). This study showed that when subjects of the experiment were exposed to natural environments the level of stress decreased rapidly, whereas during exposure to the urban environment the stress levels remained high or even increased. Another study on recovery of patients in a hospital showed that patients with rooms facing a park had 10% faster recovery and needed 50% less strong pain-relieving medication compared to patients in rooms facing a building wall (Ulrich, 1984). These studies imply that green spaces can increase the physical and psychological well-being of urban citizens. The scientific values of ecosystems are also included in this group, such as providing information services. In order to make an analysis of the state of the urban environment, the own ecosystems can be used as indicators, also known as bioindicators. Lichens, for example, are widely used to measure the air quality because of their impossibility to grow in areas with polluted air (Miller, 1994).
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URBAN NATURE’S DRAWBACKS irregular or they may be permanently present, at low or high background levels. They can be direct impacts of ecosystem properties and processes on human well-being, such as pollen allergens. They can also be present as the diminished flow of an ecosystem service, such as pests decreasing the recreational value of a tree and leading to the loss of a cultural ecosystem service (Lyytimäki, 2017).
Urban green has been proved to be the source of numerous ecosystem services. However, not everything they provide is a benefit. Nature can also be source of various types of nuisance, harm and cost. These bad aspects are known as ‘ecosystem disservices’ and are defined as “functions of ecosystems that are perceived as negative for human well-being” (Shackleton et al., 2016).
The following are various examples of the disservices incurred by urban green (Pauchard and Barbosa, 2013; Lyytimäki and Sipilä 2009; Lyytimäki et al., 2008). Although the list of possible disservices is smaller than the list of potential services provided by nature, the disbenefits need to be analysed and quantified to comprehend how human intervention can impact not only on the positive but on the negative contributions of urban green.
The drawbacks produced by urban green depend on different factors, such as species composition, location of the tree in relation to other trees and built structures, the growth patterns and life phase of the tree, stress caused by external conditions and the intensity of maintenance activities… Moreover, ecosystem disservices operate on various spatial, temporal and functional scales. The frequency at which they occur may be highly
AIR QUALITY PROBLEMS (EMISSIONS OF VOLATILE ORGANIC COMPOUNDS) Some urban vegetation species emit volatile organic compounds such as isoprene, monoterpenes, ethane, propene, butane, acetaldehyde, formaldehyde, acetic acid and formic acid, all of which can indirectly contribute to city contamination and greenhouse gas emissions (Geron et al., 1994). The amount of VOC emissions depends on the species, leaves biomass, air temperature and other environmental factors (Chaparro and Terradas 2009). DAMAGE ON INFRASTRUCTURE (UNDERGROUND AND ABOVEGROUND) Urban biodiversity can also cause damages to physical infrastructure, for instance microbial activity can result in decomposition of wood structures and bird excrement can cause corrosion of stone buildings and statues. The root systems of large scale vegetation often cause substantial damage by breaking up pavement and some animals are often perceived as a nuisance as they dig nesting holes. Sometimes even harmful species can damage those species that are cared for, bearing inevitable economic losses (herbivorous species eating plantations, pests, fungi). 43
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VIEW BLOCKAGE The vegetation shapes, heights, leaf densities and distances to buildings can generate view or sunlight blockages. The excessive shading caused by vegetation height or density, can cause the increase of the energetic expenses, bring maintenance problems and even act as a cover for criminal activity. ALLERGIES AND DISEASES Urban ecosystems may include health problems from wind-pollinated plants causing allergic reactions (D’Amato 2000). For instance, high concentrations of Mugwort (Artemisia vulgaris) pollen, a roadside common herb, cause severe health problems for people with respiratory issues such as asthma. In some cases, plants can also contain toxic substances in the leaves, fruit or trunk, causing intoxication if consumed. Regarding the urban fauna, certain animal species (as migratory birds, dogs, rodents‌) can be vectors of diseases, such as avian influenza, rabies and other viruses. ACCIDENTS Large green or blue areas can obstruct fast and comfortable transportation and moving, especially the use of motorized transportation. While trees along streets and roads may increase traffic safety because they make car drivers slow down, plants growing near traffic areas can decrease visibility and increase the risk for traffic accidents. Additionally, leaves falling from trees can increase the braking distances of cars and trams. Sometimes, large size or heavy weighted branches of trees can also entail risks for vehicles and pedestrians. FEAR AND STRESS Areas with poor management but high biodiversity are often felt unsafe, specially in night-time (Koskela and Pain, 2000). The fear to wild or semi-wild animals like bats, rats, foxes or deer in larger parks can encourage fear too, causing anxiety and inconvenience. AESTHETICS Areas that are not intensively managed are often considered unpleasant and ugly, such as parks with weeds and dense vegetation, brownfields and wastelands. Inside green spaces, certain sounds, smells or behavior of plants and animals can also irritate people, specially bird and dog excrements are considered an aesthetic and hygiene problem. Additionally, animal species such as foxes or birds searching food from trash bins can litter the environment. ECONOMIC ISSUES Fist of all, green areas prevents more profitable uses, such as construction. While economic benefits originating from a rich urban biodiversity are more difficult to assess since they are more often features not captured by current market mechanisms. From an economic perspective, urban ecological disservices increase direct expenses such as costs caused by attempts to control or remove unwanted invasive species (insects, weeds, invasive species, birds nesting in wrong places and small mammals). Additionally, the presence of protected species can also restrict other uses of the area. 45
SECOND PART HUMAN IMPACT OVER THE THEORY
In this second section, the theory meets the practice. For being socially constructed, urban nature is in fact influenced by two main features; human subjectivity and the city environment. For this reason, both, humans and the urban development need to be analysed. Firstly, a brief theoretical review together with a field research, will come to the conclusion of nature valuation pluralities, finding that explains responses over worldwide green practices. Through two study cases, three will be the human actions reported to impact on urban nature’s ability to provide benefits; design, species selection and management.
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THE SUBJECTIVITY OF NATURE’S VALUE The foundation of human impact over nature is the way we value and understand nature. Both nature’s contributions (ecosystem services) and drawbacks (disservices) are inherently anthropogenic concepts, putting emphasis on the human valuation of ecosystem properties and functions. Many contributions may be perceived as benefits or detriments depending on the individual cultural, socioeconomic, temporal, or spatial context (Lyytimäki, 2017). Therefore, what is perceived as beautiful and beneficial by one person may be considered ugly, useless, unpleasant or unsafe by another. Example can be found again on an apple tree. While the locals might be glad to pick free apples (material contribution) and make their kids learn about natural processes (nonmaterial contribution), the neighbour in whose garden the rotting fruits are dropping will perceive the tree as a disservice (economic or aesthetic issue).
or learning outcome of this green space. The consideration of the way people value nature is essential for this analysis, because it builds the foundation of the human-nature relationship. From this biocultural connection, the human impact on nature’s benefits can be evaluated. The way we comprehend nature leads to the way and the extent in which we influence it. For instance, where humans believe to be simply part of nature, they tend to leave urban green areas to provide services more freely than where humans assume to be its master. There is a further complication to this theory in the urban context, because how we value nature is inevitably associated to our understanding of it. In cities, our distance to the natural environment is multiplying and as a result, we are gradually losing basic understandings of its function and our relationship with it. Ecosystem processes such as pollination or the origin of fruit and vegetables are being forgotten as a result of this disconnection from our natural environment. This knowledge gap bears consequences over the urban biodiversity, which ends up being the subject of individual experience and appreciation. For example, if we understand that nature needs to be connected to function effectively, we will make urban planning accordingly. However, if we believe that nature serves a mere aesthetic purpose, importance will not be placed on maintaining a green infrastructure network. In the following section, the theoretical basis to the subjective valuation and understanding of nature will be given, to be able to comprehend the underlying reason for the human influences over the urban green spaces’ prosperity.
The added problem to the subjectivity is found in the inability to measure some of the objective benefits, because again, they fall within the domain of personal valuation. The material or supporting contributions, even if they can be subjectively considered, can also be easily quantified or priced, which, in turn makes human impact more obvious. However, the non-material benefits provided by nature as learning, inspiration or the physiological experiences can hardly be grasped through quantitative means and therefore their impacts tend to be unrecognised. For example, in the human decision of removing an 80-year-old tree allée, although we could measure the loss of objective contributions such as noise absorption or carbon sequestration, we will encounter difficulties to measure local place attachment (Williams, 2014), aesthetic value
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NATURE PERCEPTION Nature’s value is above all an individual appreciation, therefore a matter of personal subjectivity. The way we value urban green space is deeply connected to the way we perceive the landscape that surrounds us. As a result, the weight of the ecosystem services or disservices varies around the planet. For instance, the Tuareg nomads of the Saharan desert might prioritize the provision of fresh water, while the northern Scandinavian Sámi community may find the view blockage disservice caused by vegetation an opportunity for hiding. People’s perception of nature is deeply connected to their location, native culture and the education received. Furthermore, nature’s understanding is also
influenced by individual’s ethics, beliefs and own experiences. Studies have shown that childhood experiences appear influential for environmental attitudes measured in later life (Hartig et al., 2014). The relationship between humans and nature can be categorised into two main perspectives; whether humans stand above nature – anthropocentric view; or whether they are part of or even subordinate to nature – ecocentric view (Zweers, 2000). Many authors have made a further division into these views. In Environmental Psychology (Steg et al., 2012) human-nature relationships are analysed as follows:
MASTERS Humans stand above nature and may do with it as they want. STEWARD/GUARDIAN People have the responsibility to care for nature. PARTNER Humans and nature are of equal value. Both have their own status and work together in a dynamic process of mutual development. PARTICIPANT Humans are part of nature, not just biologically, but also on a psychological level. Biocultural diversity studies the interrelationships between nature and culture and refers to the inextricable linkages between cultural diversity and biological diversity and what these mean for nature and culture (Posey, 1999). In urban areas, it accounts the many ways in which people live with the green areas of the city. The complex biocultural relation implies that variations in how humans value urban landscapes stem from how they use and experience these urban landscapes. It is important to learn about these cultural valuations,
first because they might reveal the distinct subjective valuations over the ecosystem services’ objectiveness. Secondly, because how people value nature may change over time. Lastly, because they originate from interactions and experiences with nature in specific places (Buizer et al., 2016). Indeed, cultural valuations are subjective, dynamic and place-based, therefore they should be analysed case-specifically. The variety of biocultural connections leads to the rooting of very different nature valuations 53
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into human biology. In his work, The Value of Life, Kellert (1997) describes ‘Nine Basic Values of Nature’, and will be used in this work to explain the basis of human impacts over nature’s ability to provide benefits.
mastering; the chore of survival. People have the ability to subdue and control threatening elements of the world (challenging nature). HUMANISTIC VALUE Nature is a way for expressing emotional attachment, bonding; abilities nurtured through close association with single species. Nature creatures are “humanized”, becoming even human companions.
UTILITARIAN VALUE Emphasizes the material benefit derived from exploiting nature to satisfy human needs and desires. Life diversity provides benefits to people in form of products (food, wood…).
MORALISTIC VALUE The diversity that characterizes life on earth seems to share a basic biomolecular structure and genetic, suggesting a common origin. Nature becomes a source of spirituality, order and harmony; a guide to human conduct.
NATURALISTIC VALUE People obtain satisfaction from the direct contact of nature. Naturalistic experience can take expression through organized recreation (birding, fishing…) but also from wandering natural areas. Exploitation is independent of age and the rewards can range from relaxation and intellectual growth and creativity.
NEGATIVISTIC VALUE The natural world is a powerful carrier of hostile and negative feelings; aversion, fear and dislike. Nature can evoke threatening an antagonistic sentiments and provoke anxious reactions under varying circumstances. These emotions can either lead to destructive actions or to a distancing and respect for nature.
ECOLOGISTIC/SCIENTIFIC VALUE Emphasizes on biophysical patterns, structures and functions of nature. The ecologistic view is an integrative approach of the interdependence among species and natural habitats. The scientific understanding stresses structures and processes below the level of whole organisms an ecosystem, as individual elements. However, both perspectives converge; nature can be comprehended and controlled.
The cultural and subjective character of nature’s worth, makes the ‘value of green space’ a matter of endless debate. For this study to cover an approximation to this complex topic grounded in social sciences, an international survey about how nature is perceived has been conducted. Relevant information to this study is found in the last question, where respondents were asked about ‘what is your definition of nature’. Some of the answers, quoted in the following pages, demonstrate the pluralities of nature valuation. As a result of the biocultural interactions and relationship being very diverse, the impact over nature is also likely to vary. Nevertheless, this work does not seek to link specific nature valuations with impacts over nature, this topic will be left for environmental psychology. In this study, nature’s individual valuation is presented as the origin of the influences over green space’s ability to provide benefits to the city environment.
AESTHETIC VALUE Nature exerts an aesthetic impact on human, arousing strong emotions from the contours of a mountain to the colours of a sunset. It provokes feelings of pleasure and reflects individual’s preference and sensibility. SYMBOLIC VALUE Reflects the human tendency to use nature for communication and thought, to express ideas and emotions. Essential material for building our species’ most treasured of capacities: the ability to use language. DOMINIONISTIC VALUE Nature has always confronted humans with significant physical and mental challenges, testing the capacities for enduring, even 55
“Nature is our mother and so we should behave and treat her” Anonymous, Slovakia “Any breathtaking collective parts of the world including vegetation, animals and landscape which can bring a smile to my face is nature for me” Anonymous, Iran “Nature is the animals and plants world” Marta Moretti, Italy “Nature is not made by human and it exist on the planet from the beginning. People feel the nature, people are relaxed by the nature. Nature is good place to be in” Anonymous, Japan “Nature is the absence of human control” Jakob Valeur, Denmark “Nature is responsible for the existence of all things. We could never biuld anything without a nature element.” Marina, Brazil “Without nature we have nothing. Humans, we shall protect nature because we don’t have the power to create it; the natural world exists without human intervention” Lupe Setién, Spain “Nature is everything that grows without human intervention (e.g. a flower in the middle of the street)” Anonymous, Germany “Nature is the life that makes men live, it reminds us of our smallness in relation to its greatness, it helps us to return to the origins and encounter ourselves and others.” Lucía D’Angelo, Argentina
“Nature is all the life that ever arose on this earth without human help” Miranda Wilmsen, Holland “When I talk about nature I primarily mean wilderness. I am aware that there is technically no pure nature left, since air pollution, climate change etc. effect the whole globe and every community” Anonymous, Hungary “Nature is the source of life, something that we must protect at any price” Odile Martin, France “Nature is an ultra-complex habitat, it’s the life itself and we, as human beings are just a small part of it” Olga Barbarosh, Greece “Nature is simply everything, from the thunder to the peace after the storm, the relief of cities and what helps us breath” Ana Pezzetta, Venezuela “I was defining nature as the earth without human-made buildings” Rose Lauren Hauer, USA “For me, nature is somewhere untouched, full of vegetation, providing nice views for people. And people who live in the stressful urban life can relax there.” Anonymous, China “Any location with a diversity of flora that a diversity of fauna can inhabit” Will Drabble, England “We need nature and nature need us” Todor Todorov, Bulgaria
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CITIES AS NATURE’S CONTEXT Cities are human-made artifacts and frequently opposite to nature (Rodenburg et al., 2001). Urban growth happens in expense of nature’s reduction, which translates into habitat fragmentation, destruction and loss. If these were not enough, the conditions left for urban nature and biodiversity to survive are hugely inhibited by the levels of anthropisation, absurdly reaching the point where human and nature habitats end up being incompatible. We stand in a constant battle against the rest of urban inhabitants: we chase the moles that ruin our perfect lawns, we cut down the trees because they shade us or to avoid the droppings of the birds nesting on them.
Through urban infrastructure we modify and control the local geology, topography and even the hydrological processes. Roads and streets conform the vast extension of sealed surfaces that affect the water infiltration and nutrient cycle needed for prosperous soil conditions. Over time, the unwatered and undernourished terrain becomes infertile, offering a very poor support for any kind of nature. However, the over-impermeabilisation of the city bears further issues than the effect on urban green. The high levels of stormwater runoff from rain events are also a source of flooding and other nuisances for urban dwellers. The last obstacle for urban vegetation is found in the anthropic impact. The frequency and the type of transit above the city floor, translates into a single word: compaction. The pressure that both vehicles and pedestrians exert over the soil layers, makes the particles accommodate in the most efficient ways by occupying all gaps in between. As a result, this room left for the vegetation to obtain its base for survival (oxygen, water and nutrients) is blocked. Additionally this increment of the ground density turns to be fatal for urban vegetation, because it hampers the root expansion, leading to growth deficiencies.
Regarding the urban green, the major barriers for its prosperity are found above and below the city floor. The composition of the ground is the first inconvenience and the transit produced over it the second one. Urban terrain is characterised by an artificial formation usually derived of mineral materials such as sands and gravels, which are commonly used to improve soil drainage and provide stability to surfaces. Often, even waste and construction debris can be found in the soil composition, such as plastic, bricks, steel, concrete… Consequently, the low or inexistent content of organic matter left, inhibits the correct nutrition of urban vegetation and hampers its growth. Soil contamination is regularly an added problem to the soil composition. The presence of heavy metals and other toxic compounds is due to the industrial throw-outs, as to the adverse materials used in construction. The imbalance of the soil chemistry can be lethal for urban green areas.
All these technical problems that exist below ground are occasionally aggravated by cultural issues above ground. The coexistence of people and nature always bears some conflicts; vandalism, neglect or excessive management are some of them. This is where human actions over urban green have to be studied, and the multiple ways in which these can influence on nature’s performance.
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HUMAN ACTIONS OVER URBAN GREEN We can not forget that the urban green space results from a social construction, where authors have even defined it as ‘faked nature’ (Elliot, 1995), because of the high levels of anthropisation. The nature that we know in our cities was probably never there and if it was, it is likely to be far from its former state by now. Human efforts to subdue nature to our needs and wishes are visible in the urban green space.
and below ground. The diverse users also have different transit speeds and traffic needs. Within this puzzle, the last of the worries is normally nature, for which frequently the smallest of the spaces are left. If the characteristic hostility of the urban environment was not enough, nature is often affected by a deficient urban and architectural design. Cities are the result of the continuous human evolution. The addition of different historical periods, construction styles and technologies and even the politics are reflected in the urban patchwork. Recurrently, it happens that urban growth planning forgets the logics behind the ecosystem processes, which inevitably leads to nature fragmentation, degradation and habitat loss. The lack of a planned green infrastructure is often the first misstep. Hanski and Mononen (2011) defend that the recovery of ecosystems connectivity should be prioritized in any urban green restoration effort.
The fact that nature in the cities is an anthropic creation, restoration or manipulation, is a double-edged sword. From one side it is the clear representation of humans standing above nature and doing as they wish with it, as if we were the masters. From the other side it can be argued however, that if given the necessary room for it in the city, nature and humans can work symbiotically, benefiting one another in a partnership. It is in this way, that we could enhance nature’s contributions and reduce the disservices incurred by poor management. Human actions have a lot to do with the capacity of ecosystems and the biological diversity to produce essential goods and services. First we determine the room left for urban green. Second, we select the species that are going to be planted and third we manage them so that we can coexist in the crowded city environment. These are the three most recurrent actions that impact the green space’s ability to provide benefits in the urban environment: the design (urban and architectural), the species selection and the management of urban green.
The correct design of the green infrastructure is crucial for the functioning of urban ecosystems. However, as urban planning needs to be determined in advance, this might leave without improvement possibilities to many cities around the world, either for economic, social or geographic reasons. While anticipating an interconnected green infrastructure network might seem difficult or inaccessible for some, improving the quality of individually designed green spaces is far more feasible. Trees are the biggest and most obvious elements of the urban green. Though to different heights, they never stop growing in their lifetime and provide citizens with abundant ecosystem services. In order to exist, their needs are few and still many times unknown
DESIGN In the city context, the space is limited. It is indeed a complex network both above 60
and/or unattended. Smaller vegetation types that are extremely important for urban biodiversity are frequently unconsidered in the design process. This might be because they require greater management (if aesthetic purposes are pursued) and because they can likely become accessibility barriers for pedestrians (in which case it could be also regarded as a design mistake).
restricted health conditions, which is a clear way to losing nature’s contributions. It seems to be true that “the grass is always greener on the other side”. The introduction of exotic fauna and flora is always a matter of debate. Through history, many species have been traded for economic (as the Monterey Pine o the Eucalyptus in the industrial forestry) or aesthetic purposes and even by mistake (as the case of the Pampas grass). In many cases, the exotic vegetation invades the territory and inhibits local flora from thriving, triggering, in some cases, an environmental catastrophe. Nevertheless, there are foreign species that demonstrate great versatility and can be introduced without compromising the ecological integrity. In architecture, the best example can be found on palm trees. In Copenhagen (Denmark) palm trees imported from the south of China can be seen in Superkilen, a public space constructed in 2012. It could be possible to argue cultural or aesthetic values behind this landscape decision, but what is certain is that functionally, neither this vegetation will prosper under this climatology or support local biodiversity, nor the urban environment will extract great benefits out of it.
Regarding the design of green space, there are three measures that we have to look at; the permeability of the soil, the designed space for the green and the distance disposed to other infrastructures. These three factors determine not only the long-term success of the vegetation but the correct coexistence with other urban features. Regarding the first measure, the larger the permeable surface given to the green space, the greater the stormwater drainage and nutrient cycle, which means precipitation runoff relief and lower soil fertilization treatment. Concerning the second and third measures, the space needed for the green space and distancing to other elements will entirely depend on the characteristics of the planned vegetation; individual or group height, spread, root structure and available soil depth. It can happen that the design is highly influenced by the existing conditions; a given street width, proximity to underground infrastructure… When the spatial design is completely constrained by site limitations, the species selection should be carried out effectively.
In the urban context, selecting the correct species not only depends on its origin but in its characteristics. The way to maximize the benefits and minimize the disbenefits is selecting the proper vegetation to the situation at hand. As previously seen, this fact can be greatly influenced by local conditions like street size, building location or the presence of underground infrastructure. In this selection, the vegetations characteristics at maturity will be taken into consideration, such as the maximum height and trunk diameter, root structure, spread and depth, branch extension, canopy shape, leaf density. By adapting these dimensional attributes to the existing conditions, it is likely to provide the vegetation a prosperous space to thrive and therefore maximize its contributions. Examples of poor species selection can entail; the excessive shade of the street or building if the leaf density is not controlled; the collapse of
SPECIES SELECTION Facing the current world globalisation, there are few questions popping up; what is local and foreign? Where are and who defines the boundaries? Over the course of the Earth creation, biodiversity has always travelled through the air or water. Now it can also migrate on a human suitcase. Nature has no barriers other than its own biological limitations. For this reason we should be very careful when relocating foreign species. Additionally, people keep planting vegetation from opposite climates despite visible 61
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other urban infrastructure due to uncontrolled root expansion; or management expenses controlling horizontal branch extension.
collapse of other infrastructure, could this be considered instead a design problem? Commonly, when the previous steps have been correctly carried out, the management reduces to ensuring periodically the safety of citizens by checking the health status of the urban green. If opposingly there are mistakes in the design and species selection, the management will increase, bearing also economic disservices. Therefore the general advice for an adequate management is to take special consideration to the prior actions, in order to avoid long-term drawbacks.
Finally, other aspects such as flower color,fragrance and fruit and its consequences have to also be considered, mainly to avoid maintenance or aesthetic disservices. This last selection is an issue of great discrepancy, due to the subjectivity involved. Nevertheless, there are few recognised examples of poor species selection just by looking at these sensorial characteristics. For instance, female Ginkgo biloba trees produce a terrible rancidsmelling fruit, which causes mess and stains when dropped by the tree.
Ultimately, facing the impossibility to give an adequate space or select suitable species, which could be the case in some urban contexts, the best choice is the one that allows the vegetations survival and prosperity without excessive human intervention. Out of this decision, while the recreational or aesthetic benefits could be argued, the regulating benefits of air filtering, wind reduction or temperature cooling and the supporting benefits definitely increase with the vegetation lushness and independence. Biodiversity for instance has been proved to increase when the management of green spaces reduces (Alvey, 2006) and a positive association has also been found between the species richness in urban green spaces and the well-being of citizens (Fuller et al., 2007). Nevertheless, management is commonly tied to a design purpose (the wish of having trained trees, shaped shrubs, geometrical hedges…), this should be examined instead. Through the predicted management guidelines the benefits obtained from nature can be selected and either maximised or minimised.
MANAGEMENT Nature’s performance is is at odds with the excess of control and order that humans want to impose. What we call “order” is deeply connected to our environmental and scientific knowledge and our nature perception. Why would order be found in the Luxembourg Gardens in Paris rather than in the Schöneberger Südgelände naturepark in Berlin? It is on us to find beauty in the subdued nature or in the freedom of the environment. What we should be conscious about is that both options bear not only diverse contributions but different drawbacks. In cities, the degree of nature anthropisation or control is nearly absolute. We are in charge of the soil composition and landscape hydrology. We also decide upon the existence of floral species and therefore the fauna that surround us. When we mow the lawn or trim the top of the trees and the height of hedges in exchange for control or beauty, we influence the natural ability of vegetation to provide us with ecosystem services. Usually, the management of green space is carried out to secure the functioning of urban infrastructure elements, such as underground pipelines, asphalted streets, aerial power lines, property limits, etc. However, if we continuously need the management as a mean to ensure citizen safety or avoid the
As we cannot consider the suppression of cities on behalf of nature as a reasonable option, the limits of the coexistence between nature and humans have to be found in a middle ground. Cities need to balance and provide a tailored habitat not only for humans but for nature, so that we can synergically benefit each other. 63
RELATING HUMAN ACTION TO NATURE’S CONTRIBUTIONS The three actions that impact on nature’s ability to provide services or cause disservices, are meant to capture a global perspective. All of them can impact to some extent on each of the previously analysed objective or subjective nature contributions. They can be present individually or combined, the second one being either a common circumstance; usually, where there is a wrong design decision, the species have been selected poorly and the management has been carried out excessively. Moreover, green space’s prosperity shows a straightforward NATURE’S CONTRIBUTIONS - how to obtain: Air filtering
relationship with the simultaneity of human impacts; the correct achievement of the three of them together will improve nature’s prosperity, while the concurrent incorrect implementation will worsen nature’s ability to provide benefits. In order to relate human actions to the previously seen nature’s contributions and drawbacks, the following tables provide comprehensive ideas on how to maximise services and minimise disservices through design, species selection and management. SPECIES SELECTION
DESIGN Grouping trees instead of designing individually improves benefits
MANAGEMENT
Few or control pruning Selecting evergreen speto preserve a greater leaf cies the benefit can be surface to provide the provided along the year benefit
Micro climate regulation
Locating the vegetation in Selecting deciduous spe- Ensuring enough canopy the adequate orientation cies - minimize summer to provide shade/reduce (considering the buildsun, maximize winter sun wind speed on the street ings)
Noise reduction
Providing distancing and dense vegetation (in all levels) near the noise source
Favor dense evergreens for constant/loud noise sources
Limitate to spread control - denser vegetation increases the benefit
Rainwater drainage
Soil permeability is crucial Species root density and for the benefit; larger sur- formation (spread, depth) face = greater benefit are key for the benefit
Ensure the soil draining capacity through plant spread control
Sewage treatment
Limiting the vegetation Providing the necessary Selecting appropriate infrastructure (depending species for water treat- spread to ensure the waon users, water quantity, ment and variable humidi- ter passage and residue landscape...) ty conditions decantation
Recreational /cultural values
Control vegetation denEnhance the vegetation Provide a variety of mansity and height. Design seasonal variation, attrac- agements to ensure the different atmospheres for tive blooming, pleasing different atmospheres. recreation scents... Keep a clear/safe path
Food provision
Provide edible fruited vegSelect edible fruited Maintain (move or reetation over permeable vegetation types (trees, move) the fruit droppings away from walking paths conditions and adequate shrubs, herbs) within distancing from the built location, paving and local or other urban infrastructure environment commitment - Table 1 -
64
NATURE’S DRAWBACKS - how to avoid:
SPECIES SELECTION
DESIGN
MANAGEMENT
Air quality problems
Ensure the correct vegeta- Select the species with tion densities and spacing small contribution of volafrom the buildings tile organic compounds
Damage to infrastructure
Provide the necessary spacing of green from the rest of infrastructures
Depending on the infrastructure location, decide upon root structure
Limitate pruning to spread control and ensure other infrastructure safety
View blockage
Determine the necessary distancing to buildings, without losing benefits
Distancing will depend upon vegetation characteristics (height, spread...)
Prune to ensure the minimum spacing between vegetation and the built
Allergies and diseases
Ensure distancing from Select low-pollen rate veg- Ensure the ground clearbuildings and the suitable etation or avoid wind-pol- ing and maintenance of green spaces to avoid surfaces for pollinisation linated species near built environment pollen congestion decongestion/blow off
Accidents
Design necessary distancing for the coexistence of different urban infrastructure types
Decide upon the growth rate of vegetation, depending on the location
Carry out periodical pruning to control horizontal spread, ensuring safety of vegetation/citizens
Manage the vegetation distances and densities to create openness or closeness
Select species upon their canopy or leaf densities. Control the species heights to create levels
Limitate pruning to ensuring the vegetation openness - keep a clear and safe path
Fear and stress
Aesthetics
Perform a periodical pruning to control critical species near buildings
(subjective choice) Select Perform management Provide a diversity of atmospheres, with distinct vegetation upon aesthetic depending on the design plants and aesthetic char- characteristics (flower leaf, purpose (enhance biodiacteristics bark, scent…) versity or aesthetics…) - Table 2 -
in human action and thus demonstrate how contributions can consecutively be missing while nature’s drawbacks are strengthened. The third and last option could be to present the previous two in a comparative approach; how things can be done correctly and incorrectly. However, regarding urban nature, there are rare cases in which all the site characteristics are identical; preconditions, soil composition, nearby vegetation, nearby infrastructure and scales. As a consequence of this is can quickly become difficult to compare correlations between examples.
These general ideas can serve as a baseline or approach to comprehend the impact of human action over nature’s ability to provide benefits. Furthermore, it can be also used to guide design decisions related to green space , select species or manage them according to the desired purpose. Nevertheless, there are a myriad of other valuable options for each situation, which is why the influence of human actions has been studied case and site specifically. In order to illustrate place specific examples of human impact on urban nature, there are three possible ways to do it. The first,could be by representing all those examples in which the design, species selection and management are being well carried and therefore the services are also being enhanced and the disservices refrained. Opposingly, the second way aims to present the mistakes
In this study, the second option has been selected for being the obvious way to show different examples of urban green misconception. Through case studies, the missed nature contributions and the drawbacks caused in the urban environment will be illustrated. 65
SAN SEBASTIAN
PAU
- Image 13 -
STUDY CASES Due to the fact that human impact has to be analysed case-specifically, this study will be exposing real world examples. The aim is to illustrate the previously investigated three human actions and their consequences over the green spaces’ ability to provide benefits. For this investigation, two cities have been selected within the European context; San Sebastian in the north of Spain and Pau in the south of France (see Image 13). These locations have been designated not only for personal reasons but for the accessibility to report and photograph the current status of the urban green spaces and elements. This international illustration poses a further enriching perspective and leads to an inevitable comparison between the different field studies.
misconception, an individual analysis will be carried out by looking first at the large scale green infrastructure provision and then at different small-scale green situations in the city. The first, will be analysed graphically, based on the local planning guidelines for the urban landscape. For the individual examples, only trees have been reported due to their constant presence in the cities, great dimension and climatic and social impact. Furthermore, because of their lifespan, trees can turn into the oldest living beings of the city, making them subject to special consideration. However, the presence or absence of other layers of vegetation will be presented as a way to enhance the benefits obtained from nature. Concerning the small-scale examples, every case will open with a biological or technical specification of the tree species, presented with the aim of correlating the design solution to the vegetation characteristics. Then, the location will be presented, the circumstances explained and next a critique of the human actions will follow the previously evaluated human actions; design, species selection and management. The effects on vegetations’ ability to provide benefits will be regarded individually and simultaneously if possible. The studied situations are meant to be read together with the provided photographs, which will contain complementary annotations to this concern. Finally a summarising table will be given with the nature’s objective and subjective contributions and drawbacks that are currently being delivered.
The following examples will be briefly presented by locating the geographic and social contexts. For each case, the urban urban nature’s status will be described by means of the green surface and the number of existing trees, which is a commonly available data. Up to this point, the information will be extracted purely from online resources, such as the municipality or city hall websites. The next section will briefly introduce the general human-nature relationship that is apparent through the field study, together with the author’s local knowledge. This part aims at bringing prior foundation or understanding to the human actions that will be analysed afterwards. In order to illustrate examples of green
67
natural protection spaces/species natural spaces (nature parks) natural spaces (singular trees) areas of natural interest habitats of interesting vegetation, parks and urban gardens fauna protection areas terrains of high agrological value compatible protection areas strict protection area underground water protection area landscape protection zone corridors for ecological connectivity barriers for ecological connectivity flooding risk areas areas of geological interest ecosystem improvement degraded areas potentially polluted terrains
- Image 14 -
SAN SEBASTIAN Spain
Located in the north of the Iberian Peninsula, San Sebastián is inhabited by approximately 186.000 people. The contact with the Cantabrian Sea makes the local weather mild and rainy with an average yearly temperature of 13ºC. The urban geography is characterized by a central bay with a small island in the middle. Three beaches conform the coastline, flanked by two mountains and a central minor peak. The flat surface of the city centre blends into the undulating topography of the surroundings.
all the urban forest is reported in the landscape plan provided (see image on the left), due to their irrelevant ecological importance. Concerning the human-nature relationship, even though it is near impossible to obtain the precise understanding of every citizen in San Sebastian, an hypothesis can be reached at a cultural scale, based on the field study and personal experience. This introductory approach is meant to explain or at least render conceivable the human actions that will be evaluated throughout the coming examples. The more we manage and control urban nature, the more responsible we are of its prosperity.
The city relies firstly on the green space provided by the mountains. These are partially inhabited, but the topography restrictions and accessibility conditions makes them a difficult settlement. The remaining green spaces are ancient palace properties that have since been gifted to the city (Miramar and Cristina Enea), old classical French gardens (Plaza Guipuzkoa and Alderdi Eder) and spaces left over after planning. Urban growth has been planned without the consideration for green infrastructure connectivity. As a result, the green patches are spread over the urban fabric haphazardly. Nevertheless, the mid 19th century Hausmannian trend of making great tree allées and boulevards has slightly contributed to natures connectedness.
Nature in San Sebastian has always been controlled, mastered, in the anthropocentric sense. The flowering of many roundabouts changes meticulously with the seasons, the tree clipping and shaping happens regularly and any fallen leaves or branches are quickly removed from the city floor. There is a green brigade in charge of the city gardens, so that everything looks tidy and under control. Wild nature only happens where human and machinery reach is impeded by the topographic difficulties and yet these refuges for urban biodiversity are usually regarded as neglected and decaying. For these reasons, following the previously studied environmental psychology theory (Steg et al. 2012), human attitude can be categorized firstly as a master, shaping nature to our wishes and secondly as a steward, responsable of nature caring. Moreover, the values associated with nature (Kellert, 1997) are likely to be closer to the anthropocentric perspective rather than to the ecocentric view. Utilitarian, aesthetic and dominionistic values will potentially be predominant, followed by fewer humanistic, naturalistic and scientific values.
If we look into the quantifiable green aspects then we see that the approximate green surface of San Sebastian is 61 km2, which corresponds to about 3,5% of the city. Green spaces are distributed across 24 gardens and parks scattered over the landscape, with few or almost no connectivity. The urban forest of the city accounts around 35.000 trees (González, 2010), recorded in a restricted private inventory. Out of these trees only two individuals are protected due to their extraordinary characteristics of size, age, history, beauty or location. Nevertheless, not 69
- Images 15 -
ALTO DE ERRONDO STREET (San Sebastiรกn, reported on March 2019)
Tree species: Liquidambar styraciflua (common name: Sweet Gum) Foliage: deciduous (many colours in Autumn) Flower/fruit: insignificant/woody spiky ball Height at maturity: 10-20 m (30 max) Spread at maturity: 6-12 m Annual growth: 35 cm height/20 cm spread Tree architecture: Oval/pyramidal/open Root structure/depth: Heart-shaped roots, widely spreading and requiring much space Pollination method: (monoecious) Wind pollinated
underground enclosed growth is beginning to be visible through initial damages to the surface infrastructure. Human action analysis: Analysing the site conditions, there is an adequate distancing to buildings and spacing between individuals. However, trees are extremely close to the road, limiting root development. Signs of surface and girdling roots appear in the planting pit. The surface given to the green area is limited, both for the tree and for other flora to inhabit. This area also restricts the water absorption and nutrient intake, leading to cracked pavement caused by roots. It could be added that the space between trees has been equally paved, even though it would have been easier, cheaper and more suitable to leave it green, as it does not interrupt the walking path. Regarding the species selection, the decision could be criticised first for being a species that needs a very extensive space for root development (that has not been given) and second for being a wind pollinated tree. The last one, not only enhances the risk of allergies but also supports less biodiversity, diminishing some regulating or supporting services. Moreover, the inedibility of its fruits also refrains other material and nonmaterial contributions.
Site description: After a housing development in the year 2000, this street was redesigned and reforested. In the middle of it, a curvy section hosts 40 even aged Sweet Gums. These trees are approximately 25 years old and are located in one side of the road and with an 8.5 meter spacing between specimens. Despite their relatively young age, some control pruning has been carried out to avoid the horizontal spread across the road side, leading to a slenderness crown shape. As a result, the individuals are currently 6 to 7 meters high and 3 to 4 meters wide, having reached their reproductive maturity. The villas located adjacent to these tree are approximately nine meters high and the distance to the trees is about five meters due to an intermediary front garden. This distance is occasionally trespassed by some unpruned branches, but mainly the trees fruit drop on the street. The sidewalk is two meters wide and the trees are located barely half a meter from the road edge, leading to an unbalanced root structure development. The surface given to each individual tree is a 0.8 x 0.8 meter planting pit, covered by a mix of self-sown plants and bare soil. The paving around is composed of impermeable materials, therefore the water intake is limited to the 0,64 m2 green surface. Trees
Result over nature:
71
REDUCED nature contributions
ENHANCED nature drawbacks
micro climate regulation
damage to infrastructure
noise reduction
accidents
rainwater drainage
allegies
food provision
(aesthetics)
- Images 16 -
URBIETA STREET
(San Sebastián, reported on March 2019) Tree species: Acer saccharinum (common name: Silver Maple) Foliage: deciduous (bright yellow in Autumn) Flower/fruit: reddish clusters/winged fruit Height at maturity: 15-20 m (30 max) Spread at maturity: 12-20 m (25 max) Annual growth: 50 cm height/35 cm spread Tree architecture: Oval/open Root structure/depth: Primary roots rambling, shallow and numerous in the topsoil layer with many fibrous roots. Generally an intolerant, somewhat aggressive root system Pollination method: (mono/dioecious) Wind pollinated
drainage, thus the trees’ normal growth is inhibited and occasionally show symptoms of dehydration. Human action analysis: There are several miscalculation on the architectural design. First, a space of 3 x 3 meter has been given to a tree species that is spreading a minimum of double this size at maturity. This fact makes tree pruning an obligatory task for the coexistence of building and green space. However, knowing this structural characteristics, the trees are still being replaced by the same species. Second, the space given as a planting pit surface is clearly under-dimensioned for this species and development speed. Due to these design flaws, the vegetation is now causing damage to underground infrastructure and above ground surfaces. The species selection is therefore an issue of conflict. Additionally, the necessary periodical management is causing further damage to the trees structure, leading to slight trunk inclination and a disproportionate crown.
Site description: Located in the city center, Urbieta street has a total of 102 tres, with a minimum spacing of 6 meters. Occasionally, where trees appear on both sides of the street their crowns almost touch, ensuring summer shade. The oldest trees are roughly 80 years old (with a 50 centimeter diameter at breast height trunk), but their height and spread have been constrained through periodical prunings. In this alignment, there are some individuals that have been replaced using the same species. The youngest ones are still assisted by wooden stakes.
Result over nature:
The height of the buildings is around 24-28 meters, only a few meters higher than the mature slightly below the mature height under optimal conditions of the tree. The sidewalks are four meters wide and the tree stands 3.5 meters from the facade line, the space left for the roots to grow. The size of the planting pit is 0.7 x 0.7 meters, and in the case of the oldest trees, this space is completely covered by surpassing roots, already specified to ramble and live within a shallow depth. The remaining paving, composed by prefabricated hydraulic tiles, is essentially impermeable. Together, the tree roots’ structural crowd and the sealed surface around, allow very few water 73
REDUCED nature contributions
ENHANCED nature drawbacks
air filtering
damage to infrastructure
micro climate regulation
view blockage
noise reduction
allergies
rainwater drainage
accidents
(recreational/cultural values)
(fear/stress)
food provision
(aesthetics)
- Images 17 -
ERRONDO STREET
(San Sebastián, reported on March 2019) Tree species: Platanus x acerifolia (common name: London Plane) Foliage: deciduous Flower/fruit: droping inflorescences/woody and spiky sphere Height at maturity: 20-30 m (higher) Spread at maturity: 15-25 m Annual growth: 50 cm height/40 cm spread Tree architecture: Round/half-open Root structure/depth: Shallow root system, predominantly horizontally spreading with dense fibrous roots, main roots are vigorous, deep and densely branched Pollination method: High pollen allergens
on the concrete wall of the opposite side. As a result, we can observe in the images, that roots appear strongly in this edge, where the two different materials joint and the water is likely to infiltrate. Human action analysis: In this case, there is a first misconception in the spacing given for this species spread. However, the fact that some trees have been suppressed has slightly alleviated the situation. The second design mistake is found on the closeness to other infrastructure, as the parking line or the train tracks. Aware of the root spread of this tree, damages on the paving could have been foreseen. This leads to the discussion of the species selection. Having the purpose of hiding the view to the train trucks, the tree would have been correctly selected, even though other type of vegetation density could have been implemented to impede both the view and the sound from trespassing. However, if we take the designed site dimensions, it would have been more appropriate a smaller, slow growing species in order to avoid for instance infrastructure damage.
Site description: The street is located besides the train tracks and trees are meant to act as a visual barrier for the other side of the street ten-storey buildings. In one of the streets’ sections a total of 32 individuals where planted with an average spacing of 5 meters. Out of these trees that must be around 6070 years-old, some have long perished and have not been replaced. This extra spac is now being conquered by the larger crowns of the remaining trees. The tallest trees are approximately 20-25 meters high and their trunk reaches the 70-80 centimeter diameter at breast height. The pruning carried out to clear the way to the vehicular passage has caused a “tunnel” effect on the asymmetrical canopies, ensuring the summer shade to the street users.
Result over nature:
Regarding trees’ situation, the sidewalk which is approximately four meters wide is delimited by an uncrossable concrete wall (safeguarding the train tracks) and a asphaltcovered parking line. Around the 1,20 x 1,60 meters planting pit, the paving is composed by concrete cobblestones that have started to degrade due to erosion and the movement of roots. This surface being semi-permeable, has let the roots develop, encountering limit 75
REDUCED nature contributions
ENHANCED nature drawbacks
micro climate regulation
air quality problems
noise reduction
damage to infrastructure
rainwater drainage
allergies
(recreational/cultural values)
accidents
food provision
(aesthetics)
- Image 18 -
DR. MARAĂ‘Ă“N ALLEY (San SebastiĂĄn, reported on April 2019)
Tree species: Carya ovata (common name: Shagbark Hickory) Foliage: deciduous (bright yellow/golden in Autumn) Flower/fruit: long-stalked catkins/soft drupe, edible nut inside Height at maturity: 15-25 m (30 max) Spread at maturity: 8-10 m Annual growth: 15 cm height/10 cm spread Tree architecture: Oval/half-open Root structure/depth: Shallow root system, with large and deep tap-roots and long spreading lateral roots Pollination method: (monoecious) Wind pollinated
Human action analysis: The design solution in the case is causing the infrastructure damage that we see in the images. Firstly, there is a misplacing of the trees and the proximity to the road which will cause longterm disservices. Instead, individuals could have been located barely one meter behind, where the grass-covered planting bed is. Through this action, not only the tree would have had improved conditions for living but the paving damage could have been avoided. Secondly, the paving around the tree could also have been avoided, providing a larger green area with enhanced drainage and low level vegetation. In this way the tree roots would have developed unconstrained with no need to explore beyond the road. With all these adjustments, the species selected would have been appropriate according to the growth rate and mature dimensions. There are two further accurate decisions in the species selection; first one is the ability to provide edible nuts, which enhances the provisioning services. The second one is the remarkable autumn colour of this species, which can improve the aesthetic appreciation and provide seasonal interest. Opposingly, the fact that is a wind pollinated specie can enhance drawbacks related to allergies.
Site description: In this street, there are several tree species planted. Among them, six individuals of Shagbark Hickory are causing serious damage to the urban infrastructure and have lead to traffic accidents. These slow-growing trees, that must be around 60-70 years old, are now 7-8 meters tall and have a spread of 6-7 meters. The five meter spacing given between individuals, is completely occupied by the meeting canopies, providing a dense summer shade to the road. There is an additional green space behind the trees,where only lawn and some solitary Agave sp. have been planted. Regarding the close environment, the nearest building is located fifteen meters away and yet trees contribute to mask the view over the road. However, the tree stands barely 60 centimeters from the edge of the road, leading to an unbalanced root development. The sidewalk is composed by washed concrete, sealing the surface around the trees and blocking the nutrient intake. For this reason, the root dispersal has gone far beyond the 0.6 x 0.6 meters planting pit, conquering the material joints and cracking the paving surface.
Result over nature:
77
REDUCED nature contributions
ENHANCED nature drawbacks
micro climate regulation
damage to infrastructure
noise reduction
accidents
rainwater drainage
allergies
(recreational/cultural values)
(aesthetics)
city limits Z.P.P.A.U.P. (urban, architectural and landscape heritage protection zone) gardens green areas, parks tree alignment allĂŠe remarkable tree mainly mineral open space (yard, esplanade, square) classified heritage site building protected under Historic Monument (HM) wall protected under HM terrain protected under HM
- Image 19 -
PAU France
Located in the south of France, Pau has an average population of 80.000 inhabitants. Facing the northern side of the Pyrenees and barely one hundred kilometers away from the Atlantic coast, it benefits from a mild climate with an average year temperature of 12,5ºC. The city’s geography is characterized by being mainly flat, with a slight inclination towards the river on the south, Le Gave de Pau. The urban fabric has settled within an agricultural patch field, containing very fertile soils and a rich hydrology. Given this suitable context for nature, many types of flora species can be found in the city. However, a clear nuance can be perceived on the biodiversity richness from the city center to the outskirts, followed by the built density.
gardens that could considerably contribute to the amount of green space in the city. The surface of public and private green can be seen in the urban landscape heritage code, under the name of “Declared Wooded Area“ (Espace boisé classé, traduced). This area corresponds to the green colour on the previous map (Image 19). This level of protection hampers the owners from cutting down any tree without permission. Nevertheless, given legitimate reasons, vegetation removal can be accorded by the administration services. Regarding the biocultural relationship, as in the previous case, an hypothesis can be reached at a cultural scale, based on the field observation and personal knowledge. In Pau, the mastery of nature (Steg et al. 2012) comes from a very long history, when gardens served aesthetic styles and were accessible to the pleasure of few individuals. Ever since, there has been a steward feeling towards nature. However, it can be argued that this perception comes from the desire to care not simply for nature but for the historic heritage of the city. Out of this human-nature connection, utilitarian, aesthetic, dominionistic and symbolic values (Kellert, 1997) can be mainly perceived, followed by fewer naturalistic and scientific understandings of nature. The result is an , urban nature that can be seen to be subdued by the built environment, controlled through periodical management and given no more than the space determined by heritage.
The longevity of the town has left a historical trace on the urban green spaces. Most of the parks and gardens have been witness to several generational changes, such as the planting styles or the evolution of technology. Pau’s central Castle was built during the middle ages and yet remainings of its Renaissance gardens are still preserved. In front of them, a two hundred square meter park (le Parc du Château) contains trees that were planted in the 18th century. This green space is now included in the Natura 2000 protection network. North of the city, there is a 300 hectare forest (Forêt de Bastard) that once served to forestal resources. Nowadays, under preserved as a sensitive natural site, it has become not only the greatest green lung but also the larger recreational possibility for the citizens.
Out of this description, the following examples will have a theoretical base and human actions will be regarded certainly from another perspective. In Pau, urban nature is not merely a social construction, but a historical development that not only is being maintained but has not stopped evolving.
Together, the public green spaces of the city conform 7.5 km2, which is about the 23% of the city. However, the low density urban fabric is mainly composed of villas and single family houses, normally owning large
79
- Images 20 -
AUCHAN PARKING (Pau, reported on February 2019)
Tree species: Acer platanoides ‘drummondii‘ (common name: Norway Maple) Foliage: Deciduous bicoloured leaves (pink colour in Autumn) Flower/fruit: Beautiful golden-yellow inflorescences/winged fruit Height at maturity: 10-12 m (15 max) Spread at maturity: 7-9 m Annual growth: 45 cm height/30 cm spread Tree architecture: Pyramidal/round/closed Root structure/depth: Shallow root system, predominantly horizontally spreading with many fibrous roots Pollination method: (mono/dioecious) Insect pollinated
young character of the maples, cracks in the surface materials and damage on the root containing structure can be seen. Human action analysis: In this case, as in every parking in which the trees are planted individually, the design mistakes are various and they normally lead to economic losses and reduced nature benefits. The specific microclimate that is generated within a parking lot should instead be extensively vegetated in order to obtain temperature or wind reduction. Grouped trees would improve their life expectancy and also help each other in case of lack of resources. Moreover, aligned trees with enough space to develop their roots would also broaden their canopies faster, shading the vehicles and reducing damage to infrastructure. In this case, the damage that has been caused is still minimal, however, in the future, the asphalt surface is likely to crack, erode or be lifted by the roots, which can cause accidents and the need for future management. Regarding the species selection, the canopies of the selected variety will never meet, reducing the purpose of giving shade. This fact can either be considered as a selection error or a miscalculation of the distancing between individuals, possibly through cultivar selection.
Site description: Located few kilometers away from the city center, this is the 36.000 square meter parking space of a shopping center, Auchan. Various tree species have been planted within different areas with the same purpose; shading the vehicles. With a spacing of ten meters, this variety of Norway maple must have been planted around five years ago. However, not all the individuals have survived the harsh conditions of living in a parking lot; heavy compaction, extreme temperature shifts, limited space for water and nutrient intake. For this reason, we can observe replacement planting still staked (even though this assistance appears pointless).
Result over nature:
The trees have been established on a 0.85 x 0.85 meters planting pit that stands out 0.2 meters from the ground level. This structure, filled with bare soil, is meant to protect the tree from car impacts. The surface around the trees is a completely sealed asphalt surface, heavily compacted and transited, that constrains the access to water and nutrients. There is no watering system present and therefore the tree relies completely on the climatic conditions to survive. Despite the 81
REDUCED nature contributions
ENHANCED nature drawbacks
air filtering
air quality problems
micro climate regulation
damage to infrastructure
rainwater drainage
accidents
food provision
(aesthetics)
- Image 21 -
TOURASSE BOULEVARD (Pau, reported on April 2019)
Tree species: Pinus pinea (common name: Stone Pine) Foliage: Evergreen (ascending branches) Flower/fruit: Insignificant/cones Height at maturity: 12-25 m (30 max) Spread at maturity: 10-15 m Annual growth: 30 cm height/20 cm spread Tree architecture: Open/rounded/umbrellalike crown Root structure/depth: Shallow and aggressive surface roots, sometimes exceeding three times its crown projection. Dominated by a few large diameter roots. Pollination method: (monoecious) Wind pollinated
infrastructure and in order to avoid further accidents, the municipality has installed a provisional traffic barrier. Nevertheless, if the roots continue their expansion the decision of lifting the asphalt, poor practices as cutting the roots and remaking the road would seem likely. Human action analysis: This example is either a case of incorrect species selection or a design miscalculation on the space needed for underground development. Regarding the design, the trees are located within suitable dimensions and soil characteristics. As a result, the Pines can be seen thriving and expanding beyond the given limits. This situation however, is likely to worsen through time, bearing management or economic issues. The solution would have been either the selection of other species with a less aggressive root structure or the provision of a larger development space for this one not to cause damages to infrastructure. Regarding other possible benefits, the noise reduction could have been improved with other types of vegetation layers, which in turn would have probably increased the recreational or aesthetic value of the site. Moreover, this vegetation could have been an additional source of food provision, enhancing material and nonmaterial contributions.
Site description: Beside a housing development and its parking, this tree alignment together with other deciduous species creates a forest effect in the area. A total of 13 Stone pines were established with an approximate eight meter spacing. These almost 15 meter tall umbrellas, extend their crowns approximately 2-3 meters over the road. These trees, originate from the Mediterranean side of the country, and appear to be around 60 years of age. They appear to be planted with the purpose of shading the street and provide exotic aesthetics. The species is not very common in the urban context though, due to its continuous dropping of needles that can increase soil acidity and clog street drainage.
Result over nature:
Regarding the built environment, the trees are located in suitable permeable conditions, with a 10 meter sidewalk. The trunks stand around two meters from the edge of the road and its asphalt cover. This distance that would have seemed enough for many species, has been conquered by the roots of the pines, which are specially able to extend far beyond their crown limit. This fact is now causing damage to underground and aboveground 83
REDUCED nature contributions
ENHANCED nature drawbacks
noise reduction
damage to infrastructure
(recreational/cultural values)
accidents
food provision
(aesthetics)
- Images 22 -
EDOUARD VII AVENUE (Pau, reported on May 2019)
Tree species: Tilia platyphyllos (common name: Large-leaved Lime) Foliage: Deciduous (yellow in Autumn) Flower/fruit: Sweet scented inflorescences/ Tiny oval woody nutlet Height at maturity: 30-35 m (40 max) Spread at maturity: 18-25 m Annual growth: 45 cm height/30 cm spread Tree architecture: Ovate/rounded/closed Root structure/depth: Grows a strong symmetrical, shallow root system, predominantly horizontally spreading with dense fibrous roots. Pollination method: (monoecious) Insect pollinated. Likely allergies
left between the trees filled with a sand and fine gravel mixed material. These surfaces, despite allowing the water drainage, they do not allow the nutrient cycle happen or the establishment of any other vegetation. Furthermore, the provide an extra barrier for the expansion of the trunk and end up cracking, stained and littered, as it can be seen in the previous images. Human action analysis: In this case, the mistake comes from both, a design and dimensional misconception and a inadequate species selection. In the first hand, the street conditions are too narrow to locate a two side alignment of a species that is likely to spread up to twenty meters, which will cause sun radiation and view blockage to the buildings besides. Moreover, the spacing given between individuals has turned the management obligatory as a way to refrain the horizontal spread. Despite these efforts, the height of the trees has reached the maturity and is now causing energetic losses and social issues related to the poor lightning of the street at night. On the other hand, the species selection can also be criticised, since the choice of a smaller vegetation, adapted to the scale of the context, would have been likely to reduce the provided drawbacks.
Site description: Located in the city center, in a sixteen-meter wide street, these tree species have been established in both sides of the street and with a ten meter spacing. The first section of the street, contains the nine oldest individuals, that must be around 50-60 years old (the tenth was replaced recently). These huge trees that have been managed to grow tall and slender, reaching the height of the seven-storey building located adjacent. This vegetated barrier allows no morning sun irradiation to the first four floors along the year, causing not only greater energetic expenses but a deep darkness on the street. In the following section of the street the same species has been accomodated. These trees must be 20-25 years old and for the moment they do not cause further troubles. However, their location besides a two-storey housing building leaves no great future hopes for its residents.
Result over nature:
Concerning the provided space for the vegetation, the trees stand on a “permeability line� within an asphalt sealed street. This one meter privilege is not left for bare soil . The planting pit has been covered with a combined woodchip concrete and the space 85
REDUCED nature contributions
ENHANCED nature drawbacks
micro climate regulation
damage to infrastructure
rainwater drainage
view blockage
(recreational/cultural values)
accidents
food provision
(aesthetics)
- Images 23 -
ALSACE LORRAINE BOULEVARD (Pau, reported on May 2019)
Tree species: Tilia cordata (common name: Lime) Foliage: Deciduous (brilliant yellow in Autumn) Flower/fruit: Sweet scented inflorescences/ Tiny oval woody nutlet Height at maturity: 18-25 m (30 max) Spread at maturity: 10-15 m (20 max) Annual growth: 30 cm height/25 cm spread Tree architecture: Ovate/rounded/closed Root structure/depth: Grows a strong symmetrical, shallow root system, predominantly horizontally spreading with dense fibrous roots. Pollination method: (monoecious) Insect pollinated. Likely allergies
The epicormic shoots that can be seen in the pictures are sign of tree stress. Human action analysis: This example probably illustrates two combined misconceptions, a design deficiency and a management impediment. The first is caused by the limited conditions given to the tree to develop, that reducing the nutrient cycle and potential stormwater runoff reduction of the green space. For these reasons, the moving roots have caused damage and imperfections to the paving surface, which can be a source of frustration and aesthetic disservice. The second, is excessive management carried out on the trees to keep them in a styled shape This not only reminds us of humans in a position of mastery but also reduces benefits like air filtering, micro climate regulation or noise reduction. Moreover, the pollination technique of the selected species despite supporting various pollinator species, is also a source of allergies for humans. In order to avoid pollen congestion either a wider space should have been provided on the street or a combination of tree species implemented.
Site description: This long Boulevard has two types of tree species planted. Hardly ten years ago, in 2009, the first section of the street had 31 mature Sweet Gum trees, and were replaced by the same number of Acacias. The remaining street section stayed intact after this urban redevelopment, with a mainly even-aged 82 Lime tree alignment, located in both sides of the road within an eight meter spacing. These approximately 60 years-old trees, are just twelve meters high because their crowns have been constrained into a 3x4 meter cube through yearly pruning, shaping also known as ‘boxhead pruning’.
Result over nature:
In this case, the urban vegetation is literally inserted within the vehicular parking line, sometimes not even owning a formal planting pit. The semi-permeable concrete cobblestones almost reach the root flare in most of the individuals, leaving limited space for the trunk girth. Between this paving system however, the water can infiltrate, watering the trees’ root system and providing tiny space for appearing herbs. The space left for the roots to extend is subject to great compaction, that together with the management carried out, has caused the trees not to fully develop. 87
REDUCED nature contributions
ENHANCED nature drawbacks
air filtering
damage to infrastructure
micro climate regulation
accidents
noise reduction
view blockage
rainwater drainage
allergies
food provision
(aesthetics)
THIRD PART TOWARDS IMPROVED GREEN
In this last section, the result of the analysed urban practices will be unveiled through a comparative approach. Accordingly, a solution will be proposed to avoid or limit human actions that complicate nature’s ability to provide benefits in the urban environment. To support this idea examples will be presented showing how this has been achieved successfully elsewhere. Finally, after measuring the findings and limitations of this study the conclusion will address the hypothesis formulated at the beginning of this work.
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- Image 24 -
INTERNATIONAL COMPARISON Following the previous analysis of study cases, there are inevitable analogies that can be observed. The aim of this observation is not to judge which country is doing best or worse, as both of them show almost the same deficiencies regarding design practice, species selection or management of urban green. Moreover, this international correlation of urban greening practices might help us approach our surrounding nature differently. No matter where we live, things can always be regarded from another perspective, towards improved green spaces.
equally; disposing a temporary traffic barrier. A similar comparison can be done between Alto de Errondo street (San Sebastian) and Auchan parking (Pau). In both cases, the young individuals have been condemned to an 0.8 x 0.8 meters planting pit, defined by a solid barrier and surrounded by an impermeable surface. Having to deal with this water and nutrient shortage, roots have explored aggressively and started to cause damage to the neighbouring infrastructure. Once again, these problems could have been solved through the same solution the adequate provision of the surface needed for vegetation development.
It should be noted that the presented cities are located in distinct countries, with all the differences that that entails; language, history, culture, politics, landscape, geography, etc. This not only social, cultural and biological diversity results in particular greening practices in the urban environment. Nevertheless, similar problems arise when looking closely into the status of green space.
Concerning the species selection and management, similarities can also be found in the study cases. The examples of Urbieta street (San Sebastian) and Edouard VII avenue (Pau) have similar species selection issues that have triggered the same management requirements. In both cases, the tree species growth and dimensional characteristics have not been planned accordingly to the site conditions such as street width, building height or distance between specimens. This fact has resulted in the blocking of views, damage to infrastructure and economic losses as well as creating a mandatory periodical management of the trees, to which many other drawbacks can be associated. These similarities are important to highlight because they bring a new perspective regarding the importance of the quality of urban green space, which is internationally influenced by human action. In order to overcome the issues caused by urbanisation, blindly greening in a quantitative process, should not sacrifice the qualitative conditions necessary to provide benefits rather than disbenefits.
In both of the analysed cities there is a repeating design misconception; trees are generally left in limited planting pits, under impermeable coverings and distances to other infrastructure are rarely respected. The most related example can be found in Dr. Maraùón alley (San Sebastian) and Tourasse boulevard (Pau). Even though the trees have been established in different conditions, either a miscalculation on the root development spread or the species selection has lead to disastrous damages on the road besides. In both cases the asphalt has surrender to the moving roots, bending, eroding and ultimately breaking. These complications are not simply infrastructure damages but a risk of accidents and likely a loss of aesthetic value. It is quite coincidental though, to see that in the two situations have been solved
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PROPOSAL In order to improve the living conditions of urban nature and thus the benefits provided, human action needs to be considered. For this matter, as it has been expressed throughout this work, the way in which nature is perceived should be questioned. Due to the distance that cities have created between humans and nature, the basic understanding of ecosystems and their functions are also being also lost. To improve this first boundary, nature not only needs to be brought closer to people but also education needs to be greatly improved to reach a cultural level. This process could take several decades or longer and the appropriate means to achieve this must be provided. Both of these issues can be bridged effectively through green legislation that is site, culturally and socially specific.
indigenous flora and fauna, they provide a set of information about, design, species selection and planting guidelines among others. All this information can be found on the website of Moreland City Council. Another model of green legislation can be found in New York City (NYC), United States of America. The american metropolis not only supplies information about the benefits provided by the urban vegetation in their municipality website but also regulates tree establishment in the city environment. Urban green has to be planted as required by the NYC Department of Buildings, which follows a design manual and tree planting standards that are also accessible online. Through their guidelines, they provide specific measures for the tree planting pits, soil requirements, species selection and maintenance guidance. For instance, they promote the design of connected planting pits in order to improve the health of the urban forest. They also guide towards the reconfiguration of sidewalks instead of the suppression of vegetation. All the details can be found in the Official Website of the NYC Department of Parks and Recreation.
In almost every city, the common urban regulations relate to the built environment; architectural heritage areas, required width of sidewalks, minimum spacing between lamplights, facade lines, spacing between buildings, etc. There are ways of providing similar construction standards for green space in order to ensure not only its existence but also it’s coexistence with other infrastructure.
These two international examples still struggle to implement effective urban green areas and practices because of the great pressure created by the continuous development and rapid urbanisation. However, the proposed design guidelines aim at the correct direction.
A particular example of green standards can be found in Melbourne, Australia, where each of the municipalities has explicit legislation regarding the provision of green space and construction methods. Analysing the green standards of Moreland, one of the councils in the region of Victoria, landscape guidelines are established for the public and private domain. These instructions are proposed “to assist developers, property owners and designers in the preparation of landscape plans� (Moreland Landscape Guidelines, 2009). With the aim of encouraging effective landscape practices and the protection of
The information provided by both of the cases has been analysed and related to this work through the form of possible guidelines to apply in order to enhance or improve the urban green. The following table details some specific standards to implement in each of the studied sections; design, species selection and management. 97
- Image 25 -
GUIDELINES NEEDED TO IMPROVE NATURE’S CONTRIBUTIONS IN THE CITY DESIGN
SPECIES SELECTION
MANAGEMENT
Minimum planting pit or garden bed surfaces
Street tree/other vegetation list/ suggestions
Establishment of pruning objective types
Distancing to other infrastructure (road, building‌)
Vegetation zonification (depending on climate/soil characteristics)
Pruning season
Soil depth, composition characteristics
Study of urban microclimates
Planting season
Group or individual planting requirements
Species composition guide
Maximum pruning limitations
Provide vegetation protection standards and methods
Specification of species urban characteristics; pollen index, noise absorption..
Tree/stump removal administration
Minimum root development surface
Minimum distancing between individuals
Vegetation removal permit
Root protection requirements when construction works are being carried
Growth rate and mature structural description - suitable implantation
Management techniques for private land
Sidewalk composition/ permeability control
Soil underground conditions zonification
Maintenance work directives during the year
Required minimum green surface (in relation to the built environment)
Glossary of species special disturbances for the urban environment
Disease/pest/invasive species control
Remodeling guidelines of urban infrastructure after vegetation development
Local/exotic species idex, use limitation or permission
Water/nutrient requirements planning and calendar
- Table 3 -
These are some of the possible options that could be implemented in the green legislation of every municipality in order to enhance the contributions provided by the urban green. The objective is to provide the green space a qualitative setting. Through providing standards related to design, species selection and management, the space for nature should be correctly provided and managed. The presented concept should be
implemented into a transparent policy-making processes, providing not only a healthier urban environment but educational input to the citizens, where the involvement of urban inhabitants should also be considered. Moreover, promoting the bonding between humans and nature is likely to enhance a change at a cultural level, towards improved green spaces. 99
DISCUSSION The current study proves that human action in design, species selection and management can highly impact the benefits provided by the green spaces of cities. Moreover, through the same means, nature drawbacks can also be promoted resulting in economic losses, maintenance requirements and other annoyances. In order to improve the qualitative status of urban vegetation, green legislation should be implemented following the presented international examples, to ensure nature’s contributions. These findings open up a new perspective on city greening. Urban green has usually been measured through quantitative measures, forgetting about the status of this vegetation and its ability to provide benefits. Through the analysis proposed, the aim is to pursue not a simple quantitative approach but a qualitative measure of green space. In this issue, not only the vegetation but human behavior must be taken into consideration. The space given for nature’s contributions in the city is to some extent a human responsibility and thus it should be accordingly regarded. The presented point of view has not been regarded in any other previous studies. The probable reason is that quantitative greening strategies have been popularized first. It is quicker and easier to plant a number of new vegetation instead of accommodating the situation of the old one. However, the data provided propose not only to the scientific, but to the lay community a completely new way of looking at the green infrastructure of a city, where the green wealth is no longer measured in square meters or number of trees planted, but on the current status or ability of the green infrastructure to provide benefits. Alternatively, the findings could have been
explained by the limitations of the study. Merely two locations have been analysed and are reduced to the European context, even though nature perception and greening practices in other countries or even continents might be different. For the comparison, only few examples of the status of urban green have been reported, making possible to illustrate a rarity or exception rather than a general rule happening in cities. Moreover, the photographs reported have been taken mainly during the winter season, where the leafless trees can intensify the perception of unsuitable conditions or poor life quality of the vegetation. Further research could extend the comparison through the number of study cases, or a broader location analysis. This could bring new reflections upon the nature perception which is based on the cultural level. Another suggestion for complementary studies, could be to merge the qualitative assessment with the quantitative report. By analysing how many green spaces could be improved, we could study if this is rather an exception or a rule. This appraisal could complement the focus on this work’s proposal, introducing a mandatory status inventory into the green legislation of a city. Summing up, this research offers a new way to look at urban nature. Due to the abundant benefits that it provides, a city’s green space should be as well planned and provided as the rest of the urban infrastructure. For this, considerations of not how much but what quality of spaces should be regarded. Through the adequate legislation, the human action of designing, selecting species and managing urban green should be regulated in order to improve nature’s ability to provide benefits both to the city and to us.
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CONCLUSION In this era of rapid development and massive urbanisation, the valuable role of green space needs to be taken into consideration. Urban nature can provide numerous benefits to citizens and alleviate the many complications that cities have engendered. Some of the advantages we can extract are not only physical but also biological, and can further underpin the global economy and citizen health (TEEB, 2009). For this reason, it is no longer enough to count the green surface through square meters or number of trees planted, green spaces need to be regarded by their qualitative condition and thus the ability to provide benefits. This research on how to improve urban green space, is a possible approximation towards better greening practices. As urban nature derives from a combined social phenomena (Etingoff, 2015), we are the first responsible of its success. It is therefore necessary to analyse the ways in which human behaviour can influence the ability of green space to provide goods and services to the city environment. In this work, nature’s benefits have been proven to be determined by three main anthropological actions; design, species selection and management. Through the individual or combined presence of these three aspects, nature contributions such as air filtering, microclimate regulation or rainwater drainage can be diminished, while drawbacks such as damage to infrastructure, accidents or view blockage are being enhanced. This fact has been largely reported through an international comparison focuses on the cities of San Sebastian in Spain and Pau in France. Results show that in two different countries with diverse cultures and greening practices, the same mistakes can be committed; deficient design,
inadequate species selection and excessive management. In order to improve urban nature’s ability to provide benefits, human actions over the green space need to be controlled and regulated. It is our responsibility to provide nature the adequate space for existing and coexisting with the remaining urban infrastructure. And by doing so, we all win; a more prosperous green infrastructure will provide enhanced contributions and will reduce likely disadvantages. There are few examples that have implemented the necessary legislation in city planning to ensure adequate design standards for green space. In this investigation, the reported cases of Melbourne and New York, can probably illustrate a step forward for Europe, however, they are not the only solution to the problem we face. Further research from this perspective can be carried out, for instance, the specific design guidelines proposed by this work, could be improved to determine numeric accuracy to underpin the qualitative analysis of green space. This study aims specifically at stimulating designers and practitioners towards responsible greening approaches, with the purpose of contributing to a better urban environment, where nature’s benefits are assessed and enhanced through practice. Nevertheless, it is on every citizen to stop counting the city’s success by the quantity of green space. Instead, we need to analyse our actions over nature, in order to improve its qualitative status. If we want to secure our cities as better places to live, green spaces need to be regarded not by their existence but by their ability to provide benefits to the urban environment.
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REFERENCES
TEXT REFERENCES - Alvey, A. A. (2006). Promoting and preserving biodiversity in the urban forest. Urban Forestry & Urban Greening, 5(4), 195-201 - Benedict, M. A., & McMahon, E. T. (2002). Green infrastructure: smart conservation for the 21st century, Renewable resources journal, 20(3) - Bernatzky, A., (1983) The effects of trees on the urban climate. In: Trees in the 21st Century. Academic Publishers, Berkhamster, pp. 59–76 (based on the first International Arboricultural Conference) - Bolund, P., & Hunhammar, S. (1999) Ecosystem services in urban areas. Ecological economics, 29(2) - Braquinho C. et al. (2015) ‘A typology of urban green spaces, ecosystem provisioning services and demands’ Green Surge, V10 - Camill, P. (2010) Global Change. Nature Education Knowledge 3(10):49 - Colding, J., Lundberg, J., & Folke, C. (2006) Incorporating green-area user groups in urban ecosystem management. AMBIO: A Journal of the Human Environment, 35(5) - Costanza, R. et al. (1997) ‘The value of the world’s ecosystem services and natural capital’, Nature 387, 253-260 - Crutzen, P. P. J. (2004) ‘New directions: The growing urban heat and pollution ‘island’ effect: Impact on chemistry and climate’, Atmospherics Environment, 38(21), 3539-3540 - D’Amato, G., 2000. Urban air pollution and plant-derived respiratory allergy. Clin. Exp. Allergy 30 - De Groot, R. S., Wilson, M. A., & Boumans, R. M. (2002). A typology for the classification, description and valuation of ecosystem functions, goods and services. Ecological economics, 41(3) - Díaz, S., Pascual, U., Stenseke, M., Martín-López, B., Watson, R. T., Molnár, Z., ... & Polasky, S. (2018). Assessing nature’s contributions to people. Science, 359(6373) - Dunnett, N., Swanwick, C. and Woolley, H. (2002) Improving Urban Parks, Play Areas and Green Spaces, London, DTLR - Elliot, R. (1995) Environmental Ethics, New York, Oxford University Press - Elmqvist, T. et al. (2013) Urbanization, Biodiversity and Ecosystem Services: Challenges and Opportunities, London, Springer - Etingoff, K. (2015). Urban Ecology: Strategies for Green Infrastructure and Land Use. Apple Academic Press - Ewel, K.C., (1997) Water quality improvement by wetlands. In: Daily, G.C. (Ed.), Nature’s Services. Societal Dependence on Natural Ecosystems. Island Press, Washington, DC - Ferrini, F., van den Bosch, C. C. K., & Fini, A. (Eds.). (2017). Routledge handbook of urban forestry. Taylor & Francis
107
- Folke, C., A. Jansson, J. Larsson, and R. Costanza. 1997. Ecosystem appropriation by cities. AMBIO 26: 167–172 - Fuller, R. A., Irvine, K. N., Devine-Wright, P., Warren, P. H., & Gaston, K. J. (2007). Psychological benefits of greenspace increase with biodiversity. Biology letters, 3(4), 390-394 - Goddard, M. A., Dougill, A. J., & Benton, T. G. (2010) Scaling up from gardens: biodiversity conservation in urban environments. Trends in ecology & evolution, 25(2) - González, M. (2010) ‘Los árboles donostiarras tienen DNI’ (Trees in San Sebastián have an ID), El Diario Vasco. Accessible from www.diariovasco.com (accessed: 03 April 2019) - Green Surge (2017) Guide to valuation and integration of different valuation methods - A tool for planning support. Accessible from www.greensurge.eu (accessed: 04 March 2019) - Green Surge (2017) Urban green infrastructure, connecting people and nature for sustainable cities - A summary for policy makers. Accessible from www.greensurge.eu (accessed: 04 March 2019) - Gren, I.M., (1995) Costs and benefits of restoring wetlands. Two Swedish case studies. Ecol. Eng. 4 - Hanski, I., & Mononen, T. (2011). Eco-evolutionary dynamics of dispersal in spatially heterogeneous environments. Ecology Letters, 14 (10), 1025–1034. - Hartig T., Mitchell, R., de Vries S. and Frumkin H (2014) ‘Nature and Health’, The Annual Review of Public Health, 35:21.1–21.22 - Haughton, G. and Hunter, C. (1994) Sustainable Cities, Regional Policy and Development. Jessica Kingsley, London - Hough, M., (1989) City Form and Natural Process. Routledge, London - Kellert, S.R. (1997) The Value of Life: Biological diversity and human society, Washington D.C., Island Press - Konijnendijk, C.C., Nilsson K., Randrup T. B. and Schipperijn J. (2005) Urban Forests and Trees, Netherlands, Springer - Koskela, H., & Pain, R. (2000) Revisiting fear and place: women’s fear of attack and the built environment. Geoforum, 31(2) - Louv, R. (2008). Last child in the woods: Saving our children from nature-deficit disorder. Algonquin books - Lyytimäki, J. (2017). Disservices of urban trees. Chapter 12. Routledge handbook of urban forestry - Meiklejohn, K., Ament, R., & Tabor, G. (2009). Habitat corridors & landscape connectivity: clarifying the terminology. Center for large landscape conservation - Millennium Ecosystem Assessment (2005) Ecosystems and Human Well-being: Synthesis. Island Press, Washington, DC - Moreland Landscape Guides (2009) Available from www.moreland.vic.gov.au (accessed: 04 May 2019) - Oxford dictionary (2019) (online) Available from https://en.oxforddictionaries.com (accessed: 04 April 2019) - Pauchard, A., & Barbosa, O. (2013) Regional assessment of Latin America: rapid urban development and social economic inequity threaten biodiversity hotspots. In Urbanization, 108
biodiversity and ecosystem services: Challenges and opportunities. Springer, Dordrecht - Posey, D.A., 1999. Cultural and spiritual values of biodiversity. A complementary contribution to the global biodiversity assessment. In: Posey, D.A. (Ed.), Cultural and Spiritual Values of Biodiversity. UNEP and Intermediate Technology Publications, London, UK - Rodenburg, C., Baycan-Levent, T., Van Leeuwen, E., & Nijkamp, P. (2001) Urban Economic Indicators for Green Development in Cities, Greener Management International, (36) - Seto, K.C. and Shepherd, J. M. (2009) ‘Global urban land-use trends and climate impacts’, Current Opinion in Environmental Sustainability, 1(1), 89-95 - Shackleton, C. M., Ruwanza, S., Sanni, G. S., Bennett, S., De Lacy, P., Modipa, R., ... & Thondhlana, G. (2016) Unpacking Pandora’s box: understanding and categorising ecosystem disservices for environmental management and human wellbeing. Ecosystems, 19(4) - Shem, W. and Shepherd, M. (2009) ‘On the impact of urbanization on summertime thunderstorms in Atlanta: Two numerical model case studies’, Atmospheric Research, 92, 172189 - Steg, L., van der Berg, A.G. and de Groot, J.I.M. (2012) Environmental Psychology: An Introduction, UK, Wiley-Blackwell - Stolt, E., (1982) Vegetationens förmåga att minska expositionen för bilavgaser (The ability of vegetation in decreasing exposure to car fumes). University of Gothenburg on behalf of the Gothenburg Health Care Department (quoted from Bolund and Hunhammar, 1999) - SOU, (1993) Handlingsplan mot buller (Action Plan on noise). SOU 65, 136 Stockholm (quoted from Bolund and Hunhammar, 1999) - Sukhdev. P (2010) ‘Putting a value on nature could set scene for true green economy’ The Guardian. Available from www.theguardian.com (accessed: 27 February 2019) - TEEB – The Economics of Ecosystems & Biodiversity (2011) TEEB Manual for Cities: Ecosystem Services in Urban Management, available from www.teebweb.org - Tolly, J., (1988) Träd och trafikföroreningar samt Bil. Biologiskt filter för E4 pa˚ Hisingen (Trees and transport pollution and the car). Gothenburg City Building, Hisingen, 15 pp. (quoted from Bolund and Hunhammar, 1999) - Trowbridge, P. J., & Bassuk, N. L. (2004) Trees in the urban landscape: site assessment, design, and installation. John Wiley & Sons - Trowbridge, P. J. and Mudrak, L. (1988) Landscape Forms for Mitigating Winds on Shoreline Sites, National Endowment for the Arts and Department of Landscape Architecture, Cornell University, Ithaca, NY - Ulrich, R., (1984) View through a window may influence recovery from surgery. Science 224 - Ulrich, R.S., Simons, R.F., Losito, B.D., Fiorito, E., Miles, M.A., Zelson, M., (1991) Stress recovery during exposure to natural and urban environments. J. Environ. Psychol. 11, UN - United Nations (2019) World population prospects 2017 (online). Available from www. population.un.org/wpp (accessed: 18 February 2019) - Williams, D. R. (2014). Making sense of ‘place’: Reflections on pluralism and positionality in place research. Landscape and Urban Planning, 131, 74-82 - Zweers, W. (2000) Participating with nature, outline for an ecologization of our worldview, Utrecht, International Books
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IMAGE AND TABLE REFERENCES - Cover images have been drawn by the author - Images 1, 2, 4, 7, 8, 9, 10, 11, 12 and 24: All pictures have been drawn by the author - Image 5: Adapted version of The Millennium Ecosystem Assessment (2005) diagram ‘Ecosystem Services’, drawn by the author - Image 6: Adapted version of ‘Nature’s Contributions to people’ diagram, by Diaz et al. (2018), drawn by the author of this work - Image 13: Europe outline map, source Wikipedia (online) available from https://commons. wikimedia.org/wiki/File:Europe_blank_political_border_map.svg (accessed: 01 April 2019), adapted by the author of this work - Image 14: San Sebastian map, source San Sebastian City Council (online) available from https://www.donostia.eus/taxo.nsf/fwHome?ReadForm&idioma=cas (accessed 23 March 2019) - Images 15, 16, 17, 18, 20, 21, 22 and 23: Photographs taken by the author of this work - Image 19: Pau map, source Pau City Council (online) available from https://www.pau.fr/ article/le-plan-local-durbanisme-de-pau (accessed 23 March 2019) - Image 25: Adapted from - NYC Parks Street planting guidelines - Street Tree Planting Standards NYC (2016) available from https://www.nycgovparks.org/trees/street-tree-planting (accessed 22 April 2019) - Tables 1, 2, 3: Proposed by the author
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