Routledge Handbook of Urban Forestry

Francesco Ferrini, Cecil C. Konijnendijk van den Bosch, Alessio Fini, Francesco Ferrini, Cecil C. Konijnendijk van den Bosch, Alessio Fini

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781317237020
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Forestry
• Index: Technology & Engineering

More than half the world's population now lives in cities. Creating sustainable, healthy and aesthetic urban environments is therefore a major policy goal and research agenda. This comprehensive handbook provides a global overview of the state of the art and science of urban forestry.

It describes the multiple roles and benefits of urban green areas in general and the specific role of trees, including for issues such as air quality, human well-being and stormwater management. It reviews the various stresses experienced by trees in cities and tolerance mechanisms, as well as cultural techniques for either pre-conditioning or alleviating stress after planting. It sets out sound planning, design, species selection, establishment and management of urban trees. It shows that close interactions with the local urban communities who benefit from trees are key to success.

By drawing upon international state-of-art knowledge on arboriculture and urban forestry, the book provides a definitive overview of the field and is an essential reference text for students, researchers and practitioners.

1
Introduction

Cecil C. Konijnendijk van den Bosch, Francesco Ferrini and Alessio Fini

Our urban world needs urban forests

We are living in the Anthropocene (Crutzen and Stoermer, 2000), an epoch in which human activities have started to have a significant global impact on the Earth’s geology and ecosystems. Humankind has, in this epoch, moved from being primarily rural to urban. Soon the large majority of us will live in cities and towns of different sizes; already by 2030 this will be 60 per cent of all humans (United Nations, 2015). Urban areas make up only 3 per cent of the Earth’s land surface, but they account for no less than 60–80 per cent of energy consumption and 75 per cent of carbon emissions. Urbanization is especially dramatic in the developing world, where 95 per cent of future urban expansion will take place (United Nations, 2015). Continuing urbanization and urban sprawl places tremendous pressures on, for example, fresh water supplies, public health, and on biodiversity.

The importance of urban areas as living environments for most humans is reflected in the 2015 United Nations Sustainable Development Goals (United Nations, 2015). One specific goal, Goal no. 11, highlights urban areas, under the heading ‘Making cities inclusive, safe, resilient and sustainable’. Several targets were formulated under Goal 11, such as strengthening efforts to protect and safeguard the world’s cultural and natural heritage; reducing the adverse per capita environmental impact of cities; supporting positive economic, social and environmental links between urban, peri-urban and rural areas by strengthening regional and development planning; as well as implementation of integrated policies and plans towards resource efficiency, climate change mitigation and adaptation, social inclusion and the like. The importance of urban green spaces for better cities is stressed in the target of providing (by 2030) universal access to safe, inclusive and accessible, green and public spaces, in particular for women and children, older persons and people with disabilities. Green spaces and urban vegetation, including trees, provide a wide range of essential benefits to urban societies through a range of supporting, provisioning, regulating and cultural ecosystem services. Urban trees and urban green can help cool cities, reduce the impacts of air and water pollution, and assist cities in dealing with floods and other extreme weather events. They can provide food and fodder, while also reducing our stress levels and encouraging us to be more physically active. Moreover, urban nature provides meeting places, inspiration, opportunities for learning, while also stimulating creativity (e.g. Konijnendijk et al., 2013; Roy and Byrne, 2014; Miller et al., 2015).

Ironically, urban green spaces have come under pressure in the quest for better cities. One of the urban planning and development approaches that has gained prominence during recent years is that of densification, thought to bring efficiency gains and technological innovation while reducing resource and energy consumption (e.g. Haaland and Konijnendijk van den Bosch, 2015). Densification is seen as an answer to continuing urban sprawl and its many negative effects. However, from a green space perspective, densification is considered challenging, as both green space quantity and quality will often decrease when cities become more compact (Haaland and Konijnendijk van den Bosch, 2015). When green space declines or even disappears, adverse effects to public health and human wellbeing can be expected.

Densification adds to the major challenges urban environments pose to urban vegetation such as urban trees. When looking at the latter, urban areas constrain tree growth and survival. Drought, poor soil quality, soil compaction, light heterogeneity, transplanting shock, pollutants, salinity, pathogens, and conflicts with human activities often cause premature plant death, thus reducing the net benefit from trees (Bussotti et al., 2014; Ferrini et al., 2014). It is, therefore, important to better understand the dynamics leading to tree decline in the urban environment and to develop strategies and techniques aimed at improving the horticultural tolerance (i.e. the capacity to provide benefits, not only to survive, under stressful conditions) of urban trees (Flowers and Yeo, 1995; Fini et al., 2013). These include nursery pre-conditioning techniques and post-planting management techniques (Franco et al., 2006), but a key role is played by species selection (Fini et al., 2009, 2014). Many different species are used in the urban environment, but selection criteria are frequently based on aesthetics and on whether the species are native or not, rather than on the tolerance to the typical stresses imposed by the built environment and on the capacity to provide substantial benefits therein. This has generated limited knowledge only about the ecophysiology of shade trees, if compared to fruit trees and crop species. We also need to know more about the planning, design and management of urban vegetation and urban green spaces.

How can we make sure that urban vegetation and green spaces are part of our efforts to develop inclusive, safe, resilient and sustainable cities; cities that are not threatening public health, but rather promoting it? Urban forestry, an interdisciplinary approach to the planning and management of all woody and associated vegetation in and around dense human settlements (Miller et al., 2015), can provide at least part of the answer. Based on this premise, the current handbook provides an overview of the current art, science and practice of urban forestry, focusing on state-of-art knowledge and good practice.

Why this urban forestry handbook – and who should read it?

This book in the Routledge Handbook series is timely. It is published at a time when the field of urban forestry is thriving and where research, practice and education are under continuous development. This is reflected, for example, in the rapid growth of journals such as Urban Forestry and Urban Greening, which now receives over 500 research and review paper submissions per year. The maturing of the field is also demonstrated by the large number of international, national and local conferences, seminars and workshops taking place annually with specific focus on aspects of urban forestry. Globally, the International Society of Arboriculture (ISA) and the International Association of Forest Research Organizations (IUFRO) have provided leadership. In Europe, the annual European Forum on Urban Forestry (EFUF) has a history of close to 20 years, providing a platform for urban forestry practitioners and academics from Europe and elsewhere to meet. At a more regional level, working groups such as Silva Mediterranea (currently under the Food and Agriculture Organization of the United Nations, FAO) have also had specific groups and networks of urban forestry. The important urban forestry book by Miller (the latest edition in 2015) has served as a textbook for university students in North America and across the globe. In 2005, publication of the book ‘Urban Forests and Trees’ (Konijnendijk et al., 2005) was another milestone.

However, urban forestry keeps developing rapidly and there is a need for comprehensive, state-of-art publications that provide guidance to students and experts through the growing forest of studies and practices. Taking a global perspective on urban forestry, this handbook aims to fulfil part of this need, with the following objectives:

• To stimulate interest in the multiple roles and benefits of urban green areas.
• To provide insights about the multiple stresses experienced by trees in cities. This also relates to details about tolerance mechanisms of species with validated and potential ornamental use, as well as to cultural techniques for either pre-conditioning plants in the nursery or alleviating stress after planting.
• To promote sound planning, design, establishment and management of urban trees and urban forests for the optimization of their benefits is the domain of the fields of arboriculture and urban forestry. These fields draw upon a wide range of disciplines and have generated a large amount of knowledge and good practice during the past decades. Close interactions with the local urban communities who benefit from trees – and in some cases also are affected by tree disservices – are key to successful arboriculture and urban forestry.

By drawing upon international state-of-art knowledge on urban forestry and urban arboriculture, this book provides a comprehensive overview of the current state of the field. The book will be an essential handbook for researchers, students and practitioners dealing with urban trees in one way or another. It provides a unique perspective by having the tree and its growing site in focus, looking at biotic, abiotic and anthropogenic interactions between the tree and its environment.

What is urban forestry all about?

Chapter 2 provides some insight into the emergence and development of the concept of urban forestry in different parts of the world. Although its roots are in North America, with professor Eric Jorgensen at the University of Toronto famously coining the term during the 1960s (e.g. Konijnendijk et al., 2006), other continents can build on a rich heritage of planning and managing urban trees and urban woodlands. Konijnendijk et al. (2006) offer a comprehensive review of definitions of urban forestry in both North America and Europe, showing important differences. In North America, street trees and their role as ‘shade trees’ have often been in focus, while the Europeans tended to focus on their heritage of ‘town forestry’ which focused on woodlands that often had been in city ownership for centuries. However, most scholars would agree today that urban forestry should be defined in a more comprehensive way, as in the spirit of the definition provided by the Society of American Foresters (Helms, 1998) urban forestry is the ‘art, science and technology of managing trees and forest resources in and around urban community ecosystems for the physiological, sociological, economic and aesthetic benefits trees provide society’. Thus urban forestry is about all trees in urban and peri-urban areas, ranging from individual trees in private gardens, through street trees and trees in parks, to urban woodland. Moreover, trees should be seen in connection with associated vegetation, such as shrubs and grass. However, this also shows the diversity of approaches needed in urban forestry, from sound arboricultural practices for individual trees to specific silvicultural approaches for urban woodland stands, and from single tree assessments to city-wide assessments of urban forest cover and benefits.

Urban forestry is multi- or even interdisciplinary, combining expertise, theories and methods from a range of disciplines. Obviously forestry is an important contributor, with its long-term perspective on natural resource management and its sustainability thinking, but so are landscape planning and landscape architecture, horticulture and arboriculture, ecology, biology, plant diseases, and the like. Moreover, urban forestry links the natural sciences with the social sciences and humanities. Urban forestry is just as much about people as about trees, and thus important contributions are made by sociology, environmental psychology and economics, as well as by the design fields (architecture, landscape architecture, art). Moreover, urban planning is crucial to successful and strategic urban forestry.

Many definitions of, and scholarly works on urban forestry, have stressed its socially-inclusive nature. This normative perspective recognizes that urban forestry can only be truly successful when it is done in close collaboration with local (urban) communities. Thus governance and public engagement are often given considerable attention. Through close collaboration between municipal and other experts with local residents, non-governmental organizations, but also private businesses, more resilient urban forests that provide a range of relevant benefits can be developed and maintained.

As mentioned above, a key aspect of urban forestry is that it is about growing trees and other vegetation in urban and highly artificial environments. In some cases, urban settings are very dense and growing space is limited. This challenge is very different from other types of natural resource management, with forestry for example typically focusing on natural or rural settings.

Urban forestry in relation to emerging approaches

With the growing recognition of the importance of urban green spaces for the quality of urban life and environment, and in the light of the need for more strategic approaches to green spaces planning and management, several approaches have emerged during recent times. Urban forestry should be seen within the context of these. Approaches related to the planning of greenbelts, green wedges and green structure gained popularity first of all in the Western world and then were also implemented in other parts of the globe (e.g. Xiu et al., 2016). During recent years, green infrastructure is a concept often used as referring to integrated networks / structures of green (and blue) space, either in urban or rural areas. Chapter 14 provides an in-depth perspective on green infrastructure and green infrastructure planning, tracing back its roots and defining some of its key characteristics as relating to, for example, connectivity and multi-functionality. Green infrastructure thinking has gained following at, for example, the European Union level, where it is seen as a potential tool for linking up urban with rural landscapes, and for creating synergies between nature conservation and other policy domains (Lafortezza et al., 2013). Urban planners, engineers and others can more easily relate to green infrastructure as one of the types of essential infrastructure for cities, in line with e.g. road networks, sewage systems and utility networks.

Even more recently, Europe has led the world in promoting the concept of nature-bases solutions, meaning solutions aimed to help societies address a variety of environmental, social and economic challenges in sustainable ways. They are

actions which are inspired by, supported by or copied from nature. Some involve using and enhancing existing natural solutions to challenges, while others are exploring more novel solutions, for example mimicking how non-human organisms and communities cope with environmental extremes. Nature-based solutions use the features and complex system processes of nature, such as its ability to store carbon and regulate water flow, in order to achieve desired outcomes, such as reduced disaster risk, improved human well-being and socially inclusive green growth. Maintaining and enhancing natural capital, therefore, is of crucial importance, as it forms the basis for implementing solutions.

(Horizon 2020 Expert Group, 2015, p. 5)

In other words, urban green spaces, urban forests and urban trees are typical nature-based solutions (or even just ‘nature solutions’) as they provide a range of ecosystem services that help cities meet important challenges, such as those related to climate change and public health and wellbeing.

As also argued elsewhere in this handbook, urban forestry still very much has a role to play today, in a time of emerging concepts and growing attention for green space and ‘green solutions’. Building on at least 50 years of history and expertise, urban forestry focuses on trees as key provider of natural benefits in urban areas. It represents a comprehensive and integrative approach, supported by a wide range of disciplines, but increasingly also with a set of theories, methods and practices of its own. Where green infrastructure and nature-based solutions can sound abstract and technical, perhaps less related to specific place and people, urban forestry can serve as a delivery mechanism, building on its key component of linking people and trees at the local level. This urban forestry handbook was compiled in this spirit.

The structure of this book

This book was compiled as a comprehensive handbook covering most aspects of urban forestry, but obviously not all. It aims to discuss urban forestry from different angles, providing information about its background, rationale and current practice.

After this introductory chapter which sets the scene, defines urban forestry in the context of the book and provides insight into the structure of the handbook, focus of Chapter 2 by Richard J. Hauer et al. is on the history and development of urban forestry. The chapter describes the early use of trees in cities, before focusing on European tree landscapes. Unlike many earlier texts on urban forest history, however, the chapter also introduces historical development in the Asia-Pacific region, Central and South America, before it goes into greater detail with a history of shade tree programmes and urban forestry in North America. The chapter identifies the distinct, but also interwoven historical development of the fields of urban forestry and arboriculture. Chapter 3 by Justin Morgenroth and Johan Östberg introduces the urban forest as a resource with different components, and focuses on ways of measuring and monitoring this resource. As the chapter shows, in spite of many tools for measuring and monitoring, we often lack information on the urban forest resource in different places. The chapter introduces common variables for measurement, relating to estimating ecosystems services and long-term monitoring, for example. It also highlights the importance of standardization, which currently is often lacking. An overview is provided of common tools for measuring urban trees and urban forests, with special attention for recent technological advances, such as those related to LiDAR technology. Different types of inventories are presented. The final part of the chapter presents who measures the urban forest – from researchers and municipal authorities to local residents.

Chapter 4 on ecosystem services, by Cynnamon Dobbs and colleagues, sets the scene for a series of chapters on the benefits of urban forests. The chapter introduces the ecosystem service concept, which represents a new way of looking at the products and services that nature provides to us humans, and the main categories of services. Some basic information is provided on how to assess these different services, which is often not easy, for example in the case of cultural ecosystem services. The focus then shifts to urban forests and urban trees specifically. An ecosystem service framework is presented for application of a socio-ecological approach to urban areas. Finally the importance of including information about ecosystem service provision into decision making and management is discussed. Chapter 5, by Kathleen Wo...