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This book offers an overview of recent scientific and professional literature on urban greening and urban ecology, focusing on diverse disciplines such as landscape architecture, geography, urban ecology, urban climatology, biodiversity conservation, urban governance, architecture and urban hydrology. It includes contributions in which academics, public policy experts and practitioners share their considerable knowledge on the multi-faceted aspects of greening cities. The greening of cities has witnessed a global resurgence over the past two decades and has made a significant contribution to urban liveability and sustainability, as well as increasing resilience. As urban greening efforts continue to expand, it is useful to promote recent advances in our understanding of various aspects of planning, design and management of urban greenery, but at the same time, it is also important to realize that there are important gaps in our knowledge and that further research is needed. The book is organized in three main parts: concepts, functions and forms of urban greening. The first part examines the historical roots of greening cities and how the burgeoning field of urban ecology can contribute useful principles and strategies to guide the planning, design and management of urban greening. The second part shifts the focus to the diverse range of services – the functions – provided by urban greening, such as those related to urban climate, urban biodiversity, human health, and community building. The final part explores conventional, often neglected, but important forms of urban greenery such as urban woodlands and urban farms, as well as relatively recent forms of urban greenery like those integrated with buildings and waterways. It offers a ready reference resource for researchers, practitioners and policy-makers to grasp the critical issues and trigger further studies and applications in the quest for high-performance green cities.



Chapter 1. Introduction to Green City Idea and Ideal

Without Abstract
Chi Yung Jim, Puay Yok Tan

Urban Greening as a Component of Urban Development


Chapter 2. Perspectives on Greening of Cities Through an Ecological Lens

The increasing focus on urban green spaces (UGS) leads to them becoming an important component of the physical makeup of cities. However, it is useful to be mindful that UGS implementation competes for precious land resources in cities, incur carbon and energy footprint, and can have long payback periods for net benefits to be achieved. The net benefits provided by UGS are thus not assured by its mere presence; functional benefits need to be achieved through deliberate design. In particular, it is suggested here that combining design with an understanding of urban ecological knowledge is a useful approach to increase the ecological functions of UGS. A conceptual model using coupled human-ecological function is described to explain how increasing ecological functions of UGS to reduce resource consumption, restore ecological processes and functions, and reduce waste generation can shift the coupled human-ecological function for both humans and the environment. Four principles distilled from conceptual advances in urban ecology and landscape ecology are proposed as a means to bridge scientific knowledge and UGS implementation through design: (1) spatial patterns of UGS across different scales influence the ecological functions of UGS; (2) heterogeneity of UGS determines its resilience to disturbances; (3) urban ecosystems are dynamic; and (4) ecological processes remain important in cities. More application-focused strategies are in turn, derived from these principles, and how these can be applied to UGS are highlighted. It is also suggested that while current scientific knowledge still limits the application of ecological principles in many aspects of UGS design and management, the increasing emphasis on UGS in cities provides good learning opportunities for scientists, practitioners and policy makers to work in concert to enhance the ecological functions of UGS.
Puay Yok Tan

Chapter 3. Imperatives for Greening Cities: A Historical Perspective

Although co-ordinated and comprehensive efforts at citywide greening had only emerged in the last two centuries, green spaces and vegetation have been a vital part of urban history, across periods and locales. Urban dwellers have inserted and maintained urban greenery for a wide variety of reasons. Some of these imperatives are persistent throughout time, while others have emerged with new knowledge and societal developments. More often than not, multiple motivations are embedded in urban greening projects. Based on a review of existing literature spanning multiple disciplines, we provide an overview of the range of reasons why urban dwellers have embarked on greening projects in their environments. We identify nine themes that continue to be highly relevant today, and provide brief historical perspective on each. By extending the discussion of urban greening beyond its potential to meet contemporary challenges, we hope to provide a more long-ranging view of why greenery has been incorporated in cities.
Yuanqiu Feng, Puay Yok Tan

The Functions of Urban Green Spaces


Chapter 4. Urban Greening and Microclimate Modification

Vegetation is promoted widely all over the world as a means of creating a better quality of life in cities. Plants are credited with lowering air temperature and development of green spaces is considered one of the main strategies for mitigating the urban heat island. This chapter examines the mechanisms by which plants can modify the urban microclimate, with an emphasis on air temperature and outdoor thermal comfort. It outlines a scheme for classifying urban vegetation according to its location in the city and its intended role, which may be useful for planners and landscape architects. The chapter concludes with a methodology for integrating vegetation in the urban planning process to best achieve the desired microclimatic effects.
Evyatar Erell

Chapter 5. Urban Greening and Its Role in Fostering Human Well-Being

Population growth coupled with urbanisation has led to a decline in natural ecosystems throughout the world. Particularly in cities, urban developments continue to displace natural ecosystems and lead to cities being dominated by concrete and steel. However, with increasing recognition of the benefits of human interaction with nature, planning and design professionals are now making more deliberate attempts to introduce greenery into the built environment. Indeed, the fields of urban planning, public health, and park planning provide a rich account of the role that urban greening plays in human well-being. History of urban planning and greenspace began in Europe and America in the early 1800s. Early park settings were intended to benefit urban dwellers and factory workers who lacked exposure to clean air and greenery, whereas today planners develop green recreation areas for passive and active leisure pursuits. An interesting programme that started in the United States is ‘Park Prescriptions’, which is ‘designed in collaboration with healthcare providers and community partners to utilise parks, trails, and open space for the purpose of improving individual and community health’. Horticultural therapy is another compelling initiative which promotes greater inclusion of greenery and active movement within healthcare settings, both inside buildings and the nearby environment. In such initiatives, park planners and managers work closely with urban planners and neighborhood developments to enhance access and leisure services in order to maximise associated physical and mental health and social benefits.
Christine A. Vogt, Cybil Kho, Angelia Sia

Chapter 6. Urban Community Gardens as Multimodal Social Spaces

This chapter examines the social and collective dimensions of urban gardening. Through a review of recent literature and cases around the world, it examines urban community gardens in terms of their multiple modalities, specifically as a convivial space, a cultura l space, an inclusive space, a restorative space, a democratic space, and a resilient space. As convivial spaces, urban gardens build and nurture agency of individuals as well as social ties in a community. As inclusive, cultural spaces, urban gardens can function as a place for cross-cultural learning and understanding and building of connections across social and cultural divides. As restorative space, urban gardens contribute to individual and community health and well-being. As democratic spaces, urban gardens serve as a vehicle to engage individuals and communities in efforts toward other social and environmental initiatives. As resilient space, urban gardens function as social safety nets and provide for the community in time of calamity and struggles. Through these different expressions and opportunities for active engagement by communities and citizens, the chapter argues that urban gardening can serve as a model for other urban greening strategies to incorporate considerations for multiple social, cultural, and economic goals.
Jeffrey Hou

Chapter 7. Urban Green and Biodiversity

The chapter explores the relationship between urban green and biodiversity . Cities are home to a large number of native plant and animal species. Non-native species are an essential component for the species richness in the cities worldwide. The population of animal and plant species is not stable and the number of native species has been declining over the last decades and the portion of non-native species is increasing. Public and private gardening are main causes for the introduction of non-native species. The different contrasting attitudes towards non-native species between urban dwellers and nature conservationists are discussed. Three approaches are described representing different scales, namely the city in the region, the urban matrix and green patches. These three approaches offer a sophisticated view about the relationship between urban green and biodiversity and provide ways for a tailored management to improve biodiversity in urban areas. For each scale, recommendations for the management of urban green are presented. The chapter ends with basic principles for the development and management of green areas and green structures to enhance urban biodiversity and ecosystem services in cities.
Peter Werner, John G. Kelcey

Chapter 8. Urban Agriculture as a Productive Green Infrastructure for Environmental and Social Well-Being

Urban agricultural (UA) systems appear in many forms, from community farms and rooftop gardens to edible landscaping and urban orchards. They can be productive features of cities, providing important environmental and social services that benefit and support urban communities. These benefits include the provision of high levels of biodiversity and ecosystem services that contribute to urban nature and environmental processes as well as a range of social benefits, such as food and nutrition, cultural resources and recreational benefits. However, there are a number of challenges that prevent UA from expanding despite various acknowledged benefits. Increasing competition for space and environmental constraints often limits the ability to establish UA systems in many city areas, and negative spillover from UA to urban areas can create hazards to the natural environment and the local community. Further expansion and development of UA as a productive green infrastructure will require win-win strategies that maximize environmental and social benefits while taking advantage of vacant or under-utilized pockets of urban land.
Brenda B. Lin, Stacy M. Philpott, Shalene Jha, Heidi Liere

Chapter 9. Urban Nature and Urban Ecosystem Services

Worldwide more and more people live and work in cities, where urban nature and their ecosystem services are the basis for economic development and social wellbeing. Therefore, how to ensure that cities in the present and future can provide a whole range of ecosystem services to meet urban dwellers’ needs become a front and center issue in urban resilience and sustainability on the global agenda. This article presents a literature review that explores our understanding about various natural elements in cities (including urban green and blue spaces) and their diverse ecosystem services and some disservices. While the importance of urban nature and urban ecosystem services has been increasingly recognized, the integration of ecological, social and economic understanding of urban ecosystem services into relevant policy making processes is still at an embryonic stage. Some pertinent challenges are highlighted for the theorization and governance of urban ecosystem services.
Wendy Y. Chen

The Forms of Urban Green Spaces


Chapter 10. Blue-Green Infrastructure: New Frontier for Sustainable Urban Stormwater Management

Blue-green infrastructure (BGI) has been recognized as an important tool for sustainable urban stormwater management. BGI is ecosystem-based, relying on biophysical processes, such as detention, storage, infiltration, and biological uptake of pollutants, to manage stormwater quantity and quality. Rain gardens, bioswales, constructed wetlands, retention and detention basins, and green roofs are most commonly used BGI systems. Unlike the single-functioned grey infrastructure, which is the conventional urban drainage system, these landscape systems collectively provide multiple ecosystem services, including flood risk mitigation, water quality treatment, thermal reduction, and urban biodiversity enhancement. In recent years, BGI is increasingly embraced through different initiatives around the world, driven by the urgency to tackle different local challenges, such as water quality standards, water security, increased flood risk, and aquatic ecosystem degradation. Whereas BGI is a relatively new term, the idea and practice are not new. In this chapter, we also showcase four cities—Portland, New York City, Singapore, and Zhenjiang—that are active and progressive in implementing BGI. Although BGI receives increasing attention, mainstreaming BGI remains a challenge today. To promote widespread BGI implementation, future research should focus on case studies on practical BGI experiences to inform strategies for overcoming the barriers to mainstreaming BGI in different cities.
Kuei-Hsien Liao, Shinuo Deng, Puay Yok Tan

Chapter 11. Highrise Greenery: Ancient Invention with New Lease of Life

Many cities especially compact ones are beset by urban heat island effect compounded by climate change and poor environmental quality. Urban green infrastructure can provide promising relief, but its implementation in dense cities is constrained by inadequate solution space. Departing from conventional thinking, greenroofs offer an innovative alternative of converting the negative amenity of barren roofs to pleasant greenery plus handsome bonus of multiple ecosystem services. The ancient origin of greenroofs is traced to the pragmatic need to build primitive shelters in harsh climate. Gradual refinement of the precursor has allowed development of a cultural invention. Despite continued installation in rural areas, its adoption in cities remained scanty in historical times. The notable classical exemplars in pre-industrial and industrial periods are assessed as pioneers. With fortuitous combination of factors, the idea was revived in Germany from the 1960s, spearheaded by scientific research and technological innovations. The new materials and designs, in conjunction with enabling public policies, have pump-primed the modern greenroof movement which subsequently spread to other European countries and then worldwide. The critical technological advances and the directions for further improvements are critically evaluated. The need to deepen understanding and enhance the key functions of cooling, warming and stormwater management is highlighted. Some inspiring recent projects are surveyed with respect to their outstanding innovative elements. Future developments could focus on tailor-made, cost-effective and environmentally-friendly dimensions.
Chi Yung Jim

Chapter 12. Urban Ecological Networks for Biodiversity Conservation in Cities

Triggered by concerns of global biodiversity loss, cities are increasingly called upon to play an increased role in biodiversity conservation, leading to a surge in interest in urban biodiversity conservation. In playing this role, greening of cities needs to move beyond mere provision of amenities or ecosystem services to one of providing habitats for native biodiversity. This chapter describes one of the approaches for enhancing urban biodiversity conservation through the ecological network approach. The concept of ecological networks is not new in the field of ecology. However, its application to cities, both in conceptual and operational forms, is highly limited. As a high-rise, high-density city in which biodiversity conservation is threatened by other competing land uses, Singapore is used as an example to illustrate the development and application of the ecological network approach. The ecological network is built on the concept of network, spatial and landscape cohesions. Using methods in landscape ecology, remote sensing, biodiversity conservation and the Analytic Hierarchy Process, this chapter describes how a toolkit for ecological network can be developed, as well as the efficacy of its use for biodiversity management. The toolkit is categorized into monitoring tools, mapping tools, and communication and decision making tools. The learning outcomes gleaned from the research are presented as the 5-multis: multispecies, multiscalar, multilevel, multifunctionality, and multidisciplinarity.
Abdul Rahim Hamid, Puay Yok Tan

Chapter 13. Urban Heritage Trees: Natural-Cultural Significance Informing Management and Conservation

Trees with outstanding traits have always attracted human attention, echoed by 60 epithets harvested from the literature. They have been formally designated as heritage trees using diverse criteria, such as size, tree form, historical-cultural associations, and sacred-mythical connotations. Ancient trees with veteran features offer varied micro-habitats to support a surprising assemblage of companion organisms. Other large trees furnish keystone structures with far-reaching ecological impacts. Inventory and scientific data can reinforce community awareness and improve management. Engaging citizens and the business sector could cultivate ownership and muster support. Assessing their economic value could explain multiple benefits, strengthen public-funding justifications, and raise prestige and value of property development. Preserving initial genial site conditions is critical for tree survival in the urban setting. The hitherto neglected soil domain deserves meticulous protection and improvement. Harmful grade change of tree sites should be avoided. Badly degraded sites could be rehabilitated using tailor-made site-specific techniques. The ageing tree-population structure demands proactive nurturing of younger successors to sustain the lineage. The statutory approach is advocated for assured protection and conservation. Overzealous and aggressive tree care should be replaced by a sympathetic and dedicated approach. The frequent omission of lightning protection should be promptly rectified. Conflicts with developments should be settled by in situ preservation, and transplanting should be the last resort. Sentimental and emotional responses towards tree loss could be carefully massaged employing public-relation skills. Heritage-tree conservation could be enhanced by transgenerational urban forestry, precision arboricultural practices, and joint venture of government and citizens.
Chi Yung Jim

Chapter 14. Conservation and Creation of Urban Woodlands

Many cities especially compact ones are deprived of natural elements. High-quality pre-urbanization natural ecosystems such as forests are often obliterated in the course of city growth. Surveys of the key ecological and environmental benefits of urban woodlands provide the basis to advocate conservation and creation. Urban woodlands tend to be isolated or fragmented remnant pockets enveloped by built-up areas. They are threatened by urban sprawl, and degraded by pollutant penetration, recreational impacts, inappropriate management, detachment from propagule sources, declining regeneration capacity, exotic invasion, and native-species pauperization. Sustainable management should be based firmly on ecological principles, to restore natural factors and processes, introduce minimum inputs, guard against intrusions, and foster spontaneous rehabilitation of degraded sites. Conservation strategy can aim at preserving large woodland patches, enlarging existing patches, fusing or connecting small woodlots with habitat corridors, and merging with adjacent natural areas. New woodlands can be proactively created at suitable green, brown and grey (rooftop) fields. Spontaneous colonization could trigger and sustain woodland succession to deliver urban woodlands on green and brown fields without human help. Afforestation with ameliorative treatments could be applied to harsh sites especially with poor substrate properties and scanty seed arrivals. On intractable sites, innovative techniques such as assisted relay floristics using an initial exotic nurse crop and direct plantation of grey fields could pump-prime woodland establishment. As a hybrid urban green space amalgamating nature and human influences in the novel urban setting, urban woodland conservation and management demand innovative and fusion solutions.
Chi Yung Jim

Chapter 15. Urban Waterfront Revivals of the Future

Urban waterfronts form part of cities’ critical intersection between the natural and man-made environment, linking the city and its inhabitants with water. In the context of high density urban environments, they are integral to the network of green and public spaces and have the potential to encompass a range of uses including residential, commercial, leisure, recreational, heritage and art offering a multitude of economic, social, environmental benefits. The cases of HafenCity Hamburg and Waterfront Toronto discussed in this paper demonstrate successful approaches to achieving social and environmental sustainability at the waterfronts, highlighting the importance of ensuring mixed uses, public access, sustainable design and construction of buildings and infrastructure including climate change adaptations. Integrated and incremental planning of waterfronts in conjunction with citywide planning alongside careful consideration for greening, urban ecology, biodiversity, and aquatic ecosystems is also critical. In an era of rapidly urbanizing and homogenized waterfront developments, distinctiveness and authenticity derived via meaningful engagement with the local context and via engaging in participatory design processes is of increasing relevance.
Swinal Samant, Robert Brears



Chapter 16. Concluding Remarks

The greening of cities is a pursuit that has been a long standing and integral part of the urban development history of human settlements. More than any other urban elements, urban vegetation and the fauna associated with it, underscore the flawed notion that nature is only pristine and has no place in cities. Urban vegetation indeed, represents the most powerful and visible expression that nature has been, and should continue to be an inseparable part of the way cities are planned and managed.
Puay Yok Tan, Chi Yung Jim


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