- Table View
- List View
Urban Galapagos: Transition to Sustainability in Complex Adaptive Systems (Social and Ecological Interactions in the Galapagos Islands)
by Thomas Kvan Justyna KarakiewiczThis book addresses the future of urbanisation on the Galapagos Islands from a systems, governance and design perspective with the competing parameters of liveability, economic and ecological, using the Galapagos as a laboratory for the theoretical and postulative understanding of evolving settlement and habitation. The Galapagos islands are one of the world’s most examined and reported examples of a series of naturally evolving ecosystems. The biodiversity of these island ecosystems are the focus of tourism and the image across the world yet human settlement are part of the local ecology. While human intervention is limited, the islands are a distinctive context in which to consider the impact of human habitation as a part of our ecosystems. In this book, authors take the framework of complex adaptive systems (CAS) in which to model systems that grow and evolve, the relations between these various sectors change; systems that get more complex as they evolve. Tested and applied discretely in the two realms of natural and urban, for the first time this text will bring the two together in understanding options for the future of urban settlements on the Galapagos Islands and, by extension, consider how the approach can be used globally in other contexts.
Urban Gardening as Politics (Routledge Equity, Justice and the Sustainable City series)
by Chiara Certomà Chiara TornaghiWhile most of the existing literature on community gardens and urban agriculture share a tendency towards either an advocacy view or a rather dismissive approach on the grounds of the co-optation of food growing, self-help and voluntarism to the neoliberal agenda, this collection investigates and reflects on the complex and sometimes contradictory nature of these initiatives. It questions to what extent they address social inequality and injustice and interrogates them as forms of political agency that contest, transform and re-signify ‘the urban’. Claims for land access, the right to food, the social benefits of city greening/community conviviality, and insurgent forms of planning, are multiplying within policy, advocacy and academic literature; and are becoming increasingly manifested through the practice of urban gardening. These claims are symptomatic of the way issues of social reproduction intersect with the environment, as well as the fact that urban planning and the production of space remains a crucial point of an ever-evolving debate on equity and justice in the city. Amid a mushrooming over positive literature, this book explores the initiatives of urban gardening critically rather than apologetically. The contributors acknowledge that these initiatives are happening within neoliberal environments, which promote –among other things - urban competition, the dismantling of the welfare state, the erasure of public space and ongoing austerity. These initiatives, thus, can either be manifestation of new forms of solidarity, political agency and citizenship or new tools for enclosure, inequality and exclusion. In designing this book, the progressive stance of these initiatives has therefore been taken as a research question, rather than as an assumption. The result is a collection of chapters that explore potentials and limitations of political gardening as a practice to envision and implement a more sustainable and just city.
Urban Green
by Colin FisherIn early twentieth-century America, affluent city-dwellers made a habit of venturing out of doors and vacationing in resorts and national parks. Yet the rich and the privileged were not the only ones who sought respite in nature. In this pathbreaking book, historian Colin Fisher demonstrates that working-class white immigrants and African Americans in rapidly industrializing Chicago also fled the urban environment during their scarce leisure time. If they had the means, they traveled to wilderness parks just past the city limits as well as to rural resorts in Wisconsin and Michigan. But lacking time and money, they most often sought out nature within the city itself--at urban parks and commercial groves, along the Lake Michigan shore, even in vacant lots. Chicagoans enjoyed a variety of outdoor recreational activities in these green spaces, and they used them to forge ethnic and working-class community. While narrating a crucial era in the history of Chicago's urban development, Fisher makes important interventions in debates about working-class leisure, the history of urban parks, environmental justice, the African American experience, immigration history, and the cultural history of nature.
Urban Growth Patterns in India: Spatial Analysis for Sustainable Development
by Bharath H. Aithal T. V. RamachandraThis book uses spatio-temporal analysis to understand urbanisation in Indian cities and explain the concept and impact of global greenhouse gas (GHG) emissions. It creates a GHG footprint for Indian cities and engages in a discussion about the United Nations Sustainable Development Goals (SDGs) and smart city initiatives within an Indian context. Understanding the spatial patterns of land use/land cover (LULC) dynamics in the rapidly urbanising cities of India, the readers will be able to simulate future urbanisation patterns and use spatial temporal analysis as a tool for implementing appropriate mitigation measures. Features Analyses the complete urbanisation and urban sprawl of major cities in India using advanced geospatial modelling techniques Highlights the best practices and methods used in modelling urban growth Discusses greenhouse gas emissions from various sectors and their effects in local environments Addresses the increase of local temperature in cities due to unplanned land use change and its impact on environmental sustainability and resilience Fills the need for data-driven governance and policy decisions by introducing various analyses through spatial mapping Highlighting some of the best practices and tools being used for modelling urban growth through case studies, the book is useful to those interested in using new technologies and methods for data collection and problem solving. It focuses on the major environmental issues in India, which are prevalent in most developing countries.
Urban Growth in Emerging Economies: Lessons from the BRICS
by George Martine Gordon McGranahanAlong with globalization, urban transitions have been central in the southward shift in economic power towards the newly emerging economies. As this book shows, however, these transitions have not been painless, and it is important for the rest of the urbanizing world to learn from the mistakes. It examines the role of urbanization and urban growth in the emerging economies, taking the BRICS countries (Brazil, Russia, India, China and South Africa) as case studies. Their different approaches towards urbanization have shaped their historical development paths and assisted or constrained their futures. Several of the BRICS bear heavy burdens from past failures to accommodate urban growth inclusively and efficiently, and many other urbanizing countries in Asia and Africa are in danger of replicating their mistakes. The overriding lesson of the book is that cities and nations must anticipate urbanization, and accommodate urban growth pro-actively, so as not to be left with an enduring legacy of inequalities and lost opportunities. This book is aimed at students and researchers in urban studies and development studies. It will also be of interest to policy advisors concerned with urbanization and the role of cities in a country’s development
Urban Health Risk and Resilience in Asian Cities (Advances in Geographical and Environmental Sciences)
by R. B. Singh Bathula Srinagesh Subhash AnandThis book focuses on understanding urban vulnerability and risk mitigation, advancing good health and wellbeing, and analysing resilience measures for various Asian cities. Today, cities are the dominant human habitat, where a large number of environmental, social, cultural and economic factors have impacts on human health and wellbeing. Cities consist of complex, dynamic, socio-ecological, and technological systems that serve multiple functions in human health and wellbeing. Currently half of Asia’s population is urban, and that figure is expected to rise to 66 percent by 2050. Since urban areas are often most vulnerable to hazards, the people living in them need good health infrastructure facilities and technological support at various scales. As such, the need of the hour is to enhance the adaptive capacity, strengthen resilience, reduce vulnerability, and take risk mitigation measures in urban areas, which requires a systematic approach based on science–policy interface that is transformative, trans-disciplinary and integrative for a sustainable urban future. Global sustainable development goals are closely tied to urban human health and wellbeing: (1) the third of the United Nations’ Sustainable Development Goals is to “Ensure healthy lives and promote wellbeing for all at all ages” and (2) the eleventh is to “Make cities inclusive, safe, resilient and sustainable”. By addressing these goals, this book offers a highly useful resource for anyone concerned with healthy and resilient cities in Asia, today and tomorrow.
Urban Health and Wellbeing Programme: Policy Briefs: Volume 1 (Urban Health and Wellbeing)
by Franz W. GatzweilerThis book is a compilation of the policy briefs produced by the International Science Council’s program on Urban Health and Wellbeing: A Systems Approach over the past five years. Intended for urban decision-makers at all levels, it highlights policy-relevant findings and research insights to encourage the co-creation of knowledge for healthy urban environments and people. The book shows how variations on the systems approach developed and promoted by the program have been implemented in regions around the world and contributed to improving urban health. These policy briefs summarize research findings and scientific events concerning urban health-related topics that are relevant for public health professionals, urban planners, urban stakeholder groups and the public at large.
Urban Health and Wellbeing Programme: Policy Briefs: Volume 2 (Urban Health and Wellbeing)
by Franz W. GatzweilerThis book is a collection of policy briefs produced from research presented at the 16th Conference on Urban Health in Xiamen, China, November 4–8, 2019, under the theme “People Oriented Urbanisation: Transforming Cities for Health and Well-Being”, co-organized by the Urban Health and Wellbeing (UHWB) programme of the International Science Council (ISC). The UHWB programme takes an interdisciplinary, cross-sectoral and systemic view on issues of health and wellbeing in cities which include the urban economy and finance systems, education, employment, mobility and transport, food, energy and water resources, access to public services, urban planning, public spaces and urban green, as well as social inclusion. Contributions to this book have been made by scientists from multidisciplinary research fields. The policy briefs in this book present the background and context of an urban health issue, research findings and recommendations for policy/decision-makers and action-takers. In some cases, they inform about relevant events and developments from the science community or important opinion pieces which address health emergencies, like the current COVID-19 pandemic. The book is intended for citizens and political decision-makers, who are interested in systems perspectives on urban health and wellbeing, examples of how to deal with the increasing complexity of cities and the accompanying environmental and social impacts of increasing urbanization. Furthermore, it hopes to inspire decision-makers to facilitate finding solutions, in order to reach the goal of advancing global urban health and wellbeing.
Urban Health and Wellbeing Programme: Policy Briefs: Volume 3 (Urban Health and Wellbeing)
by Franz W. GatzweilerThis book presents the background and context of an urban health issue, research findings, and recommendations for policy/decision-makers and action-takers. This book is a collection of policy briefs produced from research presented at the 16th Conference on Urban Health in Xiamen, China, during November 4–8, 2019, under the theme “People Oriented Urbanisation: Transforming Cities for Health and Well-Being,” co-organized by the Urban Health and Wellbeing (UHWB) programme of the International Science Council (ISC), The 15th Annual Session of Global Forum on Human Settlements in Shenzhen, China, during October 15–16, 2020, and the Chinese Academy of Sciences & Technology (CAST) International Conference on "Digital economy and green development" held during November 2020. The UHWB programme takes an interdisciplinary, cross-sectoral, and systemic view on issues of health and well-being in cities which include the urban economy and finance systems, education, employment, mobility and transport, food, energy and water resources, access to public services, urban planning, public spaces and urban green, as well as social inclusion. Contributions to this book have been made by scientists from multidisciplinary research fields. The policy briefs in this book provide an interdisciplinary and cross-sectoral perspective on urban health and human well-being issues, primarily food security, urban infrastructure, public services, traffic and transportation, smart city building, urban health and safety, social cohesion sustainable development policies, and urban planning. In some case, it informs about urban health issues in different regions of the world, the current status, and key insights into addressing related issues, with emphasis on factual cases in the current COVID-19 pandemic. The book is intended for citizens and political decision-makers, who are interested in systems perspectives on urban health and well-being, examples of how to deal with the increasing complexity of cities and the accompanying environmental and social impacts of increasing urbanization. Furthermore, it hopes to inspire decision-makers to facilitate finding solutions, in order to reach the goal of advancing global urban health and well-being.
Urban Heat Island: Hot and Humid Regions (Advances in 21st Century Human Settlements)
by Ursula Eicker Napoleon Enteria Matteos SantamourisThis book discusses the concepts and technologies associated with the mitigation of urban heat islands (UHIs) that are applicable in hot and humid regions. It presents several city case studies on how UHIs can be reduced in various areas to provide readers, researchers, and policymakers with insights into the concepts and technologies that should be considered when planning and constructing urban centres and buildings. The rapid development of urban areas in hot and humid regions has led to an increase in urban temperatures, a decrease in ventilation in buildings, and a transformation of the once green outdoor environment into areas full of solar-energy-absorbing concrete and asphalt. This situation has increased the discomfort of people living in these areas regardless of whether they occupy concrete structures. This is because indoor and outdoor air quality have both suffered from urbanisation. The development of urban areas has also increased energy consumption so that the occupants of buildings can enjoy indoor thermal comfort and air quality that they need via air conditioning systems. This book offers solutions to the recent increase in the number of heat islands in hot and humid regions.
Urban Hydrology, Watershed Management and Socio-Economic Aspects
by Vijay P. Singh Arup K. Sarma Suresh A. Kartha Rajib K. BhattacharjyaThe book brings together high-quality research articles on advanced hydrological analysis, advanced computational methods, and the ecological and sociological aspects of urban watershed management under one umbrella. The rapid pace of urbanization, not accompanied by any farsighted, holistic plan, has reduced many cities in the developing world into multi-hazard areas. The most perceptible consequence of urbanization is the change in land-use and land cover, which in turn impacts hydrological systems. Accordingly, scientific studies on urban hydrology with due emphasis on ecological and sociological aspects under changing climate are vital to the appropriate design of urban landscapes and civil infrastructure works. This book addresses precisely these issues, offering a useful guide for environmentalists, hydrologists, and a broad range of socio-economic scientists exploring the environmental vulnerabilities arising from urbanization.
Urban Jungle: The History and Future of Nature in the City
by Ben WilsonIn this exhilarating look at cities, past and future, Ben Wilson proposes that, in our world of rising seas and threatening weather, the natural world may prove the city's savior.Since the beginning of civilization, humans have built cities to wall nature out, then glorified it in beloved but quite artificial parks. In Urban Jungle Ben Wilson—the author of Metropolis, a seven-thousand-year history of cities that the Wall Street Journal called &“a towering achievement&”—looks to the fraught relationship between nature and the city for clues to how the planet can survive in an age of climate crisis.Whether it was the market farmers of Paris, Germans in medieval forest cities, or the Aztecs in the floating city of Tenochtitlan, pre-modern humans had an essential bond with nature. But when the day came that water was piped in and food flown from distant fields, that relationship was lost. Today, urban areas are the fastest-growing habitat on Earth and in Urban Jungle Ben Wilson finds that we are at last acknowledging that human engineering is not enough to protect us from extremes of weather. He takes us to places where efforts to rewild the city are under way: to Los Angeles, where the city&’s concrete river will run blue again, to New York City, where a bleak landfill will be a vast grassland preserve. The pinnacle of this strategy will be Amsterdam: a city that is its own ecosystem, that makes no waste and produces its own energy. In many cities, Wilson finds, nature is already thriving. Koalas are settling in Brisbane, wild boar may raid your picnic in Berlin. Green canopies, wildflowers, wildlife: the things that will help cities survive, he notes, also make people happy.Urban Jungle offers the pleasures of history—how backyard gardens spread exotic species all over the world, how war produces biodiversity—alongside a fantastic vision of the lush green cities of our future. Climate change, Ben Wilson believes, is only the latest chapter in the dramatic human story of nature and the city.
Urban Land Use: Community-Based Planning
by Kimberly EtingoffThis compendium volume, Urban Land Use: Community-Based Planning, covers a range of land use planning and community engagement issues. Part I explores the connections between land use decisions and consequences for urban residents, particularly in the areas of health and health equity. The chapters in Part II provide a closer look at community land use planning practice in several case studies. Part III offers several practical and innovative tools for integrating community decisions into land use planning.
Urban Landscape Ecology: Science, policy and practice (Routledge Studies in Urban Ecology)
by Robert A. Francis Michael A. Chadwick James D.A. MillingtonThe growth of cities poses ever-increasing challenges for the natural environment on which they impact and depend, not only within their boundaries but also in surrounding peri-urban areas. Landscape ecology – the study of interactions across space and time between the structure and function of physical, biological and cultural components of landscapes – has a pivotal role to play in identifying sustainable solutions. This book brings together examples of research at the cutting edge of urban landscape ecology across multiple contexts that investigate the state, maintenance and restoration of healthy and functional natural environments across urban and peri-urban landscapes. An explicit focus is on urban landscapes in contrast to other books which have considered urban ecosystems and ecology without specific focus on spatial connections. It integrates research and perspectives from across academia, public and private practitioners of urban conservation, planning and design. It provides a much needed summary of current thinking on how urban landscapes can provide the foundation of sustained economic growth, prospering communities and personal well-being.
Urban Microclimate Modelling for Comfort and Energy Studies
by Massimo Palme Agnese SalvatiThis book discusses urban microclimate and heat-related risks in urban areas, brought on by the combination of global climate change effects and local modification of climate determined by extensive urbanization such as the ‘Urban heat island’ phenomenon. This matter is relevant to almost all urbanized areas in the world, where the increase of urban population and air temperature is expected to endanger both the overall health of the population and the energy supply for the functioning of urban systems. The book details the inter-relationship between urban morphology, microclimate and building energy performance and presents a multidisciplinary approach that brings together Urban Climatology, Engineering and Architectural knowledge to support the development of reliable models and tools for research and practice. This book is a useful tool for architects and building energy modelers, urban planners and geographers who need a practical guide to realize basic urban microclimate simulation for use in both academic research and planning practice.
Urban Mining Systems
by Takashi Nakamura Kohmei HaladaThis book focuses on the fundamental concept of and current endeavors in "urban mining" among those who are interested in both metal resources and ecology. Systems for recycling and reusing precious metals and rare-earth minerals contained in used and discarded electronics are introduced in this book. The target audience is not academic researchers in the resource management and ecology fields but, rather, citizens who are concerned about our future environment and want to do something for the future.
Urban Mining and Sustainable Waste Management
by Sadhan Kumar GhoshThis book gathers selected high-quality research papers presented at the IconSWM 2018 conference, which explore various aspects of urban mining. In addition, they discuss how to achieve sustainable waste management systems, urban mining, landfill mining, material recovery, circular economy, etc., with the aid of effective waste management practices. Additional topics covered include maximum resource circulation and efficiency, key differences between landfill mining and urban mining, and how urban mining can be combined with the concepts of circular economy and sustainability.
Urban Mobility: How the iPhone, COVID, and Climate Changed Everything
by Shauna Brail Betsy DonaldUrban Mobility sheds light on mobility in twenty-first-century Canadian cities. The book explores the profound changes associated with technological innovation, pandemic-induced impacts on travel behaviour, and the urgent need for mobility to respond meaningfully to the climate crisis. Featuring contributions from leading Canadian and American scholars and researchers, this edited collection traverses disciplines including geography, engineering, management, policy studies, political science, and urban planning. Chapters illuminate novel research findings related to a variety of modes of mobility, including public transit, e-scooters, bike-sharing, ride-hailing, and autonomous vehicles. Contributors draw out the connections between urban challenges, technological change, societal need, and governance mechanisms. The collection demonstrates why the smart phone, COVID-19, and climate present a crucial lens through which we can understand the present and future of urban mobility. The way we move in cities has been disrupted and altered because of technological innovation, the lingering impacts of COVID-19, and efforts to reduce transport-related emissions. Urban Mobility concludes that the path forward requires good public policy from all levels of government, working in partnership with the private sector and non-profits to direct and address the best urban mobility framework for Canadian cities.
Urban Nature Conservation: Landscape Management in the Urban Countryside
by Stephen Forbes Tony KendleUrban nature conservation is a field that has grown rapidly in importance over the past 20 years and will continue to do so in the coming years as landscape ecology and greenspace planning become established disciplines. A widespread concern and interest in the wild plants and animal life found in urban areas now influences the policies and practices of land management organizations. This book provides a comprehensive overview of the subject. It will assist professionals in formulating strategic management policies that integrate urban nature conservation into the wider context of landscape management and urban planning.
Urban Nature: Enriching Belonging, Wellbeing and Bioculture (Routledge Studies in Urban Ecology)
by Michelle L. Cocks and Charlie M. ShackletonThis book showcases the diversity of ways in which urban residents from varying cultural contexts view, interact, engage with and give meaning to urban nature, aiming to counterbalance the dominance of Western depictions and values of urban nature and design. Urban nature has up to now largely been defined, planned and managed in a way that is heavily dominated by Western understandings, values and appreciations, which has spread through colonialism and globalisation. As cities increasingly represent a diversity of cultures, and urban nature is being increasingly recognised as contributing to residents' wellbeing, belonging and overall quality of life, it is important to consider the numerous ways in which urban nature is understood and appreciated. This collection of case studies includes examples from Africa, Asia, Europe, North and South America, and reflects on the multi-dimensional aspects of engagements with urban nature through a biocultural diversity lens. The chapters cover several themes such as how engagements with nature contribute to a sense of wellbeing and belonging; the implications that diversity has on the provision, design and management of urban environments; and the threats inhibiting residents’ abilities to engage meaningfully with nature. The book challenges the dominant discourse, Western ideological understandings and meta-narratives of modernisation and unilineal urban transitions. A timely addition to the literature, Urban Nature: Enriching Belonging, Wellbeing and Bioculture offers an alternative to Western ideological understandings of nature and values and will be of great interest to those working in human and environmental urban ecology. It will also be key reading for students in the relevant fields of anthropology, development studies, geography, social ecology and urban studies.
Urban Nature: New Directions for City Futures
by Kes McCormick Bernadett Kiss Yuliya Voytenko Palgan Harriet Bulkeley McKenna Davis Rob Raven Andrés Luque-Ayala Kathrin HörschelmannThis introductory textbook with a global scope aims to train students of geography, sustainability, and urban and environmental studies to re-imagine and transform cities to meet climate, biodiversity, and sustainability challenges. A dedicated team of authors critically examine the relationships between nature and urban areas, sharing an inspiring account of how nature helps us re-think our cities and their futures. Prior to this textbook, literature for courses covering urban nature was written by and for practitioners, whereas this textbook is written by experienced course instructors specifically to be accessible to diverse students. The textbook is illustrated with numerous photos and figures which bring key topics, challenges, and opportunities to life. It contains focus boxes and case studies from every continent, offering students an international scope and multiple entry points into the field. Chapters conclude with thought-provoking follow-up questions and recommended reading. The authors provide an array of supplementary online resources.
Urban Natures: Living the More-than-Human City (Urban Anthropology Unbound #1)
by Ida Nilstad Pettersen Ferne Edwards, Lucia Alexandra PopartanEfforts to create greener urban spaces have historically taken many forms, often disorganized and undisciplined. Recently, however, the push towards greener cities has evolved into a more cohesive movement. Drawing from multidisciplinary case studies, Urban Natures examines the possibilities of an ethical lively multi-species city with the understanding that humanity’s relationship to nature is politically constructed. Covering a wide range of sectors, cities, and urban spaces, as well as topics ranging from edible cities to issues of power, and more-than-human methodologies, this volume pushes our imagination of a green urban future.
Urban Planning for Climate Change (Routledge Advances in Climate Change Research)
by Barbara NormanThis book tackles the future challenges and opportunities for planning our cities and towns in a changing climate and recommends key actions for more resilient urban futures. Urban Planning for Climate Change focusses on how urban planning is fundamental to action on climate change. In doing so it particularly looks at current practice and opportunities for innovation and capacity building in the future - carbon neutral development, building back better and creating more resilient urban settlements around the world. The complex challenge of possible urban resettlement from the impact of climate change is covered as a special issue bringing a focus on adaptation, working with nature and delivering real action on climate change with local communities. Norman recommends ten essential actions for urban planning for climate change along with some suggestions to inspire the next generations to embrace these opportunities with creativity and innovation. Featuring key messages and implications for practice in each chapter, this book will be of great interest to students, scholars, practitioners and communities involved in planning more climate resilient urban and regional futures.
Urban Political Ecology in the Anthropo-obscene: Interruptions and Possibilities (Questioning Cities)
by Erik Swyngedouw Henrik ErnstsonUrban Political Ecology in the Anthropo-obscene: Interruptions and Possibilities centres on how to organize anew the articulation between emancipatory theory and political activism. Across its theoretical and empirical chapters, written by leading scholars from anthropology, geography, urban studies, and political science, the book explores new political possibilities that are opening up in an age marked by proliferating contestations, sharpening socio-ecological inequalities, and planetary processes of urbanization and environmental change. A deepened conversation between urban environmental studies and political theory is mobilized to chart a radically new direction for the field of urban political ecology and cognate disciplines: What could emancipatory politics be about in our time? What does a return of the political under the aegis of equality and freedom signal today in theory and in practice? How do political movements emerge that could re-invent equality and freedom as actually existing socio-ecological practices? The hope is to contribute discussions that can expand and rearrange critical environmental studies to remain relevant in a time of deepening depoliticization and the rise of post-truth politics. Urban Political Ecology in the Anthropo-obscene will be of interest to postgraduates, established scholars, and upper level undergraduates from any discipline or field with an interest in the interface between the urban, the environment, and the political, including: geography, urban studies, environmental studies, and political science.
Urban Pollution
by Eveline Da¼rr Rivke JaffeRe-examining Mary Douglas' work on pollution and concepts of purity, this volume explores modern expressions of these themes in urban areas, examining the intersections of material and cultural pollution. It presents ethnographic case studies from a range of cities affected by globalization processes such as neoliberal urban policies, privatization of urban space, continued migration and spatialized ethnic tension. What has changed since the appearance of Purity and Danger? How have anthropological views on pollution changed accordingly? This volume focuses on cultural meanings and values that are attached to conceptions of 'clean' and 'dirty', purity and impurity, healthy and unhealthy environments, and addresses the implications of pollution with regard to discrimination, class, urban poverty, social hierarchies and ethnic segregation in cities.