1 Introduction
In recent years, with rapid urbanization, the global landscape of science and technology, industry, energy, and finance has undergone profound changes. Concurrently, emergencies or sudden events including natural disasters (e.g., heat waves, droughts, storms, floods, sea level rise, hurricanes, earthquakes, pandemics), humaninduced disasters (e.g., oil spills, nuclear contamination, ecosystem collapses), and socio-economic crises (e.g., political conflicts, social frictions, and economic downturns) are posing unrelenting threats to regional environment and security. The concept of "resilient city, " as an important principle in contemporary urban planning, emphasizes that the capacity of urban systems to absorb the impacts and pressures caused by uncertain events while maintaining essential functions, structures, and characteristics
[1]. The construction of resilient cities has become an indispensable approach to achieving sustainable urban development.
The Resilient Cities Congress, initiated by ICLEI (International Council for Local Environment Initiatives)–Local Governments for Sustainability (ICLEI hereafter), was first held in Bonn, Germany in 2010, as the first annual global forum dedicated to resilient cities studies
[2]. In 2020, the Resilient Cities Congress was renamed the "Daring Cities, " with the aim of building on the legacy of the Resilient Cities Congress series, enhancing the leadership role of governments, researchers, business leaders, and community organizers in urban decision-making process when responding to emergencies or sudden events, and forming new methods of urban governance and multi-stakeholder partnership models
[3]. The Resilient Cities Congress series has urged and witnessed the development and transition of resilience concepts, making it become a mainstream policy and paradigm influencing planning decisions and urban governance from simply a topic of urban planning
[4]. The Resilient Cities Congress series not only provide a global platform for governors, officials, and scholars concerned with resilient city research and practice to exchange research results, showcase practice cases, and share technological innovations, but also continuously track the progress of local achievements in sustainable development and resilience goals. However, few studies have conducted systematic review or experience summarization from the materials and outcomes of the Resilient Cities Congress series and relevant policies and actions in the overall process of resilient city development. Therefore, this study comprehensively compiles the latest international consensus, research hotspots, and action cases gathered at the Resilient Cities Congress series and Daring Cities from 2010 to 2023, and accordingly divides the global resilient city development into three phases, and summarizes the global experience of resilience actions, offering a cutting-edge perspective and empirical references for China's resilient city development.
2 The Concept and Connotation of Resilient City
The concept of "resilience" was first proposed by ecologist Crawford Stanley Holling to measure the ability of ecosystems to absorb changes of various factors and still persist
[5]. Later, with the expansion of its application scope from Systems Ecology to Engineering, Social Sciences, Economy, and other fields, the connotation of "resilience" has been continuously enriched
[6][7]. Broadly speaking, the concept of "resilience" has evolved from "engineering resilience" (before 1973) to "ecological resilience" (1973 ~ 1998) and further to "social-ecological resilience" (after 1998), while developing richer conceptual and extended meanings as the adaptive cycle framework established in the socialecological resilience phase has been adopted by other disciplines
[8]. Specifically, engineering resilience emphasizes the capacity of a system to return to its original state, measuring resilience in terms of how quickly a system recovers to equilibrium after disturbance, and is considered a form of "centripetal" stability.
[5][9][10] Unlike the single ultimate equilibrium state underscored in engineering resilience, ecological resilience recognizes the existence of multiple equilibrium states, measured by the extent or degree of disturbance a system can withstand before transitioning from the current state to another; it views equilibrium as a series of polycentric, progressive development stages, and emphasizes the capacity of sustainability.
[5][9][11] Social-ecological resilience, emerging from the theory of "complex adaptive system, " views equilibrium as a decentered, cyclical evolutionary process, while resilience as the capacity of complex social-ecological systems to adapt to changes and stay within critical thresholds in response to pressures and constraints
[12]~
[14]; which can help cities better balance the sustainable development in environmental, social, and economic dimensions. Although the research scope and connotations of the above concepts differ, the academia widely recognized that the essence of "resilience" is a system's capacity to absorb external shocks and maintain its main functions during crises
[15].
With the gradual integration of resilience concepts into the studies on cities, as typical social-ecological systems, coupled with related application in the fields of urbanization, urban systems, sustainable development, and climate change response, "resilient city" has begun to receive widespread attention from scholars at home and abroad
[16]. ICLEI posits that resilient cities are those capable of absorbing and recovering from any shock or stress, while maintaining their essential functions, structures, and identity, adapting and thriving to continual changes
[2]. The construction of resilient cities, as an important component of urban planning and governance, is also an effective complement and extension of sustainable urban development
[17].
3 Evolution and Development of Resilient Cities
3.1 Global Commitment and Framework Establishment: City Transformation and Paradigm Shift (2010 ~ 2016)
With the joint efforts of countries around the world over these years, "all levels of government are now united to decrease disaster risk and losses, to reduce the impacts of climate change, and to pursue inclusive, sustainable, and resilient development, " covering social, economic, and environmental sustainability
[18]. Global frameworks developed during this period include the Sendai Framework for Disaster Risk Reduction 2015–2030 (adopted in 2015), which established four prioritized areas for actions and shifts the focus of the disaster response from loss management to risk reduction
[19]; the 2030 Agenda for Sustainable Development (adopted in 2015), which announced 17 Sustainable Development Goals (SDGs) and 169 targets, determined to end poverty in all its forms and dimensions
[20]; the Paris Agreement (adopted in 2015) based on sustainable development and poverty eradication, which established a long-term goal to achieve a balance between anthropogenic emissions and removals of greenhouse gases, and aimed to make financial flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development
[21]; the New Urban Agenda (adopted in 2016), which proposed a vision of cities for all by building urban governance structure, to promote a paradigm shift toward more resilient, sustainable, inclusive, and equitable development
[22] (Fig.1). The establishment of such global commitments and frameworks highlights the importance that governments and international organizations attach to sustainable and resilient development, while pointing the way to a global urban transformation that sees local governments as key stakeholders and contributors. It also promotes multi-level governance and multi-stakeholder collaboration, which stress the "leadership role" of national governments, while recognizing the significance of decentralization and national urban policy
[23].
Upon established resilient city studies
[4], this study decomposes the resilient city system into economic, social, ecological, infrastructure, institutional, and cyber subsystems
[24][25], and corresponds to the 17 SDGs
[20] to the six subsystems (Tab.1). It can be found that the first five subsystems are concerned correspondingly with the urban economic and industrial systems
[26], the community/public capacity to cope with stresses
[27], the maintenance of ecosystem services
[28], the resilience of the built-up urban structure and key infrastructure
[27], and the capacity of governmental and non-governmental organizations to act on risks in a preventive/organizational and managerial manner
[29]. For cyber resilience, the sixth subsystem, the development of information technology has brought unprecedented opportunities and challenges to cities: on the one hand, the Internet of Things (IoT), big data, and cloud computing have improved the efficiency of city management, the level of city intelligence, and the quality of city life; on the other hand, there might be severer risks in information and communications technologies, as cyber-attacks and leakage of sensitive city information and personal privacy data have increased dramatically
[30][31]. Cyber resilience, which emphasizes the ability of communication technology systems to maintain services in the face of cyber-attacks, natural or man-made disruptions
[4], is becoming an indispensable supplement to the SDGs. Focusing on cyber resilience not only ensures safer cities, but also promotes innovation and explores the path of digital transformation in cities.
3.2 Path Exploration and Action: Collaborative Initiatives and Practice Monitoring (2016 ~ 2019)
In 2016, New Urban Agenda, a global framework for resilient city development was adopted, marked the shift of focus of resilient city development from establishing global commitments and framework towards collaborative implementation of plans and finding of pathways
[32]. International collaborative initiative such as Transformative Actions Program, Climate KIC initiative
[18], Connecting Nature
[33][34], UrbanByNature, and East Asia Clean Air Cities
[35] have been launched to strengthen the basis for the engagement and cooperation at national, regional, and local levels. These efforts have deepened the ground for the comprehensive development of resilient cities among multi-stakeholders including public and private sectors, communities, and citizens, clarified the respective responsibilities. During this period, a great number of countries and cities, together with relevant international organizations focused on the dimensions of economic, social, ecological, infrastructure, institutional, and cyber resilience of resilient city construction, and facilitated the widespread practice for inclusive, sustainable, and resilient urban development.
This study summarizes the hot topics of global resilient cities research and practice and selected action cases gathered by the Resilient Cities Congress series (Tab.2)
[4][18][32][35][36]. It is witnessed that the development of resilient cities actively responds to urgent climate change at the policy level, manifested in the formulation of climate-adaptation planning and strategies, providing scientific and overarching guidance for the implementation of actions. At the practical level, the focus is on risk management and the development of various urban subsystems by carrying out risk assessment and disaster prevention to reduce losses, while identifying high-risk and vulnerable areas for targeted promotion of resilience, adaptability, and recovery of cities. In the development of resilient city subsystems, it prioritizes advocating for cooperative mechanisms based on multi-level governance and by multiple actors including private enterprises, insurance sector, communities, and the public. Active exploration is conducted in fields of the circular development of green economy, fair and inclusive social governance, Nature-based Solutions, eco-mobility, infrastructure upgrading and energy security, food health and sanitation management, and open data sharing and governance in the age of digitalization, aiming to pursue the coordination and sustainability of economic, social, and environmental development.
3.3 Experience Translation and Adaption: Daring Exploration and Innovation (2020 to present)
In 2020, the Resilient Cities Congress was held as online forums and was renamed the "Daring Cities, " with the focus shifted towards summarizing the existing resilient city actions over the past few years and the sharing of exemplary efforts and innovative resources. Building upon the experience and legacy accumulated in the previous decade, Daring Cities, co-organized by the municipal government of Bonn, Germany and ICLEI–Local Governments for Sustainability, continues to mobilize multiple-level governments and multiple stakeholders to boldly explore urban risks and disaster response strategies
[37]. In the face of various "black-swan" risks, "daring" signifies ambitiously exploring and addressing uncertainties, and represents a unanimous belief and a firm call for action on crises such as climate change, which needs the engagement from UN, leaders of involved nations, local governors to communities and the public
[3]. The 2023 Daring Cities saw the participation of more than 322 cities from 97 countries. It gathered perspectives on global climate actions, with activities such as the Voices of Daring Cities and Daring City Podcast, to turn pioneer cities' empirical exemplary action experiences into common resources adaptable and practical by other cities and communities
[38].
In addition, the Daring Cities highlights the critical role of alllevel decision makers of cities in urban disaster risk reduction and climate adaptation capabilities, and the importance of building allied partnerships. It provides a new framework for resilient city action framework and a reference for governance methods. Under the belief of "know more, act better, and lead together"
[3], the framework emphasizes the sharing and acquisition of case knowledge to improve the understanding of climate change crises and coping strategies, and to support and motivate effective actions. Supported by this foundational framework, the Daring Cities has discussed about a number of themes such as Naturebased Solutions, circular economy, food systems, social cohesion, sustainable urban mobility, and the opportunities and challenges posed by digitization, and promoted and shared exemplary local actions, resilience-building cases, and experiences in responding to disaster risks
[3].
Synthesizing the cases of global pioneering resilient city and regional construction cases from the Daring Cities, the experience of resilience actions can be summarized in the following five aspects.
1) Multi-level governance and multi-stakeholder collaboration. Improving multi-level governance mechanisms at the global, national, regional and local levels, carrying out multi-level actions, and guiding and promoting cooperation among governments, private sectors, and communities are key to addressing the challenges of disaster risks and enhancing cities' resilience and adaptability against disasters.
2) Developing circular economy, and financing resilience and insuring cities. To alleviate environmental pressures, it is critical to develop circular economy that relies on eco-friendly resources, promote green production, consumption, and employment modes, and reduce carbon emissions; moreover, improving the financial literacy of local governments, enhancing effective communication with financial institutions and the insurance industry, and formulating local financing mechanism for adaptive resilience programs and ensuring adequate financial support are necessary conditions for building resilient cities.
3) Nature-based Solutions. Enhancing urban ecological resilience by restoring, protecting, and managing ecosystems and biodiversity, enabling cities and natural ecosystems to effectively adapt to and mitigate crises such as climate change, are fundamental to the construction of resilient cities.
4) Equal opportunities and access to basic services. To enhance social resilience that is essential to resilient city construction and matters people's well-beings, it should prioritize the fulfillment for the needs of vulnerable groups and addressing issues such as poverty, social exclusion, and unemployment among resettled urban residents; strengthen infrastructure construction to ensure that all residents have equal access to safe food, health care, medical service, education and employment opportunities, etc.; and improve the social cohesion, inclusiveness, and engagement of cities and communities.
5) Open data and strong data governance capability. Main measures include harnessing the application potential of multisource big data and communication technologies to efficiently support governments in open, transparent, and reliable urban planning decision-making and governance; addressing cybersecurity and data privacy issues by increasing investment and maintenance of the protection and technology of reliable information, improving the relevant industry standards, and regulating the environment for cyber resilience development. Also, maintaining critical reflection on the progress of new technologies, paying attention to the limitations and negative effects of data and algorithms, recognizing the irreplaceability of human's independent thinking and analytical decision-making, and scientifically utilizing the synergistic effect of artificial intelligence to empower the digitalization, intelligence, and sustainable development of resilient cities are also important.
4 Conclusions and Discussion
According to UN's statistics and projections, 68% of the population will reside in urban areas by 2050, and the growth of the world's urban population in the next few decades will be concentrated in developing regions of Africa, South Asia, East Asia, and Southeast Asia
[39]. In this context, the construction of resilient cities emerges as a critical aspect for achieving sustainable urban development, particularly in developing countries
[4] which are socially and economically fragile, insufficient to withstand disaster risks, and more vulnerable to external disturbances and negative impacts. Thus, there is an urgent need for these countries to learn from and adopt the experience of resilient city development into effective local actions.
Throughout the previous Resilient Cities Congress series, the development of resilient cities in the past decade has evolved from theoretical exploration, framework establishment, and formulation of target strategies towards the implementation of regional and local actions and follow-up assessment, while integrating theoretical research into political decision-making that has in turn driven the progress of urban sustainable development. During this period, more than ten authoritative international climate conventions and initiatives were launched (Fig.2). Resilience building and financing based on multi-level actions, multi-stakeholder collaboration, and community participation have consistently been the core themes of the Resilient Cities Congress series, and also the pivotal areas for resilient city development. Emphasizing the role of local governments as the leading actors in such actions and taking into account the social, environmental, and economic dimensions, multidisciplinary and cross-sectoral cooperation and innovation is the key to achieving resilience and overall sustainable development.
Nowadays, with the development of big data and analytics technology, the construction of resilient cities not only requires deepening implementation at economic and social aspects, but also necessitates a series of effective measures in the field of cyber resilience to seize opportunities and mitigate risks, where information technology can and will play a vital role. For example, by promoting the integration and interactive sharing of multi-source data, enhancing information protection and technology governance capabilities, and improving technological governance mechanisms, a healthy and safe cyber development environment can be built and thus cyber resilience and the sustainable development of cities can be strengthened in the digital era.
Looking ahead, it is crucial to further promote local resilience actions and practices, and to put more efforts in filling the gaps of empirical research on resilient cities. It is of great practical significance to translate international resilience development results and action experience into localized efforts both in theory and practice at the national, regional, and city scales, so as to promote the full implementation of climate action and resilience building worldwide. China's resilient city research has gone from the recognition and introduction of resilience-related concepts to its own theoretical establishment and application practice. Through the joint efforts by governments, scholars, and technicians, China has advanced the conceptual connotation development of resilient cities in economic, social, and ecological dimensions, yielding substantial research and practice results while the construction of resilient cities becoming a national policy and strategic agenda. However, at the macro level, there remains a gap between the interpretation of resilient city policies and the implementation in the multi-level governance process at national, regional, and local scales; also, the issue of unbalanced and inadequate development of resilient city construction is still outstanding. At the micro level, the spontaneous community governance capacity and the public's participatory initiatives in coping with the risks have yet to be tapped. These problems should be responded to through the establishment of a comprehensive, systematic, and adaptive framework and step-by-step action plans at multiple scales, from community, local, regional to national. The experiences and results contributed by the Resilient Cities Congress series not only provide methodological guidance for China's resilient city development and governance, but also offer a reference of pathways for more developing countries and transitioning countries. Notably, Chinese cities are often large in number and scale and with complicated and unique localities. Additionally, considering the differences in institutional, cultural, economic, and social backgrounds, as well as public needs, between China and the pioneer countries, there is an urgent need for China to formulate flexible and differentiated methods and targeted solutions in the process of resilient city construction.
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