Modern cities exemplify complex systems, integrating interdependent social, economic, infrastructural, and ecological components that continuously evolve in response to rapid urbanization, climate change, and technological innovation. Urban environments are characterized by nonlinear dynamics, emergent behaviors, and feedback loops that create both opportunities and challenges for sustainability, resilience, and equitable growth. Understanding these dynamics is vital for designing smarter, safer, and more livable cities of the future.

At the city scale, challenges such as air pollution, resource consumption, citizen health, and social inequality demand immediate attention. Urban infrastructures –energy, housing, transport, and digital networks– interact in nonlinear ways that shape collective behavior and urban form. Understanding how these systems and interdependencies give rise to emergent patterns is essential for reimagining cities as adaptive, self-organizing systems capable of achieving sustainability, resilience, and equity. Concepts such as distributed energy systems, circular economies, and polycentric urban forms illustrate how local interactions can enhance global urban performance.

At the regional scale, urban systems extend across interconnected metropolitan areas, peri-urban zones, and the urban–rural continuum. Flows of people, resources and information couple spatially distant regions through complex feedbacks that influence development trajectories and ecological footprints. Modeling and governing these multi-scale interactions is crucial for addressing regional resilience, land-use transitions, and socio-economic cohesion.

At the global scale, cities are embedded in planetary networks of exchange—of materials, energy, ideas, and ecosystems. These networks generate cascading effects that link local decisions to global environmental change. Understanding the structural and dynamical properties of these interurban and socio-ecological systems through the lens of complexity science remains an open frontier, with implications for climate adaptation, resource governance, and sustainable globalization.

By integrating theoretical advances in complex systems with data-driven urban science and policy-relevant perspectives, this Research Topic aims to foster the development of innovative tools, models, and frameworks to understand and manage urban complexity. It seeks to bridge scales and disciplines to better capture the adaptive and interconnected nature of cities.

This Research Topic seeks to advance our understanding of urban systems as complex, adaptive, and evolving entities, where social, technological, infrastructural, and ecological dimensions interact through nonlinear dynamics and feedback loops. By integrating perspectives from physics, engineering, computer science, ecology, social sciences, and urban studies, it aims to generate theoretical and practical insights into how cities self-organize, transform, and adapt under environmental, technological, and societal pressures.

The collection encourages submissions that bridge theory and application, combining quantitative modeling, empirical analysis, and qualitative or participatory approaches. Contributions may explore cross-scale interactions, emergent behaviors, resilient and adaptive infrastructures, and innovative frameworks for sustainable and equitable urban governance. Particular emphasis is placed on integrative approaches that reveal how complexity thinking informs urban design, planning, and decision-making amid uncertainty and rapid change.

Areas of interest include but are not limited to:
● Urban networks, spatial dynamics, and emergent behaviors
● Urban morphology, land-use patterns, and network-based representations of city structure
● Network perspectives in infrastructure interdependence and service allocation
● Complex interactions among social, infrastructural, ecological, and technological subsystems
● Digital twins, agent-based models, and machine learning for urban system analysis
● Active mobility and last-mile delivery sustainable solutions,
● Data-driven modeling of city processes, urban metabolism, and systemic interdependencies
● Robustness, resilience, adaptability, and tipping points in urban and regional systems
● Urban resilience and adaptability to climate risks and natural hazards
● Urban system responses to economic, financial, and societal shocks
● Urban ecology, environmental dynamics, and ecosystem complexity in cities
● Cross-scale coupling between local actions and regional or global urban dynamics
● Energy, resource, and information flows in coupled human-environment systems
● Governance, policy, and participatory approaches for managing complex urban transformations
● Integration of quantitative and qualitative methods in urban complexity research

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Complex Urban Systems: Form, Function, and Resilience