Urban sustainability science requires a spatial systems framework: a paradigm expansion from social-ecological to social-ecological-spatial

Introduction: The Core Dilemma of Urban Sustainability

Global urbanization is reshaping the Earth's surface at an unprecedented pace. Cities are both engines of economic growth and epicenters of resource consumption, ecological degradation, and social fragmentation. How to balance economic growth, ecological integrity, and social equity has become a central challenge for urban governance in the 21st century. However, existing analytical frameworks often reduce cities to a binary interaction between humans and nature, overlooking the element that occupies the vast majority of urban physical entities—the built environment.

A systematic review article recently published in Communications Sustainability, through quantitative and qualitative analysis of 630 academic papers, reveals this structural flaw: over 90% of urban social-ecological system (SES) studies treat the built environment as a passive backdrop rather than an active system with its own logic of configuration, materiality, and historicity. The study then proposes a social-ecological-spatial system (SESS) framework, positioning the spatial system as a third domain alongside ecology and society. This proposition is not only of academic relevance but also profoundly influences the formulation of global urban strategies.

Why Traditional SES Frameworks Fail in Cities

The social-ecological system framework originates from Elinor Ostrom's groundbreaking work on the governance of common-pool resources. From its inception, the framework presupposed that natural ecosystems are the core resources around which human institutions are organized. However, cities are not forests or fisheries. The street grids, building forms, infrastructure networks, and historical legacies in cities—these artificial constructs are not merely "containers" for ecological processes; they possess independent causal power. A high-rise building can alter local wind fields and sunlight, the physical form of a historic district can influence community identity and social networks, and a city's spatial configuration can even determine population mobility patterns and resource allocation efficiency.

When researchers directly transplant the SES framework to cities, the spatial dimension is reduced to technical variables such as "land use," "infrastructure layout," or "landscape connectivity." This is akin to using a fishpond management manual to design a metropolis—there appears to be a framework, but the essence is lost. The systematic review in the paper confirms this: among the 630 urban SES papers, only 8.1% of studies treated space as a system and subjected it to theoretical analysis. The vast majority either completely ignored space (61.8%) or merely used it as a location or variable (30.0%).

Spatial Systems: Morphology, Materiality, and Historicity

To fill this gap, the paper's authors integrated urban morphology, spatial production theory (Lefebvre), urban metabolism, and complexity science to propose the social-ecological-spatial system framework. This framework defines the spatial system through three interrelated dimensions:- Morphology and Configuration: How spatial structures such as street networks, block scales, and building density influence social interactions and ecological processes. For example, Barcelona’s "superblocks" improved public space quality and reduced traffic emissions by altering road morphology.

• Materiality and Metabolism: Material processes such as building materials, energy flows, and waste cycles. The physical infrastructure of cities (e.g., concrete, steel) not only has a significant carbon footprint, but its aging and renewal also create time-lag effects that impact climate adaptation strategies.
• Historicity and Memory: The built environment is a result of historical sedimentation. Venice's canal walls, London's Victorian sewers, and Beijing's siheyuan—these spatial legacies carry institutional inertia, cultural identity, and path dependence.

The paper uses Venice's MOSE flood barrier as an example to demonstrate the diagnostic power of the SESS framework. The MOSE system is a massive project built to protect the lagoon and historic city from tidal surges, but its permanent alteration of the waterfront landscape, disruption of the lagoon ecosystem, and engineering constraints determined by the scale of historic districts are not purely "technical-ecological" trade-offs. These conflicts are essentially tensions among the three attributes of form, material, and history within the spatial system. Traditional SES or SETS (Social-Ecological-Technical Systems) frameworks struggle to capture this deep contradiction.

Implications for Global Urban Strategy

The proposal of the SESS framework comes at a time when global urban competition has entered a new phase. Cities are no longer merely implementers of national economic policies; they are becoming frontlines for global climate change response, digital governance, and regional security. In this context, neglecting the systemic power of space can lead to strategic misjudgments.

First, infrastructure investment requires a spatial system perspective. Major cities worldwide are undertaking large-scale upgrades to transportation networks, water systems, and energy facilities. However, if only technical efficiency is considered while ignoring the spatial historical fabric and morphological compatibility, it may trigger social exclusion and ecological damage. For example, Paris' "Grand Paris Express" project, while improving regional connectivity, also faces the challenge of balancing spatial equity between historic city centers and suburbs.

Second, climate adaptation planning must incorporate spatial materiality. Flood control and tidal protection measures in coastal cities (such as Singapore's "Sponge City" initiative and New York's seawall system) involve massive material investments. These projects alter existing spatial structures and create long-term carbon lock-in effects. The SESS framework requires decision-makers to integrate material metabolic cycles (e.g., the carbon emissions and durability of concrete) with urban morphological evolution, rather than assessing them in isolation.Third, the spatial governance of cities in the Global South urgently requires a historical dimension. Cities in developing regions have often experienced colonial planning, rapid urbanization, and institutional transformation, with their spatial forms representing an overlay of multiple temporal layers. For example, the street network and land tenure of Dharavi slum in Mumbai, India, are both products of social self-organization and legacies of the colonial period. Any sustainable development intervention that fails to understand this spatial historical memory is highly likely to result in "planning failure."

The Long-Term Significance of Paradigm Shift

From SES to SESS is not merely a patch to the academic framework. It signifies that urban sustainability science is transitioning from a "natural resource management" paradigm to a "spatial civilization governance" paradigm. Cities are no longer just interfaces where society and ecology intersect, but complex organisms shaped by spatial form, material flows, and historical memory.

The 90% neglect rate revealed by this paper is akin to a global warning: our science of cities still fails to see the city itself. When cities compete to become "smart cities," "resilient cities," or "carbon-neutral cities," without a deep understanding of spatial systems, these goals may degenerate into technological utopias.

In the future, urban analysis requires more interdisciplinary integration like SESS. Urban planners, ecologists, sociologists, and engineers must collectively confront the "autonomy" of space—the force that silently operates in streets, bricks, and landmarks, yet determines the fate of cities. Only then can urban sustainability truly move from slogan to reality.

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This article references: Xu, J. & Duan, J. Systematic review supports a spatial system framework for social ecological systems in urban sustainability science. Communications Sustainability 1, 106 (2026).