The "Spatial Blind Spot" of Urban Sustainability Science: Why the Built Environment Cannot Just Be a Background

Spatial Blind Spots in Urban Sustainability Science: Why the Built Environment Cannot Be Merely Background

Imagine that, to protect Venice, a world heritage site, from the threat of flooding, the Italian government built the multi-billion-euro MOSE flood barrier system. These mobile barriers can hold back abnormally high tides, but they simultaneously alter the historic waterfront landscape and disturb the lagoon's delicate ecology. Is this conflict simply a trade-off between social preferences and ecological functions? Clearly not. It is rooted in Venice's unique urban morphology—narrow canals, ancient buildings, fragile foundations—material entities that possess their own logic and memory. Yet existing urban sustainability science, particularly the social-ecological system (SES) framework derived from common-pool resource management, often struggles to adequately diagnose such conflicts, because this framework treats the built environment as a passive background rather than a system with agency.

This cognitive misalignment is no small matter. As global urbanization enters an unprecedented stage, cities have become the main battleground for sustainable development and climate action. From Jakarta's slow subsidence to New York's waterfront redevelopment, from Shenzhen's rapid expansion to Singapore's land reclamation, the form, materiality, and history of urban space are profoundly shaping the interactions between social and ecological systems. If our theoretical tools cannot understand how space itself operates, we will fall into a predicament of "the blind men and the elephant."

From Common-Pool Resources to Cities: The Migration and Transformation of a Framework

The social-ecological system framework has its roots in Elinor Ostrom's pioneering work on the governance of common-pool resources, such as the collective management of fisheries, forests, and irrigation systems. In this original context, the ecosystem itself is the resource, and human institutions are interwoven with natural systems. But when this framework was migrated to the urban context, problems emerged. Cities are highly human-modified environments; the built environment is not merely a passive carrier of "ecosystems"—it is itself a complex system with configurational logic, materiality, and historicity. However, a systematic review of 630 urban SES studies shows that over 90% of the literature does not treat the built environment as a dynamic system. Among them, 61.8% of the studies involve no or almost no spatial interaction, with space serving only as locational description; 30% incorporate spatial variables such as land use or infrastructure into consideration but do not theorize them; and only 8.1% engage in deep theoretical or analytical treatment of spatial systems.

This figure is striking. It reveals that although urban sustainability science claims to understand the "social-ecological" interweaving, it actually reduces space to an instrumental container. This is not accidental but is determined by the framework's origins. The SES framework was designed to analyze the collective governance of natural resources; it focuses on variables such as institutional rules, resource units, and user groups, but has never considered how the form, materials, and memory of the built environment affect governance outcomes. When the discipline migrated from natural ecosystems to urban built environments, this theoretical "maladaptation" was systematically ignored.### Space as System: Form, Materiality, and History

To fill this gap, the paper proposes the Social-Ecological-Spatial System (SESS) framework, introducing the spatial system as a third ontological domain. This framework co-constructs three dimensions of the spatial system from urban morphology, the theory of space production, and urban metabolism: morphology and configuration, materiality and metabolism, and historicity and memory. These three dimensions correspond respectively to the geometric logic, physical fluxes, and temporal depth of urban space.

Urban morphology tells us that street networks, plot divisions, and building arrangements form a distinctive spatial configuration that influences traffic flows, social interactions, and even crime rates. Materiality and metabolism focus on how cities consume and transform resources—water, energy, building materials—and how these material flows shape environmental outcomes. Historicity and memory remind us that urban space is a sedimentation of historical processes; the texture of old urban districts, architectural heritage, and collective memory all exert real influence. These attributes cannot be reduced to purely ecological processes or infrastructural functions; they must be analyzed independently.

Consider the MOSE project in Venice as an example. This flood barrier is both infrastructure and a massive intervention that transforms urban space. It alters the visual form of the historic waterfront landscape and affects sediment deposition and ecological balance in the lagoon. From the SESS framework perspective, this conflict is not merely a trade-off between flood protection and ecology, but a deep contradiction jointly shaped by Venice's spatial form (the water-city structure), material metabolism (the tidal-maintained ecological cycle), and historical memory (its identity as a World Heritage site). Existing frameworks tend to disaggregate these issues into technical or preference problems, while overlooking the intrinsic power of space itself.

Frontiers and Limitations of SETS: Why SESS Is Needed

Of course, urban sustainability science is not unaware of the tensions within the SES framework. Scholars have already proposed the Social-Ecological-Technical Systems (SETS) framework, introducing technical infrastructure as a third domain to capture infrastructure interdependence, cascading failures, and adaptive capacity. The SETS framework has made significant progress in areas such as energy, transportation, and water systems. However, the paper points out that SETS focuses on technical systems, whereas spatial systems are not equivalent to infrastructure. Space is a composite of form, materiality, and history; it encompasses infrastructure yet goes beyond it.For example, a city's road network is not only transportation infrastructure; it is also the skeleton of urban form, determining the accessibility of land parcels and the quality of public space. Road widths, block scales, and building setbacks—these morphological features are not purely determined by technology, but are products of historical planning decisions. Likewise, the preservation of a historic district involves not technical efficiency but spatial memory and identity. The SETS framework may treat historic buildings as a kind of "technology," but the SESS framework regards them as an organic component of the spatial system.

Therefore, SESS is not a substitute for SETS but a complement. SETS helps us understand the interdependence of infrastructure, while SESS helps us understand how spatial form shapes social-ecological outcomes. Both point to the same conclusion: urban sustainability must move beyond the "social-ecological" dichotomy and embrace a more complex reality.

Strategic Implications for the Global Urban Age

From a global perspective, this theoretical shift has profound strategic significance. First, it redefines the decision-making logic of urban climate adaptation. Coastal cities worldwide are investing in flood protection infrastructure, from London's Thames Barrier to Rotterdam's floating buildings, but these projects often focus only on technical efficiency and neglect their long-term impacts on urban spatial form. A poorly designed floodwall can sever waterfront public space, damage historic landscapes, and even trigger social inequity. The spatial system framework requires us to consider the interplay of form, materiality, and history from the outset of planning.

Second, it changes our understanding of urbanization in the Global South. Rapid urbanization often entails large-scale spatial restructuring—reclaiming lakes, demolishing old urban districts, and building standardized residential areas. Under the SES framework, these practices are seen as changes to social-ecological systems, but the SESS framework reveals that space itself is also undergoing dramatic morphological and material transformation. For example, Shenzhen's transformation from a fishing village to a megacity not only changed ecosystems but also created a wholly new logic of spatial configuration, which in turn shapes residents' lifestyles and social relations. Without paying attention to spatial systems, we cannot diagnose the sustainability challenges brought by new urban forms.

Third, it puts forward a new agenda for urban governance. If the built environment is an agentic system, then urban planning cannot be viewed merely as an "intervention"; it must become a continuous learning process. Spatial systems "remember" past decisions—for example, a city's zoning plan can lock in development trajectories for decades to come. This path dependence means that today's spatial decisions must be held accountable for their long-term consequences.

Conclusion: Bringing Space Back to the Core of Sustainability ScienceCities are the most complex human-made systems on Earth. As the paper confirms, our urban sustainability science has, to this day, remained largely "blind" to space. This is not purely an academic issue, but one concerning governance effectiveness. When cities face climate crises, social inequality, and ecological degradation, we can no longer treat the built environment as a neutral backdrop. The proposal of the spatial system framework represents a significant paradigm evolution in urban sustainability science, reminding us that the sustainability of cities depends not only on the balance between society and ecology, but also on how we understand, design, and govern the very spaces that shape daily life.

In the future, we need more research of this kind that brings spatial systems into the analytical framework of urban science. Only in this way can we more accurately diagnose Venice-like complex conflicts, and more wisely plan the next century of cities worldwide.