Mega cities hold paramount importance in China’s national governance system. These urban centers serve as dense spatial hubs where diverse flows—including natural, material, economic, social, and informational currents—intersect and circulate within limited geographical confines, rendering them susceptible to a variety of risks.

Municipal-level “urban giant” Chongqing, for example, spans 82,400 square kilometers—roughly the size of Austria and equivalent to 13 Shanghais or 5 Beijings. Beijing’s jurisdiction is comparable in size to Greece, and its permanent population approaches that of Australia.

Such mega cities commonly feature vast administrative territories governed under unified municipal governments, displaying a distinct “core-periphery” spatial structure where central districts concentrate critical functions like municipal administration and cultural institutions. Confronted with daily passenger flows exceeding tens of millions, the production and living needs of populations surpassing 10 million, and latent risks embedded throughout urban operations, mega city governments bear extraordinary governance pressures.

The hyper-concentration of elements in mega cities tends to give rise to systemic operational risks. By nature, these cities are complex, giant systems where various factors converge. The excessive density of population, capital, and infrastructure, coupled with the high interdependence of utilities like water, electricity, gas, heating, transportation, and communication networks, means that local failures at any node could result in systemic urban paralysis. At the same time, as massive numbers of people and resources converge rapidly in confined spaces, infrastructure becomes strained, social services are prone to overload and breakdown, and social friction costs inevitably rise.

Furthermore, mega cities exhibit strong social heterogeneity, resulting in imbalanced resource allocation. This social heterogeneity is a crucial variable for systemic risks, as diverse groups demonstrate significant disparities in cultural backgrounds, resource access, and risk perception. These differences make it challenging to build effective consensus on public issues and precisely align public service provision with demographic structures. Additionally, spatial and demographic disparities in risk prevention resources further heighten urban vulnerability and magnify systemic risk. When factor concentration surpasses critical thresholds, the pressure and costs of risk prevention and control in mega cities escalate rapidly.

At the same time, mega cities are confronting emerging “non-traditional security” risks. Energy serves as the lifeblood of urban operations, yet supply security is becoming increasingly precarious in these vast urban centers. Financial risks pose another form of systemic vulnerability—as economic engines of their regions and the nation, mega cities aggregate vast flows of capital and accumulate numerous financial institutions. Real estate market fluctuations, local government debt pressures, or operational risks within financial entities can trigger powerful cascades. Just as crucial is cybersecurity—these cities, as major information hubs and data centers, are prime targets for network attacks that could undermine critical urban systems.

Risk governance in mega cities fundamentally aims at a dynamic equilibrium between development and security. It requires both proactive measures against preventable and controllable risks through robust defense mechanisms, and rational approaches to extreme risks by establishing scientifically calibrated protection standards with built-in recovery capacity. Only by adhering to a pragmatic path of targeted interventions, social coordination, and cost-effective solutions can the foundation for mega cities’ sustained stability and long-term prosperity be consolidated.

Wu Xiaolin is a senior research fellow from the Institute of Chinese Path to Modernization at Nankai University.