Resilient Economies Strategies for Sinking Cities and Flood Risks 2025

The scale of sinking cities is immense and uneven in its impacts across continents, countries and local economies. Today, an estimated 6.3 million square kilometres (km²) of land globally is experiencing subsidence, an area equivalent to the combined size of India, Argentina and Japan – affecting an estimated two billion people worldwide.34 Accelerating sea-level rise further compounds this issue. Over the past three decades, the rate of global sea-level rise has more than doubled, now reaching about 3.3mm per year. Projections suggest that levels could reach 16.9cm in the next 30 years.35,36 Critically, in several coastal cities, land is sinking at rates that exceed the pace of sea-level rise, amplifying flood and other risks. Subsidence is not a uniform phenomenon; its impacts are concentrated in specific areas.37 Recent analyses of 99 coastal cities, using data from 2015 and 2020, reveal that 33 cities are subsiding at rates equal to or up to five times faster than global sea-level rise. For example, coastal Shanghai has recorded areas with subsidence rates of up to 10mm per year. The fastest rates are observed in South, South-East and East Asian cities.38 In some cities, localized areas are subsiding at rates 10 to 20 times faster than sea-level rise, with extreme cases documented in cities such as Tianjin, Semarang and Jakarta. Notably, Jakarta’s northwest coast has experienced land subsidence of up to 280mm per year. While cities like Jakarta and Shanghai continue to face acute subsidence, targeted policy interventions have slowed rates in some areas, underscoring the critical role of governance and adaptive management.39 This challenge is not limited to Asia. In the US, high-resolution satellite data from 2015 to 2021 indicate that 20% of urban areas across 28 cities are experiencing subsidence, potentially affecting 34 million people, approximately 12% of the national population. In 25 of these cities, at least 65% of the examined land area is subsiding, with cities such as Houston, Dallas, Fort Worth, Chicago, New York and Detroit seeing over 70% of their land affected. Since 2000, more than 90 flood incidents have occurred in eight US cities with subsidence rates above 3mm per year. In addition, 29,000 buildings are classified as high or very high risk, stressing the widespread vulnerability to critical infrastructure.40 The most affected regions are low-lying, densely populated coastal areas, river deltas and small islands. Importantly, land subsidence affects inland cities, including Mexico City and Tehran, where impacts are compounded by other climate crises, such as heatwaves and drought.41,42 These findings highlight the urgent need for ongoing monitoring, a deeper understanding of subsidence dynamics, along with prevention, mitigation and adaptation strategies. Without significant attention, consensus and collective action, portions of several major cities may become uninhabitable in the coming decades due to combined effects of subsidence and the climate crisis.1.1 How widespread is urban sinking? Without significant attention, consensus and collective action, portions of several major cities may become uninhabitable in the coming decades. Resilient Economies: Strategies for Sinking Cities and Flood Risks 12