China’s Coastal Megacities Confront Rising Seas and Sinking Land
China’s coastal zone faces a precarious future. Considered a global manufacturing powerhouse and home to millions of people, it is threatened by rising sea levels and sinking land, particularly in its most economically vital cities. Within major delta regions, such as the Yangtze and Pearl River Deltas, which encompass megacities such as Shanghai, Shenzhen, and Hong Kong, the combination of global sea-level rise and localized land subsidence, often driven by excessive groundwater extraction, poses a “double crisis.”
The Effects: Property, Community, and the Global Supply Chain
The impact of rising sea levels, compounded by land subsidence, is profound and immediate for properties and communities in China’s low-lying delta regions.
Property and Infrastructure Damage
Increased flooding from high tides and storm surges, amplified by higher sea levels, threatens roads, bridges, and buildings. The vulnerability is severe: parts of Shanghai sank more than one meter during the 20th century due to groundwater use, making it exceptionally sensitive to even small increases in sea level. This greatly compromises the stability of critical international manufacturing hubs, placing the global supply chain under threat.
Rising Home Insurance Rates
While national data on insurance rate hikes isn’t publicly detailed, the economic risk is clear. As climate-related disasters become more frequent and intense, new risk modeling tools assess individual property exposure, translating to higher premiums and limited policy availability in high-risk zones. The estimated average annual economic losses for China from rising sea levels and land subsidence have already reached US$1.5 billion per year.
Community Resources and Geography
Coastal erosion and saltwater intrusion are significant threats, contaminating freshwater supplies for drinking and agriculture in estuaries. Furthermore, the delicate balance of coastal ecosystems is being disrupted. Sea-level rise and reduced sediment load from major rivers (due to reservoir construction) accelerate coastal erosion and threaten the restoration of vital coastal wetlands.
Trends in Sea Level Rise: 1975 to 2050 and Beyond
Sea level along the coast of China has been rising faster than the global average and accelerating.
1975 to 2025: The Acceleration Phase
Based on observed data, the rate of sea level rise has accelerated, approximately from 1975 to 2025. The South China Sea has experienced some of the fastest increases. Crucially, human-caused subsidence, particularly from groundwater extraction, has drastically accelerated the effective relative sea level rise in many major cities.
2025 to 2050 and Beyond: Policy vs. Climate
Future sea level rise is highly likely due to the ocean’s thermal inertia and continued ice sheet melting. However, the most critical factor for China’s future flood exposure may not be global climate models, but local policy decisions. Studies show that China’s coastal development policies and subsidence controls may be a greater determinant of flood exposure by 2100 than the magnitude of global sea-level rise alone.
Adjustment and Counteraction Efforts
The Chinese government has recognized this vulnerability and is shifting planning from relying solely on hard defenses toward integrated strategies that include stricter land-use planning and ecological protection.
Key Adaptation Strategies
- Subsidence Control: Cities like Shanghai have implemented successful, proactive adaptation measures, notably regulating groundwater use and even reinjecting freshwater into aquifers. This has successfully slowed the sinking rate.
- “Sponge City” Concept: China is developing the “Sponge City” concept to manage increased rainfall and to redesign stormwater systems, a key component of building climate-resilient coastal cities.
- Hard Defenses: China has constructed and periodically reinforced over 12,000 km of dykes.
Cost and Timeline
Efforts are ongoing, with the national goal of strengthening climate adaptation by 2035.
- Adaptation Costs: The cost of implementing climate-resilient urban systems, such as the “Sponge City” concept, is high, but pilot cities have shown investment and operational cost savings compared to traditional, rigid approaches.
- Mitigation Costs: The most fundamental effort—addressing the root cause of global sea level rise—involves China’s commitment to peak carbon emissions by 2030 and achieve carbon neutrality by 2060. This requires trillions of dollars in energy transition and R&D.
Limits on Future Sea Level Property Development
The prevailing scientific and policy analyses strongly suggest that limits on future sea-level property development are necessary and critical for managing flood risk. Experts caution against overreliance on levees and seawalls, which can create a “levee effect,“ a false sense of security that encourages riskier development and raises the ultimate cost of future breaches.
By 2100, future flood exposure will be more strongly determined by policy decisions on land use than by the magnitude of sea-level rise itself, making strategic spatial planning paramount. The government’s comprehensive development strategy for coastal cities includes “rigidly restricting the reclamation of the sea and island” and “controlling the spatial development direction” in high-risk zones.
This Post was submitted by Climate Scorecard China Country Manager, Vincent Mao.
Resources:
Rising Seas and Sinking Cities Signal a Coastal Crisis in China | Rutgers University
Sea level rise: Everything you need to know – The World Economic Forum
Climate Change Impacts on Coasts | US EPA
Sea level rise along China coast in the last 60 years | ResearchGate
China – Projections | Climate Change Knowledge Portal
Rising seas and sinking cities signal a coastal crisis in China – PreventionWeb.net
Local decisions in China affect coastal flood exposure more than global sea-level rise
Development strategy of China’s coastal cities for addressing climate change
The coasts of China and issues of sea level rise – ResearchGate