Global cities face sinking crisis and rising sea levels
Major global cities are sinking due to excessive groundwater extraction combined with rising sea levels driven by climate change.
- Major global cities are facing a dual crisis of land subsidence (sinking) and rising sea levels, with a study finding that over 71% of the world's coastal population lives in subsiding areas.
- The primary driver of land subsidence is excessive groundwater extraction to meet the demands of rapid urbanization, which causes underground sediment to compact under the weight of cities.
- The sinking crisis is most severe in developing nations, particularly in Asia and North America, with cities like Mexico City and Medan, Indonesia, experiencing some of the fastest subsidence rates globally.
- Simultaneously, rising sea levels caused by melting polar ice sheets are compounding the threat to coastal cities, with Antarctic melt alone projected to raise sea levels by up to 25 centimeters by 2100.
Major metropolitan areas across the globe are confronting an escalating crisis of land subsidence and rising sea levels driven by climate change and human activity, directly threatening urban infrastructure, public safety, and local ecosystems.
Groundwater extraction accelerates land subsidence
According to an international study published in the journal Nature Communications, over 71% of the world's coastal population resides in areas experiencing land subsidence, predominantly dense urban centers heavily threatened by flooding.
Researchers from Peking University analyzed nine years of high-resolution radar data from 2014 to 2023 using the European Space Agency's Sentinel-1 satellite, surveying land movement across 465 major cities in 107 countries with populations exceeding one million.
The study reveals that rapid urbanization and soaring water demand have driven excessive groundwater pumping. This heavy extraction reduces pore water pressure in underground sediment layers, causing the soil to compact under the immense weight of buildings and structures above, ultimately triggering surface subsidence.
Severe sinking rates in developing regions
Cities in developing nations exhibit significantly faster subsidence rates than those in developed countries, with the most severe rates concentrated in Asia and North America.
Among global cities, Mexico City experiences the fastest localized subsidence in the world, with certain areas sinking at rates up to 217 millimeters per year, while the city-wide average is approximately 8 millimeters per year.
In Asia, median sinking rates are particularly severe, led by Medan in Indonesia at an average of 33 millimeters per year, followed by Bandung at 22 millimeters per year.
Mashhad and Isfahan in Iran, Chittagong in Bangladesh, and Yangon in Myanmar also rank among the cities with the highest subsidence rates globally. Conversely, cities such as London, Tokyo, Seoul, and Sydney demonstrate relative stability with subsidence rates between 0.1 and 1.9 millimeters per year.
Melting ice sheets drive sea-level rise
Coastal cities are simultaneously confronting rising sea levels fueled by polar ice melt. Assistant Professor Lin Yucheng from the School of Energy and Environment at the City University of Hong Kong noted that even if global warming is limited to 1.5 degrees Celsius under the Paris Agreement, Antarctica still faces a 92% probability of losing ice mass this century.
Research indicates that Antarctic ice melt alone will raise global sea levels by up to 25 centimeters by 2100, threatening over 10 million people with permanent coastal flooding and massive economic losses.
In Jakarta, northern coastal communities such as Muara Angke experience subsidence rates of up to 7 centimeters per year, leaving areas below sea level and prompting Indonesia to plan large sea walls and strict groundwater controls.
Scientists emphasize that subsidence caused by groundwater extraction can be mitigated and reversed through managed aquifer recharge projects, which have already succeeded in cities like Las Vegas, Shanghai, and Beijing, provided they are paired with comprehensive water management and greenhouse gas reductions.
Source: Bangkokbiznews
