International UNESCO research team to publish the first global subsidence map
A new global map, published in Science, shows that land subsidence as a result of the depletion of our groundwater resources is a global anthropogenic hazard that produces relevant environmental, social and economic impacts. According to the researchers, nineteen percent of the global population and twelve percent of the global gross domestic product may face a high probability of subsidence. Eighty six percent of the exposed global population lives in Asia, and by 2040 the subsidence threat may increase flooding risk for 635 million inhabitants.
Land subsidence is a slow and gradual geological hazard that usually affects soft sediments, for example when groundwater is pumped from aquifers. It can permanently reduce the storage capacity of aquifer systems, damage buildings and infrastructures, and increase the flooding risk in alluvial areas and coastal plains. “Most research on subsidence focuses its efforts on studying and solving local subsidence problems, but after we identified the main environment settings of these cases we were able to make an extensive global subsidence map,” says Gilles Erkens, quaternary geologist at Utrecht University and Deltares, co-author of the paper
Eighty six percent of the exposed global population lives in Asia
Potential subsidence areas threaten 1.2 billion inhabitants and 21% of the major cities worldwide, with 86% of the exposed population living in Asia. Even though further research is still needed to fully understand the global impact of land subsidence, the paper estimates that the current economic exposure to potential subsidence amounts to US$8.17 trillion, or 12% of the global gross domestic product. Moreover, the research indicates that by 2040, an estimated 635 million inhabitants will be living in flood prone areas, where land subsidence could increase the flooding risk.
“These numbers give a much needed first estimate of the global potential exposure to and damage from land subsidence,” says Erkens. “This will help us identify areas where land subsidence may occur but has so far not been recognized as such.”
Prevention or mitigation in the context of the global change
The research and the global map aim to raise global awareness and inform public authorities about this subsidence hazard. It can help to better understand subsidence phenomena, discover new subsiding areas and guide mitigation efforts. “Land planners, urban managers and water authorities could use this information to prevent or mitigate the impact of land subsidence, especially in the context of the global change,” claims Dr. Herrera-García, head author and researcher at the Geological Survey of Spain.
Herrera-García et al., Mapping the global threat of land subsidence. 2020, Science, Vol. 371, Issue 6524, pp. 34-36. DOI: 10.1126/science.abb8549