Large swathes of land in densely populated parts of the world are subsiding rapidly as a result of groundwater depletion. Paired with rising sea levels caused by global warming, this could place many coastal cities at risk of severe flooding by 2040.
A UNESCO-funded report published on the Policy Forum of Science Journal deploys a large-scale review of subsidence over the past century and predictions of subsidence susceptibility modelled using a combination of spatial and statistical analyses. The latter was based on factors such as flooding and groundwater depletion caused by human activities.
The model found that most of the 635 million people living in areas susceptible to subsidence are in Asia.
In a report by the Guardian newspaper, a lead report author Gerardo Herrera-García said: “Areas that are heavily populated or areas that need irrigation for agriculture … need to pump the water from underground. The natural recharge of the aquifer is smaller than the volume of water they are pumping out.”
One dramatic example of subsidence is Jakarta, which has sunk by more than 2.5 metres in the past ten years.
Herrera-García went on to comment that groundwater in the USA, Mexico, China and India is being rapidly drained to meet global food demand, but insisted that it was possible to do this sustainably. He identified tighter regulation of groundwater usage as one solution, while others include more efficient agriculture practices, alternative water sources and injecting water back into aquifers