Land subsidence will affect 635 million people by 2040

By 2040, an estimated 635 million people will be impacted by the sinking of the ground’s surface, according to a study from AAAS. This potentially destructive hazard, known as land subsidence, has a range of natural and human-induced causes such as groundwater removal.

“Subsidence due to groundwater depletion is a slow and gradual process that develops on large time scales (months to years), producing progressive loss of land elevation (centimeters to decimeters per year) typically over very large areas and variably affects urban and agricultural areas worldwide,” explained the researchers.

“Subsidence permanently reduces aquifer-system storage capacity, causes earth fissures, damages buildings and civil infrastructure, and increases flood susceptibility and risk.” 

A research team led by Gerardo Herrera Garcia conducted a large-scale literature review which revealed that, during the past century, land subsidence due to groundwater depletion occurred at 200 locations in 34 countries. 

The study indicates that within the next two decades, 19 percent of the world’s population – accounting for 21 percent of the global Gross Domestic Product – will be affected by land subsidence.

“During the next decades, global population and economic growth will continue to increase groundwater demand and accompanying groundwater depletion and, when exacerbated by droughts, will probably increase land subsidence occurrence and related damages or impacts.”

“To raise awareness and inform decision-making, we evaluate potential global subsidence due to groundwater depletion, a key first step toward formulating effective land-subsidence policies that are lacking in most countries worldwide.”

Policies that implement constant monitoring of high-risk areas and damage evaluation could help reduce the impacts of subsidence where it will hit hardest. These will be areas with increased population density, high groundwater demand, and irrigated areas that are suffering water stress.

The researchers found that their model is 94 percent capable of distinguishing between subsidence and non-subsidence areas. The model showed that most of the 635 million inhabitants in high-risk areas are located in Asia, with a total exposed GDP of $9.78 trillion. 

The experts noted that while the model does not consider existing mitigation measures, potentially resulting in overestimates of subsidence exposure, their research still represents a step forward to effective policies.

The study is published in the journal Science.

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By Chrissy Sexton, Earth.com Staff Writer