American scientists from the Colorado School of Mines have discovered that about a quarter of the world’s population lives in areas with land subsidence, which can lead to the destruction of buildings and other infrastructure. The study was published in the scientific journal magazine Geophysical Research Letters (GRL).
Land subsidence is a geological hazard resulting from the sudden or gradual (years to decades) collapse of the earth’s surface due to the removal of underground material. It can be associated with a variety of factors, both natural (such as earthquakes, volcanic activity, and compaction of fine-grained loose sediments) and anthropogenic (such as mining and groundwater extraction).
Geologists used existing land subsidence and remote sensing data to create a training dataset of 46,000 subsidence scenarios. These, along with 23 climate, geographic and topographic conditions (including rainfall, soil composition, sediment thickness and slope), were used to train artificial intelligence (AI) that was able to estimate the total land area at risk. depression and the population in these areas.
They determined that more than 6.3 million square kilometers of the Earth’s surface (~5% of the world’s total land area) suffered subsidence rates thought to be significant enough to cause damage. The population of high-risk areas is approximately 2 billion people.
AI found that groundwater extraction remains a significant factor in land subsidence. This is followed by seismic activity, sediment thickness, average temperature of the warmest months, soil clay content and population density.
According to the model, South Asia has the largest land area at risk of subsidence (2.2% of its total area experiences subsidence rates of more than 50 mm per year) and the largest number of people who will be affected. by this phenomenon (20 million people). Other countries where subsidence rates exceed 50 mm per year include the Philippines, Iran, Costa Rica, Indonesia and Uzbekistan.
As population growth increases our dependence on groundwater and climate change worsens droughts, the impact of groundwater depletion on land subsidence will continue to be a pressing issue in the coming decades.
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