Land subsidence threatens 19 percent of the world's population

The abstraction of groundwater causes severe subsidence in many regions of the world, which can destroy buildings and make flooding more likely. In some regions land subsidence is 30 centimeters per year.

Many regions of the world that are close to the sea and rivers are acutely threatened by increasing subsidence. This affects the Netherlands, the river deltas of Asia and the coast of California, among others. In addition to the natural nature of the soil, this creeping subsidence is mainly due to the extraction of underground resources and groundwater. The consequences are damage to buildings and a high degree of susceptibility to flooding and flooding.

A team of scientists led by Gerardo Herrera-Garcia from the Spanish Geological Service has now published a study in the journal Science that examined in detail the regions and countries in which the falling groundwater levels lead to land subsidence the most. To do this, they analyzed the data from numerous publications and maps from recent years.

Subsidence affects 34 countries heavily

According to the results, the subsidence due to groundwater affects 200 regions in 34 countries. These include Tokyo, where the ground sank four meters over the course of the 20th century, and many Chinese cities that are located in the country's large sedimentary basin.

Gerardo Herrera-Garcia: In Indonesia, the subsidence of the coastline in Jakarta is so severe that the government authorities are planning to relocate the capital to the island of Borneo.

30 centimeters of land subsidence per year

Gerardo Herrera-Garcia: Iran is home to some of the fastest sinking cities in the world, they are sinking by 25 centimeters a year.

Mexico has been hit even harder by land subsidence, where subsidence reaches 30 centimeters per year in some regions. In Europe, alongside the Netherlands, Italy's Po Valley is threatened by land subsidence. Currently about a third of the Italian population lives in one area.

Metropolitan areas threatened by land subsidence

The land subsidence is already affecting metropolitan areas and large cities, which are already at great risk from floods and storm surges. A model by the scientists shows that the problem will increase in the future and that by 2040,19 percent of the world population (1.6 billion people) will be threatened by subsidence. 635 million of them would be acutely at risk from river or sea floods.

Gerardo Herrera-Garcia: In view of the fact that subsidence could affect 635 million people in flood-prone areas worldwide, this must increasingly be included in flood risk analyzes and the planning of countermeasures,According to the model, 1,596 of the 7,343 (22%) of the world's megacities are in current or future subsidence zones. In some countries, including the Netherlands, the Philippines, Bangladesh and Mexico, according to the model, 80 percent of the population could be affected by land subsidence in 2040.

Poorer countries hit hardest by subsidence

54 percent of the people who live in regions with high subsidence belong to the population of poor countries.

Gerardo Herrera-Garcia: It is to be expected that these countries will only have a limited ability to implement the necessary political, regulatory and socio-economic countermeasures.

In contrast, land subsidence threatens only 11 percent of the population in high-income countries.