A new analysis suggests that sinking land, known as erosion, could affect 8 percent of the world’s land surface and 19 percent of the population in the coming decades. Grants are initiated through processes such as groundwater depletion and cause large areas of land to be submerged over months and years. This can have dangerous and costly effects on affected areas, including increasing the risk of flooding, causing explosions, permanently reducing the capacity of aquifers, and damaging buildings and infrastructure. It is predicted that the demand for groundwater will increase in the future due to population and economic growth, further exacerbating this process. Climate change may also make grants worse due to changes in rainfall, frequent and severe floods and droughts, and increased evaporation.
The study, published in Science, began with a review of large-scale systematic literature on global damage. They found that groundwater depletion decreased at 200 locations in more than 34 countries. The subsidy rate in Mexico is one of the highest in the world, at 30 centimeters (11.8 inches) per year. Contributing to the floods, the Po River threatens 30 percent of Italy’s population frozen in the plains. Due to uncontrolled groundwater pumping, Iran has several rapidly sinking cities, accumulating up to 25 centimeters (9.8 inches) a year. Over the past century, Tokyo has seen a decline of 4 meters (13.1 feet), and Central Valley, California, has seen a decline of up to 9 meters (29.5 feet). The Netherlands is 25 percent below the main sea level, mainly due to the decline. The Indonesian capital, Jakarta, has been hit so hard that the government plans to relocate the capital to Borneo.
The authors of the study proposed a global model that they claimed could predict global loss sensitivity at a resolution of 1 km (0.6 miles) square. It does this through statistical analysis of lithology (physical rock properties), surface operation of terrestrial, terrestrial, and Cape-Jigger climate classes. It also estimates the potential for groundwater depletion, identifying areas underwater pressure or with high groundwater demand.
The results of the modeling prove that 12 million square kilometers (7.5 million square miles) of global land area could potentially be reduced – 8 percent of the Earth’s surface. Risk areas were concentrated in and around dense urban areas and irrigation areas. 2.2 million square kilometers (1.4 million square miles) was considered high or very high risk. These regions account for 1.2 billion people or 19 percent of the world’s population.86 percent of Asia’s population faces a potential decline compared to North America and Europe. Egypt and the Netherlands were shown to be the most populous inhabited areas of potential erosion below sea level. The results identified 1,596 major cities in potentially flood-prone areas, including 57 percent in flood-prone areas.
The researchers cited a lack of information as a limitation of their approach, as only a third record in the literature review contained information on the amount of reduction, and information on effects and mitigation measures was very limited. However, the authors say that this model could help identify areas of frequent risk for further analysis and intervention.