Decline, or the gradual collapse of land, could affect 19% of the world population by 2040, according to new research funded by Unesco.
If left unchecked, human activity, coupled with drought and rising sea levels could be exacerbated by global warming, endangering many of the world’s coastal cities.
Jakarta has sunk more than 2.5 meters in the past ten years, causing the Indonesian government to move the country’s capital to the island of Borneo.
In Europe, subsidence is responsible for placing 25% of the Netherlands below sea level. Flat coastal regions, as well as urban and agricultural centers in arid climates, run the greatest danger.
Gerardo Herrera-García, lead researcher on the project, which is affiliated with the Geological and Mining Institute of Spain, said: “Areas with a large population or areas that need irrigation for agriculture, because it is located in places that are for long periods are dry from time to time they have to pump the water from underground. When they pump the water, the natural recharge of the aquifer is smaller than the amount of water they pump out. ”
This extraction of water from the soil causes the surface to sink. But the lack of pump regulations and the rapidly growing population of people are the most likely factors contributing to the slump figures.
In Iran, the population has more than doubled in the last 50 years, while the pumping of groundwater has remained unregulated. The country’s cities are now among the fastest sinking urban centers in the world, falling by up to 25 cm every year.
While subsidence was a common problem during the 20th century, it was previously only analyzed in a local context.
The new project, developed by an international team of scientists, sought to consolidate existing research. The scientists developed a universally applicable model to predict in which areas the risk of falling is greatest.
The results showed that subsidence was a global problem, linked to global warming as well as unsustainable farming practices. “The largest aquifers in the world are being depleted for agricultural purposes,” Herrera-García said.
According to Herrera-García, groundwater in the US, Mexico, China and India is being drained rapidly to meet global food demand. Continued subsidence in those areas will affect populations worldwide. Herrera-García has made it possible to make global food production sustainable, but the problem will have to be addressed soon.
In addition, global warming is expected to cause long periods of drought, which will accelerate subsidence as more water is pumped underground.
Meanwhile, sea levels are expected to rise by up to a meter in the next century. This means that more coastal cities will experience the same problems as Jakarta, as more areas will be prone to flooding.
Herrera-García said that the subsidence is a major threat to the global environment, but that it can be corrected much more easily than climate change. Technologies, such as satellites and radars, can quickly identify slump areas, while ‘simple policies and tools’ can be used by local authorities to combat the problem effectively.
‘In Tokyo, they had a very big problem of collapse in the first part of the last century. They applied groundwater regulations and they solved the problem. ”
Other solutions for subsidence include finding alternative water sources, practicing efficient agriculture to use as little water as possible, and injecting water into aquifers.
“These solutions are the same everywhere and can be applied to large aquifers and smaller ones,” Herrera-García said. “I think we are on time. The solutions are there, and it’s time to implement them. ”