Holland is a delta from the geographical point of view, and its soil sinks faster than expected due to human action and climate change. The very hot summers of recent years have accelerated the sinking of the land, and in areas where peat predominates – the coal formed by the decomposition of vegetables – the process is irreversible. A new digital map has collected a process of environmental deterioration that, according to the Environmental Assessment Agency, will cost 22,000 million euros by 2050. Both the countryside and the city are affected, and their evolution will be updated from now on a daily basis.
The decline of the land in much of the Netherlands used to be compensated by the sand and clay deposited during the floods by the large rivers that cross it, in particular the Rhine, Meuse and Scheldt. But the construction of dykes goes back to the Middle Ages, and the rivers no longer overflow with periodicity.
"We have been pumping water for 400 years to grow and raise animals on dry land, and the ground has been falling below sea level. We already knew, but with this new map we see clearly that in the west of the country, with clay and peat soils, the latter disappears once exposed due to the periodic suction of water. It oxidizes when it comes in contact with the air and contributes to CO2 emissions, "says Ramón Hanssen, professor of Geodesy and Earth Observation via Satellite, of the Technical University of Delft, and principal investigator of the work on the map. Updated with information from satellites, their measurements are accurate and will serve to differentiate the natural causes, and caused, from the collapse of the soil.
"It is a problem that not only can change the typical Dutch landscape, with its meadows, mills and monumental cities. The damage caused to the foundations of houses and streets is visible in some cities. " Gouda, located in the west of the country and famous for its cheeses, you can tell. With about 73,000 inhabitants, its old center drops an average of three millimeters per year, and up to 10 millimeters in some points, according to the City Council.
The facades and doors of some buildings are unbalanced, there are cracks in the walls and the problem reaches the sewers. The local authorities have decided to approach the situation structurally, since many buildings are built on wooden pylons, something that happens in the rest of the historical neighborhoods of Holland.
"Climate change has aggravated the problem, with increasingly hot summers and droughts that have accelerated the disappearance of peat," says Hanssen. The extraction of natural gas has also influenced, of which the Netherlands has one of the largest deposits in the world in the province of Groningen, in the northeast of the country. Obtaining it causes earthquakes (about 400 since the late 1980s) of up to 4.5 degrees, according to seismologists. "The map will show if reducing extraction reduces soil deterioration," concludes Hanssen.
The new digital map of the Dutch soil, presented by the Center for Geodesy and Geo Informática of the country, points red in the zones where the pavement sinks to the rhythm of five millimeters per year. Yellow is for those that fall a millimeter a year, and blue -exceptional and especially in the south of the country- for the land that rises because the water pumped by mining returns to the bottom.
If measures are not taken promptly, the researchers point out that the sinking of soil in the Netherlands can exceed 50 centimeters in the next 50 years.
With 31 million measurement points, the map reveals "an inescapable problem, aggravated by climate change, another unavoidable reality," according to Ramón Hanssen, leader of the study.
In a country accustomed to dealing with water, proposals to raise the streets of affected cities have quickly emerged. Some municipalities evaluate the properties of lava, or even extruded polystyrene, a rigid foam that can be used as a thermal insulator. In the field, the best way to avoid soil decay is to keep it wet, something that is not convenient for livestock. However, for the tifa or bulrush, an aquatic plant, or blueberries, a wet surface is not a problem.