In Italy's Po delta, decades of methane extraction caused land to sink 3-3.5 meters below sea level, with ongoing challenges from rising seas and renewed drilling.
Methane extraction caused land to sink
The ground in the fields of Mea in Porto Viro and Ex Valli in Porto Tolle is currently between 3.00 and 3.50 meters below sea level. This negative altitude is the result of decades of pumping water loaded with methane from under the Po delta.Methane wells closed in 1964
The last methane wells were closed on May 25, 1964, and the ground has not regained its previous height. The subsidence is not due to a dike collapse but rather the ground receding over time.1951 flood unrelated to methane wells
The flood of Polésine on November 14, 2026, will be 75 years old, but this 1951 flood is unrelated to the methane wells, as the rupture occurred at Occhiobello, upstream, not in the delta.Rapid subsidence after 1951 flood
The years following the 1951 flood saw the most rapid subsidence, with a maximum of 250 mm per year between 1951 and 1957 according to scientific literature. This period marked the peak of ground loss in the region.Thousands of methane wells drilled
More than 4,000 methane wells were drilled between Rovigo and Ferrara between 1938 and 1960. Methane extraction began between 1936 and 1938 when the fascist regime explored the Polésine subsurface for autarkic projects.Methane extraction and ground settling
The gas is pumped from shallow sediments along with water loaded with methane. Removing this water from young sediment deprives it of what prevents it from settling, causing the ground to sink several centimeters each year.Polésine as a major gas source
The Polésine area became an energy heavy-hitter, providing 40% of Italian gas. By the end of the 1950s, production reached about 290 million cubic meters per year, equivalent to 116,000 Olympic swimming pools.Closure of wells showed subsidence link
No one connected the extraction to the land's condition until the closure of the wells in the early 1960s empirically demonstrated the link. The natural subsidence rate of the delta is about 5 mm per year, but it accelerated significantly during methane extraction.Subsidence peaks and government response
Between 1956 and 1960, the subsidence rate was 30 to 60 times faster, or 10 to 25 cm per year. The government suspended extractions in 1961 and expanded the suspension zone in March 1963, with the final closure on May 25, 1964.Continued subsidence after closure
The ground continued to sink even after the wells were closed. Between the 1950s and the early 1970s, about 3 meters of elevation disappeared. The Italian Chamber of Deputies and the delta drainage consortium report peaks of more than 3 meters of subsidence.Ongoing measurements and debate
Measurements from the University of Padua show an additional 50 cm of subsidence between 1983 and 2008. The exact timeline of the end of the subsidence phenomenon remains debated, but the ground has not returned to its original altitude.Current subsidence and land management
Today, Mea and Ex Valli are located 3.00–3.50 meters below sea level. A land placed below sea level remains cultivable only if the water is continuously drained, requiring significant investment in infrastructure.Rising sea level and subsidence
The Po delta now faces a combination of ground subsidence and rising sea levels. A researcher from the Euro-Mediterranean Center on Climate Change highlighted this dual challenge during a conference in Taglio di Po in 2026.Recent gas extraction projects
In 2021, the Ministry of Ecological Transition approved seven hydrocarbon extraction projects across Italy, from Veneto to Sicily. This has raised concerns about a possible return of subsidence in the region.Conference on subsidence awareness
The Taglio di Po conference had the title Subsidenza, vietato dimenticare ("Subsidence, forbidden to forget"), emphasizing the need to remember the historical impact of methane extraction on the landscape.
